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Durability Studies on Concrete Containing Treated Used Foundry Sand
Construction and Building Materials 201 (2019) 651–661
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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Durability Studies on Concrete Containing Treated Used Foundry Sand N. Gurumoorthy a,⇑, K. Arunachalam b a b
Department of Civil Engineering, PSNA College of Engineering and Technology, Dindigul, Tamilnadu, India Thiagarajar College of Engineering, Madurai, Tamilnadu, India
h i g h l i g h t s Silica in the sand is enriched by treating and called as TUFS. Water absorption and permeability characteristics of TUFS concrete are investigated. Effect of TUFS concrete on exposure to various environments. Optimum TUFS content is found to be 30% by weight.
a r t i c l e
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Article history: Received 27 July 2018 Received in revised form 1 January 2019 Accepted 3 January 2019
Keywords: TUFS Water absorption RCPT Acid resistance Sulphate resistance
a b s t r a c t Use of waste products from foundry industry in concrete not only makes it economical, but also helps in reducing disposal problems and environmental degradation. The waste materials required for the replacement of fine aggregate are processed to the required specifications that could match with the properties of fine aggregate to be used in concrete. Such type of industrial waste by-product namely waste foundry sand was treated and used as partial replacement material for fine aggregate in concrete. Experiments were conducted to study the durability characteristics of Treated Used Foundry Sand (TUFS) as partial replacement for fine aggregate. Fine aggregate was replaced with various percentages of TUFS by weight. Tests were conducted for water absorption, sorptivity and Rapid Chloride Permeability. Further these concrete specimens were exposed to chemical solutions and marine environment for 7, 28, 56 and 90 days. After the exposure period, these specimens were tested for loss in weight and compressive strength. Test results indicated better performance of concrete with TUFS than control specimen and established that concrete with 30% TUFS is more impermeable than control concrete with better durability properties also proved that TUFS can be effectively used in making good quality concrete. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction Concrete is the most widely and universally used construction material in construction industry. Slightly more than a ton of concrete is produced every year for every human being on the planet. Over the past several decades, the demand for concrete has been increasing rapidly due to infrastructure development. Between 1900 and 2010, the global volume of natural resources used in buildings and transport infrastructure increased 23-fold [1]. Sand and gravel are the largest portion of these primary material inputs (79% or 28.6 gigatons per year in 2010) and are most extracted group of materials worldwide. Comparative evolution of the post-World War II (WWII) global cement, steel, and plastic produc-
⇑ Corresponding author. E-mail address: [email protected] (N. Gurumoorthy). https://doi.org/10.1016/j.conbuildmat.2019.01.014 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved.
tions (Top), and same data plotted as material use per capita vs world population (Bottom) are shown in Fig. 1. The concrete constitutes various ingredients like cement, fine aggregate and coarse aggregate. Out of these, river sand is used as a fine aggregate in concrete production for several decades. The demand for river sand increased due to depletion of sand. The production of aggregates (including both coarse and fine aggregates) reached about 40 billion tonnes in the year of 2014 [3] At present, many researches are carried out to overcome the stress and the demand for river sand by using industrial wastes like foundry sand, fly ash, bottom ash and slag which can result in significant improvement in overall energy efficiency and environmental performance [4]. In industries, numerous waste materials are generated during manufacturing processes. The increasing awareness about environment has tremendously contributed in the disposal of generated wastes. With the scarcity of space for land filling and unavailability
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dry sand has beneficial applications in other industries. Estimation of industry is that 100 million tons of sand is used in production annually of that 6–10 million tons are discarded annually as waste and are available to be recycled into other products [6]. It has been found that UFS produced by iron, steel, and aluminium foundries are rarely hazardous. Only about 15 percent of UFS are recycled. This is mainly due to lack of knowledge on its possible beneficial reuse. Beneficial reuse of UFS continues to become a more accepted practice as more end-users are introduced to the concept. The foundry sand from non-ferrous metal casting industry can be directly used in concrete [7]. This has been proved by many researchers. The ferrous metal casting industry discarded foundry sand contains more iron content which will affect the binding properties of concrete and decrease the strength parameter. As per ASTMC330 and C641, iron content in the sand will cause staining effect and also affect the durability for this reason iron content has to be removed or reduced for UFS. After removing iron content by treatment, the UFS is called as Treated Used Foundry Sand (TUFS) [4]. The objectives of this study are to investigate the effect of TUFS as partial replacement of fine aggregates in various percentages (0–40%), on exposure to various environment like acid, sulphate and marine. Moreover, the study will focus on sorpitivity and Rapid Chloride Permeability Test (RCPT) as there is no much research on durability studies in concrete with UFS. The basic experimental studies for above tests are taken from some other researchers utilizing materials other than UFS [8–12]. 2. Experimental investigations 2.1. Materials
Fig. 1. Top: Comparative evolution of the post-WWII global cement, steel, and plastic productions, Bottom: Same data plotted as material use per capita vs world population [Van Damme, H. (2018) [2].
of natural sand, waste product utilization has become an attractive alternative which can be used in concrete as a replaceable material. The use of waste products in concrete not only makes it economical, but also helps in mitigating disposal problems. Ministry of Environment, India enforces regulation and rules for disposal of Solid Waste Management rules in 2016 S.O 1357 (E) [08.04.2016]. The materials required for replacement of fine aggregate are processed to necessary specifications that could match with the properties of fine aggregate to be used in concrete. Such type of industrial by-product namely Used Foundry Sand (UFS) is treated and used as a partially replacement material for fine aggregate in concrete. Foundry industry produces a large amount of side product material during casting process. It is high quality silicate sand with uniform physical and chemical characteristics produced by ferrous and non ferrous metal casting industries. These industries reuse the sand many times and after many cycle it is removed and disposed to nearby sites. This waste sand from foundry is termed as Used Foundry Sand (UFS). Alike regular sand, UFS also mainly consists of silica but its silica content has been found similar to regular sand. The properties of foundry sand depend on casting process and the nature of industry from which it comes. About 85–90% of its particles are smaller than 100 mm. It is principally made up of sand which is evident from the particle size (0.05 mm–2 mm) of UFS, obtained form 39 foundries, ranging from 76.6% to 100%, with a median of 90.3% [5].The automotive industries are the major generators of used foundry sand. Like many waste products, foun-
2.1.1. Cement Ordinary Portland Cement (53 grade) cement was used conforming to IS: 12269-2013[13]. It was tested as Per the Indian Standard Specifications IS: 12269-2013 [13] and specific gravity of cement was 3.12. 2.1.2. Fine aggregate Natural river sand having a 4.75 mm nominal size conforming to zone III of IS: 383-1970[14] and specific gravity of 2.59 was used in this study. The element composition of natural river sand is shown in Fig. 2. 2.1.3. Coarse aggregate Locally available crushed angular granite with nominal size of 20 mm as per IS: 383-1970 [14] and its specific gravity of 2.72 were used. 2.1.4. Super plasticizer Modified melamine formaldehyde chemical based admixture was used to increase the workability. The dosage was uniform for all mix at 0.3% by weight of cement. 2.1.5. Used foundry sand The UFS was collected from moulding process of ferrous metal casting industry near Ganapati, Coimbatore, India. The UFS had the specific gravity 2.32 and fineness modulus 1.74, which was very fine as stated by Singh, et al. [15]. The study was made to determine the elemental composition of UFS by EDAX test as shown in Fig. 3. From EDAX test report, it was perceived that there was a presence of 10.85% iron content in UFS sample. The presence of iron content will reduce the binding property and also increases rate of corrosion. Chemical treatment of UFS was carried out to remove the iron content.
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Fig. 2. Elemental composition of Natural River Sand by EDAX.
Fig. 3. Elemental composition of UFS by EDAX.
