Alkali-silica Reaction Expansion Research Articles

The Effect of Different Proportions of Waste Rubber Substitution on Alkali-Silica Reaction and Mechanical Properties in Mortars

This study investigates the alkali-silica reaction (ASR) and mechanical properties of mortars containing crumb and powder rubber instead of river sand. In this regard, mortars were produced using waste rubber whose ratios in the mixture are 0%, 3%, 6%, 9%, 12%, 15%, 18%, and 21%. ASR expansion, compressive and flexural strength tests were conducted on the samples. ASR measurements were performed on days 3, 7, 14, 21, and 28. Besides, at the end of the ASR experiment, the microstructures of the mortars were examined using scanning electron microscope (SEM) images. Examining the results of this study reveals that the use of waste rubber in rising portions in the mortars led to an increase in the ASR expansions of the mortars. The study shows that the ASR expansions of the mortar samples that have 9% and 15% waste rubber replacement are comparatively higher than the other mortar samples. Furthermore, the results of the SEM analysis verified this finding. The study demonstrates that 3% of waste rubber mortar samples have the highest compressive and flexural strengths. On the other side, the ASR expansion of the mortars with 3% substituted waste rubber was considerably low compared to other mortars containing waste rubber. These findings (ASR, compressive and flexural strength tests results) show that using 3% waste rubber is ideal for producing mortars and supports a sustainable production approach in the sector.

Evaluation of multiple machine learning models for ASR expansion of concrete

Machine learning algorithms (MLA) show promise in predicting alkali-silica reaction (ASR) expansion. Nevertheless, the predictive performance of different machine learning algorithms (MLAs) varies across various engineering scenarios and datasets. Given that, this study was devoted to constructing an appropriate predictive model for ASR expansion of concrete. Multiple MLAs including evolutionary-based, support vector-based, assembly-based, and neural network-based algorithms, were employed to establish predictive models. An optimization technique, the particle swarm optimization algorithm, was also utilized and integrated with the aforementioned MLA models to effectively search for optimal hyperparameters and topological structures. The predictive performance was evaluated using statistical methods, which showed that the extreme gradient boosting (XGBoost) model had the best fitting goodness among the standard algorithms, with an R2 value of 0.9695. Moreover, the Particle Swarm Optimization (PSO) model significantly improved the predictive performance of all Machine Learning Algorithm (MLA) models. The error distribution analysis was then performed. There are fewer large errors in the predicted values of the PSO-XGBoost model. Monte Carlo simulation and probability distribution functions were used to thoroughly analyze the stability of each model after multiple independent runs. The results show that all models have excellent stability. The PSO-XGBoost model performed the best and was subsequently employed to conduct feature analysis to determine the significance of each input parameter and capture the underlying evidence of ASR expansion.

Influences of aggregate gradation on alkali-silica reaction of seawater and sea sand concrete

The application of seawater and sea sand concrete (SWSSC) is beneficial for marine engineering, but the impact of aggregate gradation on its alkali-silica reaction (ASR) remains poorly understood. This study aims to bridge this gap by analyzing ASR products, pore characteristics and expansion rate of specimens. The test results reveal that ordinary concrete (OC) exhibits an inhibitory effect on ASR in comparison with to SWSSC. The 14-day expansion of ordinary concrete and SWSSC with the same aggregate gradation are 0.130 % and 0.212 %, showing potential and high risk of ASR, respectively. Moreover, particle size and gradation of aggregate are the key factors influencing the ASR degree of SWSSC. Compared with coarser aggregate, specimens with finer aggregate consume more K+ and Ca2+ ions, generate more ASR-P1, form less porosity, and produce a larger expansion. Additionally, specimens with gap-graded aggregates, as opposed to those with uniform or continuous gradation, show greater consumption of K+ and Ca2+ ions, increased ASR-P1 formation, more harmful pore formation, and a larger expansion. These results offer insights into optimizing aggregate gradation to reduce ASR in SWSSC and improve its durability.

