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Influence of Selected Metal Oxides in Micro and Nanoscale on the Mechanical and Physical Properties of the Cement Mortars
Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 172 (2017) 1031 – 1038
Modern Building Materials, Structures and Techniques, MBMST 2016
Influence of selected metal oxides in micro and nanoscale on the mechanical and physical properties of the cement mortars Agnieszka Ślosarczyk*1, Anna Kwiecińska, Emilia Pełszyk Poznan University of Technology, Institute of Structural Engineering, Piotrowo 5 str., Poznan 60-965, Poland
Abstract The paper describes the results of the influence of three metal oxides’ particles: microparticles of Fe2O3 (d ≤ 5μm) and Fe3O4 (d ≤ 5μm) as well as nanoparticles of NiO (d ≤ 50nm) on the cement matrix properties. Four different contents of each metal oxides’ particles were applied: 0.5, 1, 2 and 3 wt.%. The studies regarding different physical and chemical parameters of cement matrix specimens such as compressive strength, water absorption, microscopic and structural properties have been carried out and the results of these studies are presented and discussed. It was shown that the micro and nanoparticles in the amounts of 2÷3 wt.% can influence the cement hydration process and thereby enhance the compressive strength of mortar. The higher enhancement was obtained during the first seven days of hardening due to so called filling effect. In the following stage of hydration the strengthening effect diminished. This phenomena was convergent with the XRD analysis, which proved that the micro- and nano-particles did not react with the cement paste components. © Published by Elsevier Ltd. Ltd. This is an open access article under the CC BY-NC-ND license ©2017 2016The TheAuthors. Authors. Published by Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of MBMST 2016. Peer-review under responsibility of the organizing committee of MBMST 2016 Keywords: silica aerogel; chemical modification; isulation material; BET and TG/DSC analysis.
1. Introduction Quick development of nanotechnology in last years caused that many ideas and concepts came into being. Some of them have already been used in world-wide scale, some are still in a research-phase. The application of these ideas
* Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . E-mail address: [email protected]
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of MBMST 2016
doi:10.1016/j.proeng.2017.02.155
Agnieszka Ślosarczyk et al. / Procedia Engineering 172 (2017) 1031 – 1038
1032
may provide not only with more durable, smarter, and cheaper but also more efficient products. Below is presented the list of feasible developments of nanotechnology in construction industry: x nanoparticles and nanostructures fillers, fibers and admixtures: carbon nanotubes or nanostripes, ceramic nanopowders, nanolayers, which could be incorporated in bulk construction materials or deposited on surfaces as functional reinforcements or films (it confers new or improved properties, like polymer-based nanocomposites with higher fire resistance and durability); x nanostructure modified materials (e.g. steel, cement, composites): development of less energy-demanding cements based on the use of industrial waste residues by enhancing the puzzolanic properties of some of them, synthesis of entirely novel binders (less energy-demanding, environmentally friendly, cheaper) to partly replace Portland cement in concrete like new functional and structural materials; x surface/interface assessment, engineering; special coatings, paints and thin films; integrated structural monitoring and diagnostic systems; self-repairing and smart materials; new thermal and insulation materials; intelligent construction tools, control device/systems; energy applications for buildings – new fuel cells and solar cells; photocatalytic self-cleaning glass; water repellent glazing [1,2]. Since concrete is the main building material, that is used in huge quantities almost everywhere in the world, the scientists have been looking for solutions that can improve its properties. A lot of fillers and additives were tested, added in different amounts, concentration and binding phases. Nanotechnology, as befits interdisciplinary science, resulted with thousands of new researches in this field and of course with new discoveries. Modifications at nanoscale are no longer novelty and nanoparticulated materials are widely used in construction e.g.: carbon black nanoparticles have been added to rubber to increase wear resistance; nanoclay and nanotubes/fibers are used as a reinforcement in high performance composites; nano-silica powders are used as concrete admixtures – improvement of segregation resistance for fresh self-compacting concrete; nano-metallic-oxides are used to improve the mechanical properties of concrete; nanotechnology is used in polymer-modified concrete [3-5]. The most widely used nanoparticles in cement and concrete are nano-oxides, especially SiO2 and Fe2O3. It was found, that addition of nano-SiO2 could significantly increase the compressive strength of concrete, that contains large volume of fly ash and improve pore size distribution by filling the pores between large fly ash and cement particles at nanoscale. Nanosilica is also used in self-compacting concrete in order to improve its segregation resistance. NanoFe2O3 and nano-SiO2 were also used to increase the abrasion resistance of concrete for pavements. Other nanocomposite, such as zeolite, has been added to cement and provided with the improvement of the overall microstructure [6-8]. Relatively little attention in the literature is devoted to the influence of small amounts of micro- and nanoparticles on the cement matrix properties. The nanoparticles as an additive to cement composite are usually used in the amounts exceeding 3 wt.%, mostly 6-7 wt.% and higher [5,9]. Therefore, the aim of this work was to investigate the influence of small amounts of nano- and micro-additives (below 3 wt.%) on the physical, chemical and mechanical properties of the cement matrix. The studies regarding different physical and chemical parameters of cement matrix specimens such as compressive strength, water absorption, microscopic and structural properties have been carried out and the results of these studies are presented and discussed. 2. Experimental part The high-early strength Portland cement CEM I 42.5 R conforming to PN-EN 197-1 standard was used. The other materials used in this study were: normalized sand with particles smaller than 1.0 mm, distilled water, and superplasticizer. The particles of Fe2O3, Fe3O4, NiO were added in the amounts of 0.5%, 1%, 2% and 3% by weight of binder. The properties of micro Fe2O3, Fe3O4 and nano NiO are shown in Table 1. The water-binder ratio for every mixture was 0.5 and the binder content was taken without the amount of nanoparticles. The mixtures’ proportions are given in Table 2. Table 1. The properties of micro-Fe2O3, -Fe3O4 and nano-NiO.