2.2. Treatment of used foundry sand UFS was treated with different concentration of Hydrochloric acid as 2.5%, 5% and 10% by weight.To treat in 2.5% concentration HCl solutions, 100 g of UFS was added to 487.5 ml of distilled water and 12.5 ml of HCl. Similarly for treating with 5% HCl strength, 100 g of UFS was added to 475 ml of distilled water and 25 ml of HCl acid and for 10% HCl strength, 100 g of UFS was added to 450 ml distilled water and 50 ml of HCL. The above prepared samples were then stirred with magnetic stirrer for 24 h as adopted by Monosi, et al. [16]. After 24 h, the solutions were separated by centrifugation, filtered with 0.2 mm filter paper and the collected UFS was washed with distilled water thoroughly, again separated by centrifugation, and dried for 24 h. The above samples are considered Treated Used Foundry Sand. EDAX test were done on them to analyze the elemental composition [2]. The EDAX test reports of treated UFS are shown
in Figs. 4–6. The Elemental comparison of natural sand, UFS and TUFS are shown in Table 1.in that AN means Atomic Number, K means equilibrium constant and C. norm means the normalised concentration in weight percent of the element 2.3. Comparison of EDAX test results EDAX test results showed that the TUFS treated with 2.5% concentration HCl contained 73% silica and 9% iron content, the 5% concentration HCl contained 80% silica and 3% iron content. Similarly TUFS treated with 10% concentration HCl contained 73% silica and 0.5% iron content. The silica content was decreased for 10% concentration of HCl. The reason for reduction in silica content is due to the reaction between silicon and HCl to form silicon tetrachloride and release of hydrogen gas. By associating the test results of TUFS, it was found that there was an increase in silica content
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Fig. 4. EDAX test result of UFS treated with 2.5% HCL.
Fig. 5. EDAX test result of UFS treated with 5% HCL.
and decrease in iron content in UFS treated with 5% HCl. It will give higher binding property than untreated UFS and UFS treated with other concentration. From the test results obtained, it was found that the UFS required for casting should be treated with 5% of HCl. This treatment process was done in a container. The contents were stirred and dried under sunlight [4]. Moreover, the chloride content present in the TUFS was brought down due to acid treatment from 1.57% to 0.45% by washing it in water, thus bringing the chloride level less than the allowable limit of 1% as per ACI 318-08 Standard [17]. 2.4. Mix proportions and specimen casting Control Concrete (CC) was designed to have 28-day target compressive strength of 27 MPa as per IS: 10262-2009 [18]. The con-
crete mix proportion was 1:1.6:2.98 with 1 part cement, 1.6 part fine aggregates, and 2.98 part coarse aggregates having water cement ratio of 0.5. Four additional concrete mixtures R10, R20, R30 and R40 were proportioned where sand (fine aggregate) was replaced with 10%, 20%, 30% and 40% TUFS by mass respectively. The slump of all mixtures was 110 ± 5 mm. Details of mixtures are presented in Table 2. 150 mm concrete cubes were cast for acid test, water absorption test, sorpitivity test and 100 mm diameter 50 mm thick cylinders for Rapid Chloride Penetration Test. All the specimens were prepared in accordance with IS: 11991959 [19]. Soon after casting, test specimens were left in the casting room for 24 h at a temperature of about 27 ± 1 °C. They were demolded after 24 h and were put into a water-curing chamber until the time of testing. Three specimens were tested for each test and the average value was taken.
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Fig. 6. EDAX test result of UFS treated with 10% HCL.
Table 1 Elemental comparison of natural sand, UFS and TUFS. El
AN
Series
C. norm [wt%] of River Sand
C. norm [wt%] of UFS
C. norm [wt%] of 2.5% TUFS
C. norm [wt%] of 5% TUFS
C. norm [wt%] of 10% TUFS
O C Si Al Fe Mg Na Ca K Ti Cr
8 6 14 13 26 12 11 20 19 22 24
K-Series K-Series K-Series K-Series K-Series K-Series K-Series K-Series K-Series K-Series K-Series Total
58.90 12.48 25.85 1.21 1.57 — —— —— — — —— 100
40.63 12.13 23.75 7.35 10.85 1.21 0.81 1.24 0.88 0.57 0.57 100
46.06 12.79 24.57 3.27 9.07 0.97 0.93 1.17 0.55 0.62 — 100
44.68 12.65 35.00 2.98 3.07 0.44 —— 0.78 —— 0.40 —— 100
51.13 7.39 22.52 8.49 0.31 — 2.95 0.32 6.88 —— —— 100
Table 2 Mixture proportions of concrete mixtures containing TUFS. Sl. No
Mix Designation
Cement (kg/m3)
TUFS (kg/m3)
Fine Aggregate (kg/m3)
Coarse Aggregate (kg/m3)
Water (ltr/m3)
Super Plasticizer (ltr/m3)
1 2 3 4 5
CC R10 R20 R30 R40
394.3 394.3 394.3 394.3 394.3
0 63.12 126.24 189.36 252.48
631.60 568.44 505.28 442.12 378.96
1178.52 1178.52 1178.52 1178.52 1178.52
197.16 197.16 197.16 197.16 197.16
1.20 1.20 1.20 1.20 1.20
3. Test procedures 3.1. Water absorption test The test for determining the water absorption characteristics of various mixtures were conducted on three number of 150 mm size concrete cubes for each proportion as per ASTM C 642-06 [20]. After 28 and 90 days of casting, the specimens immersed in curing tank were taken out to measure the saturated weight (Ws). Then the specimens were dried in an oven at a temperature of 105° C and weights of the specimens were found out. This drying process was repeated until the two successive measurements of weight were almost the same. Thus the weight of the oven dried specimens (Wd) after cooled to room temperature were found out. From these values, Saturated Water Absorption (SWA) was calculated as
SWA ¼ ½ðWs Wd Þ=Wd 100 where, Ws-Weight of the specimen at fully saturated condition in kg. Wd-Weight of oven- dried specimens in kg. 3.2. Sorptivity Sorptivity is a material property which indicates the characteristics of a porous material to absorb and transmit the water by capillary action. The test was conducted as per the German Standard DIN 52 617[21]. It can be measured by the capillary rise absorption rate of the material. The concrete cube specimens of size 150 mm were cast and immersed in water for curing. After 28 days, the specimens were dried in normal room temperature. The initial
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weights of the cubes were measured. The side of the concrete specimens were coated with wax sealant except the test surface on bottom and top of specimen which were kept free of wax sealant. The initial weight of the concrete cube was taken. The concrete cube specimen was kept partially immersed to a depth of 5 mm in the water as shown in Fig. 7.The specimen’s masses were recorded at time intervals of 2 min, 4 min, 8 min, 16 min, 30 min, 1 h, 2 h, 4 h, 8 h, 16 h, 32 h and 64 h. The specimens were quickly removed from the water and its test surface patted with a paper towel to remove excess water and the sample was weighed. The sorptivity values of concrete specimens were calculated using the following formula
pffiffi i¼s t where i is the cumulative water absorption per unit area of inflow surface (Kg/m2), s is the sorptivity (m/s1/2) and t is the time elapsed (s).
distilled water. After curing, the concrete specimens were subjected to RCPT test by impressing a voltage of 60 V. It is a two compartment air and water tight cell assembly. The cathode compartment was filled with 3% NaCl solution and anode compartment was filled with 0.3 N NaOH solutions. The concrete disc specimens were subjected to RCPT by impressing a 60 V form DC power source between the anode and cathode. Current was monitored up to 6 h at an interval of 30 min. From the current values, the total charge in Coulomb has been found to relate to the resistance of the specimen to chloride ion penetration.
