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Hydration effect of sodium silicate on cement slurry doped with xanthan
Construction and Building Materials 223 (2019) 976–985
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Hydration effect of sodium silicate on cement slurry doped with xanthan Qi Yanhan, Li Shucai, Li Zhaofeng ⇑,1, Zhang Jian, Li Haiyan Geotechnical and Structural Engineering Research Center, Shandong University, Ji’nan 250000, Shandong, PR China
h i g h l i g h t s The effect of polyhydroxy xanthan on the corresponding hydration process of cement and regulation mechanism was discussed. Sodium silicate as coagulant was added and its accelerating mechanism for the retarding effect of xanthan in cement paste was investigated. Established a ‘‘suppression-excitation” system of cement slurry.
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Article history: Received 11 April 2019 Received in revised form 20 July 2019 Accepted 30 July 2019 Available online 6 August 2019 Keywords: Sodium silicate Xanthan Hydration of cement Suppression-excitation system Mechanism research
a b s t r a c t The effect of polyhydroxy xanthan on the corresponding hydration process of cement and regulation mechanism was discussed, then sodium silicate as coagulant was added into the xanthan-retarded cement paste and its accelerating mechanism for the retarding effect of xanthan was investigated. The results indicate that due to chemisorption between hydrophilic hydroxyl and carboxyl and calcium ions, the core-shell construction of xanthan-cement to a certain extent hinders the hydration process of cement particles, adding sodium silicate in the cement-added xanthan significantly inhibits the retardation of the xanthan, shortens the setting time of the retarding cement, improves the compressive strength of the retarded cement, and to some extent promotes the hydration of C3A. The early hydration of C3A, C3S and sodium silicate rapidly formed a large amount of C-S-H, which was bound with the ettringite skeleton to promote coagulation hardening of the cement slurry, further established a ‘‘suppression-ex citation” system between xanthan and sodium silicate in cement slurry. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction In recent years, with the rapid development of engineering construction around the world, Cementitious slurry and concrete products have been widely used in all field, such as water conservancy and hydropower, mine dam, subway and tunnel construction underground and other aspects. However, according to different actual working conditions and challenging climate, the performance parameters of traditional cement slurry and fresh cement concrete are required differently, and there are generally technical problems shown up in the process of construction, which includes flexible setting/placement time, strength development of cement paste and long-distance transport. In the actual process of production and construction, due to some unexpected factors, such as geological disaster, challenging climate, damaged equipment etc., the fresh cement slurry and concrete can’t be used in time,
⇑ Corresponding author. E-mail address: [email protected] (Z. Li). Lecturer, mainly engaged in the prevention of underground engineering disaster and grouting material’s research and development. 1
https://doi.org/10.1016/j.conbuildmat.2019.07.327 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved.
resulting in the gradual loss of its performance and eventually abandoned, which to a certain extent increases the project cost, delay the limit time for a project, resulting in unnecessary waste of resources, contributing to a generally increasing production of waste worldwide [1]. Setting time is one of the important parameters to be controlled in the construction of cement slurry, which is highly dependent on the composition of the materials [2,3]. Therefore, the research on adjusting the setting time of slurry with additives has gradually become a hotpot in recent years. At present, the setting time of cement is usually controlled by adding retarders or coagulants based on the two working principles of physical coating and chemical reaction intervention, and adjusted by controlling the type and dosage of retarders and coagulants [4–6], further established a kind of ‘‘suppression-excitation” system, which has better flexibility, purpose and pertinence in engineering construction. Reiter [7] proposed to wake up a heavily delayed cement mixture by the use of mineral addition that cancels the effect of the set retarder. In his study concrete is put to sleep with a high dosage of PCE superplasticizer and woken up in the plan by the use of bentonite with a high affinity to bind PCE superplasticizer.
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Riding [8] has conducted similar research that a new type of ultrahigh surface area supplementary cementitious material was made from biomass pretreated used as the nucleating agent in his study and shown to be successful in restarting the hydration of systems with very long set times due to additions of either sucrose or zinc oxide. Sun [9] investigate compensation function of aluminum sulfate for calcium sulfoaluminate cement containing citric acid and the results show that aluminum sulfate acts as a setting accelerator to offset excessive retarding caused by citric acid, which promotes C4A hydration and development of AFt. Franco [10] investigated chemical (calcium chloride), physical (fine limestone powder) and pre-washing strategies as means to reduce the setting retardation effect of high-SO3 fly ash (HSFA) on cement paste, which has greatly positive potential influence on engineer application. Hydroxyl carboxylate is adsorbed on the surface of cement particles and forms unstable complex with Ca2+ in alkaline environment [11], which controls the concentration of Ca2+ and the formation of hydration products in the initial stage of cement hydration and has a strong inhibitory effect on the initial stage of cement hydration to a certain extent. Due to this property, hydroxy carboxylate is widely used to prolong setting time of cement slurry and delay cement process [12]. Xanthan gum is an extracellular polysaccharide obtained by fermentation using bacteria of the genus Xanthomonas, which is composed of d-glucose, d-mannose, d-glucuronic acid and d-mannuronic acid to form a polysaccharide biomacromolecules [13,14]. Due to its rheological properties and stability in a wide range of pH and temperatures, Xanthan gum has been widely used and studied in the field of food chemistry and hydrocolloids [15–17], carbohydrate polymers [18,19], pharmaceutics [20,21], etc. For that having multiple active hydroxyl and carboxyl functional groups, therefore, Xanthan gum
should possess the familiar retarding effect on cement slurry as hydroxy carboxylate theoretically. Recently, scholars in the world are focusing their attention on hydroxy carboxylate retarders, such as sodium gluconate [22–25], tartaric acid [26–28], sodium citrate [25,29–31] and citric acid [31,32], etc., aiming to study mechanism of the effect on the hydration process of cement. However, there are few studies on the effect of xanthan gum on the hydration of cement particles and the elimination of retarding action of xanthan. Therefore, in this paper sodium silicate was added as the coagulant promoting component to cement slurry mixed with xanthan gum to analyze its influence on cement setting time, strength development of cement paste, porosity of cement solid, heat of hydration, hydration products, and to a certain extent, the suppressing mechanism of xanthan gum and the exciting mechanism of sodium silicate were scientifically explained.
2. Experimental section Materials and instruments: The cement used in this paper was Portland Cement (P.O. 42.5) at a water to cement ratio of 1:1 and purchased from Shandong Sunnsy cement Group Co., Ltd (Jinan China). Its chemical composites and physical parameters are shown in Table 1. Xanthan was purchased from Sigma-Aldrich Co., and its chemical structure is shown in Fig. 1. Sodium silicate was purchased from sheng peng pao hua jian Co., Ltd (Zao Zhuang, China) The specification of sodium silicate is that, Baume (Be0 ) = 39, Modulus (M) = 3.3. The setting time of cement paste in the experiment was conducted according to the national standard, which its serial number is JC/T 2536-2019. The strength development of cement paste was obtained using a MTS CDT1305-2 electronic
Table 1 Chemical compositions of cement and its physical parameters. SiO2
Fe2O3
Al2O3
CaO
MgO
SO3
Loss
Average primary particle size
Surface area
18.45%
4.35%
5.95%
62.73%
4.37%
2.1%
0.52%
15.32 lm
320 m2/kg
Fig. 1. The chemical structure of xanthan gum.
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pressure testing machine controlled microcomputer. The changing porosity of cement solid was analyzed by Mercury intrusion porosimetry (Poremaster-60, Quanta). The hydration processes of slurry were carried out on a hydration heat tester (Tianjin Gangyuan Instrument Co., Ltd., china). Scan electron microscopy (SEM) was obtained using a Thermo Fisher Quattro S electron microscope. Phase analysis of X-ray diffraction (XRD) was carried out on a Thermo Fisher ARL-EQUINOS-1000X spectrophotometer. Main chain, trisaccharide side chain, and binding sites for cation (M+). Experimental process and method: Research object is made of two components, A and B. Component A is the simple cement slurry, which its water cement mass ratio is 1:1, with the condition that planet mixer constant speed stirring to ensure slurry level uniform. Component B is composed of xanthan solution and sodium silicate. Putting the common ratio of double-liquid slurry in practical engineering as a reference, the volume ratio of the component A/B is set at 3:1. In order to explore the relationship between xanthan concentration and hydration process of cement slurry in this paper, the mass percentage of xanthan solution (P(xanthan)) was 0.3%/0.5%/0.7%/0.9% respectively, sodium silicate, as a common coagulant to accelerate the hydration process of cement paste and shorten experiment cycle [33], was added and the mass percentage of the total was set at 70%; In order to investigate the effect of sodium silicate on the cement slurry with xanthan, the sodium silicate’s percent (P(sodium silicate)) accounts respectively for 10%, 30%, 50% and 70% in component B, and the mass percent of xanthan solution 0.5%. Then, the setting time, heat of hydration, porosity, compressive strength and phase changes in the hydration process of the slurry were investigated and analyzed. Setting time test: For that sodium silicate is added as an accelerant to shorten the setting time compared to purely cement slurry’s, Therefore the pour cup method was adopted to measure the initial and final setting time of the double-liquid slurry, as Fig. 2 shows. Keeping the cement slurry falling back and forth with two cups, When the slurry is loss of liquidity with cups inclined 45° is used for initial setting time; Curing 6 h/12 h/24 h/3 d/7 d/28 d under the condition of national standards (ISO methods) GB/T176711999, which temperature should be kept at 20 °C ± 1.0 °C and humidity should be no less than 90% respectively. The time when the hardness of slurry body is in the state of stone is the time of final setting time. Hydration heat test: The hydration heat of the two-component cement slurry was determined by the ZTM 14-channels thermal
conductivity isothermal calorimeter, and the water-cement mass ratio was 1:1. Component A/B has a volume ratio of 3:1. Compressive strength test: The cement slurry was mixed uniformly and then poured into the model for curing and the model’s size was elected as 40 mm*40 mm*160 mm. The compressive strength test was conducted according to cement mortar strength inspection method (ISO method), which its serial number is GB/T 17671-1999. Porosity test: Break the cement slurry body when curing to the specified age. Take equal quality samples (0.6 g ± 0.02 g) in the anhydrous ethanol to stop the hydration process. Drying in the vacuum oven of 35 before porosity test. Phase analysis of X-ray diffraction (XRD): The sample preparation method is the same as above. After drying, the equivalent samples grinded to powder below 0.08 mm were for XRD test. The X-ray diffraction analyzer condition is set to that, wavelength is 0.154 nm, voltage is 40Kv, electric current is 30 mA, diffraction Angle 2h ranges from 10° to 90°.
