Acta Polytechnica CTU Proceedings https://doi.org/10.14311/APP.2022.34.0075 Acta Polytechnica CTU Proceedings 34:75–79, 2022 © 2022 The Author(s). Licensed under a CC-BY 4.0 licence Published by the Czech Technical University in Prague SULPHATE CORROSION OF CEMENT PASTES WITH A HIGH CONTENT OF WASTE MARBLE POWDER Zdeněk Prošeka,b,∗, Pavel Tesáreka a Czech Technical University in Prague, Faculty of Civil Engineering, Thákurova 7, 166 29 Prague 6, Czech Republic b Czech Technical University in Prague, University Centre for Energy Efficient Buildings, Třinecká 1024, 273 43 Buštěhrad, Czech Republic ∗ corresponding author: zdenek.prosek@fsv.cvut.cz Abstract. The article focuses on sulphate corrosion of cement pastes with a high content of waste micronized marble powder. Micronized marble powder is used as a substitute for Portland cement CEM I 42.5R. The amount of micronized marble powder used is from 5 to 50 wt. %. The research also tested a reference mixture composed only of Portland cement. The used accelerated sulphate corrosion consists of cyclic saturation and drying with 10% Na2SO4 solution for 56 days. During sulphate corrosion, samples are placed in a controlled environment at 5 ± 1 ◦C and 85 % relative humidity to allow thaumasite to form. During cycling, samples were continuously visually monitored and documented. Subsequently, after 56 days, the samples were destructively tested for compressive strength. The research revealed a negative effect of micronized marble powder on the resistance to sulphate corrosion, where in contrast to the reference mixture the decrease in compressive strength is up to twofold. Keywords: Sulphate corrosion, thaumasite, cement pastes, visual inspection, compressive strength. 1. Introduction Currently, the most common way to use recycled marble waste is to apply it to cement-based compos- ite materials. Cement-based composite materials (in the form of monolithic reinforced concrete, prefabri- cated parts, etc.) are currently probably the most widespread and most used building material in world. From the point of view of sustainable development, three basic components (cement, sand and water) are needed for the production of cement composite. How- ever, their extraction, treatment and processing have negative effect on nature and the environment [1]. Specifically, cement production accounts for 7 % of global CO2 production and large amounts of NOx. The use of recycled marble in the form of admixtures will significantly reduce the cost of raw material for concrete [2]. For example, the use of waste marble powder in a cement composite reduces CO2 emissions by 12 % and reduces the cost of the composite from 40 USD/m3 on 33 USD/m3 [3]. One of the most common applications of marble powder is in the form of admixtures, where it forms a substitute for a binder. When replacing up to 15 wt. % there is no significant decrease of mechanical proper- ties [4–7] and when replacing 50 wt. % cement pastes have twice value the flexural strength [5]. According to the ČSN EN 206 standard, marble powder is considered as an inert admixture, which does not participate in the hydration of cement. In the case of white and beige marble, it is a mineral filler that contains more than 75 % CaCO3 [8]. The chemical composition is very similar to limestone, which does not behave completely inertly during the hydration of cement [9]. Fine limestone grains act in the cement as nucleation centers for CH crystals and accelerate the hydration of silicate and aluminate phases. As a result, it affects the initial increase in the strength of the ce- ment composite and accelerates the setting and curing time. In addition, even finely ground limestone can participate in hydration processes. It is mainly the hy- dration of C3S from clinker to form calcium carbonate aluminate hydrate (3CaO · Al2O3 · 3CaCO3 · 32H2O) in cements with a higher content of C3A. Tricar- bonate can transform into a more stable monocar- bonate [10] in later stages. The biggest disadvan- tage of limestone, and thus of sediment formed from CaCO3, is its sulphate corrosion in combination with silicates in a C-S-H gel. During sulphate corrosion at lower temperatures, crystalline thaumasite is formed (CaSiO3 · CaCO3 · CaSO4 · 15H2O), which by volume changes it disrupts the structure, thus deteriorating the mechanical properties and integrity of the cement composite [11]. This article investigates the sulphate corrosion