Q ¼ 900ðI0 þ 2I30 þ 2I60 þ . . . . . . þ 2I300 þ 2I330 þ I360 Þ where: Q = charge passed (Coulombs) I0 = current (amperes) immediately after voltage is applied and It = current (amperes) at t min after voltage is applied 3.4. Chemical resistance test
3.3. Rapid chloride permeability test This test was conducted as per ASTM C1202-12 [22]. A durable concrete is the one that performs satisfactorily under anticipated exposure condition during its life span. One of the main characteristics influencing the durability of concrete is its permeability to ingress of chloride. The chloride ion present in the concrete can have harmful effect on concrete as well as on the reinforcement. 100 mm dia and 50 mm thick concrete disc specimens were cast using with and without TUFS as shown in Fig. 8. After 24 h, the disc specimens were removed from the mould and cured for 28 days in
3.4.1. Acid resistance –HCl and H2SO4 Acid attack test was conducted as per ASTM C267- 01(2012) [23]. For acid resistance, the cube specimens were immersed in 5% of 1 M HCl solution by volume added to water and the pH observed in the solution was 3.10 at the initial stage. Similarly another set of cube specimens were immersed in 5% of 1 M H2SO4 solution by volume added to water and the pH observed in the solution was 2.10 at the initial stage. The percentage of loss in weight and strength was determined by,
Fig. 7. Sorptivity test setup.
Fig. 8. RCPT test setup.
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ðW1 W2Þ Percentage loss in weight ¼ x100 W1 where, w1 – weight of specimens before immersed in solution. w2 – weight of specimens after immersed in solution.
Percentage of strength loss ¼
ðfc1 fc2Þ x100 fc1
where, fc1 – compressive strength of concrete under normal exposure. fc2 – compressive strength of concrete under acid exposure. 3.4.2. Sulphate resistance (Na2SO4) Sulphate resistance test was conducted accordance with the ASTM C1012 [24]. 10% Na2SO4 by weight was added to distilled water to make sodium sulphate solution. 3.4.3. Marine environment Composition of the solution prepared to represent marine environment is shown in Table 3 was prepared as per ASTM D1141 [25]. All chemical resistance tests were carried out at 7, 28, 56 and 90 days. Test specimens of 150 mm size cubes were cast and kept under curing. Twelve specimens were cast for each test. The pH concentration of the solution at initial stage was maintained throughout the all the stages by checking it periodically. After the completion of curing time, the specimens were taken out and the surface of the specimens were scraped and surface deposits were removed, washed and dried for 2 to 3 h and weighed again. The deterioration of concrete specimens were measured as a percentage loss in weight at 7, 28, 56 and 90 days and percentage loss in compressive strength of concrete at 7, 28, 56 and 90 days.
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specimens are shown in Fig. 9. It is noted that with increase in TUFS content the water absorption gets decreased when compared with Control Concrete. The water absorption percentage varied between 3.47% and 3.72% at 28 days. This is lower compared to the values obtained by Siddique et al.[26] which varied between 7.3% and 8.2%.As per ASTM C 642 – 06 [20], the water absorption percentage lesser than 5% is excellent. This indicates that TUFS acts as a filler material which fills the pores and thereby reduces water absorption. And also it is found that, water absorption percentage by weight has the higher percentage at 28 days compared to 90 days. It indicates that water absorption decreases with increase in curing time. R30 mix has the least value at 28 days and 90 days indicating that 30% replacement is found to be very effective in reducing the water absorption.
4.2. Sorptivity test The comparison of Cumulative water absorption values of CC, R10, R20, R30, R40 is shown in Fig. 10 and The slope of best fitting line was reported as the Sorptivity of concrete with various TUFS replacement after 114 hrs is shown in Fig. 11. It was observed that in general, there was decrease in sorptivity value for all the mixtures with TUFS when compared to the CC at the initial stage. R, Siddique et al. [26] reported that compressive strength increased as sorptivity decreased and vice versa. In our previous work [4] the strength was increased up to R30 compared to CC, which was correlated with the above statement.
4. Results and discussion 4.1. Water absorption test The results of water absorption test at the age of 28 days and 90 days and influence of different ratios of TUFS in concrete Table 3 Composition for marine water. Composition
Concentration g/l
NaCl Magnesium chloride Sodium sulphate Calcium chloride Potassium chloride
24.53 5.2 4.09 1.16 0.695
Fig. 9. Percentage of water absorption for various TUFS replacement.
Fig. 10. Cumulative water absorption vs Time for various TUFS replacement.
Fig. 11. Sorptivity of concrete with various TUFS replacement at 114 h.
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Later there was slight increase in sorptivity value in R40 compared to R30. But at all the time period, there is decrease in sorptivity for R30 when compared to CC. This means that time taken for water to rise by capillary action in R30 was longer. TUFS is finer than normal sand which acts as micro fillers and fills most of the pores in the core portion of concrete. From the test results, it indicates TUFS concrete are less porous and better resistance to transport water compared to CC [27]. The Regression coefficient for sorptivity indices was 0.97, 0.96, 0.97, 0.97 and 0.97 for CC, R10, R20, R20, R30 and R40 respectively were found out through Fig. 10. 4.3. Rapid chloride permeability test The rapid chloride permeability test results for the concrete specimens are shown in Table 4. It can be seen that the Coulomb value decreased with increase in TUFS content up to 30% TUFS, which indicates that concrete becomes denser. However, R40 shows a slight increase in Coulomb value compared to R30. This observation is for concrete at the age of 28 days. All concrete mixtures showed low permeability (Coulombs between 1000 and 2000) as per ASTM C 1202-2012 [22]. Low and moderate chloride ion permeability is the key to good durability. The penetration resistance increased due to reduction in calcium ions in the gel pore fluids and subsequent depletion of pH. As the pore structures become relatively more refined due to pozzolanic reaction, the high conductivity path for the ions will decrease. Singh et al. [15] stated that decrease in chloride ion penetration in concrete by including Waste Foundry Sand, indicate that concrete has become denser and impermeable. This is in good agreement with the findings of this investigation. Maximum reduction in RCPT value is observed at R30 as shown in Fig. 12.It means that at 30% replacement, concrete exhibits more resistance to chloride ion permeability though, all concrete mixtures have low permeability to chloride ion permeability as per ASTM C 1202-2012. Siddique et al. [28] indicated in the study that UFS mixes showed good chloride penetration resistance with low charges passed as per ASTM C 1202-2012[15]. Finer particles of TUFS act as a good filler material and reduce the voids between
Table 4 RCPT results. Sl. No
Mix Proportion
Charges passed in Coulombs
Chloride ion permeability as per ASTM C1202-09
1 2 3 4 5
CC R10 R20 R30 R40
1739 1523 1347 1249 1289
Low Low Low Low Low
Fig. 12. RCPT results.
ingredients of concrete and create a stronger internal structure of concrete matrix. 4.4. Chemical resistance test 4.4.1. Acid attack studies The acid resistance test was conducted separately by using sulphuric acid and hydrochloric acid at the concentration explained already. In H2SO4 environment, the maximum percentage of weight loss was observed for CC at 7, 28, 56 and 90 days as 5.15%, 15.52%, 21.27% and 25.13% respectively. Similarly the percentage of weight loss for R10, R20, R30, and R40 were calculated and shown in Fig. 13. The percentage of weight loss for R30 is 3.79%, 7.42%, 18.87% and 20.95% at7, 28, 56 and 90 days respectively. Maruthachalam et al. [9] stated that the porosity of concrete getting reduced is the reason for the decrease in weight loss. It is correlated with present research work because TUFS is finer than normal sand which fills the pores and decreases the weight loss with an increase in TUFS. This is validated by Scanning Electron Microscopy (SEM) analysis discussed by the authors in a previous work [3] that, the number of voids in the mix has significantly reduced. Significant formation of thin strands is noticed. The paste has spread very finely and firmly throughout the sample and effect of combined paste. From the test results, it is found that percentage of weight loss is higher in CC compared to the concrete with TUFS. This shows that the TUFS concrete has better resistance to acid attack. It is also observed that H2SO4 environment fully erodes the mortar exposing the coarse aggregate as stated by Maruthachalam et al. [9]. Along with percentage of weight loss, the percentage loss of compressive strength also was found out and results are shown in Fig. 14. Maruthachalam et al.[9] reported that the acid attack and leaching away of the calcium compounds of the cement paste formed in concrete during the hydration process as well as calcium in calcareous aggregate reduced the strength of structural concrete and affected the durability. In case of HCl acid environment the leaching is minimum or low, the percentage loss of weight and compressive strength is less compared to H2SO4 acid environment. The percentage of weight and strength loss is shown in Figs. 15 and 16. The maximum percentage weight loss is 4.32% at 90 days for CC which is higher compared to 3.85% for R30 at 90 days. Similarly the strength loss of CC is 33.5% which is higher compared to R30 is 24.53% at 90 days. Concrete cubes exposed to HCl solution showed sign of corrosion by turning brown in colour and also leaching was minimum or low. The compressive strength of concrete mix exposed to HCl environment is significantly reduced because the acid attack completely converts the hardened cement paste destroying the entire pore system. Compared to CC, TUFS concrete performed better because of increase in fineness and rich in silica content leading
Fig. 13. Weight loss under H2SO4 environment.
