Sulfate Resistance Of Concrete Research Articles

Investigating the sulfate resistance of mortars with multiple mineral admixtures in ammonium–magnesium sulfate solution

Sulfate resistance is evaluated in mortars containing sulfate-resistant cementitious materials (SRCMs) developed by mixing ground granulated blast furnace slag, fly ash, silica fume and desulfurisation gypsum. Compressive strength testing, X-ray diffraction analysis, differential thermal analysis and mercury intrusion porosimetry are carried out. Results show that the sulfate resistance of mortars mixed with SRCMs at a replacement percentage of 74 wt% is superior to that of mortars with 30 wt% fly ash when exposed to drying–wetting cycles in sodium sulfate solution, because adding SRCMs decreases the calcium hydroxide content, causing a reduction in gypsum formation. Moreover, reducing the water-to-binder ratio (W/B) from 0.50 to 0.35 increases the loss of compressive strength ratio (Lf) of mortars with SRCMs immersed in ammonium–magnesium sulfate complex solution. Specifically, the Lf values of mortars with W/B of 0.50 and 0.35 are 42.7% and 36.0% after 100 days of immersion, respectively. Furthermore, the main component of samples subjected to complex solution is identified as gypsum. In addition, both Lf and porosity exhibit a strong linear positive correlation with W/B. Finally, the findings confirm that optimising the composition of cementitious materials and lowering W/B could improve the sulfate resistance of concretes used for a sulfate-rich sewage environment.

Impact of treatment temperature of metakaolin on strength and sulfate resistance of concrete

Calcined clay, a widely studied supplementary cementitious material, has shown positive impacts on concrete's microstructural properties, strength development, and durability. The variation in raw clay mineral concentration across different locations influences the optimal calcination temperature needed to activate its pozzolanic reactivity. This investigation focuses on studying the effects of calcination temperature on the characterization and pozzolanic reactivity of Nigerian Kaolinite clay. The clay was calcined at temperatures ranging from 600˚C to 900˚C for 2 hours. Characterization involved X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Scanning Electron Microscope (SEM) analyses. Blended mixtures, incorporating 10%, 20%, 30%, and 40% metakaolin as cement replacement, were assessed for workability, strength, and durability properties at 7, 14, 28, and 56 days to determine the clay's pozzolanic reactivity. XRF categorized the metakaolin as a class N pozzolan, while XRD indicated that 800˚C for 2 hours was necessary for complete dihydroxylation. Compressive, tensile, and sulfate resistance tests confirmed that treating the clay at 800˚C for 2 hours optimized its performance. The mix with 10% metakaolin outperformed the control by 6.4%, 14.7%, and 14.1% in compressive strength at 14th, 28th, and 56th days, respectively. While the best performance was at 10% replacement, levels up to 30% also demonstrated satisfactory results compared to the control, showing potential for achieving desired strengths. Linear regression models were also developed to establish the relationship between compressive and split tensile strengths across curing periods. The resulting equations demonstrate excellent predictive performance with correlation coefficients ranging from 0.928 to 0.991.

Durability of Green Concrete in Severe Environment

In this paper, the effects of different mineral admixtures and sulfate solution types on the appearance, mass change rate, relative dynamic elastic modulus, and corrosion resistance coefficient of concrete were systematically studied. X-ray Diffraction (XRD), Mercury Intrusion Porosimetry (MIP), Scanning Electron Microscopy (SEM), and X-ray Computed Tomography (X-CT) were used to explore and analyze the changes in the microstructure and the corrosion products of concrete in the sulfate solution. The results show that the existence of magnesium ions accelerates concrete deterioration. There is a critical dosage of fly ash for magnesium sulfate resistance of concrete. The magnesium sulfate resistance of concrete is improved when the fly ash content is less than 20%. Slag can significantly improve the corrosion resistance of concrete to magnesium sulfate. The diffusion of sulfate ions into concrete is a gradual process. In the early stages of corrosion, sulfate ion content in the concrete immersed in the magnesium sulfate solution is slightly less than that of the concrete immersed in the sodium sulfate solution. However, in the later stage of corrosion, the sulfate ion content in the concrete immersed in the magnesium sulfate solution is significantly higher than that of the concrete immersed in the sodium sulfate solution.