re- sistance of a cement composite containing waste mar- ble powder. Marble (crystalline CaCO3) has a simi- lar chemical composition to limestone (sedimentary CaCO3) and thus thaumisite can form during sulphate corrosion, which negatively affects the durability of structures. The sulphate corrosion of a cement com- posite containing marble powder and limestone pow- der was deal in an experimental study by M. Uysal et al. [12]. The results of the experiments were the 75 https://doi.org/10.14311/APP.2022.34.0075 https://creativecommons.org/licenses/by/4.0/ https://www.cvut.cz/en Zdeněk Prošek, Pavel Tesárek Acta Polytechnica CTU Proceedings Set Percentage CEM I 42,5R Micronized marble Water ratio replacement [%] [kg] powder [kg] w/b M0 0 3.00 0.00 0.35 M5 5 2.85 0.15 0.32 M10 10 2.70 0.30 0.32 M15 15 2.55 0.45 0.32 M50 50 1.50 1.50 0.32 Table 1. Composition of tested sets. 0,E+0 5,E+4 1,E+5 2,E+5 2,E+5 3,E+5 3,E+5 4,E+5 4,E+5 5 15 25 35 45 55 65 75 R e la ti ve in te si ty ( co u n ts ) Position 2ϴ [°] PC WMP ● CaCO3 * Quartz + C3S □ C2S * ● ● ● ● ● ●* ● +□ +□ + +□ +□ □ + 4.0 · 105 3.5 · 105 3.0 · 105 2.5 · 105 2.0 · 105 1.5 · 105 1.0 · 105 0.5 · 105 0.0 +□+□ ● Marble powder CEM 42.5 R Figure 1. XRD patterns for portland cement CEM 42.5R and micronized marble powder. percentage loss of compressive strength, where the samples with reference cement and samples with lime- stone and marble powder had the greatest loss of strength, namely 13 %. Samples with 30 wt. % mar- ble powder as a substitute for cement, which had bet- ter mechanical properties than the reference samples. The loss of strength in this mixture was approximately 9 %. The authors attributed the improvement of the resistance to sulphate corrosion to the reduced poros- ity and especially to the permeability of the cement composite. 2. Materials and samples The experiments were performed on cement pastes, where part of the cement was replaced by waste mi- cronized marble powder. The Used portland cement was CEM 42.5R Radotín. It is a cement with a high C3S content of 74.6 % and a lower C3A content of 8.1 %, C2S 7.2 %, C4AF 8.5 % and MgO 1.6 %. The micronized marble powder was created by recycling waste generated from the process of mining and pro- cessing of marble stone. The recycling of marble waste was performed using a high-speed mill, which guar- antees the separation of individual clumps, reduces the grain size of the material (0–50 microns) and ho- mogenizes the waste material. The research used a high-speed mill from Lavaris s.r.o. S1000. According to XRF analysis, micronized marble powder has a high CaO content of 62.3 % together with a high loss of ignition of 33.7 %. This indicates a high content of CaCO3, which can react to thaumasite during sul- phate corrosion. XRD analysis was performed for confirmation. Figure 1 shows a diffractogram of port- land cement and micronized marble powder. The results confirmed the previous assumption. Thus, the micronized marble powder is composed of 98 wt. % CaCO3 and the remaining 2 wt. % are other clay minerals contained in marble. The composition of all tested mixtures is shown in Table 1. The first mixture was a reference and contained only portland cement. In other mixtures, part of the cement was replaced by micronized marble powder in various weight percentages, from 5 to 50 %. The ratio of water to the total weight of the dry mixture (water-to-binder ratio w/b) was designed to maintain the same workability of the fresh mixtures in flow table test. The flow varied for individual mixtures up to a maximum size of 5 mm. Specifically, the flow was determined to be 180 mm after 15 impacts. All samples tested had nominal dimensions of 40×40×40mm. The samples were produced in steel triple molds whit dimensions of 40×40×160 mm ac- cording to ČSN EN 196-1 [13] and subsequently cut to final dimensions. 6 samples were taken from each set 76 vol. 34/2022 Sulphate corrosion of cement pastes M0 the 1st day the 14th day the 28th day the 56th day M5 M10 M15 M50 Figure 2. Visual determination of sulphate corrosion. (mixture). On the second day after production, the test specimens were demolded and stored loose in a laboratory environment at a temperature of 22 ± 1 ◦C and a relative humidity of 50 ± 2 %. After 28 days, the samples were cut and subjected to sulfate corrosion resistance testing. 