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Fig. 14. Strength loss under H2SO4 environment. Fig. 17. Weight loss under Na2SO4 environment.
Fig. 15. Weight loss under HCl environment.
Fig. 18. Strength loss under Na2SO4 environment.
Fig. 16. Strength loss under HCl environment.
to durable concrete in acid exposure. There, both acid resistance tests, TUFS concrete mixture R30 mix showed the minimum weight and strength loss percentage compared to remaining mix proportion.
4.4.2. Sulphate attack test The percentage loss in weight as well as compressive strength due to sulphate attack is shown in Figs. 17 and 18 respectively. The percentage weight loss of CC is 0.12%, 0.72%, 0.91% and 1.03% at 7, 28, 60, and 90 days respectively. It is observed that the percentage weight loss is decreased with an increase in TUFS from R10 to R30 and slight increase of R40 at 7, 28, 56, and 90 days. The percentage of weight loss of R30 is 0.02%, 0.11%, 0.6%, and 0.69% at 7, 28, 56 and 90 days respectively which is lower than control concrete and other TUFS concrete. It shows that R30 is optimum compared to remaining replacement. The higher C3A content
in the cement paste makes concrete more vulnerable to sulphate attack. The loss of weight in sulphate environment is less than 1%; hence it is negligible. Rajesh kumar et al. [29] also stated that the percentage of weight loss was not observed much in sulphate resistance test; it seemed to be negligible. The specimens exposed to Na2SO4 environment not show much difference compared to water exposed specimens. The maximum percentage loss in compressive strength was observed for CC as 1.95% at 90 days and for R30, it was 1.51% at 90 days. It is clear that the TUFS as replacement material in concrete enhances the sulphate resistance of concrete.
4.4.3. Marine environment studies The percentage loss in weight and strength was very less at initial stage of 7 days exposure. At later days, the weight loss percentage was somewhat higher in control concrete compared to TUFS replacements. The results are shown in Fig. 19. The percentage of weight loss in CC was 2.05% at 90 days which is higher compared to R10, R20, R30, and R40 values of 1.75%, 1.44%, 1.25% and 1.55% respectively. It shows that R30 was optimum one and weight loss percentage was less compared to remaining mix. The white patches were on the cube specimens after exposing to marine environment. The compressive strength loss percentage was 1.77 for CC which was higher compared with R10, R20, R30 and R40 values of 1.57, 1.44, 1.31 and 1.4 at 90 days respectively as shown in Fig. 20. From the percentage of strength loss results, it is found that there is a decrease with an increase in TUFS concrete. It shows that TUFS concrete shows better resistance in marine environment compared to the control concrete.
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6. In sulphate resistance, percentages of weight loss and strength loss were 1.03 and 1.95 for CC which is more than R30 with a value of 0.69 and 1.51 respectively. It indicates that TUFS concrete shows better sulphate resistance characteristics. 7. Under marine water environment also, percentage of weight loss and strength loss in CC were higher compared to TUFS concrete. Similar to sulphate resistance, TUFS concrete shows better resistance in marine environment compared to the CC. 8. As per this investigation, concrete with 30% TUFS as fine aggregate replacement is found to be very effective under different environmental exposure conditions. Thus the use of Treated Used Foundry Sand in concrete can save the metal industries from the disposal problem and produce greener concrete for construction as an innovative construction material. Fig. 19. Weight loss of under marine environment.
Conflict of interest On behalf of both authors, I wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome. And also I confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed.
References
Fig. 20. Strength loss of under marine environment.
5. Conclusion This study was conducted to investigate the effect of using TUFS as partial replacement of fine aggregate in concrete under various environmental conditions with respect to water absorption, sorptivity, chloride ion penetration, weight and strength loss. The following conclusions are drawn from this study. 1. The percentage of water absorption decreases as TUFS increases compared to control specimens. It is found that R30 showed 23% lower water absorption than control concrete. This indicates that TUFS acts as a good filler material. Further it shows that with increase in curing time, there is decrease in water absorption percentage. 2. Sorptivity value of R30 is 0.040 mm/min0.5 which is lesser compared to CC with value of 0.032 mm/min0.5. It indicates that TUFS concrete is less porous and shows better resistance to transport of water compared to control concrete. 3. All the mix proportion shows good resistance to chloride ion penetration particularly R30 with 40% lower value compared to control concrete. It shows that TUFS concrete offer more resistance to chloride ion permeability. 4. It was observed that the loss in weight of TUFS concrete was found to be 20.95% which is lesser than CC with 25.13% when exposed to H2SO4 for 90 days. Similarly loss in strength of TUFS concrete was 61.8% which is lesser than CC with a value of 72.17%. 5. It was found that the loss in weight was 3.85% for R30 which is lesser than CC with a value of 4.32% when exposed to HCl for 90 days. Similarly loss in strength was 24.53% for R30 which is lesser than CC with a value of 32.74%.
