Sulfate Attack Research Articles

Sulphate resistance prediction of RAC considering the coupling effect of RCA and water-binder ratio based on experimental analysis and LSSVM

ABSTRACT Waste concrete removed from old pavement can be crushed and sieved as recycled aggregate to prepare concrete, and the application of recycled aggregate concrete (RAC) can reduce the occupation of land resources by the waste concrete and save natural aggregate. In this paper, the influence of proportion of recycled coarse aggregate (RCA) replacing natural coarse aggregate (NCA) and water-binder ratio on the sulphate resistance of RAC was studied, and the compressive strength degradation rate (Df ) was introduced to evaluate the sulphate resistance of RAC. The experimental results showed that the compressive strength of RAC before and after sulphate attacks linearly decreased with the growth of the replacement rate of RCA, water-binder ratio, and the number of sulphate wet-dry cycles, respectively; while Df of RAC increased with the rise of the replacement rate of RCA, water-binder ratio, and sulphate wet-dry cycles, respectively. The results also indicated that Df of all groups of RAC was less than 25%, which can meet the engineering requirements. In addition, the Df model of RAC under a sulphate attack based on experimental data and that based on Least-Squares Support Vector Machine (LSSVM) was built and compared, and both models predict the sulphate resistance of RAC well. The prediction model based on LSSVM has higher prediction accuracy.

Eggshell catalysed rubber aggregates for the sustainable green mortar constructions

Sustainability growth in the infrastructure field demands the need for environmentally friendly construction without compromising its structural properties. In this paper, a durable rubberized geopolymer mortar was developed by using the eggshell catalyzation technique. In order to enhance the interfacial bonding of rubber aggregates with the potassium-based geopolymer mortar, the eggshell catalyst was employed as a natural surface modifier. The developed eggshell catalyzed rubber was used to replace 5% by weight of the fine aggregate system and the sustainability of the rubberized geopolymer mortars was studied by assessing the strength and durability characteristics. From the results, it was inferred that the eggshell catalyst transformed the rubber surface into highly hydrophilic and showed a water contact angle of 10°. The trans-esterification process induced by the eggshell-catalyzed rubber aggregates resulted in 10% improved workability and 98.8% recovery in compressive strength of the rubberized geopolymer mortar. Also, due to the formation of secondary gels around the eggshell-catalyzed rubber, the geopolymer mortar becomes denser which prevents the intrusion of foreign ions and showed a 27.9% change in mass under sulphate attack and 33.86 MPa residual compressive strength after 90 days of acid immersion. This attributed the rubberized geopolymer mortar with eggshell catalyzation process to maintain its structural integrity even in the aggressive chemical environment for the feasible applications of deck slab, piers, underground pipe construction, etc.

Innovative GQDs and supra-GQDs assemblies for developing high strength and conductive cement composites

Recently, there has been significant interest in using several types of graphene derivatives to enhance the performance of cement composites. There are novel graphene quantum materials called graphene quantum dots (GQDs) in ultrafine scales, and none has been explored in cement materials. This work presents the effects of these two synthesized graphene derivatives (Qds and BC) on the flow, bulk density, permeable void, water absorption, compressive strength, flexural strength, sulphate attack, electrical conductivity, thermal conductivity, and microstructures of cement composites, compared with commercial graphene oxide (GO) and plain mix. The findings show that the composites containing GQDs have excellent fresh, physical, mechanical, and sulphate attack properties. The 1.2% BC composites has the highest compressive and flexural strengths, with 40% and 108% higher than the control, respectively. Moreover, their electrical and thermal conductivity properties increased as a function of GQDs content. The microstructural bridging mechanism regarding the seeding and crystal growth of C-S-H phase were seen. This study offers novel insights into the role of using GQDs in cement composites such that the materials can be used as a high performance, high conductive concrete, which can be a future of the GQDs in the construction industry.