Long-Term Performance of Concrete Made with Different Types of Cement under Severe Sulfate Exposure

Concrete sulfate attack is of great interest as it represents one of the main reasons of concrete deterioration and poor durability for concrete structures. In this research, the effect of different cement types on concrete sulfate resistance was investigated. This included three concrete classes, namely, low strength concrete, medium strength concrete, and high strength concrete. Blast furnace cement (BFC), sulfate resisting Portland cement (CEM I-SR5), and ordinary Portland cement (OPC) were used in a total of eighteen concrete mixes. Three binder contents of 250 kg/m3, 350 kg/m3, and 450 kg/m3 and a constant silica fume (SF) content were applied in this experimental study. The water/binder (w/b) ratio was varied between 0.4 and 0.8. Concrete specimens were immersed in highly severe effective sodium sulfate solutions (10,000 ppm) for 180 days after standard curing for 28 days. The fresh concrete performance was evaluated through a slump test to attain proper workability. Concrete compressive strength and mass change at 28 days and 180 days were measured before and after immersion in the solution to evaluate the long-term effect of sulfate attack on the proposed concrete durability. Scanning electron microscopy (SEM) analysis was conducted to study the concrete microstructure and its deterioration stages. The obtained results revealed that BFC cement has the best resistance to aggressive sulfate attacks. The strength deterioration of BFC cement was 3.5% with w/b of 0.4 and it increased to about 7.8% when increasing the w/b ratio to 0.6, which are comparable to other types of cement used. The findings of this research confirmed that the quality of concrete, specifically its composition of low permeability, is the best and recommended protection against sulfate attack.

Performance evaluation and lifetime prediction of steel slag coarse aggregate concrete under sulfate attack

The durability of steel slag coarse aggregate concrete limits the application of steel slag in construction engineering. This study carried out the erosion test, material mechanics test, and microscopic test of steel slag coarse aggregate concrete under the action of different mass fractions of sulfate solution to investigate the effect law and mechanism of steel slag coarse aggregate on sulfate erosion resistance of concrete. The deterioration laws of performance indexes such as compressive strength, mass change, and relative dynamic elastic modulus of steel slag coarse aggregate concrete under sulfate erosion were investigated. X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used to examine the erosion products and microstructure changes of samples before and after sulfate erosion, and the GM (1, 1) model of grey theory was used to forecast the service life of steel slag coarse aggregate concrete under various conditions. The results demonstrate that utilizing steel slag instead of coarse aggregate to prepare concrete may significantly alleviate the damage caused by the attack of sulfate solutions. And in 15% sulfate erosion environment, the maximum compressive strength increase rate of 20.7% was obtained when the steel slag substitution rate was 60%. Microscopic study reveals that the active components (such as dicalcium silicate (C2S) and tricalcium silicate (C3S)) in steel slag can promote the production of hydrated calcium silicate gel in concrete, improving the strength and durability of the material. To a certain extent, the addition of steel slag can improve the sulfate resistance of concrete. The prediction results of the GM (1, 1) model show that the service lifetime of concrete with 60% steel slag coarse aggregate substitution rate under sulfate solution erosion is better than that of the other three groups, and the predicted results are compatible with the experimental results.