[1] A. Torres, J. Brandt, K. Lear, J. Liu, ’A looming tragedy of the sand commons, Science 357 (2017) 970–971. [2] H. Van Damme, Concrete material science: past, present, and future innovations, Cem. Concr. Res. (2018). org/10.1016. [3] J. Xiao, C. Qiang, A. Nanni, K. Zhang, Use of sea-sand and seawater in concrete construction: current status and future opportunities, Constr. Build. Mater 155 (2017) 1101–1111. [4] N. Gurumoorthy, K. Arunachalam, Micro and mechanical behaviour of treated used foundry sand concrete, Constr. Build. Mater. 123 (2016) 184–190. [5] E.A.Dayton, S.D.Whitacre, R.S.Dungan, N.T.Basta, Characterization of Physical and chemical properties of spent foundry sands pertinent to beneficial use in manufactured soils, plant soil, 329 (2010), pp 27-33.doi: 10.1007/s 11104-0090120-0. [6] R. Siddique, G. Schutter, A. Noumowee, Effect of used foundry sand on the mechanical properties of concrete, Constr. Build. Mater. 23 (2009) 976–980. [7] F. Tittarelli, Waste foundry sand- Waste and supplementary Cementitious Materials in Concrete, Woodhead Publishing Series Civil Struct. Eng. 5 (2018) 121–147. [8] S. Dhiyaneshwaran, P. Ramanathan, I. Baskar, R. Venkatasubramani, Study on durability characteristics of self-compacting concrete with fly ash, Jordan J. Civ. Engg. 7 (3) (2013) 342–353. [9] D. Maruthachalam, M. Gurunathan, I, Padmanaban, B.GVishnuram, Durability Properties of Fibrillated Polypropylene fibre reinforced high performance concrete, J. Struc. Engg. 38 (1) (2011) 1–9. [10] N. Ganesan, P.V. Indira, P.T. Santhosh Kumar, Durability aspects of steel fibre – reinforced SCC, Indian Concr. J. (2006) 31–37. [11] P. Srinivasa Rao, T. Seshadri Sekhar, P.W. Sravana, Durability studies on glass fibre SCC, The, Indian Concr. J. (2009) 44–52. [12] P. Neelam, R. Siddique, Effect of elevated temperatures on properties of selfcompacting concrete containing fly ash and spent foundry sand, Constr. Build. Mater. 34 (2012) 512–521. [13] IS: 12269-2013. Specifications for 53 Grade Portland cement. New Delhi, India: Bureau of Indian Standards [14] IS: 383-1970. Specifications for coarse and fine aggregates from Natural sources for concrete. New Delhi, India: Bureau of Indian Standards. [15] G. Singh, R. Siddique, Effect of waste foundry sand (WFS) as partial replacement of sand on the strength, ultrasonic pulse velocity and permeability of concrete, Constr. Build. Mater. 26 (2012) 416–422. [16] S. Monosi, F. Tittrarelli, C. Giosue, M.L. Ruello, Effect of two different sources and washing treatment on the properties of UFS by-products for mortar and concrete production, Constr. Build. Mater. 44 (2013) 260–266. [17] ACI 318-08, ‘Building code requirements for structural concrete and commentary (ACI 318R-99)’. Detroit: American Concrete Institute. [18] IS: 10262-2009. Recommended guidelines for concrete mix design. New Delhi, India: Bureau of Indian Standards. [19] IS: 1199-1959. Indian standard methods of sampling and analysis of concrete. New Delhi, India: BIS
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[25] American Society for Testing and Materials (ASTM) D 1141: Standard Practice for the preparation of substitute Ocean Water. [26] R. Siddique, E.H. Kadri, Effect of metakaolin and foundry sand on the near surface characteristics of concrete, Constr. Build. Mater. 25 (2011) 3257–3266. [27] J.M. Khatib, B.A. Herki, S. Kenai, Capillarity of concrete incorporating waste foundry sand, Constr. Build. Mater. 47 (2013) 867–871. [28] R. Siddique, Y. Agarwal, P. Agarwal, E.H. Hardi, R. Bennacer, Strength, durability and microstructural properties of concrete made with used foundry sand (UFS), Constr. Build. Mater. 25 (2011) 1916–1925. [29] K. Rajesh Kumar, N. Mahendran, Durability performance of hybrid fibre reinforced self compacting concrete containing Class F fly ash, Aust. J. Basic Appl. Sci. 9 (27) (2015) 61–68.
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Durability Studies on Concrete Containing Treated Used Foundry Sand N. Gurumoorthy a,⇑, K. Arunachalam b a b
Department of Civil Engineering, PSNA College of Engineering and Technology, Dindigul, Tamilnadu, India Thiagarajar College of Engineering, Madurai, Tamilnadu, India
h i g h l i g h t s Silica in the sand is enriched by treating and called as TUFS. Water absorption and permeability characteristics of TUFS concrete are investigated. Effect of TUFS concrete on exposure to various environments. Optimum TUFS content is found to be 30% by weight.
a r t i c l e
i n f o
Article history: Received 27 July 2018 Received in revised form 1 January 2019 Accepted 3 January 2019
Keywords: TUFS Water absorption RCPT Acid resistance Sulphate resistance
a b s t r a c t Use of waste products from foundry industry in concrete not only makes it economical, but also helps in reducing disposal problems and environmental degradation. The waste materials required for the replacement of fine aggregate are processed to the required specifications that could match with the properties of fine aggregate to be used in concrete. Such type of industrial waste by-product namely waste foundry sand was treated and used as partial replacement material for fine aggregate in concrete. Experiments were conducted to study the durability characteristics of Treated Used Foundry Sand (TUFS) as partial replacement for fine aggregate. Fine aggregate was replaced with various percentages of TUFS by weight. Tests were conducted for water absorption, sorptivity and Rapid Chloride Permeability. Further these concrete specimens were exposed to chemical solutions and marine environment for 7, 28, 56 and 90 days. After the exposure period, these specimens were tested for loss in weight and compressive strength. Test results indicated better performance of concrete with TUFS than control specimen and established that concrete with 30% TUFS is more impermeable than control concrete with better durability properties also proved that TUFS can be effectively used in making good quality concrete. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction Concrete is the most widely and universally used construction material in construction industry. Slightly more than a ton of concrete is produced every year for every human being on the planet. Over the past several decades, the demand for concrete has been increasing rapidly due to infrastructure development. Between 1900 and 2010, the global volume of natural resources used in buildings and transport infrastructure increased 23-fold [1]. Sand and gravel are the largest portion of these primary material inputs (79% or 28.6 gigatons per year in 2010) and are most extracted group of materials worldwide. Comparative evolution of the post-World War II (WWII) global cement, steel, and plastic produc-
⇑ Corresponding author. E-mail address: [email protected] (N. Gurumoorthy). https://doi.org/10.1016/j.conbuildmat.2019.01.014 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved.
tions (Top), and same data plotted as material use per capita vs world population (Bottom) are shown in Fig. 1. The concrete constitutes various ingredients like cement, fine aggregate and coarse aggregate. Out of these, river sand is used as a fine aggregate in concrete production for several decades. The demand for river sand increased due to depletion of sand. The production of aggregates (including both coarse and fine aggregates) reached about 40 billion tonnes in the year of 2014 [3] At present, many researches are carried out to overcome the stress and the demand for river sand by using industrial wastes like foundry sand, fly ash, bottom ash and slag which can result in significant improvement in overall energy efficiency and environmental performance [4]. In industries, numerous waste materials are generated during manufacturing processes. The increasing awareness about environment has tremendously contributed in the disposal of generated wastes. With the scarcity of space for land filling and unavailability
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dry sand has beneficial applications in other industries. Estimation of industry is that 100 million tons of sand is used in production annually of that 6–10 million tons are discarded annually as waste and are available to be recycled into other products [6]. It has been found that UFS produced by iron, steel, and aluminium foundries are rarely hazardous. Only about 15 percent of UFS are recycled. This is mainly due to lack of knowledge on its possible beneficial reuse. Beneficial reuse of UFS continues to become a more accepted practice as more end-users are introduced to the concept. The foundry sand from non-ferrous metal casting industry can be directly used in concrete [7]. This has been proved by many researchers. The ferrous metal casting industry discarded foundry sand contains more iron content which will affect the binding properties of concrete and decrease the strength parameter. As per ASTMC330 and C641, iron content in the sand will cause staining effect and also affect the durability for this reason iron content has to be removed or reduced for UFS. After removing iron content by treatment, the UFS is called as Treated Used Foundry Sand (TUFS) [4]. The objectives of this study are to investigate the effect of TUFS as partial replacement of fine aggregates in various percentages (0–40%), on exposure to various environment like acid, sulphate and marine. Moreover, the study will focus on sorpitivity and Rapid Chloride Permeability Test (RCPT) as there is no much research on durability studies in concrete with UFS. The basic experimental studies for above tests are taken from some other researchers utilizing materials other than UFS [8–12]. 2. Experimental investigations 2.1. Materials
Fig. 1. Top: Comparative evolution of the post-WWII global cement, steel, and plastic productions, Bottom: Same data plotted as material use per capita vs world population [Van Damme, H. (2018) [2].