Mechanical and Durability Studies about the use of Municipal Solid Waste Landfill in Concrete

The best way to keep the required format of the manuscript is to overwrite these instructions with its text. Papers should be written in English. Manuscripts s Landfilling is the most common and cheapest method of waste management practice in India. Municipal Solid Waste Landfills (MSWL) became a nuisance affecting the health, hygiene, sanitation and aesthetics of the surrounding area. Aggregates occupy almost 70% of concrete, so replacing waste materials with them could be a rewarding choice. In the current work, an experimental investigation is being carried out to test the addition of MSWL as a substitution with fine aggregate for concrete production. Out of the different aged samples available at the dumpsite, the most aged sample is chosen for experimental investigations according to the basic physical properties. Concrete mixes, with 0%, 4%, 5%, 7% and 10% partial replacement of fine aggregate with MSWL are tested for mechanical properties such as compressive strength, split tensile strength, flexural strength, and non-destructive test and have proved to be a partial substitute for fine aggregate. Durability studies such as water absorption, acid attack and sulphate attack also gave better experimental proof for the sustainable reuse of this waste material. The research reveals 5% replacement is the optimum considering all the test result values. The paper leads to advanced research for the suitability of the material in the construction industry.

Properties of Self-Compacting Concrete (SCC) Prepared with Binary and Ternary Blended Calcined Clay and Steel Slag

The recent emphasis on sustainable development in the construction industry has made it essential to develop construction and building materials that are not only affordable, but have minimal negative impact on the environment. This study investigates the valorisation of steel slag, which is mostly considered to be a waste material in several parts of the world, by blending with calcined impure kaolinitic clay to partially replace ordinary Portland cement (OPC) in the preparation of self-compacting concrete (SCC). OPC was substituted with steel slag at a constant level of 10%, whereas calcined clay replaced OPC at varying levels, ranging from 10 to 30% in a ternary blended mix. The hardened properties evaluated include compressive and flexural strengths. Samples containing only calcined clay showed a lower fluidity, which was significantly improved when steel slag was added to the mix. SCC containing 10% steel slag and 20% calcined clay obtained 28 days compressive strength, which was 3.6% higher than the reference cement concrete. An XRD analysis revealed a significant decrease in the peak heights of portlandite in mixtures containing steel slag and calcined clay, regardless of their replacement percentage. Generally, all the blended cement samples performed appreciably in resisting sulphate attack. The results of this study demonstrate that using steel slag and calcined clay together can significantly improve the fresh and hardened properties of SCC without compromising its mechanical properties.

Assessment of mechanical, durability and microstructural performance of sulphate-resisting cement concrete over portland cement in the presence of salinity

The current understanding of the sulphate attack mechanism on ordinary Portland cement (OPC) concrete within the construction sector is not yet well understood. The primary objective of this study is to focus on and discuss how to minimize the sulphate attack on concrete. The main purpose of this research is to better understand and improve the mechanical, durability, and microstructural characteristics of concrete under saline and non-saline/normal environments. This investigation involved the use of artificial seawater in the concrete mixing process and ensuring saline conditions for the concrete specimens in the laboratory. In addition, an approach for assessing the influence of using sulphate-resisting cement (SRC) in concrete to differentiate the performance from OPC concrete is also investigated. Silica fume (SF) is used as a partial cementitious material in SRC concrete by 10% and 20%. The concrete performances were examined by several rheological, mechanical, durability, and microstructural tests and compared the corresponding performances with the SRC-artificial seawater (SRCASW) and OPC-freshwater (OPCFW) concrete. Test results show that the strength of concrete decreased linearly from the OPCFW to SRCASW. Among SRC-artificial seawater concrete mixes, the mix with 10% SF shows the best strength outcomes i.e., 28.84, 36.22, and 37.54 MPa at 7, 28, and 56 days respectively, which is an average of 12.5% higher than the mix with 20% SF. A concrete mix of SRC with 10% SF displays the highest durable behavior, achieving chloride penetration and electrical resistivity at a very low range (936 columbus and 290.7 Ω-m, respectively). In addition, microstructural images of the SRC concrete mixes indicate no visible crack due to sulphate inclusion. An analytical approach has provided a conservative estimate with the experimental results and standard code of practice for predicting mechanical properties. Finally, this study revealed that SRC incorporation in concrete increased the long-term serviceability of the structures against salinity.