Alkali-silica reaction of ferronickel slag fine aggregate in Portland cement and alkali-activated slag mortars: Pessimum effect investigation

Ferronickel slag (FNS) with dense and hard nature exhibits great potential to be utilized as recycled aggregate in concrete production. This study investigated the alkali-silica reaction (ASR) and the pessimum proportion of FNS fine aggregate in Portland cement (PC) and alkali-activated ground granulated bast furnace slag (AAS) mortars as a substitute for river sand. Over a 120-day period, the accelerated mortar bar test revealed that the addition of FNS fine aggregate in both cases resulted in harmless ASR expansion. In PC mortars, the ASR expansion consistently decreased from 0.569 % to 0.114 % as the FNS content increased. In comparison, AAS mortars with higher pore solution alkalinity had the pessimum proportion of 30 % FNS. The ASR expansion values initially increased from 0.472 % to 0.554 % with an increase in FNS content from 0 % to 30 %, but then decreased to 0.146 % as the FNS content was further raised to 100 %. The amorphous ASR gel was identified as a hydrated alkali silicate gel and present within the existing veins in the river sand grain. The ASR reaction of FNS fine aggregate exhibited a self-mitigating effect on the deleterious expansion through its pessimum behavior. Additionally, the addition of FNS fine aggregate yielded a beneficial outcome by reducing the cumulative pore volume in the mortars, and thus enhanced the compressive strengths.

Crack-filling effect of gel on time-dependent mechanical behavior of concrete damaged by alkali–silica reaction

This study aims to investigate the crack-filling effect of gel generated by the alkali–silica reaction (ASR) on the mechanical behavior of concrete and propose an analytical model to predict the compression behavior of ASR-damaged concrete. To identify the mechanical contribution of the gel-filling cracks, the distribution of the chemical compositions and elastic moduli of the crack-filling gels were observed using SEM–EDS analysis and nano-indentation tests. The experimental results showed that the elastic modulus of the gel with a high-calcium composition ranged from 30 to 40 GPa, which is comparable to the elastic modulus of concrete. In addition, through literature reviews of the time-dependent compression behaviors of ASR-affected concrete, it was hypothesized that crack-filling gels can contribute to the recovery of ASR damage, and that the mechanical contribution of gels depends on the ASR crack patterns and changes with time. Based on these assumptions, the resistance of the gels filling the cracks in the compression, shear, and recontact behaviors of ASR-damaged concrete was reflected in the proposed model, in which the gel resistance increased with time and became larger as the ratio of microcracks to total cracks increased. The proposed model was verified through a comprehensive comparison of analysis and test results of compression behavior of ASR-damaged specimens, and it appeared that the change in mechanical properties of concrete according to the degree of damage (ASR expansion) and time was well simulated by the proposed model.

A novel foaming-sintering technique for developing eco-friendly lightweight aggregates for high strength lightweight aggregate concrete

To address the scarcity of natural aggregates and reduce energy consumption in the concrete industry, a sustainable lightweight aggregate (LWA) was prepared with a self-foaming and sintering method by utilizing waste glass powder as the primary precursor and incineration bottom ash as a foaming agent. The effect of NaOH content (0 M, 2 M, and 8 M) on the physical properties of LWA was investigated. Replacing manufactured sand with sintered LWA (0 M-LWA and 2 M-LWA) by 50 vol% and 100 vol% to investigate their impact on the physical properties, mechanical properties, shrinkage, and alkali-silica reaction of high strength LWA concrete. The high strength LWA concrete prepared with 0 M-LWA possessed a density of 2127 kg/m3 and compressive strength of 108.7 MPa, which were slightly lower than that with manufactured sand. Due to the porous and lightweight nature of 2 M-LWA, the density and compressive strength of LWA concrete significantly decreased with the increased 2 M-LWA volume. Nevertheless, 100%-2M showed satisfying density of 1835 kg/m3 and compressive strength of 50 MPa. The internal curing effect of 2 M-LWA effectively mitigated the autogenous shrinkage of LWA concrete. The alkali-silica reaction expansion of all LWA was innocuous.