3. Results and discussion 3.1. Effect of xanthan on the hydration of cement slurry 3.1.1. Effect of xanthan on setting time The influence of different amounts of xanthan gum on the setting time of the slurry is shown in Fig. 3. It demonstrated that with the increase of the percent of xanthan gum in cement slurry, the effect of the extension of the initial setting time and the final setting time of the cement is more obvious. At this time when the percent of xanthan gum is 0.5%, the initial and final setting time of the cement slurry is extended to 19.67 s/37 min, and the growth rate is 6.75 s/40 min, respectively. When the percent of xanthan gum is 0.8%, the initial setting time and the final setting time of the cement slurry is increased to 22.17 s/54.22 min, and the growth rate is 12.25 s/85 min, respectively. It is worth mentioning that xanthan gum not only extends the setting time of the cement, but also increases the time interval between the initial setting time and the final setting time of the slurry with the increase of xanthan gum percent. When the percent of xanthan gum is 0.3%, the time interval between initial and final setting is only 29 min 41 s. When the percent of xanthan gum increased to 0.7%, the time interval between initial and final setting is extended to 45 min 39 s. Therefore, with the increase of xanthan gum content, the time interval between initial and final setting is getting longer and longer.
Fig. 2. Schematic diagram (left) and samples (right) of pouring cup methods.
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Fig. 3. Effect of Xanthan gum on setting time of cement.
Fig. 4. Effect of different xanthan percentage on hydration heat evolution rates.
3.1.2. Effect of xanthan on the hydration process of cement slurry The effect of different amounts of xanthan gum on the hydration process of slurry is shown in Fig. 4. It illustrated that the first exothermic peak that occurs during cement slurry hydration process is about 30 min after the hydration process, which is delayed by nearly 20 min from the first exothermic peak of the cement single slurry hydration process, the pre-induction period. With the increase of the xanthan gum content, the first exothermic peak of cement hydration shows a gradual decrease trend, and the peak appearance time is shorter, which is due to the unique volcanic ash effect and hydration reaction of the cement mineral component tricalcium aluminate. During the acceleration period, that is, the second exothermic peak of the cement is significantly reduced and moved backward, and the hydration temperature peak is gradually widened. When the amount of gum is 30%, the second exothermic peak of cement hydration is extended to 3 h, and when the dosage is increased to 70%, the second exothermic peak is sharply moved back to 7.8 h. Therefore, In a same percentage of sodium silicate condition, the xanthan gum solution can inhibit the initial hydration of the cement slurry, delay the heat release rate of cement hydration, weaken the peak of hydration heat, and reduce the heat releasing in the process of hydration process. In addition, a flank peak appears in the hydration heat curve with the condition of 30% xanthan content, which the hydration time is about at 11 h, this may be due to insufficient slurry agitation to cause a decrease in the local gypsum content of the solution, and high-sulfur type hydrated calcium sulphoaluminate crystals (AFt) in the solution
and hydrated calcium aluminate, calcium hydroxide, etc. are gradually converted into low-sulfur hydrated calcium sulphate crystals (AFm) to increase the heat of hydration process and the mechanism was shown as Eq. (1).
3CaO Al2 O3 3CaSO4 32H2 O þ 2ð3CaO Al2 O3 6H2 OÞ ! 3ð3CaO AlO3 CaSO4 12H2 OÞðAFmÞ
ð1Þ
3.1.3. Effect of xanthan on pore size distribution The pore size distribution of samples with different xanthan contents is shown in Fig. 5. Porosity of the samples with the percent of xanthan 0.5% and 0.9% is 18.8% and 22.4% respectively curing for 3 d. As can be seen that the pore distribution of the consolidation sample is concentrated in the <100 nm range. With the passage of curing time, the pore diameter of the sample has a gradually decreasing trend, accounting for a gradually increasing total porosity. This is caused by the continuous hydration of cement slurry, which results in cross-linking of gelling substances, filling of macropores and consequent gradual reduction of pore structure. The maximum pore sizes of 0.5% and 0.9% xanthan are concentrated in the range of 10–100 nm, and their distribution peaks are about 0.68 ml/g, 0.65 ml/g in 6 h curing age, 0.77 ml/g, 0.70 ml/g in 24 h curing age, 1.11 ml/g, 0.96 ml/g in 3 d curing age, 1.08 ml/g, 0.98 ml/g in 7 d curing age, It is apparent to see that, the distribution peaks of sample with percent of xanthan is 0.9% is lower than sample whose percent of xanthan is 0.5%. This shows that the difference of
Fig. 5. Effect of xanthan content on pore size distribution at different curing age, the percent of xanthan in the sample is 0.5% and 0.9% respectively from left to right.
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Fig. 6. Effect of xanthan content on compressive strength at different curing age (left), Compressive strength-Time curve with the condition that Percent xanthan gum is 0.3% (right).
xanthan content obviously changes the void structure of cementbased materials, further indicating that high content of xanthan can mitigate the hydration process of cement slurry. 3.1.4. Effect of xanthan on compressive strength The Fig. 6 above shows the variation of compressive strength of the cement sample with different percent xanthan along the curing ages (left) and compressive strength-time curve with the condition that Percent xanthan gum is 0.3% (right). From Fig. 5 (left) it is apparent to see that with the increase of curing age, the peak compressive strength of cement sample in same xanthan content gradually increases because of the continuous hydration process of cement slurry, while the growth rate increases at first and then decreases along with the curing time. With the increase of the percentage of xanthan gum, the compressive strength of the cement sample gradually decreases, which is because the xanthan gum slows down the hydration reaction to a certain extent and hinders the formation of gelling substances. Related with pore size distribution, Fig. 5 above shows that with the percentage of xanthan increases, the pore distribution of the consolidation sample gradually transitions to the large aperture interval, which posed negative influence on compressive of the consolidation sample, macroscopically reduced compressive strength. As Fig. 6 (right) indicated that under the equal xanthan gum content conditions, the samples with different curing ages have different time to reach the peak of compressive strength curve. Along the curing age increases, the time taken for the sample to reach the peak of compressive strength curve increases gradually, This is because under the same xanthan content, the porosity of the consolidation samples changes from a large-size interval, which is negative to compressive strength, to a small-size interval, which has positive influence on th compressive strength, with the prolonging of curing time, as shown in Fig. 5, therefore, the compactness of consolidation sample increases and the compressive strength increases. What’s more, Fig. 6 (right) shows that the cement standard samples possess high compressive strength at 6 h curing ages. That’s because that sodium silicate shortened the setting time of cement slurry significantly, a large amount of hydration products was produced in the early age, the compressive strength increased remarkably in the early age and the sodium silicate addition play a positive role on the early compressive strength. 3.1.5. Mechanism analyzing Hydrated minerals of consolidation sample at different curing age are analyzed by XRD as showed in Fig. 7, the spectrum top
means pure cement sample without addition and the spectrum bottom is consolidation sample doped different xanthan content. From Fig. 7, it can be seen that the XRD spectrum of the consolidation sample mixed with xanthan has no change in the peak shape and position of the diffraction peak compared with that of the cement single slurry blank sample, which shows that the addition of xanthan in cement has no obvious influence and change on the types of cement hydration products and CH, Aft, C3S and alite are the main hydration products of cement slurry. In addition, in Fig. 7 (top), the characteristic diffraction peak of unhydrated tricalcium silicate C3S (34, 2h) is obviously enhanced with the increase of the percentage content of xanthan, which indicates that the hydration pressing effect of xanthan on silicate phase is obvious. With the increase of the amount of xanthan, the peak intensity of CH (18,2h) diffraction is obviously reduced. When the concentration of xanthan gum is 0.9%, the diffraction peak of CH almost disappears on the XRD spectrum. It can be seen that the addition of xanthan gum in the cement slurry can delay the crystallization of CH crystal, and the hydration of the C3S mineral phase in the cement clinker is inhibited. For the characteristic diffraction peak of Aft (16, 2h), the more xanthan is added in cement slurry, the characteristic diffraction peak possesses an enhanced trend, which shows that the low percentage of xanthan promotes the hydration of tricalcium aluminate (C3A) mineral phase and increases the content of Aft in slurry. The hydration effect of high percentage xanthan on C3A mineral phase will be the next topic of research. Under the condition of a constant amount of sodium silicate, in the cement-xanthan-water system, the effect of xanthan on cement hydration includes two aspects, the schematic is shown in Fig. 8. First, referring to the M. E. Tadros’s work [34], due to the inconsistent dissolution property in the hydration process of cement particles, silicate ions (SiO2 3 ) are enriched in the cement particles to form a cement particle with negative charge. Calcium ions (Ca2+) free in the solution gather to the cement particles under the electrostatic action and form a double electron layer on the surface of the particles. Hydrophilic hydroxyl and carboxyl in the xanthan solution form a complex similar-chelates with calcium ions (Ca2+) [12], to reduce the calcium ion concentration during the cement hydration induction period, prevent the precipitation of strong calcium oxide and calcium salt crystals, accelerate the dissolution of sulfate in the gypsum, with the reaction among sulfate, water and tricalcium aluminate (C3A), which possesses quickly reaction with water in the cement hydration process, It promotes the formation of insoluble needle-shaped ettringite (AFt) to a certain extent, which covers the surface of cement
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Fig. 7. XRD spectrum of pure cement sample (bottom) and cement sample (top) with percent of xanthan is 0.5% and 0.9% respectively at different curing time.