Effect of magnesia expansion agent with different activity on mechanical property, autogenous shrinkage and durability of concrete

The addition of Magnesia Expansion Agent (MEA) to reduce shrinkage of concrete has attracted attention gradually. In this study, three types of MEA with different activity, i.e. R, M, and S were added into concrete by 5% weight of cement. The effects of MEA on hydration, mechanical properties, shrinkage and durability of concrete were comprehensively evaluated. The results indicated that MEA has a certain delaying effect on hydration of cement and the effect is related to its activity. The addition of MEA exhibites a larger porosity at early curing age leading to negative effects on the mechanical properties of concrete. Later, the microstructure of concrete is refined due to the micro-expansion of MEA. As a result, the mechanical strength of concrete increases 5–20 % at 84 d. Meanwhile, the autogenous shrinkage of concrete with MEA of type R, M, and S decreases by 47.6 %, 49.7 %, and 23.8 % at 90 d, respectively. Because of the smaller MPPD and lower porosity, concrete with MEA of higher activity presents better resistance to chloride penetration. In addition, the models of shrinkage and chloride diffusion coefficient of concrete with MEA of different activity were proposed and verified, which can be used in the shrinkage and service life prediction of concrete with MEA. Furthermore, with the increase of MEA activity, the frost resistance of concrete decreases. On the contrary, the lower the MEA activity, the lower the sulfate resistance of concrete.

A new performance test to evaluate the sulfate resistance of concrete by tensile strength measurements

Concrete structures without sufficient durability can be damaged by sulfates in groundwater and from surrounding rock layers. To evaluate the performance of a concrete mixture, precise and performance-oriented test methods are a must. Therefore, a new a performance oriented concrete test procedure based on tensile strength measurements was developed considering experiences reported in international literature and recommendations of state-of-the-art reports. A vast parameter study with approx. 3850 tensile tests on ASTM briquets, 1900 flexural tensile tests on standard prisms and 2100 expansion tests on mortar flat prisms of different ages and with different storage conditions was statistically assessed. Based on the results a performance-oriented test method could be defined which considers not only the chemical, but also the physical resistance of a concrete against sulfate attack. The method was verified by 23 concretes with different cements or cement fly ash combinations and additional field tests. It could clearly be demonstrated that the results represent the performance of a practical concrete in case of sulfate attack. Furthermore, it leads much faster to an evaluation of the sulfate resistance compared to the most other practical oriented methods.

Energy Evolution Characteristics and Performance Parameter Degradation of Rubber-Mixed Concrete in Sulfate Attack Environment

In order to study the sulfate resistance of rubber concrete (RC), the compressive strength test of RC with different contents (0%, 5%, 10%, and 15%) was carried out, and the proportion of RC with standard curing for 28 days was optimized. Sulfate attack test was carried out on the selected RC and compared with normal concrete (NC). The degradation degree was measured from the effective porosity, relative dynamic elastic modulus, SO42− concentration, and SEM microstructure observation after different attack times. The energy analysis method is used to study the evolution law of total strain energy, elastic strain energy, and dissipated strain energy of NC and RC in the process of deformation and failure after different attack times, and the influence of sulfate attack on concrete is explored from the perspective of energy. The results show that with the progress of sulfate attack, the effective porosity of NC and RC both decreases first and then increases, and the relative dynamic elastic modulus increases first and then decreases. Rubber is beneficial to improve the sulfate resistance of concrete, delay the attack of SO42− on concrete, and improve the ductile deformation of concrete. This study can provide a theoretical reference for the application of RC in practical engineering.

Enhancing concrete sulfate resistance by adding NaCl

This study aimed to investigate the effects of adding NaCl on sulfate resistance of ordinary concrete. Concrete specimens were fabricated with 0.1%, 0.5%, and 1.0% NaCl (by weight of cement) and subjected to 10% Na2SO4 solution. The visual appearance of concrete was observed regularly. The compressive strength, ultrasonic velocity, and SO42− ion concentrations in concrete were also determined. Results indicated that incorporating NaCl in concrete can effectively inhibit the entry of external SO42− ions, consume the corrodible cement hydration products, and reduce corrosion product formation in concrete, thereby substantially enhancing the sulfate resistance of concrete. Under either full or partial immersion corrosion test, adding NaCl can reduce the compressive strength loss of concrete, lessen the development of concrete damaged layer thickness, and prevent the decline of concrete’s relative dynamic modulus. The sulfate resistance of concrete is approximately linear with NaCl content, particularly for concrete under partial immersion sulfate attack condition.