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Fe 2O3
Fe 3O4
NiO
(denoted as F)
(denoted as M)
(denoted as N)
Diameter
≤ 5 μm
≤ 50 μm
≤ 50 nm
Molecular weight
159.69 g/mol
231.53 g/mol
74.69 g/mol
Density
5.12 g/cm 3
4.8 ÷ 5.1 g/cm 3
6.67 g/cm 3
Purity
99.0 %
95.0 %
99.8 %
Table 2. The proportions of cement composite with and without additives. Sample’s name
O F0.5 F1 F2 F3 M0.5 M1 M2 M3 N0.5 N1 N2 N3
Material Cement
Water
Sand
Fe 2O3
Fe 3O4
NiO
Superplasticizer
[g]
[g]
[g]
[g]
[g]
[g]
[ml]
90 90 90 90 90 90 90 90 90 90 90 90 90
45 45 45 45 45 45 45 45 45 45 45 45 45
270 270 270 270 270 270 270 270 270 270 270 270 270
0.45 0.9 1.8 2.7 -
0.45 0.9 1.8 2.7 -
0.45 0.9 1.8 2.7
1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8
Cement, sand and the nanoparticles (if applicable) were firstly mixed together by hand and then the dissolved in water superplasticizer was added. Subsequently, all ingredients were stirred at high speed (350 rpm) for 1.5 min in a vacuum mortar mixer Renfert Twister. The mortar was poured into oiled molds to form cylinders of size 20mm x 20mm x 20mm and cuboids of size 10mm x 10mm x 600mm for all mix proportions. The samples were demolded after 24h and cured in water for 7, 28 and 90 days. Compressive strength tests were performed after 7, 28, and 90 days of curing under water. At each curing time, fifteen to eighteen cylinders of each mixtures were subjected to compressive strength test and the average value was recorded as MPa. This was accomplished using a Zwick Roell Modell Y machine for maximum load of 20 kN. Absorbability test was performed in order to determine the rate of absorption of water by mortar. For this test cuboid samples 10 mm x 10 mm x 600 mm were used. After complete water saturation, samples were placed in drier machine WHL-65B and dried in the temperature of 105°C as long as the constant weight for each sample was noted. Measurements were made with accuracy of 0.2% of weight. The microstructures of hardened control cement paste were investigated with S-3400N Hitachi microscope, using acceleration voltage of electron beam adjusted to 20 keV. The phase composition of the cement mortars, with and without metal oxides was detected with the use of a Bruker X-ray diffractometer, model AXS D8 Advance. 3. Results and discussion 3.1. Mechanical characterization of cement mortars with oxide micro and nanoparticles The compressive strength results of the cement mortars admixed with 0, 0.5, 1, 2 and 3 wt.% of metal oxides (micro-Fe2O3, micro-Fe3O4 and nano-NiO) are presented in Table 3. Table 3. Comparison of compressive strength for cement mortars with and without metallic oxides micro- and nanoparticles after 7, 28 and 90 days of curing (s 7, 28, 90 ± SD – average value of compressive strength with standard deviation after 7, 28 and 90 days of curing, respectively).