Enhancing Sulfate Erosion Resistance in Ultra-High-Performance Concrete through Mix Design Optimization Using the Modified Andreasen and Andersen Method

This study presents an in-depth investigation into optimizing the mix design of ultra-high-performance concrete (UHPC) for enhanced sulfate erosion resistance, utilizing the modified Andreasen and Andersen (MAA) method. By testing the mechanical properties and slump flow of UHPC, it was determined that the optimal W/B = 0.2, and the best volume content of steel fibers is 2%. Through long-term tests lasting 360 days on three groups of UHPC specimens under different curing conditions, their mass loss, compressive strength corrosion resistance coefficient, surface appearance, and erosion layer thickness were tested. The results indicate that under sulfate attack, the mass and compressive strength corrosion resistance coefficients of UHPC specimens showed a trend of first increasing and then decreasing, due to the formation and expansion of ettringite and gypsum. The thickness of the erosion layer increases over time. By 360 days, the internal damage caused by sulfate attack is about twice as severe as it was after 60 days. However, the addition of steel fibers was found to effectively mitigate these effects, reducing mass loss and preserving the structural integrity of UHPC.

Influence of Aggressive Environment in Macro and Microstructural Properties of Bottom Ash Geopolymer Concrete

India generates 759.02 million metric tons of coal ash annually. Part of that quantity is successfully utilized, and the remaining portion of the ash is discarded into a landfill. There also is a need to address pollution. Cement industries are responsible for 7% of global warming. Cement has been replaced entirely by thermal power plant waste, and bottom ash is used as a binder to overcome those issues. A few researchers have carried out strength characterization, but an extensive study needs to be carried out under different environmental exposures. Therefore, the present study investigated macro and micro properties of bottom ash geopolymer concrete (BAGPC) subjected to aggressive ecological exposure conditions such as acid, salt, and sulfate attack. Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) of eight molarities were used as activators for the bottom ash geopolymer concrete (BAGPC) binder. Further bonding between steel and conventional concrete BAGPC mixes was investigated. The durability of conventional concrete (CC) was taken as the control mix to compare the durability of the optimized mix (B4) of bottom ash geopolymer. The test samples were cured for 28 days under ambient temperature and tested for the effect of MgSO4, NaCl, and HCl. The strength loss and weight loss of the BAGPC B4 mix after 7, 28, 56, 90, and 180 days under aggressive conditions showed better performance than CC. It has been observed that geopolymer concrete has good bonding in nature, and the bond strength results indicate excellent bonding between steel and concrete. Microstructure studies revealed that the BAGPC B4 mix had a strong microstructure and not as much of a porous structure. It is concluded that BAGPC has potential value in the construction industry based on all aspects of the experiment.

Effect of external sulfate attack on the tensile properties of fiber-reinforced sprayed concrete

This paper presents an investigation on the effect of external sulfate attack (ESA) on the mechanical and microstructural properties of steel fiber-reinforced sprayed concrete (SFRSC). Crimped carbon steel fibers, 40 mm-long, were used as reinforcement in three different mixtures with specified fiber contents of 30 kg/m³, 60 kg/m³ and 90 kg/m³. Cylindrical specimens, drilled from SFRSC panels, were subjected to sulfate attack for up to 270 days. Double-punch tests (DPT) were used to determine the matrix crack strength and the post-crack tensile strength of the SFRSC. The effective fiber content of each specimen was determined by inductive tests and subsequently correlated with the mechanical results. Scanning electron microscopy (SEM) was used to evaluate the phases formed in the concrete pores during the sulfate attack. Results indicated that fiber reinforcement may reduce cracking due to ESA.