Resistance against sulphate attack in concrete by addition of nano alumina

The nano materials improve the mechanical properties of a cement concrete is a remarkable achievement in the field of nano composites. Matrix cement has a relatively loosely bonded structure which can be filled with Nano alumina which significantly improves the mechanical properties of cement. The present study discusses the development, manufacture and properties of the concrete made by nano materials. In the present study, the sulphate resistance of concrete is improved by the addition of Nano Alumina by partial replacement of cement. The study is carried out by partial replacement of cement by colloidal nano alumina- Al2O3 (CNA) particles with varying percentage (0%, 1%, 2%, 3%, 4%, and 5%) in the M55 grade of concrete. The study also evaluates an optimum dose of nano alumina at which maximum compressive strength of concrete is achieved with minimal sulphate attack observed in form of mass reduction in the concrete. It is observed that by an addition of 2.3% of CNA, the maximum sulphate resistance of concrete is achieved after 28 days. It was also observed that by an addition of 2% to 2.5% of Nano Alumina the compressive strength of concrete increases with a decrease in trend observed at 3% addition of Nano Alumina.

Study on mechanical properties and air-void structure characteristics of hybrid fiber fly ash concrete under sulfate attack

Sulfate attack is one of the common durability problems of concrete. The concrete structure in saline soil is particularly susceptible to sulfate attack. The aim of this paper was to investigate the effect of fly ash on the mechanical properties and pore structure of fiber reinforced concrete under sulfate attack. The sulfate resistance of different content of fly ash (0%, 10%, 20%) at different sulfate attack ages (0 d, 30 d, 60 d, 90 d, 120 d, 150 d) was presented. By analyzing the variation of mass loss rate, ultrasonic wave velocity, relative compressive strength and relative splitting tensile strength, the mechanical properties of concrete under sulfate attack were studied. In addition, the air-void structure test was carried out to explore the pore structure characteristics of concrete. The test results suggested that the contribution of fly ash could improve the sulfate resistance of concrete. At the same sulfate attack age, compared with other contents, the hybrid fiber fly ash concrete with 10% fly ash could strong against sulfate attack. At the later stage of sulfate attack, the corrosion resistance of concrete weakened, the mass loss rate, wave velocity, relative compressive strength and relative splitting tensile strength were reduced, while the pore structure parameters showed that fly ash could fill large pores for reducing corrosion damage. Adding 10% fly ash refined pores and enhanced the strength of concrete. The generation of pores is main factor for the deterioration of concrete structure. The fractal dimension well expressed the changes of pores in concrete. Based on fractal dimension and fly ash content, the damage model was established, which could predict the damage deterioration of hybrid fiber fly ash concrete under sulfate attack.

Long-Term Efficiency of Silica Fume in Terms of Sulfate Resistance of Concrete Immersed in Sulfate Solutions and Seawater

Long-Term Efficiency of Silica Fume in Terms of Sulfate Resistance of Concrete Immersed in Sulfate Solutions and Seawater

Performance Test for Sulfate Resistance of Concrete by Tensile Strength Measurements: Determination of Test Criteria

The European standard EN 206-1 contains descriptive requirements for concrete to withstand sulfate attack in the field. This approach limits the use of feasible concrete mixtures that don’t comply with these requirements. A performance approach based on the residual tensile strength of concrete briquet specimen according to ASTM C307 after storage in sodium sulfate solution close to field conditions is suggested by the authors. The newly developed test method is verified on a variety of 23 binders. Threshold values for the determination of the sulfate resistance of concrete after nine months of storage in 6000 mg SO42−/L sulfate solution at 5 °C are proposed. A first repeatability test as well as thermodynamic calculations prove the suitability of the method to test the performance of concrete during sulfate attack under practical conditions.