of natural sand, waste product utilization has become an attractive alternative which can be used in concrete as a replaceable material. The use of waste products in concrete not only makes it economical, but also helps in mitigating disposal problems. Ministry of Environment, India enforces regulation and rules for disposal of Solid Waste Management rules in 2016 S.O 1357 (E) [08.04.2016]. The materials required for replacement of fine aggregate are processed to necessary specifications that could match with the properties of fine aggregate to be used in concrete. Such type of industrial by-product namely Used Foundry Sand (UFS) is treated and used as a partially replacement material for fine aggregate in concrete. Foundry industry produces a large amount of side product material during casting process. It is high quality silicate sand with uniform physical and chemical characteristics produced by ferrous and non ferrous metal casting industries. These industries reuse the sand many times and after many cycle it is removed and disposed to nearby sites. This waste sand from foundry is termed as Used Foundry Sand (UFS). Alike regular sand, UFS also mainly consists of silica but its silica content has been found similar to regular sand. The properties of foundry sand depend on casting process and the nature of industry from which it comes. About 85–90% of its particles are smaller than 100 mm. It is principally made up of sand which is evident from the particle size (0.05 mm–2 mm) of UFS, obtained form 39 foundries, ranging from 76.6% to 100%, with a median of 90.3% [5].The automotive industries are the major generators of used foundry sand. Like many waste products, foun-
2.1.1. Cement Ordinary Portland Cement (53 grade) cement was used conforming to IS: 12269-2013[13]. It was tested as Per the Indian Standard Specifications IS: 12269-2013 [13] and specific gravity of cement was 3.12. 2.1.2. Fine aggregate Natural river sand having a 4.75 mm nominal size conforming to zone III of IS: 383-1970[14] and specific gravity of 2.59 was used in this study. The element composition of natural river sand is shown in Fig. 2. 2.1.3. Coarse aggregate Locally available crushed angular granite with nominal size of 20 mm as per IS: 383-1970 [14] and its specific gravity of 2.72 were used. 2.1.4. Super plasticizer Modified melamine formaldehyde chemical based admixture was used to increase the workability. The dosage was uniform for all mix at 0.3% by weight of cement. 2.1.5. Used foundry sand The UFS was collected from moulding process of ferrous metal casting industry near Ganapati, Coimbatore, India. The UFS had the specific gravity 2.32 and fineness modulus 1.74, which was very fine as stated by Singh, et al. [15]. The study was made to determine the elemental composition of UFS by EDAX test as shown in Fig. 3. From EDAX test report, it was perceived that there was a presence of 10.85% iron content in UFS sample. The presence of iron content will reduce the binding property and also increases rate of corrosion. Chemical treatment of UFS was carried out to remove the iron content.
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Fig. 2. Elemental composition of Natural River Sand by EDAX.
Fig. 3. Elemental composition of UFS by EDAX.
2.2. Treatment of used foundry sand UFS was treated with different concentration of Hydrochloric acid as 2.5%, 5% and 10% by weight.To treat in 2.5% concentration HCl solutions, 100 g of UFS was added to 487.5 ml of distilled water and 12.5 ml of HCl. Similarly for treating with 5% HCl strength, 100 g of UFS was added to 475 ml of distilled water and 25 ml of HCl acid and for 10% HCl strength, 100 g of UFS was added to 450 ml distilled water and 50 ml of HCL. The above prepared samples were then stirred with magnetic stirrer for 24 h as adopted by Monosi, et al. [16]. After 24 h, the solutions were separated by centrifugation, filtered with 0.2 mm filter paper and the collected UFS was washed with distilled water thoroughly, again separated by centrifugation, and dried for 24 h. The above samples are considered Treated Used Foundry Sand. EDAX test were done on them to analyze the elemental composition [2]. The EDAX test reports of treated UFS are shown
in Figs. 4–6. The Elemental comparison of natural sand, UFS and TUFS are shown in Table 1.in that AN means Atomic Number, K means equilibrium constant and C. norm means the normalised concentration in weight percent of the element 2.3. Comparison of EDAX test results EDAX test results showed that the TUFS treated with 2.5% concentration HCl contained 73% silica and 9% iron content, the 5% concentration HCl contained 80% silica and 3% iron content. Similarly TUFS treated with 10% concentration HCl contained 73% silica and 0.5% iron content. The silica content was decreased for 10% concentration of HCl. The reason for reduction in silica content is due to the reaction between silicon and HCl to form silicon tetrachloride and release of hydrogen gas. By associating the test results of TUFS, it was found that there was an increase in silica content
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Fig. 4. EDAX test result of UFS treated with 2.5% HCL.
Fig. 5. EDAX test result of UFS treated with 5% HCL.
and decrease in iron content in UFS treated with 5% HCl. It will give higher binding property than untreated UFS and UFS treated with other concentration. From the test results obtained, it was found that the UFS required for casting should be treated with 5% of HCl. This treatment process was done in a container. The contents were stirred and dried under sunlight [4]. Moreover, the chloride content present in the TUFS was brought down due to acid treatment from 1.57% to 0.45% by washing it in water, thus bringing the chloride level less than the allowable limit of 1% as per ACI 318-08 Standard [17]. 2.4. Mix proportions and specimen casting Control Concrete (CC) was designed to have 28-day target compressive strength of 27 MPa as per IS: 10262-2009 [18]. The con-
crete mix proportion was 1:1.6:2.98 with 1 part cement, 1.6 part fine aggregates, and 2.98 part coarse aggregates having water cement ratio of 0.5. Four additional concrete mixtures R10, R20, R30 and R40 were proportioned where sand (fine aggregate) was replaced with 10%, 20%, 30% and 40% TUFS by mass respectively. The slump of all mixtures was 110 ± 5 mm. Details of mixtures are presented in Table 2. 150 mm concrete cubes were cast for acid test, water absorption test, sorpitivity test and 100 mm diameter 50 mm thick cylinders for Rapid Chloride Penetration Test. All the specimens were prepared in accordance with IS: 11991959 [19]. Soon after casting, test specimens were left in the casting room for 24 h at a temperature of about 27 ± 1 °C. They were demolded after 24 h and were put into a water-curing chamber until the time of testing. Three specimens were tested for each test and the average value was taken.
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Fig. 6. EDAX test result of UFS treated with 10% HCL.
Table 1 Elemental comparison of natural sand, UFS and TUFS. El
AN
Series
C. norm [wt%] of River Sand
C. norm [wt%] of UFS
C. norm [wt%] of 2.5% TUFS
C. norm [wt%] of 5% TUFS
C. norm [wt%] of 10% TUFS
O C Si Al Fe Mg Na Ca K Ti Cr
8 6 14 13 26 12 11 20 19 22 24
K-Series K-Series K-Series K-Series K-Series K-Series K-Series K-Series K-Series K-Series K-Series Total
58.90 12.48 25.85 1.21 1.57 — —— —— — — —— 100
40.63 12.13 23.75 7.35 10.85 1.21 0.81 1.24 0.88 0.57 0.57 100
46.06 12.79 24.57 3.27 9.07 0.97 0.93 1.17 0.55 0.62 — 100
44.68 12.65 35.00 2.98 3.07 0.44 —— 0.78 —— 0.40 —— 100
51.13 7.39 22.52 8.49 0.31 — 2.95 0.32 6.88 —— —— 100
Table 2 Mixture proportions of concrete mixtures containing TUFS. Sl. No
Mix Designation
Cement (kg/m3)
TUFS (kg/m3)
Fine Aggregate (kg/m3)
Coarse Aggregate (kg/m3)
Water (ltr/m3)
Super Plasticizer (ltr/m3)
1 2 3 4 5
CC R10 R20 R30 R40
394.3 394.3 394.3 394.3 394.3
0 63.12 126.24 189.36 252.48
631.60 568.44 505.28 442.12 378.96
1178.52 1178.52 1178.52 1178.52 1178.52
197.16 197.16 197.16 197.16 197.16
1.20 1.20 1.20 1.20 1.20
3. Test procedures 3.1. Water absorption test The test for determining the water absorption characteristics of various mixtures were conducted on three number of 150 mm size concrete cubes for each proportion as per ASTM C 642-06 [20]. After 28 and 90 days of casting, the specimens immersed in curing tank were taken out to measure the saturated weight (Ws). Then the specimens were dried in an oven at a temperature of 105° C and weights of the specimens were found out. This drying process was repeated until the two successive measurements of weight were almost the same. Thus the weight of the oven dried specimens (Wd) after cooled to room temperature were found out. From these values, Saturated Water Absorption (SWA) was calculated as
SWA ¼ ½ðWs Wd Þ=Wd 100 where, Ws-Weight of the specimen at fully saturated condition in kg. Wd-Weight of oven- dried specimens in kg. 3.2. Sorptivity Sorptivity is a material property which indicates the characteristics of a porous material to absorb and transmit the water by capillary action. The test was conducted as per the German Standard DIN 52 617[21]. It can be measured by the capillary rise absorption rate of the material. The concrete cube specimens of size 150 mm were cast and immersed in water for curing. After 28 days, the specimens were dried in normal room temperature. The initial
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weights of the cubes were measured. The side of the concrete specimens were coated with wax sealant except the test surface on bottom and top of specimen which were kept free of wax sealant. The initial weight of the concrete cube was taken. The concrete cube specimen was kept partially immersed to a depth of 5 mm in the water as shown in Fig. 7.The specimen’s masses were recorded at time intervals of 2 min, 4 min, 8 min, 16 min, 30 min, 1 h, 2 h, 4 h, 8 h, 16 h, 32 h and 64 h. The specimens were quickly removed from the water and its test surface patted with a paper towel to remove excess water and the sample was weighed. The sorptivity values of concrete specimens were calculated using the following formula
pffiffi i¼s t where i is the cumulative water absorption per unit area of inflow surface (Kg/m2), s is the sorptivity (m/s1/2) and t is the time elapsed (s).