Experimental feasibility study of using eco- and user-friendly mechanochemically activated slag/fly ash geopolymer for soil stabilization

This study focuses on the development of eco and user-friendly mechanochemically-activated geopolymeric stabilizers, surpassing the limitations inherent in traditional geopolymerization methods. A comparative analysis was undertaken with conventionally activated geopolymer stabilizers to establish benchmarks for effectiveness in soil stabilization applications. Additionally, the research delves into the impact of granulated blast-furnace slag (GGBS) content on the mechanical and durability properties of stabilized soil samples. In addition, the investigation focuses on the influence of the activation method on soil effectiveness and strength post-exposure to sulfate attack. The durability performance is rigorously assessed through the immersion of specimens in a 1 % magnesium sulfate (MgSO4) solution for 60 and 120 days. The comprehensive evaluation includes visual appearance, mass changes, Ultrasonic Pulse Velocity (UPV), Unconfined Compressive Strength (UCS), and Fourier-Transform Infrared (FTIR) spectra of geopolymer-stabilized soil specimens. The results showed that before the exposure to the MgSO4 solution, the UCS of mechanochemically activated geopolymer (MAG) samples was higher (12–45 %) than that of conventionally activated geopolymer (CAG)-stabilized soil. Furthermore, the strength of the geopolymer-stabilized soil improved by 114 %, 247 %, and 361 %, at 50, 75, and 100 % GGBS content, respectively. On the other hand, after exposure to the MgSO4 solution, the results showed that the mechanochemically activated geopolymer-stabilized soil has better resistance to sulfate erosion than the conventionally activated geopolymer-stabilized soil. The residual UCS for MAG and CAG samples were 93 % and 89 % when exposed to 1 % magnesium sulfate solution for 60 days, whereas they declined to 70 % and 58 %, respectively, after 120 days of immersion.

New Methods for Assessing External Sulfate Attack on Cement-Based Specimens

This paper presents two original methods for monitoring and evaluating concrete specimens/structures affected by external sulfate attack (ESA). The first is a drying method developed to assess the penetration depth of sulfate ions in a concrete structure, as this parameter is a relevant indicator of the progress of the ESA. This method has been specifically designed for on-site investigations. The second experimental method involves the use of optical fibers capable of measuring the swelling response of specimens to ESA in real time. According to the results obtained, these two new methods seem likely to be used to complement or replace traditional methods such as inductively coupled plasma (ICP) for determining the penetration depth of sulfate ions or as extensometers for measuring swelling. These traditional methods (ICP and extensometers) are generally considered painful and time-consuming, whereas, because of its simplicity, the proposed drying method will enable experts to regularly inspect concrete structures and make informed decisions on the measures to be taken to repair or prevent further damage induced by ESA, while the second method appears promising for experimental studies involving the monitoring of a large number of ESA-affected specimens.

Current Knowledge and Pending Research on Sulfate Resistance of Recycled Aggregate Concrete

The building sector’s sustainability requires construction and demolition waste (CDW) to contribute to the circular economy. Among the CDW, recycled concrete aggregates (RA) have been mainly studied to replace natural aggregates. Still, the approval of their use in regulations and standards is slower. Some barriers to the adoption of RA are related to the durability of recycled aggregate concrete (RAC). However, their physical and mechanical properties have been extensively studied. The durability risks associated with sulfate attacks have been solved for conventional concrete. However, sulfate attack on recycled concrete still raises numerous unsolved questions. In this literature review, the experience of sulfate attack on RAC is compiled and analyzed using a compressive framework highlighting the most relevant aspects of the new matrix in RAC and the old matrix of RA to support its relevance to the damaging sulfate process. Suggestions for further research are presented to understand the full extent of this issue and contribute to incorporating and extending recycled aggregates into existing regulations.

Probabilistic modelling of deterioration of reinforced concrete structures

Reinforced concrete (RC) structures deteriorate over time which affects their strength and serviceability. To develop measures for protecting new RC structures against deterioration and assess the condition of existing RC structures subjected to deterioration an understanding of the deterioration processes and the ability to predict their development, including structural consequences, are essential. This problem has attracted significant attention from researchers, including those working in the area of structural reliability (in particular within the JCSS) since there are major uncertainties associated with the deterioration processes and their structural effects. The paper presents an overview of the probabilistic modelling of various deterioration processes affecting RC structures such as corrosion of reinforcing steel, freezing-thawing, alkali-aggregate reaction, sulphate attack and fatigue, and their structural implications, including the historical perspective and current state-of-the-art. It also addresses the issues related to the inspection/monitoring of deteriorating RC structures and the analysis of collected data taking into account relevant uncertainties. Examples illustrating the application of the presented probabilistic models are provided. Finally, the current gaps in the knowledge related to the problem, which require further attention, are discussed.