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Sample
s7 ± SD
Variation
s28 ± SD
Variation
s90 ± SD
Variation
[MPa]
[%]
[MPa]
[%]
[MPa]
[%]
O
13.9
±
4.3
-
22.5
±
7.2
-
26.6
±
2.4
-
F0.5
15.8
±
1.2
13.4%
22.2
±
4.5
-1.5%
24.0
±
3.7
-9.8%
M0.5
10.4
±
1.8
-24.9%
25.6
±
3.6
13.8%
24.8
±
4.1
-6.6%
N0.5
13.6
±
1.9
-2.0%
27.8
±
2.7
23.5%
27.7
±
3.8
4.3%
F1
15.8
±
2.1
13.8%
30.6
±
4.7
35.8%
23.8
±
4.3
-10.5%
M1
15.7
±
2.4
12.8%
24.1
±
2.4
7.0%
27.5
±
3.3
3.4%
N1
13.7
±
1.8
-1.0%
24.7
±
4.6
9.6%
23.8
±
2.8
-10.4%
F2
17.2
±
2.3
24.0%
33.4
±
3.4
48.2%
29.7
±
3.3
11.6%
M2
19.6
±
3.1
41.0%
23.6
±
3.0
4.9%
27.0
±
2.9
1.5%
N2
19.6
±
3.4
41.2%
25.6
±
4.6
13.5%
30.6
±
5.0
15.4%
F3
21.1
±
3.6
52.3%
27.3
±
3.7
21.3%
30.0
±
3.9
12.8%
M3
20.5
±
3.3
47.6%
25.2
±
4.0
11.9%
29.8
±
4.7
12.1%
N3
21.6
±
3.4
55.9%
24.4
±
4.5
8.4%
31.1
±
4.5
17.0%
Evidently, all the specimens, which contained 2 and 3 wt.% of metal oxides showed an increase in the compressive strength values with increasing age of hydration up to 90 days. The results have shown that the addition of microFe2O3 and nano-NiO in the amount of 1 wt.% and below change the properties of cement matrix, but the results have not been as expected: both, the enhancement and reduction of mechanical properties were noted. However, the cement mortar with micro-Fe2O3 always showed the increase of mechanical properties. Results for samples with particles contribution of 2% and 3% for each metal oxide have shown improvement in all carried tests. What is more, it can be distinguished that the compressive strength’s increase and the hydration process in the first 7 days were very rapid for samples with 2% of Fe3O4 and NiO, and for all samples with 3% of metal oxide additives. Further results for these samples after 28 and 90 days of curing have shown that the increase of compressive strength was still occurring but not in a such fast rate. However, for samples with 2% of Fe 2O3 another relation can be noticed, the most intensive growth of mechanical properties is around the 28th day of hydration process. In the second part of hydration process, after 28 days of curing, the results of compressive strength fluctuate between 22.2 MPa (for 0.5% Fe 2O3) and 33.0 MPa (for 2% Fe2O3) in comparison to pure cement samples (22.5 MPa). Most of the samples, eleven out of twelve, indicated growth of compressive strength. The results of the research after 90 days of curing, revealed that only eight out of twelve mixtures’ types characterized with increased compressive strength in comparison to pure samples. Four of them, had smaller compressive strength (from 23.8 MPa for 1% Fe 2O3 to 24.8 MPa for 0.5% Fe3O4) than in case of pure mortar (26.6 MPa). Moreover, the increase of the compressive strength is considerably smaller than in previous results (after 7 and 28 days of curing). The enhancement was only from 1.52% (for 2% Fe3O4) to 17.02% (for 3% NiO) in comparison to pure cement mortar. Eventually, it can be distinguished that the best enhancement of the compressive strength for examined samples was noticed for cement mortars with 3 wt.% of metal oxide addition in the whole period of hydration. It can be also noticed that the most effective results were obtained for the specimens with 3 wt.% of nano-NiO, with the final 90 days compressive strength improved by 17%. The density and water absorbability results of the cement mortars admixed with 0, 0.5, 1, 2 and 3 wt.% of metal oxides (micro-Fe2O3, micro-Fe3O4 and nano-NiO) are presented in Table 4. It was shown that in eight out of twelve cases the addition of particles have reduced mortar’ absorbability. For all samples containing 2 and 3 wt.% of additives the improvement in the range from 2% (for samples which contained 3 wt.% NiO) to 10% (for 2 wt.% Fe 2O3) was observed. Samples with 0.5% of additives have shown small reduction of absorbability which oscillated in the range from 0.3% to 2.7%. None of the samples, containing 1 wt.% of particles, have shown any enhancement. The best results for all three types of particles were noted for 2% content of additives. In ten out of twelve cases the addition
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of metal oxide particles have increased concrete’ density. For all samples containing 2 and 3 wt.% of additives the increase in range from 1.42% (for samples containing 2 wt.% Fe3O4) to 5.41% (for samples with 3% Fe2O3) was observed. Addition of Fe3O4 in all concentrations increased density in comparison with pure samples: from 0.91% to 3.73% enhancement, for 0.5 and 3 wt.% content of Fe3O4 respectively. The significant increase of density was observed for Fe2O3 – the two highest increases were noted for this metal oxide: 4.61% and 5.41%, for 2 and 3 wt.% particles’ concentration, respectively. Table 4. The density and water absorbability results of the cement mortars admixed with 0, 0.5, 1, 2 and 3 wt.% of metal oxides.