distilled water. After curing, the concrete specimens were subjected to RCPT test by impressing a voltage of 60 V. It is a two compartment air and water tight cell assembly. The cathode compartment was filled with 3% NaCl solution and anode compartment was filled with 0.3 N NaOH solutions. The concrete disc specimens were subjected to RCPT by impressing a 60 V form DC power source between the anode and cathode. Current was monitored up to 6 h at an interval of 30 min. From the current values, the total charge in Coulomb has been found to relate to the resistance of the specimen to chloride ion penetration.
Q ¼ 900ðI0 þ 2I30 þ 2I60 þ . . . . . . þ 2I300 þ 2I330 þ I360 Þ where: Q = charge passed (Coulombs) I0 = current (amperes) immediately after voltage is applied and It = current (amperes) at t min after voltage is applied 3.4. Chemical resistance test
3.3. Rapid chloride permeability test This test was conducted as per ASTM C1202-12 [22]. A durable concrete is the one that performs satisfactorily under anticipated exposure condition during its life span. One of the main characteristics influencing the durability of concrete is its permeability to ingress of chloride. The chloride ion present in the concrete can have harmful effect on concrete as well as on the reinforcement. 100 mm dia and 50 mm thick concrete disc specimens were cast using with and without TUFS as shown in Fig. 8. After 24 h, the disc specimens were removed from the mould and cured for 28 days in
3.4.1. Acid resistance –HCl and H2SO4 Acid attack test was conducted as per ASTM C267- 01(2012) [23]. For acid resistance, the cube specimens were immersed in 5% of 1 M HCl solution by volume added to water and the pH observed in the solution was 3.10 at the initial stage. Similarly another set of cube specimens were immersed in 5% of 1 M H2SO4 solution by volume added to water and the pH observed in the solution was 2.10 at the initial stage. The percentage of loss in weight and strength was determined by,
Fig. 7. Sorptivity test setup.
Fig. 8. RCPT test setup.
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ðW1 W2Þ Percentage loss in weight ¼ x100 W1 where, w1 – weight of specimens before immersed in solution. w2 – weight of specimens after immersed in solution.
Percentage of strength loss ¼
ðfc1 fc2Þ x100 fc1
where, fc1 – compressive strength of concrete under normal exposure. fc2 – compressive strength of concrete under acid exposure. 3.4.2. Sulphate resistance (Na2SO4) Sulphate resistance test was conducted accordance with the ASTM C1012 [24]. 10% Na2SO4 by weight was added to distilled water to make sodium sulphate solution. 3.4.3. Marine environment Composition of the solution prepared to represent marine environment is shown in Table 3 was prepared as per ASTM D1141 [25]. All chemical resistance tests were carried out at 7, 28, 56 and 90 days. Test specimens of 150 mm size cubes were cast and kept under curing. Twelve specimens were cast for each test. The pH concentration of the solution at initial stage was maintained throughout the all the stages by checking it periodically. After the completion of curing time, the specimens were taken out and the surface of the specimens were scraped and surface deposits were removed, washed and dried for 2 to 3 h and weighed again. The deterioration of concrete specimens were measured as a percentage loss in weight at 7, 28, 56 and 90 days and percentage loss in compressive strength of concrete at 7, 28, 56 and 90 days.
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specimens are shown in Fig. 9. It is noted that with increase in TUFS content the water absorption gets decreased when compared with Control Concrete. The water absorption percentage varied between 3.47% and 3.72% at 28 days. This is lower compared to the values obtained by Siddique et al.[26] which varied between 7.3% and 8.2%.As per ASTM C 642 – 06 [20], the water absorption percentage lesser than 5% is excellent. This indicates that TUFS acts as a filler material which fills the pores and thereby reduces water absorption. And also it is found that, water absorption percentage by weight has the higher percentage at 28 days compared to 90 days. It indicates that water absorption decreases with increase in curing time. R30 mix has the least value at 28 days and 90 days indicating that 30% replacement is found to be very effective in reducing the water absorption.
4.2. Sorptivity test The comparison of Cumulative water absorption values of CC, R10, R20, R30, R40 is shown in Fig. 10 and The slope of best fitting line was reported as the Sorptivity of concrete with various TUFS replacement after 114 hrs is shown in Fig. 11. It was observed that in general, there was decrease in sorptivity value for all the mixtures with TUFS when compared to the CC at the initial stage. R, Siddique et al. [26] reported that compressive strength increased as sorptivity decreased and vice versa. In our previous work [4] the strength was increased up to R30 compared to CC, which was correlated with the above statement.
4. Results and discussion 4.1. Water absorption test The results of water absorption test at the age of 28 days and 90 days and influence of different ratios of TUFS in concrete Table 3 Composition for marine water. Composition
Concentration g/l
NaCl Magnesium chloride Sodium sulphate Calcium chloride Potassium chloride
24.53 5.2 4.09 1.16 0.695
Fig. 9. Percentage of water absorption for various TUFS replacement.
Fig. 10. Cumulative water absorption vs Time for various TUFS replacement.
Fig. 11. Sorptivity of concrete with various TUFS replacement at 114 h.
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Later there was slight increase in sorptivity value in R40 compared to R30. But at all the time period, there is decrease in sorptivity for R30 when compared to CC. This means that time taken for water to rise by capillary action in R30 was longer. TUFS is finer than normal sand which acts as micro fillers and fills most of the pores in the core portion of concrete. From the test results, it indicates TUFS concrete are less porous and better resistance to transport water compared to CC [27]. The Regression coefficient for sorptivity indices was 0.97, 0.96, 0.97, 0.97 and 0.97 for CC, R10, R20, R20, R30 and R40 respectively were found out through Fig. 10. 4.3. Rapid chloride permeability test The rapid chloride permeability test results for the concrete specimens are shown in Table 4. It can be seen that the Coulomb value decreased with increase in TUFS content up to 30% TUFS, which indicates that concrete becomes denser. However, R40 shows a slight increase in Coulomb value compared to R30. This observation is for concrete at the age of 28 days. All concrete mixtures showed low permeability (Coulombs between 1000 and 2000) as per ASTM C 1202-2012 [22]. Low and moderate chloride ion permeability is the key to good durability. The penetration resistance increased due to reduction in calcium ions in the gel pore fluids and subsequent depletion of pH. As the pore structures become relatively more refined due to pozzolanic reaction, the high conductivity path for the ions will decrease. Singh et al. [15] stated that decrease in chloride ion penetration in concrete by including Waste Foundry Sand, indicate that concrete has become denser and impermeable. This is in good agreement with the findings of this investigation. Maximum reduction in RCPT value is observed at R30 as shown in Fig. 12.It means that at 30% replacement, concrete exhibits more resistance to chloride ion permeability though, all concrete mixtures have low permeability to chloride ion permeability as per ASTM C 1202-2012. Siddique et al. [28] indicated in the study that UFS mixes showed good chloride penetration resistance with low charges passed as per ASTM C 1202-2012[15]. Finer particles of TUFS act as a good filler material and reduce the voids between
Table 4 RCPT results. Sl. No
Mix Proportion
Charges passed in Coulombs
Chloride ion permeability as per ASTM C1202-09
1 2 3 4 5
CC R10 R20 R30 R40
1739 1523 1347 1249 1289
Low Low Low Low Low
Fig. 12. RCPT results.