77 Zdeněk Prošek, Pavel Tesárek Acta Polytechnica CTU Proceedings 0 0.2 0.4 0.6 0.8 1 1.2 M0 M5 M10 M15 M50 W e ig h t lo ss [ % ] Figure 3. Percentage weight loss due to sulphate corrosion for 56 days, with standard deviations. 0 2 4 6 8 10 12 14 16 18 M0 M5 M10 M15 M50 C o m p re ss iv e s tr en gt h lo ss [ % ] Figure 4. Percentage decrease in compressive strength due to sulphate corrosion for 56 days, with standard deviations. 3. Experimental methods Depending on the composition of the recycled mate- rial, the resistance to sulphate corrosion was solved. ASTM C1012-04 [14] has been modified for this pur- pose. The test samples were stored in a 10% Na2SO4 solution. Due to possible thaumasite formation, the ambient temperature was set to 5 ± 1 ◦C and the rel- ative humidity was 85 ± 5 %. The whole process for accelerated sulfate corrosion was taken from Nielsen et al. [15]. The process uses a cycle of alternating saturation and drying of the samples, where one cycle consists of seven days of saturation of the sample with the solution and then another seven days of its natural drying. The samples were visually inspected during cycling and assessed after each completed cycle. Sub- sequently, the samples were weighed and destructively tested for determining compressive strength. The compressive strength was determined using a Heckert (FP100 model) hydraulic press. The compres- sive strength was determined by a uniaxial pressure test. Testing was controlled by displacement at a constant rate of 3 mm/min. The test was performed on 6 samples with dimensions of 40×40×40 mm. The compressive strength was determined according to ČSN EN 196-1 [13]. The compressive strength of a material is the amount of stress achieved at the point of failure when the integrity of the material is lost. The compressive strength was calculated from the maximum force achieved during the test Fc,max as: fc = Fc,max ab , (1) where: fc is the compressive strength in Pa, Fc,max is the maximum force in N, a is the width of the sample in m, b is the height of the sample in m. Corrosion resistance coefficients were calculated from the obtained compressive strengths of samples in a corrosive environment and samples stored in water, as: kko = fc fref , (2) where: kko is corrosion resistance coefficients, fc is the compressive strength in 10% Na2SO4 solution [Pa], fref is the compressive strength in water [Pa]. 4. Results and discussion The process of visual examination of the tested mix- tures can be observed in Figure 2. The monitored samples M50, M15 and M10 showed visible formation of white crystals on their surface after 14 days of accel- erated sulphate corrosion in 10% Na2SO4, . Reaction of sodium sulfate with the cement matrix at low tem- peratures produced thaumasite crystals with a larger volume. The first cracks formed in all examined sam- ples, except for the reference mixture, after 28 days of sulfate corrosion. These were mainly capillary cracks caused by the crystallization of thaumasite. There was no further expansion of cracks after another 28 days (day 56), but leaching of calcium, which subsequently crystallized on the surface of the tested materials. After 56 days, the cement pastes were tested for weight loss due to calcium leaching (Figure 3) and compressive strength (Figure 4), which are used to determine the corrosion resistance coefficient. All mixtures with marble powder lost weight. The largest weight loss was in the sample M50, namely 0.95 wt. %. This decrease indicates deteriorated sulfate corrosion resistance. The assumption was subsequently confirmed by the compressive strength test, where the sample M50 achieved a 15.5 % lower compressive strength after 56 days in a 10% solution of Na2SO4. The corrosion resistance coefficient was 78 vol. 34/2022 Sulphate corrosion of cement pastes 0.845. The remaining materials with micronized mar- ble powder achieved a corrosion resistance coefficient of 0.9. The results are in agreement with other au- thors who have dealt with sulphate corrosion in their research [16]. In contrast to accelerated sulphate cor- rosion, they used the traditional method, which lasted one (whole) year. After a year, samples composed of 20 wt. % CaCO3 had lower compressive strength by 20 %. 