Pure sample
Water absorbability, wt.%
Density, g/cm3
9.3
1.96
Fe2O3
Fe3O4
NiO
Fe2O3
Fe3O4
NiO
0.5 %
9.5
9.3
9.0
1.94
1.98
1.99
1.0 %
9.4
9.5
9.5
1.99
2.00
1.94
2.0 %
8.3
8.6
9.0
2.05
1.99
2.03
3.0 %
8.7
9.0
9.1
2.07
2.03
2.02
3.2. XRD and SEM characterization of cement mortars with oxide micro and nanoparticles Analysis of the phase composition of the cement mortars with addition of micro-Fe2O3, micro-Fe3O4 and nano-NiO is presented in Figure 1. Analysis of pure mortar presented in Figure 1a shows typical phases present in mortar based on clinker cement without pozzolanic additives, that is: calcium silicates, brownmillerite, quarz, portlandite, etringite, gypsum and calcium carbonate. In case of a mortar with the addition of micro-Fe2O3, micro-Fe3O4 and nano-NiO (Fig. 1 b, c, d, respectively), the X-ray structural analysis proved the presence of all oxides in the cement mortar. A comparison of phases present in pure cement mortar and in mortars with additions of metal oxides implies a lack of chemical reaction between additives and cement paste. The analysis of the microstructure of the cement mortars with and without addition of micro-Fe2O3, micro-Fe3O4 and nano-NiO is presented in Figure 2. In the all pictures it is seen a well crystallised phase C-S-H. Microstructure is coherent and well compacted, in case of pure cement mortar, as well as in case of mortars with micro and nanoparticles of metal oxides. For cement mortar with nano-NiO between C-S-H phase there are visible small agglomerates of nanoparticles.
(a)
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(b)
(c)
(d) Fig. 1. Phase composition of cement mortars with micro-Fe2O3, micro-Fe3O4 and nano-NiO.
Agnieszka Ślosarczyk et al. / Procedia Engineering 172 (2017) 1031 – 1038
Pure cement mortar
Cement mortar with Fe2O3
Cement mortar with Fe3O4
Cement mortar with NiO
Fig. 2. SEM photography of pure cement mortar and with micro and nanoparticles of metal oxides.
4. Conclusions Observable influence of particles’ presence in cement paste on the mechanical and physical properties of investigated samples lets to conclude that as small amounts of micro and nanoparticles as 2÷3 wt.% can influence the cement hydration process and thereby enhance the strength of mortar. The biggest enhancement after 7 days of curing is connected with so called filling effect. Small particles fill the gaps between cement particles and as consequence more dense, stronger and water resistant structure can be obtained. Thereby, the microstructure of cement paste is more compacted and the adhesion of cement paste to aggregate is increased. Result of that is a significant improvement of compressive strength in comparison with samples without metal oxide additives. References [1] A. Porro, Integration of European nanotechnology research in construction, in The 1st International Symposium of Nanotechnology Construction, Paisley, Scotland, 2003. [2] W. Zhu, J. Gibbs and B. J.M., Application of nanotechnology in construction – current status and future potential, in The 1st International Symposium of Nanotechnology Construction, Paisley, Scotland, 2003. [3] N. Stankiewicz and M. Lelusz, Nanotechnologia w budownictwie – przegląd zastosowań, Civil and Environmental Engineering 5 (2014) 101112.
1037
1038
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[4] J. Makar and J. Beaudoin, Carbon nanotubes and their application in the construction industry, in The 1st International Symposium of Nanotechnology Construction, Paisley, Scotland, 2003. [5] L. Hui, X. Hui-gang and O. Jin-ping, A study on mechanical and pressure-sensitive properties of cement mortar with nanophase materials, Cement and Concrete Research 34 (2004) 435-438. [6] B. Bhuvaneshwari, S. Sasmal, T. Baskaran and N. Iyer, Role of nano-oxides for improving cementitious building, Journal of Civil Engineering and Science 1 (2012) 52-58. [7] F. Sanchez and K. Sobolev, Nanotechnology in concrete – a review, Construction and Building Materials 24 (2010) 2060-2071. [8] G. Quercia and H. Brouwers, Application of nano-silica (nS) in concrete mixtures, in 8th fib PhD Symposium, Kgs. Lyngby, Denmark, 2010. [9] H. S. Lee, J-Y. Lee, M-Y. Yu, Influence of iron oxide pigments on the properties of concrete interlocking blocks, Cement and Concrete Research 11 (2003) 1889-1896.