Fig. 8. Mechanism diagram of effect of xanthan on cement hydration process.
particles and further plays an negative role in the hydration process of cement. On the other hand, the hydroxyl groups and carboxyl groups in the xanthan compound with calcium ions (Ca2+) on the surface of the cement particles [35] to form a passivation
layer, which form a core-shell structure with the cement particles as the core and the xanthan molecule as the shell, as SEM image shown in Fig. 9, inhibiting the hydration of C3S and the crystallization of CH, thereby prolonging the setting time.
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Fig. 9. SEM image of xanthan-cement core-shell construction.
3.2. Effect of sodium silicate on the hydration of cement slurry doped with xanthan 3.2.1. Effect of sodium silicate on setting time of cement slurry doped with xanthan Sodium silicate is added to the cement paste mixed with gum (0.5%, the same below) as coagulant, and the test operation is carried out under the same environment to obtain the effect of sodium silicate coagulant on the setting time of the cement mixed with xanthan, as shown in Fig. 10. As can be seen from Fig. 10, when the percent of sodium silicate (P(sodium silicate)) is increased from 30% to 70%, the initial setting time of the xanthan-mixed retarded cement is shortened from 70 s to 20 s, the final setting time is also shortened from 1.8 h to 0.55 h, however, the initial setting time of the cement single slurry is about 1.2 h and the final setting time is about 8 h, therefore, the addition of the accelerating component obviously shortens the setting time of the xanthan-mixed cement slurry. The setting time of cement paste mixed with xanthan is obviously shortened along the increasing of the content of sodium silicate, and the influence is more obvious with the increase of the content. 3.2.2. Effect of sodium silicate on the hydration process cement slurry doped xanthan Sodium silicate as coagulant was added to the cement slurry doped with the equal xanthan and tested under the same experimental environment. The effect of sodium silicate on the hydration heat evolution rates of the cement mixed with xanthan is shown in Fig. 11. Fig. 11 illustrated that sodium silicate added to cement slurry mixed with xanthan can obviously increase the peak heat of hydration process of cement slurry, and the hydration rate of cement slurry also increased. It is apparent to see that when the percent of sodium silicate is 10%, 30% respectively, there are two absorption peaks in the hydration process, the first absorption peak occurs at 3.8 h, and the second exothermic peak occurs at 22 h, 14 h respectively. What’s more, along the increase of sodium silicate content, the occurring time of the second exothermic peak is obviously shortened, and the amount of exothermic heat is gradually reduced. However, when the content of sodium silicate exceeds 50%, the second exothermic peak has disappeared, the occurring time of the first exothermic peak in the hydration process is unchanged. The peak heat gradually increases with the content of sodium silicate increasing, which indicates that the first exothermic peak is caused by sodium silicate as coagulant partici-
Fig. 10. Effect of sodium silicate on setting time of xanthan-retarded cement.
Fig. 11. Effect of sodium silicate on hydration heat evolution rates of xanthanretarded cement.
pating in the hydration reaction, promoting the hydration process of the slurry and increasing the exothermic quantity. The second exothermic peak is the result of hydration process of minerals in the cement slurry itself. Therefore, the addition of coagulant
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Fig. 12. Effect of different xanthan content on pore size distribution at different curing age, the percent of sodium silicate in the sample is 30% and 70% respectively.
sodium silicate plays a role in promoting the hydration of the cement slurry mixed with xanthan.
3.2.3. Effect of sodium silicate on pore distribution of cement slurry doped xanthan The pore size distribution of consolidation samples with different sodium silicate contents is shown in Fig. 12. As can be seen from Fig. 12, the pore size of the samples has a gradually decreasing trend along the passage of curing time, which is caused by the continuous hydration of the cement slurry. When the curing age is 3 d or 7 d, the pore distribution of serous consolidation samples with 30% sodium silicate content is concentrated in the 103– 104 nm range and 102–104 nm range respectively, and the mode pore-size is 0.55 and 0.35 ml/g respectively. when the percent of sodium silicate is increased to 70%, the pore distribution of serous consolidation samples is concentrated in the 10–100 nm range, mode pore-size is 1.13, 1.08 ml/g respectively. It is apparent to see that, the pore size distribution of sample with 70% sodium silicate is lower than sample with 50% sodium silicate, which indicates that the difference in sodium silicate content significantly controlled the quantity of gel product, and changes the pore structure of cement-based materials and further indicates that sodium silicate, a coagulant component, has an inhibitory effect on the retarding of xanthan.
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3.2.4. Effect of sodium silicate on compressive strength of cement slurry doped xanthan Effect of sodium silicate on compressive strength of xanthanretarded cement is shown in Fig. 13. It can be seen from Fig. 13 (left) that the compressive strength of the consolidation samples decreases with the increase of sodium silicate content within the range where the sodium silicate content is less than 50% and within the same curing age, which shows that the hydration reaction of cement mineral components plays a dominant role in the aspect of the consolidation body’ compressive strength due to the hydration products filling the cracks. As can be seen from Fig. 12, the internal pores of the junction are mostly large holes, which has negative effect on the compressive strength. When the content of sodium silicate exceeds 50%, the compressive strength of the consolidation sample shows an increasing trend with the increasing of the content of sodium silicate, which indicates that sodium silicate coagulant participates in the hydration process of cement slurry, produces more C-S-H gelling, and the compressive strength rises, the internal pore structure of consolidation samples is mainly composed of gel pores, which have positive effect on the. As can be seen from the Fig. 13, with the increase of curing age, the compressive strength of consolidation sample gradually increases and the growth rate gradually increases. 3.2.5. Mechanism analyzing The XRD spectrum of xanthan-retarded cement sample doped with percent of sodium silicate is 30% and 70% respectively at different curing time is shown in Fig. 14. As can be seen from Fig. 14, in the cement slurry doped with xanthan, the addition of sodium silicate enhances the diffraction characteristic peak of CH (18,2h) of cement hydration products and weakens the diffraction characteristic peak of C3S (34,2h), which indicates that sodium silicate as a coagulant promotes the early hydration of C3S (34,2h) in the cement slurry doped with xanthan. Sodium silicate rapidly reacts with CH (18,2h) in solution to form C-S-H gel and to some extent promote hydration of C3A/C3S due to its high polar performance than hydrophilic group, and the mechanism was shown as Eqs. (2) and (3), It can inhibit the retarding mechanism of xanthan, wake up the hydration process of cement slurry, promote the consolidation and hardening of slurry then form stone body with certain strength.
3CaO SiO2 þ nH2 O ! 2CaO SiO2 ðn 1ÞH2 O þ CaðOHÞ2
ð2Þ
CaðOHÞ2 þ nSiO2 Na2 O þ mH2 O ! CaO nSiO2 mH2 O þ 2NaOH ð3Þ
Fig. 13. Effect of sodium silicate on compressive strength of xanthan-retarded cement (left), Compressive strength-Time curve of samples at different curing time with the percent of sodium silicate 30% (right).
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Fig. 14. XRD spectrum of cement sample with percent of sodium silicate is 30% and 70% respectively at different curing time.
4. Conclusion 1) The xanthan has a perfect retarding effect. In the initial stage of cement hydration, the xanthan adsorbs on the surface of the cement particles and complexes with calcium ions (Ca2+), which accelerates the dissolution of C3A to a certain extent, promotes the formation of AFt, and inhibits the hydration of C3S and the generation of CH. 2) Adding sodium silicate as a procoagulant component in the cement-added xanthan significantly inhibits the retardation of the xanthan gum, shortens the setting time of the retarding cement, improves the compressive strength of the retarded cement, and promotes the hydration of C3A, which promotes to some extent. When the percent of sodium silicate exceeds 50%, the hydration process and strength of the slurry change obviously, waking up the hydration reaction of cement doped with xanthan. The early hydration of C3S, C3A and sodium silicate rapidly formed a large amount of C-S-H gel, which was bound with the ettringite skeleton to promote coagulation hardening of the cement slurry. 3) Sodium silicate inhibits the retardation of the xanthan gum in cement slurry, and the sodium silicate-xanthan gum can be used as a ‘‘suppression-excitation” system to control the setting time of the cement theoretically.