Development of a Sulfate Resistance Performance Test for Concrete by Tensile Strength Measurements: Determination of Test Conditions

Assessing the sulfate resistance of concrete is essential for the use of concrete in sulfate rich environments. A multitude of test methods exists worldwide, showing the relevance of the problem and the difficulty to find a suitable test setup. Testing the relative tensile strength of ASTM C307 concrete briquette specimens after exposure to a sulfate solution is a new direct method to assess the degree of deterioration. The aim of this study is to develop a new performance test, which considers both the chemical and physical resistance of a specific concrete mix against sulfate attack. In the experimental investigations, the binder type, storage temperature, type and concentration of sulfate solution, and concrete composition were varied, and the remaining tensile strength evaluated to define the test parameters. To gain significantly distinguishable data within nine months of storage, the use of sodium sulfate solution with 6000 mg SO42−/L at 5 °C is proposed.

Investigation of isophorone diisocyanate microcapsules to improve self-healing properties and sulfate resistance of concrete

Sulfate attack causes internal cracking of concrete and affects the durability of concrete structures. The durability of concrete under sulfate attack is crucial to structural safety and serviceability. Microcapsules can self-heal microcracks in concrete and improve its durability. Microcapsules with isophorone diisocyanate (IPDI) as the healing agent and paraffin wax, polyethylene wax, and nano silica as shells were prepared to improve the sulfate resistance and self-healing properties of concrete. The mass loss, mechanical properties, impermeability, and pore size distribution of the concrete after sulfate dry-wet cycles were determined. Ultrasonic testing was used to evaluate concrete sulfate resistance and self-healing properties, as a prominent nondestructive testing technique. The results showed that the addition of microcapsules significantly improved the sulfate resistance and self-healing properties. Concrete containing nano silica/paraffin wax/polyethylene wax encapsulated IPDI microcapsules exhibited good sulfate resistance and self-healing properties. Scanning electron microscopy revealed that concrete containing microcapsules exposed to sulfate attack produced healing products with a mesh-like structure in the pores after a 14-d self-healing. These healing products can improve microstructure and self-healing properties.

Deterioration of concrete containing limestone powder exposed to sulfate attack at ambient temperature

This study investigates the deterioration of concrete containing limestone powder exposed to sulfate solution under ambient temperature (20~25 °C). Microstructure and mineral phases within the attacked concrete were measured by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). It was found that the addition of limestone powder increased the initial porosity of concrete. Consequently, a larger amount of SO2–4 ions diffused into the concrete containing limestone powder, and their degree of deterioration caused by sulfate attack increased with the increase in limestone powder content. At ambient temperature, gypsum and ettringite were the major attack products, respectively within the surface and nearsurface portions of concrete containing limestone powder, which was consistent with the products of sulfate attack within concrete without limestone powder. Therefore, the type and distribution of the attack products in concrete had not been revised due to the addition of limestone powder. Nevertheless, the adverse influence of limestone powder on the sulfate resistance of concrete, even at ambient temperature, should be considered. Furthermore, effective measures should be implemented to improve the durability of concrete containing limestone powder in this environment.

Thermodynamic Study of Cement Paste under Sulfate Attack: A Review

Sulfate attack reduces the service life of concrete structures, which isn't possible to repair simply. Implementation of many factors influencing the sulfate resistance, sample scaling, and results in the least possible time is some problems of experimental studies. Therefore, numerical simulations, as well as the new methods along with experimental studies, have been led to better evaluation of sulfate attack within a shorter time and at a lower cost. In the present study, the effective factors, causes, and mechanisms of sulfate attack, examples of this phenomenon in real projects, and the previous studies in this regard, in particular, the development of the thermodynamic study of cement under sulfate attack as a fast and inexpensive solution have been reviewed. The present investigation is divided into three parts, first the sulfate attack mechanism, second the factors influencing phases containing sulfate formation, and third a review of the methods and results of the studies, focusing on the development of thermodynamic models in cement sulfate attack especially. Finally, the results of the studies show that common experimental methods related to concrete sulfate resistance evaluation can't always simulate what is actually happening; subsequently, the results of experimental studies and real cases are sometimes different. So, numerical models, in particular, thermodynamic simulation, either alone or in combination with experimental studies, can be a desirable solution for enhancing the ability to predict engineering behavior of concrete structures in the sulfate environment. Subsequently, it results in making better decisions to tackle and prevent deterioration caused by sulfate attack.