ScienceDirect Procedia Engineering 172 (2017) 1031 – 1038
Modern Building Materials, Structures and Techniques, MBMST 2016
Influence of selected metal oxides in micro and nanoscale on the mechanical and physical properties of the cement mortars Agnieszka Ślosarczyk*1, Anna Kwiecińska, Emilia Pełszyk Poznan University of Technology, Institute of Structural Engineering, Piotrowo 5 str., Poznan 60-965, Poland
Abstract The paper describes the results of the influence of three metal oxides’ particles: microparticles of Fe2O3 (d ≤ 5μm) and Fe3O4 (d ≤ 5μm) as well as nanoparticles of NiO (d ≤ 50nm) on the cement matrix properties. Four different contents of each metal oxides’ particles were applied: 0.5, 1, 2 and 3 wt.%. The studies regarding different physical and chemical parameters of cement matrix specimens such as compressive strength, water absorption, microscopic and structural properties have been carried out and the results of these studies are presented and discussed. It was shown that the micro and nanoparticles in the amounts of 2÷3 wt.% can influence the cement hydration process and thereby enhance the compressive strength of mortar. The higher enhancement was obtained during the first seven days of hardening due to so called filling effect. In the following stage of hydration the strengthening effect diminished. This phenomena was convergent with the XRD analysis, which proved that the micro- and nano-particles did not react with the cement paste components. © Published by Elsevier Ltd. Ltd. This is an open access article under the CC BY-NC-ND license ©2017 2016The TheAuthors. Authors. Published by Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of MBMST 2016. Peer-review under responsibility of the organizing committee of MBMST 2016 Keywords: silica aerogel; chemical modification; isulation material; BET and TG/DSC analysis.
1. Introduction Quick development of nanotechnology in last years caused that many ideas and concepts came into being. Some of them have already been used in world-wide scale, some are still in a research-phase. The application of these ideas
* Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . E-mail address: [email protected]
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of MBMST 2016
doi:10.1016/j.proeng.2017.02.155
Agnieszka Ślosarczyk et al. / Procedia Engineering 172 (2017) 1031 – 1038
1032
may provide not only with more durable, smarter, and cheaper but also more efficient products. Below is presented the list of feasible developments of nanotechnology in construction industry: x nanoparticles and nanostructures fillers, fibers and admixtures: carbon nanotubes or nanostripes, ceramic nanopowders, nanolayers, which could be incorporated in bulk construction materials or deposited on surfaces as functional reinforcements or films (it confers new or improved properties, like polymer-based nanocomposites with higher fire resistance and durability); x nanostructure modified materials (e.g. steel, cement, composites): development of less energy-demanding cements based on the use of industrial waste residues by enhancing the puzzolanic properties of some of them, synthesis of entirely novel binders (less energy-demanding, environmentally friendly, cheaper) to partly replace Portland cement in concrete like new functional and structural materials; x surface/interface assessment, engineering; special coatings, paints and thin films; integrated structural monitoring and diagnostic systems; self-repairing and smart materials; new thermal and insulation materials; intelligent construction tools, control device/systems; energy applications for buildings – new fuel cells and solar cells; photocatalytic self-cleaning glass; water repellent glazing [1,2]. Since concrete is the main building material, that is used in huge quantities almost everywhere in the world, the scientists have been looking for solutions that can improve its properties. A lot of fillers and additives were tested, added in different amounts, concentration and binding phases. Nanotechnology, as befits interdisciplinary science, resulted with thousands of new researches in this field and of course with new discoveries. Modifications at nanoscale are no longer novelty and nanoparticulated materials are widely used in construction e.g.: carbon black nanoparticles have been added to rubber to increase wear resistance; nanoclay and nanotubes/fibers are used as a reinforcement in high performance composites; nano-silica powders are used as concrete admixtures – improvement of segregation resistance for fresh self-compacting concrete; nano-metallic-oxides are used to improve the mechanical properties of concrete; nanotechnology is used in polymer-modified concrete [3-5]. The most widely used nanoparticles in cement and concrete are nano-oxides, especially SiO2 and Fe2O3. It was found, that addition of nano-SiO2 could significantly increase the compressive strength of concrete, that contains large volume of fly ash and improve pore size distribution by filling the pores between large fly ash and cement particles at nanoscale. Nanosilica is also used in self-compacting concrete in order to improve its segregation resistance. NanoFe2O3 and nano-SiO2 were also used to increase the abrasion resistance of concrete for pavements. Other nanocomposite, such as zeolite, has been added to cement and provided with the improvement of the overall microstructure [6-8]. Relatively little attention in the literature is devoted to the influence of small amounts of micro- and nanoparticles on the cement matrix properties. The nanoparticles as an additive to cement composite are usually used in the amounts exceeding 3 wt.%, mostly 6-7 wt.% and higher [5,9]. Therefore, the aim of this work was to investigate the influence of small amounts of nano- and micro-additives (below 3 wt.%) on the physical, chemical and mechanical properties of the cement matrix. The studies regarding different physical and chemical parameters of cement matrix specimens such as compressive strength, water absorption, microscopic and structural properties have been carried out and the results of these studies are presented and discussed. 2. Experimental part The high-early strength Portland cement CEM I 42.5 R conforming to PN-EN 197-1 standard was used. The other materials used in this study were: normalized sand with particles smaller than 1.0 mm, distilled water, and superplasticizer. The particles of Fe2O3, Fe3O4, NiO were added in the amounts of 0.5%, 1%, 2% and 3% by weight of binder. The properties of micro Fe2O3, Fe3O4 and nano NiO are shown in Table 1. The water-binder ratio for every mixture was 0.5 and the binder content was taken without the amount of nanoparticles. The mixtures’ proportions are given in Table 2. Table 1. The properties of micro-Fe2O3, -Fe3O4 and nano-NiO.