Declaration of Competing Interest The authors declared that they have no conflicts of interest to this work. Acknowledgments This work was supported by the Major basic Project of Shandong Provincial Natural Science Foundation of China, China (Project Nos. ZR2017ZC0734), the Major Project of Chinese National Programs for Fundamental Research and Development (Project No. 2017YFC0703100), the Young Scientists Funds of National Natural Science Foundation of China, China (Grants Nos. 51709158), the China Postdoctoral Science Foundation, China, Funded Project (No. 2018M632676) and the Fundamental Research Funds of Shandong University, China (Grants No. 2016GN027).
References [1] J. Glymph, Evolution of the digital design process, in: B. Kolarevic (Ed.), Architecture in the Digital Age – Design and Manufacturing, Spon Press, New York, 2009. [2] K. Ellis, R. Silvestrini, B. Varela, N. Alharbi, R. Hailstone, Modeling setting time and compressive strength in sodium carbonate activated blast furnace slag mortars using statistical mixture design, Cem. Concr. Compos. 74 (2016) 1–6. [3] C. Dupuy, A. Gharzouni, N. Texier-Mandoki, X. Bourbon, S. Rossignol, Metakaolin-based geopolymer: formation of new phases influencing the setting time with the use of additives, Constr. Build. Mater. 200 (2019) 272– 281. [4] E. Lloret, A.R. Shahab, M. Linus, R.J. Flatt, F. Gramazio, M. Kohler, et al., Complex concrete structures: merging existing casting techniques with digital fabrication, Comput. Aided Des. 60 (2015) 40–49. [5] J. Han, K. Wang, J. Shi, W. Yue, Mechanism of triethanolamine on Portland cement hydration process and microstructure characteristics, Constr. Build. Mater. 93 (2015) 457–462. [6] Y.L. Yaphary, Z. Yu, R.H.W. Lam, D. Lau, Effect of triethanolamine on cement hydration toward initial setting time, Constr. Build. Mater. 141 (Complete) (2017) 94–103. [7] L. Reiter, R. Käßmann, A. Shahab, T. Wangler, R. Flatt, Strategies to wake up sleeping concrete, in: Proceedings of 14th International Conference on the Chemistry of Cement, Beijing, 2015, p. 340. [8] K.A.A.F. Riding, S. Taylor-Lange, Time-of set control through delayed addition of ultra-high surface area supplementary cementitious material, 2015, p. 356. [9] Y.Z. Jinfeng Sun, Xiaodong Shen, Xuerun Li, Compensation function of aluminum sulfate for alite calcium sulfoaluminate cement containing citric acid, in: Proceedings of 14th International Conference on the Chemistry of Cement, Beijing, 2015, p. 399. [10] F. Zunino, D.P. Bentz, J. Castro, Reducing setting time of blended cement paste containing high-SO3 fly ash (HSFA) using chemical/physical accelerators and by fly ash pre-washing, Cem. Concr. Compos. 90 (2018) 14–26. [11] J. Plank, C. Winter, Competitive adsorption between superplasticizer and retarder molecules on mineral binder surface, Cem. Concr. Res. 38 (5) (2008) 599–605. [12] J. Plank, B. Sachsenhauser, Experimental determination of the effective anionic charge density of polycarboxylate superplasticizers in cement pore solution, Cem. Concr. Res. 39 (1) (2009) 1–5. [13] G. Sworn. 8-Xanthan gum. Handbook of Hydrocolloids (Second edition): Woodhead Publishing Series in Food Science, Technology and Nutrition, 2009. p. 186–203. [14] Louise C. Candido da Silva, Brenda N. Targino, Marianna M. Furtado, Xanthan: biotechnological production and applications, Microbial Production of Food Ingredients and Additives (2017) 385–422. ACADEMIC PERSS. [15] S.Y. Mohsen Dabestani, Effect of Persian gum and Xanthan gum on foaming properties and stability of pasteurized fresh egg white foam, Food Hydrocolloids 87 (2019) 550–560. [16] M.M. Veljko Krstonošic´, Ljubica Dokic´, Application of different techniques in the determination of xanthan gum-SDS and xanthan gum-Tween 80 interaction, Food Hydrocolloids 87 (2019) 108–118. [17] Z.H. Jiao Xu, Maomao Zeng, Bingbing Li, Fang Qin, Linxiang Wang, Wu Shengfang, Jie Chen, Effect of xanthan gum on the release of strawberry flavor in formulated soy beverage, Food Chem. 228 (2017) 595–601. [18] M.A. Meenakshi Bhatia, Heena Mehta, Thiol derivatization of Xanthan gum and its evaluation as a mucoadhesive polymer, Carbohydr. Polym. 131 (2015) 119– 124.
Y. Qi et al. / Construction and Building Materials 223 (2019) 976–985 [19] O.O. Mengmeng Kang, Shunli Liu, Qianqian Huang, Wenjing Ma, Fang Yao, Fu Guodong, Characterization of Xanthan gum-based hydrogel with Fe3+ ions coordination and its reversible sol-gel conversion, Carbohydr. Polym. 203 (2019) 139–147. [20] X.J. Cai, S.A. Jones, Investigating the ability of nanoparticle-loaded hydroxypropyl methylcellulose and xanthan gum gels to enhance drug penetration into the skin, Int. J. Pharm. 513 (1–2) (2016) 302–308. [21] P.K. Alessia Lazzari, Klaus Knop, Xanthan gum as a rate-controlling polymer for the development of alcohol resistant matrix tablets and mini-tablets, Int. J. Pharm. 536 (1) (2018) 440–449. [22] N.B. Singh, Effect of gluconates on the hydration of cement, Cem. Concr. Res. 6 (4) (1976) 455–460. [23] L. Pelletier-Chaignat, F. Winnefeld, B. Lothenbach, G.L. Saout, C.J. Müller, C. Famy, Influence of the calcium sulphate source on the hydration mechanism of Portland cement–calcium sulphoaluminate clinker–calcium sulphate binders, Cem. Concr. Compos. 33 (5) (2011) 551–561. [24] S. Ma, W. Li, S. Zhang, D. Ge, Y. Jin, X. Shen, Influence of sodium gluconate on the performance and hydration of Portland cement, Constr. Build. Mater. 91 (2015) 138–144. [25] Y.H. Xiaowei Zhang, Chunxia Lu, Zhou Huang, Effects of sodium gluconate on early hydration and mortar performance of Portland cement-calcium aluminate cement-anhydrite binder, Constr. Build. Mater. 157 (2017) 1065– 1073. [26] L. Coppola, D. Coffetti, E. Crotti, Use of tartaric acid for the production of sustainable Portland-free CSA-based mortars, Constr. Build. Mater. 171 (2018) 243–249.
985
[27] M. García-Maté, D. Londono-Zuluaga, A.G.D.L. Torre, E.R. Losilla, A. Cabeza, M. A.G. Aranda, et al., Tailored setting times with high compressive strengths in bassanite calcium sulfoaluminate eco-cements, Cem. Concr. Compos. 72 (2016) 39–47. [28] X. Zhang, C. Lu, J. Shen, Influence of tartaric acid on early hydration and mortar performance of Portland cement-calcium aluminate cement-anhydrite binder, Constr. Build. Mater. 112 (2016) 877–884. [29] S. Alahrache, F. Winnefeld, J.B. Champenois, F. Hesselbarth, B. Lothenbach, Chemical activation of hybrid binders based on siliceous fly ash and Portland cement, Cem. Concr. Compos. 66 (2016) 10–23. [30] Y.J. Linglei Zhang, Jun Li, Furong Gao, Guodong Huang, Effect of retarders on the early hydration and mechanical properties of reactivated cementitious material, Constr. Build. Mater. 212 (2019) 192–201. [31] H.Y. Nan Wang, Wanli Bi, Yongshan Tan, Na Zhang, Wu Chengyou, Haiyan Ma, Shi Hua, Effects of sodium citrate and citric acid on the properties of magnesium oxysulfate cement, Constr. Build. Mater. 169 (2018) 697–704. [32] A. Çolak, Density and strength characteristics of foamed gypsum, Cem. Concr. Compos. 22 (3) (2000) 193–200. [33] F.L.S. Sha, R.T. Liu, et al. Performance of typical cement suspension-sodium silicate double slurry grout. 2019, 200, 408–419. [34] M.E. Tadros, J. Skalny, R.S. Kalyoncu, Early hydration of tricalcium silicate, J. Am. Ceram. Soc. 59 (7–8) (2010) 344–347. [35] B. Vidick, P. Fletcher, M. Michaux, Evolution at early hydration times of the chemical composition of liquid phase of oil-well cement pastes with and without additives Part II. Cement pastes containing additives, Cem. Concr. Res. 19 (4) (1989) 567–578.