Effect of biomineralization technique on the strength and durability characteristics of recycled aggregate concrete

The recycling of waste in concrete prevents the depletion of natural resources, preserves the environment and also manages the disposal of waste. As aggregates in concrete are in higher volume, hence using construction and demolition waste (CDW) as recycled aggregate would make concrete construction more sustainable. In this study, the technique of biomineralization has been addressed to improve the strength and durability properties of recycled aggregate concrete (RAC). For this, RAC mixes with and without bacteria were prepared with 50% and 100% recycled coarse aggregate (RCA). The compressive strength, water absorption, water permeability, electrical resistivity, durability against sulfate resistance of concrete were tested. In addition, microstructure analysis of concrete was carried out using SEM, EDS and XRD. Tests for durability were performed on 28, 56, 120 days and for strength on 7, 28, 56, 120 days. Results show that the compressive strength of 100% RAC concrete was increased by 19.0% on 120 days from the CaCO3 precipitations accumulated by bacteria and durability properties in terms of water absorption, water permeability, electrical resistance were also enhanced by 12.7%, 42.9%, 100.8% respectively The bacterial activity could resist the penetration of sulfates and hence improved strength performance was recorded in the sulfate environment of the bacterial recycled aggregate concrete (BRAC). Moreover, the presence of crystals of bacterial CaCO3 precipitation and sulfate salts were observed in the micrographs of SEM, which was confirmed by the results of EDS and XRD analysis. Further, the benefit-cost ratio reveals that the improvements that have been achieved in 100% RAC properties with bacteria show that 100% BRAC production is economically feasible.

PERFORMANCE OF FLY ASH CONCRETE AGAINST SULFATE ATTACK

In this research, the effect of using fly ash on sulfate resistance of concrete was investigated. Studied mixes in this work are part of a research project that investigates the influence of using binary and ternary cementitious materials on different properties of concrete. In this paper, three groups of concrete mixtures were studied; each group includes three mixes. The concrete mix proportions were adjusted to produce concrete with certain values of air content and slump. The used water / binder material ratios were 0.4, 0.5 and 0.6. Concrete samples were cured in water until testing day. After 28 days of water curing, samples were immersed in sodium sulfate solution for 6 months. The hardened concrete properties were investigated through destructive and nondestructive tests at various samples’ age. The research results showed that using fly ash improved the resistance of concrete to sulfate attack. Therefore, with considerable proportions, using fly ash in concrete industry improves the performance of concrete for sulfate resistance and its durability.

Evaluation of sulfate resistance of protective biological coating mortars

The effectiveness of biological coating mortars was examined by testing the variations of the compressive strength and mass of concrete and the transition of hydration products of the cement matrix in 5% sulfuric acid solutions. These biological coating mortars were originally developed in the previous investigation for enhancing the sulfate resistance of concrete. Based on the block membrane action of the glycocalyx generated from bacterial activity, Rhodobacter capsulatus was isolated and immobilized in expanded vermiculite together with a bacterial medium. Concrete cylinders were coated with a thickness of 2.5 mm using three types of mortar: conventional mortar C without bacteria and bacterial agents, mortar B with non-immobilized bacteria, and mortar I with bacteria immobilized in accordance with the proposed technique. The glycocalyx formation and the survival of bacteria in the coating mortars immersed in sulfuric acid solutions were traced by scanning electron microscopy image and the viable cell count method. Test results revealed that the proposed biological coating technique is significantly favorable for restricting the decrease in the compressive strength of concrete exposed to sulfuric acid solution, with no delamination or cracks in the concrete. Moreover, the concrete specimen I under sulfuric acid solutions exhibited very close profiles for X-ray diffraction and thermogravimetric analysis to those of virgin concrete cured under the conventional environment. There were less gypsum and ettringite from the reaction between the hydration products of cement and sulfuric acid. Overall, the proposed biological coating technique facilitates biomimetic activity, even in a strong sulfuric acid environment.