Concrete containing recycled concrete coarse aggregate and crushed glass sand: Mitigating the effect of alkali–silica reaction

AbstractThe utilization of recycled concrete and glass aggregates in concrete production has emerged as a highly promising method to significantly increase the recycling rate of waste materials. However, the interaction between alkaline environment and silica present in concrete detrimentally impacts mechanical properties and durability of the concrete due to the significant silica content of the aggregates. This study aims to develop a high‐performance and sustainable concrete to resist alkali–silica reaction (ASR). The study focuses on the use of a blend of ground granulated blast furnace slag (GGBS) and fly ash (FA) as binder materials to mitigate negative effects of the ASR on the mechanical properties and and durability of concrete made with crushed glass sand and coarse recycled concrete aggregate (RCA). Various tests, including ASR expansion, flow, slump, density, compression, three‐point bending, water absorption, and chloride attack, were conducted. Furthermore, microanalysis using scanning electron microscopy and energy‐dispersive x‐ray spectroscopy was performed. Based on the results, it is found that the GGBS is less effective than the FA in reducing the ASR expansion of the concrete, with only 3%, 9%, and 12% decreased expansion as a result of the addition of 20%, 40%, and 70% GGBS to the concrete containing 30% FA, respectively. It is also shown that combining 20% GGBS with 30% FA in the RCA concrete containing glass sand develops similar compressive and flexural strengths and water absorption compared to that containing natural sand. This can be related to the pozzolanic reaction of the FA and GGBS, which helps to retain the alkalis for reducing the crack development and propagation in the concrete. However, further GGBS content leads to a decrease in the strengths and an increase in the water absorption of the concrete. The results of this study point to the significant potential of combining FA and GGBS at an optimum ratio to mitigate the ASR effect on RCA concretes containing crushed glass sand. This approach helps in minimizing the emission of greenhouse gases and other pollutants generated during cement production, thereby mitigating environmental pollution. Additionally, it helps the preservation of natural resources by reducing the depletion of natural sand and coarse aggregate.

Studying the effectiveness of sewage sludge ash and its combination with natural pozzolans in controlling alkali–silica reaction

AbstractSewage sludge ash (SSA), obtained by the incineration of sewage sludge, which is a byproduct of water treatment, could be used as a cement replacement material (CSR) to promote sustainability. SSA characteristics differ due to its different sources, compositions, and incineration methods. On the other hand, extensive investigations have highlighted the CSRs' ability to control alkali–silica reaction (ASR) as a destructive phenomenon, threatening durability. Hence, this study was conducted in order to study the ability of SSA with two finenesses, three replacement levels, and also its ternaries with trass or pumice, as natural pozzolans, to control ASR. The utilized SSA did not meet the requirements of a pozzolan at either finenesses. The results revealed that despite the fact that SSA generally reduced ASR expansion significantly, it only managed to control ASR at 50% replacement level. This was true for both finenesses. Furthermore, ternaries improved resistance against ASR expansion significantly, providing the ability to control ASR at lower replacement levels of SSA. The Si/Ca ratio was the key reason of SSA's ability to control ASR as it contained 1.5 and 2.5 times more SiO2 and Al2O3 than Portland cement respectively, and about one third of its CaO. Scanning electron microscopey (SEM), energy dispersive spectroscopy (EDS), and mapping confirmed that the relative amounts of Si, Al, and Ca in the SSA was crucial.

Modelagem Numérica de RAA: um método semi-empírico atualizado

Abstract Alkali-silica reaction (ASR) is a deleterious expansion phenomenon affecting concrete structures worldwide. It occurs when a susceptible chemical composition of concrete components is present, and it is particularly rampant in inherently humid environments. This phenomenon is exacerbated when found in mass concrete structures such as dams and foundations. The amount of volumetric ASR strain used to be deemed as nearly constant, however, recent advances have shown that it is actually affected by the distribution of volumetric stresses. Therefore, this behavior demands an update in the numerical models that have been devised to simulate the anisotropic ASR-driven expansion. This paper deals with Saouma & Perotti’s thermo-chemo-mechanical coupled model, which has been applied in a solely mechanical manner, and updated to account for a varying volumetric strain. A simulation of the experiment that shed new light on the variation of ASR volumetric strain was then carried out with the finite element method package COMSOL. As a result, significantly smaller errors in predicted strains were attained by the updated model in comparison to the original one, and consequently, the new model poses a promising tool for a more accurate simulation of ASR expansion.