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Hydration effect of sodium silicate on cement slurry doped with xanthan Qi Yanhan, Li Shucai, Li Zhaofeng ⇑,1, Zhang Jian, Li Haiyan Geotechnical and Structural Engineering Research Center, Shandong University, Ji’nan 250000, Shandong, PR China
h i g h l i g h t s The effect of polyhydroxy xanthan on the corresponding hydration process of cement and regulation mechanism was discussed. Sodium silicate as coagulant was added and its accelerating mechanism for the retarding effect of xanthan in cement paste was investigated. Established a ‘‘suppression-excitation” system of cement slurry.
a r t i c l e
i n f o
Article history: Received 11 April 2019 Received in revised form 20 July 2019 Accepted 30 July 2019 Available online 6 August 2019 Keywords: Sodium silicate Xanthan Hydration of cement Suppression-excitation system Mechanism research
a b s t r a c t The effect of polyhydroxy xanthan on the corresponding hydration process of cement and regulation mechanism was discussed, then sodium silicate as coagulant was added into the xanthan-retarded cement paste and its accelerating mechanism for the retarding effect of xanthan was investigated. The results indicate that due to chemisorption between hydrophilic hydroxyl and carboxyl and calcium ions, the core-shell construction of xanthan-cement to a certain extent hinders the hydration process of cement particles, adding sodium silicate in the cement-added xanthan significantly inhibits the retardation of the xanthan, shortens the setting time of the retarding cement, improves the compressive strength of the retarded cement, and to some extent promotes the hydration of C3A. The early hydration of C3A, C3S and sodium silicate rapidly formed a large amount of C-S-H, which was bound with the ettringite skeleton to promote coagulation hardening of the cement slurry, further established a ‘‘suppression-ex citation” system between xanthan and sodium silicate in cement slurry. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction In recent years, with the rapid development of engineering construction around the world, Cementitious slurry and concrete products have been widely used in all field, such as water conservancy and hydropower, mine dam, subway and tunnel construction underground and other aspects. However, according to different actual working conditions and challenging climate, the performance parameters of traditional cement slurry and fresh cement concrete are required differently, and there are generally technical problems shown up in the process of construction, which includes flexible setting/placement time, strength development of cement paste and long-distance transport. In the actual process of production and construction, due to some unexpected factors, such as geological disaster, challenging climate, damaged equipment etc., the fresh cement slurry and concrete can’t be used in time,
⇑ Corresponding author. E-mail address: [email protected] (Z. Li). Lecturer, mainly engaged in the prevention of underground engineering disaster and grouting material’s research and development. 1
https://doi.org/10.1016/j.conbuildmat.2019.07.327 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved.
resulting in the gradual loss of its performance and eventually abandoned, which to a certain extent increases the project cost, delay the limit time for a project, resulting in unnecessary waste of resources, contributing to a generally increasing production of waste worldwide [1]. Setting time is one of the important parameters to be controlled in the construction of cement slurry, which is highly dependent on the composition of the materials [2,3]. Therefore, the research on adjusting the setting time of slurry with additives has gradually become a hotpot in recent years. At present, the setting time of cement is usually controlled by adding retarders or coagulants based on the two working principles of physical coating and chemical reaction intervention, and adjusted by controlling the type and dosage of retarders and coagulants [4–6], further established a kind of ‘‘suppression-excitation” system, which has better flexibility, purpose and pertinence in engineering construction. Reiter [7] proposed to wake up a heavily delayed cement mixture by the use of mineral addition that cancels the effect of the set retarder. In his study concrete is put to sleep with a high dosage of PCE superplasticizer and woken up in the plan by the use of bentonite with a high affinity to bind PCE superplasticizer.
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Riding [8] has conducted similar research that a new type of ultrahigh surface area supplementary cementitious material was made from biomass pretreated used as the nucleating agent in his study and shown to be successful in restarting the hydration of systems with very long set times due to additions of either sucrose or zinc oxide. Sun [9] investigate compensation function of aluminum sulfate for calcium sulfoaluminate cement containing citric acid and the results show that aluminum sulfate acts as a setting accelerator to offset excessive retarding caused by citric acid, which promotes C4A hydration and development of AFt. Franco [10] investigated chemical (calcium chloride), physical (fine limestone powder) and pre-washing strategies as means to reduce the setting retardation effect of high-SO3 fly ash (HSFA) on cement paste, which has greatly positive potential influence on engineer application. Hydroxyl carboxylate is adsorbed on the surface of cement particles and forms unstable complex with Ca2+ in alkaline environment [11], which controls the concentration of Ca2+ and the formation of hydration products in the initial stage of cement hydration and has a strong inhibitory effect on the initial stage of cement hydration to a certain extent. Due to this property, hydroxy carboxylate is widely used to prolong setting time of cement slurry and delay cement process [12]. Xanthan gum is an extracellular polysaccharide obtained by fermentation using bacteria of the genus Xanthomonas, which is composed of d-glucose, d-mannose, d-glucuronic acid and d-mannuronic acid to form a polysaccharide biomacromolecules [13,14]. Due to its rheological properties and stability in a wide range of pH and temperatures, Xanthan gum has been widely used and studied in the field of food chemistry and hydrocolloids [15–17], carbohydrate polymers [18,19], pharmaceutics [20,21], etc. For that having multiple active hydroxyl and carboxyl functional groups, therefore, Xanthan gum
should possess the familiar retarding effect on cement slurry as hydroxy carboxylate theoretically. Recently, scholars in the world are focusing their attention on hydroxy carboxylate retarders, such as sodium gluconate [22–25], tartaric acid [26–28], sodium citrate [25,29–31] and citric acid [31,32], etc., aiming to study mechanism of the effect on the hydration process of cement. However, there are few studies on the effect of xanthan gum on the hydration of cement particles and the elimination of retarding action of xanthan. Therefore, in this paper sodium silicate was added as the coagulant promoting component to cement slurry mixed with xanthan gum to analyze its influence on cement setting time, strength development of cement paste, porosity of cement solid, heat of hydration, hydration products, and to a certain extent, the suppressing mechanism of xanthan gum and the exciting mechanism of sodium silicate were scientifically explained.
2. Experimental section Materials and instruments: The cement used in this paper was Portland Cement (P.O. 42.5) at a water to cement ratio of 1:1 and purchased from Shandong Sunnsy cement Group Co., Ltd (Jinan China). Its chemical composites and physical parameters are shown in Table 1. Xanthan was purchased from Sigma-Aldrich Co., and its chemical structure is shown in Fig. 1. Sodium silicate was purchased from sheng peng pao hua jian Co., Ltd (Zao Zhuang, China) The specification of sodium silicate is that, Baume (Be0 ) = 39, Modulus (M) = 3.3. The setting time of cement paste in the experiment was conducted according to the national standard, which its serial number is JC/T 2536-2019. The strength development of cement paste was obtained using a MTS CDT1305-2 electronic
Table 1 Chemical compositions of cement and its physical parameters. SiO2
Fe2O3
Al2O3
CaO
MgO
SO3
Loss
Average primary particle size
Surface area
18.45%
4.35%
5.95%
62.73%
4.37%
2.1%
0.52%
15.32 lm
320 m2/kg
Fig. 1. The chemical structure of xanthan gum.
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pressure testing machine controlled microcomputer. The changing porosity of cement solid was analyzed by Mercury intrusion porosimetry (Poremaster-60, Quanta). The hydration processes of slurry were carried out on a hydration heat tester (Tianjin Gangyuan Instrument Co., Ltd., china). Scan electron microscopy (SEM) was obtained using a Thermo Fisher Quattro S electron microscope. Phase analysis of X-ray diffraction (XRD) was carried out on a Thermo Fisher ARL-EQUINOS-1000X spectrophotometer. Main chain, trisaccharide side chain, and binding sites for cation (M+). Experimental process and method: Research object is made of two components, A and B. Component A is the simple cement slurry, which its water cement mass ratio is 1:1, with the condition that planet mixer constant speed stirring to ensure slurry level uniform. Component B is composed of xanthan solution and sodium silicate. Putting the common ratio of double-liquid slurry in practical engineering as a reference, the volume ratio of the component A/B is set at 3:1. In order to explore the relationship between xanthan concentration and hydration process of cement slurry in this paper, the mass percentage of xanthan solution (P(xanthan)) was 0.3%/0.5%/0.7%/0.9% respectively, sodium silicate, as a common coagulant to accelerate the hydration process of cement paste and shorten experiment cycle [33], was added and the mass percentage of the total was set at 70%; In order to investigate the effect of sodium silicate on the cement slurry with xanthan, the sodium silicate’s percent (P(sodium silicate)) accounts respectively for 10%, 30%, 50% and 70% in component B, and the mass percent of xanthan solution 0.5%. Then, the setting time, heat of hydration, porosity, compressive strength and phase changes in the hydration process of the slurry were investigated and analyzed. Setting time test: For that sodium silicate is added as an accelerant to shorten the setting time compared to purely cement slurry’s, Therefore the pour cup method was adopted to measure the initial and final setting time of the double-liquid slurry, as Fig. 2 shows. Keeping the cement slurry falling back and forth with two cups, When the slurry is loss of liquidity with cups inclined 45° is used for initial setting time; Curing 6 h/12 h/24 h/3 d/7 d/28 d under the condition of national standards (ISO methods) GB/T176711999, which temperature should be kept at 20 °C ± 1.0 °C and humidity should be no less than 90% respectively. The time when the hardness of slurry body is in the state of stone is the time of final setting time. Hydration heat test: The hydration heat of the two-component cement slurry was determined by the ZTM 14-channels thermal
conductivity isothermal calorimeter, and the water-cement mass ratio was 1:1. Component A/B has a volume ratio of 3:1. Compressive strength test: The cement slurry was mixed uniformly and then poured into the model for curing and the model’s size was elected as 40 mm*40 mm*160 mm. The compressive strength test was conducted according to cement mortar strength inspection method (ISO method), which its serial number is GB/T 17671-1999. Porosity test: Break the cement slurry body when curing to the specified age. Take equal quality samples (0.6 g ± 0.02 g) in the anhydrous ethanol to stop the hydration process. Drying in the vacuum oven of 35 before porosity test. Phase analysis of X-ray diffraction (XRD): The sample preparation method is the same as above. After drying, the equivalent samples grinded to powder below 0.08 mm were for XRD test. The X-ray diffraction analyzer condition is set to that, wavelength is 0.154 nm, voltage is 40Kv, electric current is 30 mA, diffraction Angle 2h ranges from 10° to 90°.