5. Conclusions This work is focused on the effect of waste micronized marble powder on the sulphate corrosion resistance of cement pastes. Accelerated sulfate corrosion at lower temperatures was used. Cement pastes are composed of mixed cement, where micronized marble powder replaces Portland clinker. The micronized marble powder was used in 4 different concentrations, namely: 5 wt. %, 10 wt. %, 15 wt. % and 50 wt. %. Based on the results, it can be concluded that: • Accelerated sulphate corrosion was used, where the results of the reference mixture were comparable to the commonly used sulphate corrosion test. • Samples with micronized marble powder showed visible formation of white crystals on their surface after 14 days and the first cracks appear after 28 days. • All samples with micronized marble powder indicate deteriorated sulfate corrosion resistance by losing your weight. • Samples with micronized marble powder had lower values of compressive strength from 9 to 15 % after sulphate corrosion. The reference mixture had a compressive strength value only lower about 5 %. Future research will build on the results in this article. In the next work, concrete mixtures will be tested. In addition, future research will use an elec- tron microscope to describe the phase changes in the structure of the cement composite. Acknowledgements This paper was financially supported by Czech Tech- nical University in Prague under No. SGS project SGS19/148/OHK1/3T/11. The authors also thank Lavaris Ltd. for the supplied samples and materials. References [1] A. Rana, P. Kalla, H. K. Verma, J. K. Mohnot. Recycling of dimensional stone waste in concrete: A review. Journal of cleaner production 135:312–331, 2016. [2] J. Lederová, P. Leber. Využití průmyslových odpadních materiálů při výrobě stavebních hmot. Stavebnictví 8(04), 2008. [3] H. Ş. Arel. Recyclability of waste marble in concrete production. Journal of Cleaner Production 131:179–188, 2016. [4] M. Singh, A. Srivastava, D. Bhunia. An investigation on effect of partial replacement of cement by waste marble slurry. Construction and Building Materials 134:471–488, 2017. https://doi.org/10.1016/j.conbuildmat.2016.12.155. [5] Z. Prošek, V. Nežerka, P. Tesárek. Enhancing cementitious pastes with waste marble sludge. Construction and Building Materials 255:119372, 2020. [6] M. J. Munir, S. M. S. Kazmi, Y. F. Wu. Efficiency of waste marble powder in controlling alkali–silica reaction of concrete: A sustainable approach. Construction and Building Materials 154:590–599, 2017. [7] A. Khodabakhshian, J. Brito, M. Ghalehnovi, E. Asadi Shamsabadi. Mechanical, environmental and economic performance of structural concrete containing silica fume and marble industry waste powder. Construction and Building Materials 169:237–251, 2018. https://doi.org/10.1016/j.conbuildmat.2018.02.192. [8] ČSN EN 206 +A1. Beton - Specifikace, vlastnosti, výroba a shoda. Praha: Úřad pro technickou normalizaci, metrologii a státní zkušebnictví 2018. [9] R. Hela. Příměsi do betonu. Beton TKS 2:4–10, 2015. [10] J. Lukáš. Současné trendy ve stavebnictví, betony speciálních vlastností. Brno, 2007. [11] J. Bensted. Thaumasite - Background and nature in deterioration of cements, mortars and concretes. Cement and Concrete Composites 21(2):117–121, 1999. https://doi.org/10.1016/S0958-9465(97)00076-0. [12] M. Uysal, M. Sumer. Performance of self-compacting concrete containing different mineral admixtures. Construction and Building materials 25(11):4112–4120, 2011. [13] ČSN EN 196-1. Metody zkoušení cementu. Část 1: Stanovení pevnosti. Praha: Úřad pro technickou normalizaci, metrologii a státní zkušebnictví 2016. [14] ASTM C1012 - 04. Standard Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate Solution. ASTM Standard Test Method 2004. https://doi.org/10.1520/C1012-04. [15] P. Nielsen, S. Nicolai, A. Darimont, X. Kestemont. Influence of cement and aggregate type on thaumasite formation in concrete. Cement and Concrete Composites 53:115–126, 2014. https://doi.org/10.1016/j.cemconcomp.2014.06.011. [16] M. Vyšvařil, M. Rovnaníková. Odolnost jemnozrnných betonů vůči síranové korozi v odpadních systémech. TZB-info 2017. Dostupné z: https://voda.tzb-info.cz/materialy-voda- kanalizace/15420-odolnost-jemnozrnnych-betonu-vuci- siranove-korozi-v-odpadnich-systemech. 79 https://doi.org/10.1016/j.conbuildmat.2016.12.155 https://doi.org/10.1016/j.conbuildmat.2018.02.192 https://doi.org/10.1016/S0958-9465(97)00076-0 https://doi.org/10.1520/C1012-04 https://doi.org/10.1016/j.cemconcomp.2014.06.011 Acta Polytechnica CTU Proceedings 34:75–79, 2022 1 Introduction 2 Materials and samples 3 Experimental methods 4 Results and discussion 5 Conclusions Acknowledgements References