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Fe 2O3
Fe 3O4
NiO
(denoted as F)
(denoted as M)
(denoted as N)
Diameter
≤ 5 μm
≤ 50 μm
≤ 50 nm
Molecular weight
159.69 g/mol
231.53 g/mol
74.69 g/mol
Density
5.12 g/cm 3
4.8 ÷ 5.1 g/cm 3
6.67 g/cm 3
Purity
99.0 %
95.0 %
99.8 %
Table 2. The proportions of cement composite with and without additives. Sample’s name
O F0.5 F1 F2 F3 M0.5 M1 M2 M3 N0.5 N1 N2 N3
Material Cement
Water
Sand
Fe 2O3
Fe 3O4
NiO
Superplasticizer
[g]
[g]
[g]
[g]
[g]
[g]
[ml]
90 90 90 90 90 90 90 90 90 90 90 90 90
45 45 45 45 45 45 45 45 45 45 45 45 45
270 270 270 270 270 270 270 270 270 270 270 270 270
0.45 0.9 1.8 2.7 -
0.45 0.9 1.8 2.7 -
0.45 0.9 1.8 2.7
1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8
Cement, sand and the nanoparticles (if applicable) were firstly mixed together by hand and then the dissolved in water superplasticizer was added. Subsequently, all ingredients were stirred at high speed (350 rpm) for 1.5 min in a vacuum mortar mixer Renfert Twister. The mortar was poured into oiled molds to form cylinders of size 20mm x 20mm x 20mm and cuboids of size 10mm x 10mm x 600mm for all mix proportions. The samples were demolded after 24h and cured in water for 7, 28 and 90 days. Compressive strength tests were performed after 7, 28, and 90 days of curing under water. At each curing time, fifteen to eighteen cylinders of each mixtures were subjected to compressive strength test and the average value was recorded as MPa. This was accomplished using a Zwick Roell Modell Y machine for maximum load of 20 kN. Absorbability test was performed in order to determine the rate of absorption of water by mortar. For this test cuboid samples 10 mm x 10 mm x 600 mm were used. After complete water saturation, samples were placed in drier machine WHL-65B and dried in the temperature of 105°C as long as the constant weight for each sample was noted. Measurements were made with accuracy of 0.2% of weight. The microstructures of hardened control cement paste were investigated with S-3400N Hitachi microscope, using acceleration voltage of electron beam adjusted to 20 keV. The phase composition of the cement mortars, with and without metal oxides was detected with the use of a Bruker X-ray diffractometer, model AXS D8 Advance. 3. Results and discussion 3.1. Mechanical characterization of cement mortars with oxide micro and nanoparticles The compressive strength results of the cement mortars admixed with 0, 0.5, 1, 2 and 3 wt.% of metal oxides (micro-Fe2O3, micro-Fe3O4 and nano-NiO) are presented in Table 3. Table 3. Comparison of compressive strength for cement mortars with and without metallic oxides micro- and nanoparticles after 7, 28 and 90 days of curing (s 7, 28, 90 ± SD – average value of compressive strength with standard deviation after 7, 28 and 90 days of curing, respectively).