3. Results and discussion 3.1. Effect of xanthan on the hydration of cement slurry 3.1.1. Effect of xanthan on setting time The influence of different amounts of xanthan gum on the setting time of the slurry is shown in Fig. 3. It demonstrated that with the increase of the percent of xanthan gum in cement slurry, the effect of the extension of the initial setting time and the final setting time of the cement is more obvious. At this time when the percent of xanthan gum is 0.5%, the initial and final setting time of the cement slurry is extended to 19.67 s/37 min, and the growth rate is 6.75 s/40 min, respectively. When the percent of xanthan gum is 0.8%, the initial setting time and the final setting time of the cement slurry is increased to 22.17 s/54.22 min, and the growth rate is 12.25 s/85 min, respectively. It is worth mentioning that xanthan gum not only extends the setting time of the cement, but also increases the time interval between the initial setting time and the final setting time of the slurry with the increase of xanthan gum percent. When the percent of xanthan gum is 0.3%, the time interval between initial and final setting is only 29 min 41 s. When the percent of xanthan gum increased to 0.7%, the time interval between initial and final setting is extended to 45 min 39 s. Therefore, with the increase of xanthan gum content, the time interval between initial and final setting is getting longer and longer.
Fig. 2. Schematic diagram (left) and samples (right) of pouring cup methods.
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Fig. 3. Effect of Xanthan gum on setting time of cement.
Fig. 4. Effect of different xanthan percentage on hydration heat evolution rates.
3.1.2. Effect of xanthan on the hydration process of cement slurry The effect of different amounts of xanthan gum on the hydration process of slurry is shown in Fig. 4. It illustrated that the first exothermic peak that occurs during cement slurry hydration process is about 30 min after the hydration process, which is delayed by nearly 20 min from the first exothermic peak of the cement single slurry hydration process, the pre-induction period. With the increase of the xanthan gum content, the first exothermic peak of cement hydration shows a gradual decrease trend, and the peak appearance time is shorter, which is due to the unique volcanic ash effect and hydration reaction of the cement mineral component tricalcium aluminate. During the acceleration period, that is, the second exothermic peak of the cement is significantly reduced and moved backward, and the hydration temperature peak is gradually widened. When the amount of gum is 30%, the second exothermic peak of cement hydration is extended to 3 h, and when the dosage is increased to 70%, the second exothermic peak is sharply moved back to 7.8 h. Therefore, In a same percentage of sodium silicate condition, the xanthan gum solution can inhibit the initial hydration of the cement slurry, delay the heat release rate of cement hydration, weaken the peak of hydration heat, and reduce the heat releasing in the process of hydration process. In addition, a flank peak appears in the hydration heat curve with the condition of 30% xanthan content, which the hydration time is about at 11 h, this may be due to insufficient slurry agitation to cause a decrease in the local gypsum content of the solution, and high-sulfur type hydrated calcium sulphoaluminate crystals (AFt) in the solution
and hydrated calcium aluminate, calcium hydroxide, etc. are gradually converted into low-sulfur hydrated calcium sulphate crystals (AFm) to increase the heat of hydration process and the mechanism was shown as Eq. (1).
3CaO Al2 O3 3CaSO4 32H2 O þ 2ð3CaO Al2 O3 6H2 OÞ ! 3ð3CaO AlO3 CaSO4 12H2 OÞðAFmÞ
ð1Þ
3.1.3. Effect of xanthan on pore size distribution The pore size distribution of samples with different xanthan contents is shown in Fig. 5. Porosity of the samples with the percent of xanthan 0.5% and 0.9% is 18.8% and 22.4% respectively curing for 3 d. As can be seen that the pore distribution of the consolidation sample is concentrated in the <100 nm range. With the passage of curing time, the pore diameter of the sample has a gradually decreasing trend, accounting for a gradually increasing total porosity. This is caused by the continuous hydration of cement slurry, which results in cross-linking of gelling substances, filling of macropores and consequent gradual reduction of pore structure. The maximum pore sizes of 0.5% and 0.9% xanthan are concentrated in the range of 10–100 nm, and their distribution peaks are about 0.68 ml/g, 0.65 ml/g in 6 h curing age, 0.77 ml/g, 0.70 ml/g in 24 h curing age, 1.11 ml/g, 0.96 ml/g in 3 d curing age, 1.08 ml/g, 0.98 ml/g in 7 d curing age, It is apparent to see that, the distribution peaks of sample with percent of xanthan is 0.9% is lower than sample whose percent of xanthan is 0.5%. This shows that the difference of
Fig. 5. Effect of xanthan content on pore size distribution at different curing age, the percent of xanthan in the sample is 0.5% and 0.9% respectively from left to right.
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Fig. 6. Effect of xanthan content on compressive strength at different curing age (left), Compressive strength-Time curve with the condition that Percent xanthan gum is 0.3% (right).
xanthan content obviously changes the void structure of cementbased materials, further indicating that high content of xanthan can mitigate the hydration process of cement slurry. 3.1.4. Effect of xanthan on compressive strength The Fig. 6 above shows the variation of compressive strength of the cement sample with different percent xanthan along the curing ages (left) and compressive strength-time curve with the condition that Percent xanthan gum is 0.3% (right). From Fig. 5 (left) it is apparent to see that with the increase of curing age, the peak compressive strength of cement sample in same xanthan content gradually increases because of the continuous hydration process of cement slurry, while the growth rate increases at first and then decreases along with the curing time. With the increase of the percentage of xanthan gum, the compressive strength of the cement sample gradually decreases, which is because the xanthan gum slows down the hydration reaction to a certain extent and hinders the formation of gelling substances. Related with pore size distribution, Fig. 5 above shows that with the percentage of xanthan increases, the pore distribution of the consolidation sample gradually transitions to the large aperture interval, which posed negative influence on compressive of the consolidation sample, macroscopically reduced compressive strength. As Fig. 6 (right) indicated that under the equal xanthan gum content conditions, the samples with different curing ages have different time to reach the peak of compressive strength curve. Along the curing age increases, the time taken for the sample to reach the peak of compressive strength curve increases gradually, This is because under the same xanthan content, the porosity of the consolidation samples changes from a large-size interval, which is negative to compressive strength, to a small-size interval, which has positive influence on th compressive strength, with the prolonging of curing time, as shown in Fig. 5, therefore, the compactness of consolidation sample increases and the compressive strength increases. What’s more, Fig. 6 (right) shows that the cement standard samples possess high compressive strength at 6 h curing ages. That’s because that sodium silicate shortened the setting time of cement slurry significantly, a large amount of hydration products was produced in the early age, the compressive strength increased remarkably in the early age and the sodium silicate addition play a positive role on the early compressive strength. 3.1.5. Mechanism analyzing Hydrated minerals of consolidation sample at different curing age are analyzed by XRD as showed in Fig. 7, the spectrum top
means pure cement sample without addition and the spectrum bottom is consolidation sample doped different xanthan content. From Fig. 7, it can be seen that the XRD spectrum of the consolidation sample mixed with xanthan has no change in the peak shape and position of the diffraction peak compared with that of the cement single slurry blank sample, which shows that the addition of xanthan in cement has no obvious influence and change on the types of cement hydration products and CH, Aft, C3S and alite are the main hydration products of cement slurry. In addition, in Fig. 7 (top), the characteristic diffraction peak of unhydrated tricalcium silicate C3S (34, 2h) is obviously enhanced with the increase of the percentage content of xanthan, which indicates that the hydration pressing effect of xanthan on silicate phase is obvious. With the increase of the amount of xanthan, the peak intensity of CH (18,2h) diffraction is obviously reduced. When the concentration of xanthan gum is 0.9%, the diffraction peak of CH almost disappears on the XRD spectrum. It can be seen that the addition of xanthan gum in the cement slurry can delay the crystallization of CH crystal, and the hydration of the C3S mineral phase in the cement clinker is inhibited. For the characteristic diffraction peak of Aft (16, 2h), the more xanthan is added in cement slurry, the characteristic diffraction peak possesses an enhanced trend, which shows that the low percentage of xanthan promotes the hydration of tricalcium aluminate (C3A) mineral phase and increases the content of Aft in slurry. The hydration effect of high percentage xanthan on C3A mineral phase will be the next topic of research. Under the condition of a constant amount of sodium silicate, in the cement-xanthan-water system, the effect of xanthan on cement hydration includes two aspects, the schematic is shown in Fig. 8. First, referring to the M. E. Tadros’s work [34], due to the inconsistent dissolution property in the hydration process of cement particles, silicate ions (SiO2 3 ) are enriched in the cement particles to form a cement particle with negative charge. Calcium ions (Ca2+) free in the solution gather to the cement particles under the electrostatic action and form a double electron layer on the surface of the particles. Hydrophilic hydroxyl and carboxyl in the xanthan solution form a complex similar-chelates with calcium ions (Ca2+) [12], to reduce the calcium ion concentration during the cement hydration induction period, prevent the precipitation of strong calcium oxide and calcium salt crystals, accelerate the dissolution of sulfate in the gypsum, with the reaction among sulfate, water and tricalcium aluminate (C3A), which possesses quickly reaction with water in the cement hydration process, It promotes the formation of insoluble needle-shaped ettringite (AFt) to a certain extent, which covers the surface of cement
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Fig. 7. XRD spectrum of pure cement sample (bottom) and cement sample (top) with percent of xanthan is 0.5% and 0.9% respectively at different curing time.