Evaluating Properties of Green Concrete Produced Using Waste Marble Powder, Quarry Dust, and Paper Pulp

AbstractIndustrial waste locks are used as raw materials to reduce harmful effects on the environment and improve environmental performance. Marble clay powder can be used as a filling aid and can fill voids in concrete structures. This article will show you how to use a maximum natural sand alternative in concrete with marble powder and quarry dust. The challenge of the 21st century is to change to a new form that can support the natural system. This necessitates a radical rethinking of how to give the community infrastructure and housing. Making a concerted effort to develop novel, innovative, and alternative construction materials may be necessary. Jungles of concrete around cause's impact on the Environment and it would result in climate change. Mankind must avoid the use of things that are detrimental to the environment. So in this paper, it is decided to address the issue by adopting the use of the green concrete concept which is environmentally friendly. Green concrete is concrete made up using industrial wastes such as marble powder, quarry dust, wood ash, paper pulp, etc. Green concrete, which is capable of sustainable development, helps to reduce the consumption of natural resources, energy use, and environmental pollution. Green concrete is more cost‐effective than ordinary concrete and reduces the cost of resultant concrete by 14%–20%. It is also observed that the alkali‐aggregate reaction and sulfate attack resistance of concrete are both significantly improved. Green concrete is a useful tool for lowering environmental pollution and enhancing concrete's resistance to harsh conditions. All stages of infrastructure construction and rehabilitation will follow this trend of using new cement and techniques. Green concrete's adaptability and its performance derivatives will meet a variety of future needs.

Optimizing Coal Ash as a Sustainable Substitute of Cement and Aggregate in Structural Concrete

The manufacture of concrete for constructing the structures like highways, bridges, and buildings requires large amounts of cement and aggregates. This high concrete production depletes natural resources like sand and gravel for the construction industry. It also negatively impacts the environment due to cement usage. This study looked at using waste materials like coal bottom ash (CBA) and fly ash (FA) in concrete as substitutes for some of the typical aggregates and cement. The goal was to reduce the environmental impact and preserve natural resources. The study made concrete with regular Portland cement, sand, 10mm coarse aggregate, locally available CBA, and FA. 15% fly ash was selected as an optimal level from initial testing. The CBA was used to replace 0-35% of the fine aggregate sand. Test cubes and cylinders were made with different mixes. Compressive strength, tensile strength, carbonation, and sulfate attack tests were done after curing. Results showed 25% CBA improved the concrete’s mechanical performance. The compressive and tensile strengths increased but not above conventional concrete. This is because CBA needs more moisture for full hydration over longer curing times. Also, the concrete’s durability improved in terms of resistance to carbonation and sulfate attack.

Effect of Sulfate Attack on the Expansion Behavior of Cement-Treated Aggregates.

The expansion induced by sulfate attack on cement-treated aggregates (SACA) is a well-known problem that can be solved. It causes obvious heaves in road bases and railway subgrades. In this paper, the effects of the sodium sulfate content, cement content, degree of compaction, sulfate types, attack types, aluminum ion supply, concentration of curing sulfate solution, and temperature on the expansion behavior induced by SACA were investigated over 60 days in the laboratory. Based on the Sobol sensitivity analysis method, the influence of the sensitivity of each factor on the expansion was quantitatively analyzed, and the dominant factor of expansion was proposed. Results show that sulfate content is the domain factor of expansion that is induced by SACA, and it presents a logarithmic function relationship with strain. The 0.5% sodium sulfate content is the minimum sulfate content which causes the expansion that is induced by SACA. When the sulfate content is less than 1%, the expansion induced by SACA is minor. When the sulfate content is between 1% and 3%, the expansion behavior is expressed in four stages as follows: rapid strain increase, followed by a short stagnation period, then a significant strain increase and, finally, constant strain. When the sulfate content is greater than 5%, there are two stages comprising the expansion behavior as follows: the rapid strain increases and constant strain occurs. Greater sulfate content, greater degree of compaction, and lower temperature have positive effects on the expansion induced by SACA. The cement content does not have a consistent effect on expansion behavior. Compared with a sodium sulfate attack, both the reaction rate and expansion of cement-treated aggregates that are attacked by gypsum are smaller, and the attack period is also longer. When the sulfate content is greater than 1%, the addition of kaolin promotes the progression of the expansion induced by SACA. A small amount of water is sufficient for the demand for the sulfate attack. When the sulfate content is at a certain level, the expansion induced by SACA that is under external attack is much smaller than the expansion that is under internal attack. This study is expected to serve as a reference for future research on the mechanics of SACA, and it attempts to provide theoretical support for amending expansions that are induced by SACA.