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Sample
s7 ± SD
Variation
s28 ± SD
Variation
s90 ± SD
Variation
[MPa]
[%]
[MPa]
[%]
[MPa]
[%]
O
13.9
±
4.3
-
22.5
±
7.2
-
26.6
±
2.4
-
F0.5
15.8
±
1.2
13.4%
22.2
±
4.5
-1.5%
24.0
±
3.7
-9.8%
M0.5
10.4
±
1.8
-24.9%
25.6
±
3.6
13.8%
24.8
±
4.1
-6.6%
N0.5
13.6
±
1.9
-2.0%
27.8
±
2.7
23.5%
27.7
±
3.8
4.3%
F1
15.8
±
2.1
13.8%
30.6
±
4.7
35.8%
23.8
±
4.3
-10.5%
M1
15.7
±
2.4
12.8%
24.1
±
2.4
7.0%
27.5
±
3.3
3.4%
N1
13.7
±
1.8
-1.0%
24.7
±
4.6
9.6%
23.8
±
2.8
-10.4%
F2
17.2
±
2.3
24.0%
33.4
±
3.4
48.2%
29.7
±
3.3
11.6%
M2
19.6
±
3.1
41.0%
23.6
±
3.0
4.9%
27.0
±
2.9
1.5%
N2
19.6
±
3.4
41.2%
25.6
±
4.6
13.5%
30.6
±
5.0
15.4%
F3
21.1
±
3.6
52.3%
27.3
±
3.7
21.3%
30.0
±
3.9
12.8%
M3
20.5
±
3.3
47.6%
25.2
±
4.0
11.9%
29.8
±
4.7
12.1%
N3
21.6
±
3.4
55.9%
24.4
±
4.5
8.4%
31.1
±
4.5
17.0%
Evidently, all the specimens, which contained 2 and 3 wt.% of metal oxides showed an increase in the compressive strength values with increasing age of hydration up to 90 days. The results have shown that the addition of microFe2O3 and nano-NiO in the amount of 1 wt.% and below change the properties of cement matrix, but the results have not been as expected: both, the enhancement and reduction of mechanical properties were noted. However, the cement mortar with micro-Fe2O3 always showed the increase of mechanical properties. Results for samples with particles contribution of 2% and 3% for each metal oxide have shown improvement in all carried tests. What is more, it can be distinguished that the compressive strength’s increase and the hydration process in the first 7 days were very rapid for samples with 2% of Fe3O4 and NiO, and for all samples with 3% of metal oxide additives. Further results for these samples after 28 and 90 days of curing have shown that the increase of compressive strength was still occurring but not in a such fast rate. However, for samples with 2% of Fe 2O3 another relation can be noticed, the most intensive growth of mechanical properties is around the 28th day of hydration process. In the second part of hydration process, after 28 days of curing, the results of compressive strength fluctuate between 22.2 MPa (for 0.5% Fe 2O3) and 33.0 MPa (for 2% Fe2O3) in comparison to pure cement samples (22.5 MPa). Most of the samples, eleven out of twelve, indicated growth of compressive strength. The results of the research after 90 days of curing, revealed that only eight out of twelve mixtures’ types characterized with increased compressive strength in comparison to pure samples. Four of them, had smaller compressive strength (from 23.8 MPa for 1% Fe 2O3 to 24.8 MPa for 0.5% Fe3O4) than in case of pure mortar (26.6 MPa). Moreover, the increase of the compressive strength is considerably smaller than in previous results (after 7 and 28 days of curing). The enhancement was only from 1.52% (for 2% Fe3O4) to 17.02% (for 3% NiO) in comparison to pure cement mortar. Eventually, it can be distinguished that the best enhancement of the compressive strength for examined samples was noticed for cement mortars with 3 wt.% of metal oxide addition in the whole period of hydration. It can be also noticed that the most effective results were obtained for the specimens with 3 wt.% of nano-NiO, with the final 90 days compressive strength improved by 17%. The density and water absorbability results of the cement mortars admixed with 0, 0.5, 1, 2 and 3 wt.% of metal oxides (micro-Fe2O3, micro-Fe3O4 and nano-NiO) are presented in Table 4. It was shown that in eight out of twelve cases the addition of particles have reduced mortar’ absorbability. For all samples containing 2 and 3 wt.% of additives the improvement in the range from 2% (for samples which contained 3 wt.% NiO) to 10% (for 2 wt.% Fe 2O3) was observed. Samples with 0.5% of additives have shown small reduction of absorbability which oscillated in the range from 0.3% to 2.7%. None of the samples, containing 1 wt.% of particles, have shown any enhancement. The best results for all three types of particles were noted for 2% content of additives. In ten out of twelve cases the addition
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of metal oxide particles have increased concrete’ density. For all samples containing 2 and 3 wt.% of additives the increase in range from 1.42% (for samples containing 2 wt.% Fe3O4) to 5.41% (for samples with 3% Fe2O3) was observed. Addition of Fe3O4 in all concentrations increased density in comparison with pure samples: from 0.91% to 3.73% enhancement, for 0.5 and 3 wt.% content of Fe3O4 respectively. The significant increase of density was observed for Fe2O3 – the two highest increases were noted for this metal oxide: 4.61% and 5.41%, for 2 and 3 wt.% particles’ concentration, respectively. Table 4. The density and water absorbability results of the cement mortars admixed with 0, 0.5, 1, 2 and 3 wt.% of metal oxides.