Fig. 8. Mechanism diagram of effect of xanthan on cement hydration process.
particles and further plays an negative role in the hydration process of cement. On the other hand, the hydroxyl groups and carboxyl groups in the xanthan compound with calcium ions (Ca2+) on the surface of the cement particles [35] to form a passivation
layer, which form a core-shell structure with the cement particles as the core and the xanthan molecule as the shell, as SEM image shown in Fig. 9, inhibiting the hydration of C3S and the crystallization of CH, thereby prolonging the setting time.
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Fig. 9. SEM image of xanthan-cement core-shell construction.
3.2. Effect of sodium silicate on the hydration of cement slurry doped with xanthan 3.2.1. Effect of sodium silicate on setting time of cement slurry doped with xanthan Sodium silicate is added to the cement paste mixed with gum (0.5%, the same below) as coagulant, and the test operation is carried out under the same environment to obtain the effect of sodium silicate coagulant on the setting time of the cement mixed with xanthan, as shown in Fig. 10. As can be seen from Fig. 10, when the percent of sodium silicate (P(sodium silicate)) is increased from 30% to 70%, the initial setting time of the xanthan-mixed retarded cement is shortened from 70 s to 20 s, the final setting time is also shortened from 1.8 h to 0.55 h, however, the initial setting time of the cement single slurry is about 1.2 h and the final setting time is about 8 h, therefore, the addition of the accelerating component obviously shortens the setting time of the xanthan-mixed cement slurry. The setting time of cement paste mixed with xanthan is obviously shortened along the increasing of the content of sodium silicate, and the influence is more obvious with the increase of the content. 3.2.2. Effect of sodium silicate on the hydration process cement slurry doped xanthan Sodium silicate as coagulant was added to the cement slurry doped with the equal xanthan and tested under the same experimental environment. The effect of sodium silicate on the hydration heat evolution rates of the cement mixed with xanthan is shown in Fig. 11. Fig. 11 illustrated that sodium silicate added to cement slurry mixed with xanthan can obviously increase the peak heat of hydration process of cement slurry, and the hydration rate of cement slurry also increased. It is apparent to see that when the percent of sodium silicate is 10%, 30% respectively, there are two absorption peaks in the hydration process, the first absorption peak occurs at 3.8 h, and the second exothermic peak occurs at 22 h, 14 h respectively. What’s more, along the increase of sodium silicate content, the occurring time of the second exothermic peak is obviously shortened, and the amount of exothermic heat is gradually reduced. However, when the content of sodium silicate exceeds 50%, the second exothermic peak has disappeared, the occurring time of the first exothermic peak in the hydration process is unchanged. The peak heat gradually increases with the content of sodium silicate increasing, which indicates that the first exothermic peak is caused by sodium silicate as coagulant partici-
Fig. 10. Effect of sodium silicate on setting time of xanthan-retarded cement.
Fig. 11. Effect of sodium silicate on hydration heat evolution rates of xanthanretarded cement.
pating in the hydration reaction, promoting the hydration process of the slurry and increasing the exothermic quantity. The second exothermic peak is the result of hydration process of minerals in the cement slurry itself. Therefore, the addition of coagulant
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Fig. 12. Effect of different xanthan content on pore size distribution at different curing age, the percent of sodium silicate in the sample is 30% and 70% respectively.
sodium silicate plays a role in promoting the hydration of the cement slurry mixed with xanthan.
3.2.3. Effect of sodium silicate on pore distribution of cement slurry doped xanthan The pore size distribution of consolidation samples with different sodium silicate contents is shown in Fig. 12. As can be seen from Fig. 12, the pore size of the samples has a gradually decreasing trend along the passage of curing time, which is caused by the continuous hydration of the cement slurry. When the curing age is 3 d or 7 d, the pore distribution of serous consolidation samples with 30% sodium silicate content is concentrated in the 103– 104 nm range and 102–104 nm range respectively, and the mode pore-size is 0.55 and 0.35 ml/g respectively. when the percent of sodium silicate is increased to 70%, the pore distribution of serous consolidation samples is concentrated in the 10–100 nm range, mode pore-size is 1.13, 1.08 ml/g respectively. It is apparent to see that, the pore size distribution of sample with 70% sodium silicate is lower than sample with 50% sodium silicate, which indicates that the difference in sodium silicate content significantly controlled the quantity of gel product, and changes the pore structure of cement-based materials and further indicates that sodium silicate, a coagulant component, has an inhibitory effect on the retarding of xanthan.
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3.2.4. Effect of sodium silicate on compressive strength of cement slurry doped xanthan Effect of sodium silicate on compressive strength of xanthanretarded cement is shown in Fig. 13. It can be seen from Fig. 13 (left) that the compressive strength of the consolidation samples decreases with the increase of sodium silicate content within the range where the sodium silicate content is less than 50% and within the same curing age, which shows that the hydration reaction of cement mineral components plays a dominant role in the aspect of the consolidation body’ compressive strength due to the hydration products filling the cracks. As can be seen from Fig. 12, the internal pores of the junction are mostly large holes, which has negative effect on the compressive strength. When the content of sodium silicate exceeds 50%, the compressive strength of the consolidation sample shows an increasing trend with the increasing of the content of sodium silicate, which indicates that sodium silicate coagulant participates in the hydration process of cement slurry, produces more C-S-H gelling, and the compressive strength rises, the internal pore structure of consolidation samples is mainly composed of gel pores, which have positive effect on the. As can be seen from the Fig. 13, with the increase of curing age, the compressive strength of consolidation sample gradually increases and the growth rate gradually increases. 3.2.5. Mechanism analyzing The XRD spectrum of xanthan-retarded cement sample doped with percent of sodium silicate is 30% and 70% respectively at different curing time is shown in Fig. 14. As can be seen from Fig. 14, in the cement slurry doped with xanthan, the addition of sodium silicate enhances the diffraction characteristic peak of CH (18,2h) of cement hydration products and weakens the diffraction characteristic peak of C3S (34,2h), which indicates that sodium silicate as a coagulant promotes the early hydration of C3S (34,2h) in the cement slurry doped with xanthan. Sodium silicate rapidly reacts with CH (18,2h) in solution to form C-S-H gel and to some extent promote hydration of C3A/C3S due to its high polar performance than hydrophilic group, and the mechanism was shown as Eqs. (2) and (3), It can inhibit the retarding mechanism of xanthan, wake up the hydration process of cement slurry, promote the consolidation and hardening of slurry then form stone body with certain strength.
3CaO SiO2 þ nH2 O ! 2CaO SiO2 ðn 1ÞH2 O þ CaðOHÞ2
ð2Þ
CaðOHÞ2 þ nSiO2 Na2 O þ mH2 O ! CaO nSiO2 mH2 O þ 2NaOH ð3Þ
Fig. 13. Effect of sodium silicate on compressive strength of xanthan-retarded cement (left), Compressive strength-Time curve of samples at different curing time with the percent of sodium silicate 30% (right).
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Fig. 14. XRD spectrum of cement sample with percent of sodium silicate is 30% and 70% respectively at different curing time.
4. Conclusion 1) The xanthan has a perfect retarding effect. In the initial stage of cement hydration, the xanthan adsorbs on the surface of the cement particles and complexes with calcium ions (Ca2+), which accelerates the dissolution of C3A to a certain extent, promotes the formation of AFt, and inhibits the hydration of C3S and the generation of CH. 2) Adding sodium silicate as a procoagulant component in the cement-added xanthan significantly inhibits the retardation of the xanthan gum, shortens the setting time of the retarding cement, improves the compressive strength of the retarded cement, and promotes the hydration of C3A, which promotes to some extent. When the percent of sodium silicate exceeds 50%, the hydration process and strength of the slurry change obviously, waking up the hydration reaction of cement doped with xanthan. The early hydration of C3S, C3A and sodium silicate rapidly formed a large amount of C-S-H gel, which was bound with the ettringite skeleton to promote coagulation hardening of the cement slurry. 3) Sodium silicate inhibits the retardation of the xanthan gum in cement slurry, and the sodium silicate-xanthan gum can be used as a ‘‘suppression-excitation” system to control the setting time of the cement theoretically.