ingredients of concrete and create a stronger internal structure of concrete matrix. 4.4. Chemical resistance test 4.4.1. Acid attack studies The acid resistance test was conducted separately by using sulphuric acid and hydrochloric acid at the concentration explained already. In H2SO4 environment, the maximum percentage of weight loss was observed for CC at 7, 28, 56 and 90 days as 5.15%, 15.52%, 21.27% and 25.13% respectively. Similarly the percentage of weight loss for R10, R20, R30, and R40 were calculated and shown in Fig. 13. The percentage of weight loss for R30 is 3.79%, 7.42%, 18.87% and 20.95% at7, 28, 56 and 90 days respectively. Maruthachalam et al. [9] stated that the porosity of concrete getting reduced is the reason for the decrease in weight loss. It is correlated with present research work because TUFS is finer than normal sand which fills the pores and decreases the weight loss with an increase in TUFS. This is validated by Scanning Electron Microscopy (SEM) analysis discussed by the authors in a previous work [3] that, the number of voids in the mix has significantly reduced. Significant formation of thin strands is noticed. The paste has spread very finely and firmly throughout the sample and effect of combined paste. From the test results, it is found that percentage of weight loss is higher in CC compared to the concrete with TUFS. This shows that the TUFS concrete has better resistance to acid attack. It is also observed that H2SO4 environment fully erodes the mortar exposing the coarse aggregate as stated by Maruthachalam et al. [9]. Along with percentage of weight loss, the percentage loss of compressive strength also was found out and results are shown in Fig. 14. Maruthachalam et al.[9] reported that the acid attack and leaching away of the calcium compounds of the cement paste formed in concrete during the hydration process as well as calcium in calcareous aggregate reduced the strength of structural concrete and affected the durability. In case of HCl acid environment the leaching is minimum or low, the percentage loss of weight and compressive strength is less compared to H2SO4 acid environment. The percentage of weight and strength loss is shown in Figs. 15 and 16. The maximum percentage weight loss is 4.32% at 90 days for CC which is higher compared to 3.85% for R30 at 90 days. Similarly the strength loss of CC is 33.5% which is higher compared to R30 is 24.53% at 90 days. Concrete cubes exposed to HCl solution showed sign of corrosion by turning brown in colour and also leaching was minimum or low. The compressive strength of concrete mix exposed to HCl environment is significantly reduced because the acid attack completely converts the hardened cement paste destroying the entire pore system. Compared to CC, TUFS concrete performed better because of increase in fineness and rich in silica content leading
Fig. 13. Weight loss under H2SO4 environment.
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Fig. 14. Strength loss under H2SO4 environment. Fig. 17. Weight loss under Na2SO4 environment.
Fig. 15. Weight loss under HCl environment.
Fig. 18. Strength loss under Na2SO4 environment.
Fig. 16. Strength loss under HCl environment.
to durable concrete in acid exposure. There, both acid resistance tests, TUFS concrete mixture R30 mix showed the minimum weight and strength loss percentage compared to remaining mix proportion.
4.4.2. Sulphate attack test The percentage loss in weight as well as compressive strength due to sulphate attack is shown in Figs. 17 and 18 respectively. The percentage weight loss of CC is 0.12%, 0.72%, 0.91% and 1.03% at 7, 28, 60, and 90 days respectively. It is observed that the percentage weight loss is decreased with an increase in TUFS from R10 to R30 and slight increase of R40 at 7, 28, 56, and 90 days. The percentage of weight loss of R30 is 0.02%, 0.11%, 0.6%, and 0.69% at 7, 28, 56 and 90 days respectively which is lower than control concrete and other TUFS concrete. It shows that R30 is optimum compared to remaining replacement. The higher C3A content
in the cement paste makes concrete more vulnerable to sulphate attack. The loss of weight in sulphate environment is less than 1%; hence it is negligible. Rajesh kumar et al. [29] also stated that the percentage of weight loss was not observed much in sulphate resistance test; it seemed to be negligible. The specimens exposed to Na2SO4 environment not show much difference compared to water exposed specimens. The maximum percentage loss in compressive strength was observed for CC as 1.95% at 90 days and for R30, it was 1.51% at 90 days. It is clear that the TUFS as replacement material in concrete enhances the sulphate resistance of concrete.
4.4.3. Marine environment studies The percentage loss in weight and strength was very less at initial stage of 7 days exposure. At later days, the weight loss percentage was somewhat higher in control concrete compared to TUFS replacements. The results are shown in Fig. 19. The percentage of weight loss in CC was 2.05% at 90 days which is higher compared to R10, R20, R30, and R40 values of 1.75%, 1.44%, 1.25% and 1.55% respectively. It shows that R30 was optimum one and weight loss percentage was less compared to remaining mix. The white patches were on the cube specimens after exposing to marine environment. The compressive strength loss percentage was 1.77 for CC which was higher compared with R10, R20, R30 and R40 values of 1.57, 1.44, 1.31 and 1.4 at 90 days respectively as shown in Fig. 20. From the percentage of strength loss results, it is found that there is a decrease with an increase in TUFS concrete. It shows that TUFS concrete shows better resistance in marine environment compared to the control concrete.
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6. In sulphate resistance, percentages of weight loss and strength loss were 1.03 and 1.95 for CC which is more than R30 with a value of 0.69 and 1.51 respectively. It indicates that TUFS concrete shows better sulphate resistance characteristics. 7. Under marine water environment also, percentage of weight loss and strength loss in CC were higher compared to TUFS concrete. Similar to sulphate resistance, TUFS concrete shows better resistance in marine environment compared to the CC. 8. As per this investigation, concrete with 30% TUFS as fine aggregate replacement is found to be very effective under different environmental exposure conditions. Thus the use of Treated Used Foundry Sand in concrete can save the metal industries from the disposal problem and produce greener concrete for construction as an innovative construction material. Fig. 19. Weight loss of under marine environment.
Conflict of interest On behalf of both authors, I wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome. And also I confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed.
References
Fig. 20. Strength loss of under marine environment.
5. Conclusion This study was conducted to investigate the effect of using TUFS as partial replacement of fine aggregate in concrete under various environmental conditions with respect to water absorption, sorptivity, chloride ion penetration, weight and strength loss. The following conclusions are drawn from this study. 1. The percentage of water absorption decreases as TUFS increases compared to control specimens. It is found that R30 showed 23% lower water absorption than control concrete. This indicates that TUFS acts as a good filler material. Further it shows that with increase in curing time, there is decrease in water absorption percentage. 2. Sorptivity value of R30 is 0.040 mm/min0.5 which is lesser compared to CC with value of 0.032 mm/min0.5. It indicates that TUFS concrete is less porous and shows better resistance to transport of water compared to control concrete. 3. All the mix proportion shows good resistance to chloride ion penetration particularly R30 with 40% lower value compared to control concrete. It shows that TUFS concrete offer more resistance to chloride ion permeability. 4. It was observed that the loss in weight of TUFS concrete was found to be 20.95% which is lesser than CC with 25.13% when exposed to H2SO4 for 90 days. Similarly loss in strength of TUFS concrete was 61.8% which is lesser than CC with a value of 72.17%. 5. It was found that the loss in weight was 3.85% for R30 which is lesser than CC with a value of 4.32% when exposed to HCl for 90 days. Similarly loss in strength was 24.53% for R30 which is lesser than CC with a value of 32.74%.
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