Pure sample
Water absorbability, wt.%
Density, g/cm3
9.3
1.96
Fe2O3
Fe3O4
NiO
Fe2O3
Fe3O4
NiO
0.5 %
9.5
9.3
9.0
1.94
1.98
1.99
1.0 %
9.4
9.5
9.5
1.99
2.00
1.94
2.0 %
8.3
8.6
9.0
2.05
1.99
2.03
3.0 %
8.7
9.0
9.1
2.07
2.03
2.02
3.2. XRD and SEM characterization of cement mortars with oxide micro and nanoparticles Analysis of the phase composition of the cement mortars with addition of micro-Fe2O3, micro-Fe3O4 and nano-NiO is presented in Figure 1. Analysis of pure mortar presented in Figure 1a shows typical phases present in mortar based on clinker cement without pozzolanic additives, that is: calcium silicates, brownmillerite, quarz, portlandite, etringite, gypsum and calcium carbonate. In case of a mortar with the addition of micro-Fe2O3, micro-Fe3O4 and nano-NiO (Fig. 1 b, c, d, respectively), the X-ray structural analysis proved the presence of all oxides in the cement mortar. A comparison of phases present in pure cement mortar and in mortars with additions of metal oxides implies a lack of chemical reaction between additives and cement paste. The analysis of the microstructure of the cement mortars with and without addition of micro-Fe2O3, micro-Fe3O4 and nano-NiO is presented in Figure 2. In the all pictures it is seen a well crystallised phase C-S-H. Microstructure is coherent and well compacted, in case of pure cement mortar, as well as in case of mortars with micro and nanoparticles of metal oxides. For cement mortar with nano-NiO between C-S-H phase there are visible small agglomerates of nanoparticles.
(a)
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(b)
(c)
(d) Fig. 1. Phase composition of cement mortars with micro-Fe2O3, micro-Fe3O4 and nano-NiO.
Agnieszka Ślosarczyk et al. / Procedia Engineering 172 (2017) 1031 – 1038
Pure cement mortar
Cement mortar with Fe2O3
Cement mortar with Fe3O4
Cement mortar with NiO
Fig. 2. SEM photography of pure cement mortar and with micro and nanoparticles of metal oxides.
4. Conclusions Observable influence of particles’ presence in cement paste on the mechanical and physical properties of investigated samples lets to conclude that as small amounts of micro and nanoparticles as 2÷3 wt.% can influence the cement hydration process and thereby enhance the strength of mortar. The biggest enhancement after 7 days of curing is connected with so called filling effect. Small particles fill the gaps between cement particles and as consequence more dense, stronger and water resistant structure can be obtained. Thereby, the microstructure of cement paste is more compacted and the adhesion of cement paste to aggregate is increased. Result of that is a significant improvement of compressive strength in comparison with samples without metal oxide additives. References [1] A. Porro, Integration of European nanotechnology research in construction, in The 1st International Symposium of Nanotechnology Construction, Paisley, Scotland, 2003. [2] W. Zhu, J. Gibbs and B. J.M., Application of nanotechnology in construction – current status and future potential, in The 1st International Symposium of Nanotechnology Construction, Paisley, Scotland, 2003. [3] N. Stankiewicz and M. Lelusz, Nanotechnologia w budownictwie – przegląd zastosowań, Civil and Environmental Engineering 5 (2014) 101112.
1037
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[4] J. Makar and J. Beaudoin, Carbon nanotubes and their application in the construction industry, in The 1st International Symposium of Nanotechnology Construction, Paisley, Scotland, 2003. [5] L. Hui, X. Hui-gang and O. Jin-ping, A study on mechanical and pressure-sensitive properties of cement mortar with nanophase materials, Cement and Concrete Research 34 (2004) 435-438. [6] B. Bhuvaneshwari, S. Sasmal, T. Baskaran and N. Iyer, Role of nano-oxides for improving cementitious building, Journal of Civil Engineering and Science 1 (2012) 52-58. [7] F. Sanchez and K. Sobolev, Nanotechnology in concrete – a review, Construction and Building Materials 24 (2010) 2060-2071. [8] G. Quercia and H. Brouwers, Application of nano-silica (nS) in concrete mixtures, in 8th fib PhD Symposium, Kgs. Lyngby, Denmark, 2010. [9] H. S. Lee, J-Y. Lee, M-Y. Yu, Influence of iron oxide pigments on the properties of concrete interlocking blocks, Cement and Concrete Research 11 (2003) 1889-1896.