Declaration of Competing Interest The authors declared that they have no conflicts of interest to this work. Acknowledgments This work was supported by the Major basic Project of Shandong Provincial Natural Science Foundation of China, China (Project Nos. ZR2017ZC0734), the Major Project of Chinese National Programs for Fundamental Research and Development (Project No. 2017YFC0703100), the Young Scientists Funds of National Natural Science Foundation of China, China (Grants Nos. 51709158), the China Postdoctoral Science Foundation, China, Funded Project (No. 2018M632676) and the Fundamental Research Funds of Shandong University, China (Grants No. 2016GN027).
References [1] J. Glymph, Evolution of the digital design process, in: B. Kolarevic (Ed.), Architecture in the Digital Age – Design and Manufacturing, Spon Press, New York, 2009. [2] K. Ellis, R. Silvestrini, B. Varela, N. Alharbi, R. Hailstone, Modeling setting time and compressive strength in sodium carbonate activated blast furnace slag mortars using statistical mixture design, Cem. Concr. Compos. 74 (2016) 1–6. [3] C. Dupuy, A. Gharzouni, N. Texier-Mandoki, X. Bourbon, S. Rossignol, Metakaolin-based geopolymer: formation of new phases influencing the setting time with the use of additives, Constr. Build. Mater. 200 (2019) 272– 281. [4] E. Lloret, A.R. Shahab, M. Linus, R.J. Flatt, F. Gramazio, M. Kohler, et al., Complex concrete structures: merging existing casting techniques with digital fabrication, Comput. Aided Des. 60 (2015) 40–49. [5] J. Han, K. Wang, J. Shi, W. Yue, Mechanism of triethanolamine on Portland cement hydration process and microstructure characteristics, Constr. Build. Mater. 93 (2015) 457–462. [6] Y.L. Yaphary, Z. Yu, R.H.W. Lam, D. Lau, Effect of triethanolamine on cement hydration toward initial setting time, Constr. Build. Mater. 141 (Complete) (2017) 94–103. [7] L. Reiter, R. Käßmann, A. Shahab, T. Wangler, R. Flatt, Strategies to wake up sleeping concrete, in: Proceedings of 14th International Conference on the Chemistry of Cement, Beijing, 2015, p. 340. [8] K.A.A.F. Riding, S. Taylor-Lange, Time-of set control through delayed addition of ultra-high surface area supplementary cementitious material, 2015, p. 356. [9] Y.Z. Jinfeng Sun, Xiaodong Shen, Xuerun Li, Compensation function of aluminum sulfate for alite calcium sulfoaluminate cement containing citric acid, in: Proceedings of 14th International Conference on the Chemistry of Cement, Beijing, 2015, p. 399. [10] F. Zunino, D.P. Bentz, J. Castro, Reducing setting time of blended cement paste containing high-SO3 fly ash (HSFA) using chemical/physical accelerators and by fly ash pre-washing, Cem. Concr. Compos. 90 (2018) 14–26. [11] J. Plank, C. Winter, Competitive adsorption between superplasticizer and retarder molecules on mineral binder surface, Cem. Concr. Res. 38 (5) (2008) 599–605. [12] J. Plank, B. Sachsenhauser, Experimental determination of the effective anionic charge density of polycarboxylate superplasticizers in cement pore solution, Cem. Concr. Res. 39 (1) (2009) 1–5. [13] G. Sworn. 8-Xanthan gum. Handbook of Hydrocolloids (Second edition): Woodhead Publishing Series in Food Science, Technology and Nutrition, 2009. p. 186–203. [14] Louise C. Candido da Silva, Brenda N. Targino, Marianna M. Furtado, Xanthan: biotechnological production and applications, Microbial Production of Food Ingredients and Additives (2017) 385–422. ACADEMIC PERSS. [15] S.Y. Mohsen Dabestani, Effect of Persian gum and Xanthan gum on foaming properties and stability of pasteurized fresh egg white foam, Food Hydrocolloids 87 (2019) 550–560. [16] M.M. Veljko Krstonošic´, Ljubica Dokic´, Application of different techniques in the determination of xanthan gum-SDS and xanthan gum-Tween 80 interaction, Food Hydrocolloids 87 (2019) 108–118. [17] Z.H. Jiao Xu, Maomao Zeng, Bingbing Li, Fang Qin, Linxiang Wang, Wu Shengfang, Jie Chen, Effect of xanthan gum on the release of strawberry flavor in formulated soy beverage, Food Chem. 228 (2017) 595–601. [18] M.A. Meenakshi Bhatia, Heena Mehta, Thiol derivatization of Xanthan gum and its evaluation as a mucoadhesive polymer, Carbohydr. Polym. 131 (2015) 119– 124.
Y. Qi et al. / Construction and Building Materials 223 (2019) 976–985 [19] O.O. Mengmeng Kang, Shunli Liu, Qianqian Huang, Wenjing Ma, Fang Yao, Fu Guodong, Characterization of Xanthan gum-based hydrogel with Fe3+ ions coordination and its reversible sol-gel conversion, Carbohydr. Polym. 203 (2019) 139–147. [20] X.J. Cai, S.A. Jones, Investigating the ability of nanoparticle-loaded hydroxypropyl methylcellulose and xanthan gum gels to enhance drug penetration into the skin, Int. J. Pharm. 513 (1–2) (2016) 302–308. [21] P.K. Alessia Lazzari, Klaus Knop, Xanthan gum as a rate-controlling polymer for the development of alcohol resistant matrix tablets and mini-tablets, Int. J. Pharm. 536 (1) (2018) 440–449. [22] N.B. Singh, Effect of gluconates on the hydration of cement, Cem. Concr. Res. 6 (4) (1976) 455–460. [23] L. Pelletier-Chaignat, F. Winnefeld, B. Lothenbach, G.L. Saout, C.J. Müller, C. Famy, Influence of the calcium sulphate source on the hydration mechanism of Portland cement–calcium sulphoaluminate clinker–calcium sulphate binders, Cem. Concr. Compos. 33 (5) (2011) 551–561. [24] S. Ma, W. Li, S. Zhang, D. Ge, Y. Jin, X. Shen, Influence of sodium gluconate on the performance and hydration of Portland cement, Constr. Build. Mater. 91 (2015) 138–144. [25] Y.H. Xiaowei Zhang, Chunxia Lu, Zhou Huang, Effects of sodium gluconate on early hydration and mortar performance of Portland cement-calcium aluminate cement-anhydrite binder, Constr. Build. Mater. 157 (2017) 1065– 1073. [26] L. Coppola, D. Coffetti, E. Crotti, Use of tartaric acid for the production of sustainable Portland-free CSA-based mortars, Constr. Build. Mater. 171 (2018) 243–249.
985
[27] M. García-Maté, D. Londono-Zuluaga, A.G.D.L. Torre, E.R. Losilla, A. Cabeza, M. A.G. Aranda, et al., Tailored setting times with high compressive strengths in bassanite calcium sulfoaluminate eco-cements, Cem. Concr. Compos. 72 (2016) 39–47. [28] X. Zhang, C. Lu, J. Shen, Influence of tartaric acid on early hydration and mortar performance of Portland cement-calcium aluminate cement-anhydrite binder, Constr. Build. Mater. 112 (2016) 877–884. [29] S. Alahrache, F. Winnefeld, J.B. Champenois, F. Hesselbarth, B. Lothenbach, Chemical activation of hybrid binders based on siliceous fly ash and Portland cement, Cem. Concr. Compos. 66 (2016) 10–23. [30] Y.J. Linglei Zhang, Jun Li, Furong Gao, Guodong Huang, Effect of retarders on the early hydration and mechanical properties of reactivated cementitious material, Constr. Build. Mater. 212 (2019) 192–201. [31] H.Y. Nan Wang, Wanli Bi, Yongshan Tan, Na Zhang, Wu Chengyou, Haiyan Ma, Shi Hua, Effects of sodium citrate and citric acid on the properties of magnesium oxysulfate cement, Constr. Build. Mater. 169 (2018) 697–704. [32] A. Çolak, Density and strength characteristics of foamed gypsum, Cem. Concr. Compos. 22 (3) (2000) 193–200. [33] F.L.S. Sha, R.T. Liu, et al. Performance of typical cement suspension-sodium silicate double slurry grout. 2019, 200, 408–419. [34] M.E. Tadros, J. Skalny, R.S. Kalyoncu, Early hydration of tricalcium silicate, J. Am. Ceram. Soc. 59 (7–8) (2010) 344–347. [35] B. Vidick, P. Fletcher, M. Michaux, Evolution at early hydration times of the chemical composition of liquid phase of oil-well cement pastes with and without additives Part II. Cement pastes containing additives, Cem. Concr. Res. 19 (4) (1989) 567–578.