Analysis of alkali-activated mineral wool-slag binders: evaluating the differences between one-part and two-part variations

Two synthesis pathways (one- and two-part) in alkali-activated binders were compared using ground granulated blast furnace slag (GGBFS), mineral wool (MW) activated using dry and liquid alkali activators with similar Na2O/SiO2 modulus. The effect of activator type on reaction kinetics, strength development, setting times, and durability shows that one-part synthesis does not only improve early strength, but also provide better durability properties. While the highest compressive strength (56 MPa, 90 days) was achieved for the one-part mix (DM), the reaction products (presence of Mg–Al layered double hydroxide and C–S–H-like phases) observed for both mortar mixes were similar. The DM mortars showed better resistance to sulfate attack than two-part mix (WM) mortars and sets faster. The results highlight the significance of the one-part pathways in the synthesis of alkali-activated materials.

Effect of Chloride and Sulphate Attack in Concrete Containing Biomass Ash and Silica Fumes

Effect of Chloride and Sulphate Attack in Concrete Containing Biomass Ash and Silica Fumes

Influence of Reclaimed Asphalt Pavement Aggregates on Strength and Durability Properties of Concrete Mixes in Rigid Pavements

The use of Reclaimed Asphalt Pavement (RAP) aggregates in rigid pavements instead of conventional aggregates in Himalayan regions solves the problem associated with shrinking natural resources and dumping of wastes. This study studied the effect of partial replacement of conventional coarse aggregates by RAP in Dry Lean Concrete (DLC) mixes suitable for rigid pavements. A total of 114 specimens (cubical and cylindrical) were cast and tested for mechanical and durability properties as per ASTM and IS code guidelines, partially replaced with CRAP by 25%, 50%, and 75% by weight. The simultaneous effect of fly ash addition by partial replacement of cement by it was also studied. The study concludes that 25% partial replacement by CRAP with 10% fly ash as partial replacement of cement led to the achievement of the strength benchmark as mandated by IRC SP 44 (2014). It was also observed that durability properties such as resistance to acid attack, sulphate attack and carbonation also improved in DLC mixes, including CRAP and fly ash, when compared to control mixes.

Bond Deterioration of GFRP Concrete Enhanced with Steel Fibers Subjected to External Sulfate Attack

Concrete structures are exposed to sulfate and chloride attacks when are used in different environments such as seawater, deicing salts or industrial waste. Sulfate corrosion is considered one of the most important factors that responses for deterioration of construction materials performance. When sulfate attacks concrete, sulfate ions interact with cement materials to form chemical compounds inside the concrete. These compounds result volume increase and create internal stresses causing cracks, spalling and reduction in concrete strength. In this paper, the effect of external sulfate attack on properties of concrete samples enhanced with and without steel fibers (SF) and on bond damage between glass fibers reinforced polymer GFRP bar and concrete were investigated. Samples were completely immersed in 10% magnesium sulfate solution for two different exposure periods (60 & 120 days) to compare with control samples. Compressive and tensile strengths, density and pulse velocity were experimentally investigated. Push-out test was also carried out to study the damage in bond between concrete and GFRP rod. The results of concrete samples immersed in magnesium sulfate solution for 60 days showed an increase in compressive strength, tensile strength and density, while the results decreased for samples immersed for 120 days.