Analysis of the Resistance of Self-Compacting Concrete (SCC) with the Use of Granite Stone Waste to Alkali-Silica Reaction

Aggregates occupy ±70% of the concrete volume and their quality must meet specifications. Concrete surfaces submerged in water for a long time cause concrete failure due to the reaction between aggregate and cement to form silica gel. The wear value of granite is less than gravel, so this study used granite as a substitute for coarse aggregate. This study was conducted to assess the resistance of SCC concrete with 0%, 25%, and 30% granite stone variations to alkali-silica reaction attack. The experimental method was applied to the study with ACI method mix design as well as 25 MPa plan fc'. Concrete cylinder samples 150 mm x 300 mm aged 28 days were used in the compressive strength test, alkali-silica reaction expansion test used mortar block samples 285 mm x 25 mm x 25 mm in 80±2˚C NaOH solution bath for 14 days. The optimum compressive strength of 32.17 MPa and the lowest percentage change in length of 0.04% was obtained by sample BG.25-SCC, indicating that granite stone is not reactive to silica alkali reaction because the percentage change in length <0.10%. This study concludes that granite stone can improve the resistance of concrete to silica alkali reaction.

Mechanical properties and alkali silica reaction of recycled glass fine aggregate mortar

The recycled glass fine aggregate (RG) causes an alkali-silica reaction (ASR) in concrete of mortar using cement materials. However, supplementary cementitious materials (SCMs) like fly ash, silica fume, blast furnace slag can reduce ASR expansion of RG. In this study, the mechanical properties and ASR behavior of RG mortar mixed with/without SCMs was evaluated. It was confirmed that the RG mortar mixed with SCMs decreased ASR expansion. However, the mechanical properties after ASR decreased as reaction days increased. This is because ASR gel was formed inside the microcracks that existed in RG. Therefore, the ASR gel inside the RG destroyed the RG and reduce the mechanical properties of mortar.

Factors affecting compressive strength and expansion due to alkali-silica reaction of fly ash-based alkaline activated mortar

The development of environmentally friendly alkaline-activated materials (AAMs) holds promise, as AAMs can be derived from waste materials. This study aims to investigate the factors influencing (i) compressive strength and (ii) expansion due to alkali-silica reaction (ASR) in AAMs. These factors include alkaline concentration, heat curing conditions, fineness of fly ash, and the liquid alkaline-to-binder (L/B) ratio. The findings indicate that the higher concentrations of NaOH solution led to an increase in AAM compressive strength due to the enhanced dissolution and polymerization rates in a more alkaline environment. Heat curing stimulated chemical reactions and structure formation, while the reduced water content resulted in lower porosity and higher compressive strength in the hardened cement. Finer fly ash yielded greater compressive strength than coarser ash, as its smaller spherical particles contributed to denser and firmer structures. The presence of calcium minerals, from both Ordinary Portland Cement (OPC) and high-calcium fly ash, bolstered the strength of hardened products. Moreover, calcium minerals like CaO, Ca(OH)2, and CaSO4 were found to induce ASR expansion by promoting gel formation, leading to later-stage expansion in the hardened cement or concrete. However, finely milled fly ash as a precursor significantly reduced ASR expansion in AAMs, by approximately 40% compared to ordinary Portland cement. This study provides valuable insights for civil engineers for better understanding of AAM behavior and makes contributions to the safety and sustainability of cement and concrete systems.

Investigating equivalency of different element models in discrete mesoscale analysis of ASR-damaged concrete

The alkali-silica reaction (ASR) is one of the most serious durability issues affecting the safety of concrete structures. Numerical simulation is useful for monitoring the internal condition of an RC structure with ASR damage and predicting its long-term behavior. A mesoscale three-dimensional rigid body spring model (3D RBSM), a type of discrete analysis model, has previously been developed to simulate ASR expansion by modeling aggregate and mortar separately. The element size in simulations using this model (known as the aggregate model) is 2–3 mm, so the number of elements is huge and computation time correspondingly long. An equivalent model with lower number of elements is required, so in this study a concrete model based on RBSM is proposed. The aggregate is not separately modeled and expansive elements are included to simulate ASR expansion, allowing a larger element size (1–2 cm). The number of elements and computation time are less than 1 % compared with the aggregate model. This proposed model is used to simulate free ASR expansion, ASR expansion under confinement, and the mechanical properties of ASR-damaged concrete, as well as pullout behavior after ASR expansion. The simulation results are compared against previously reported results obtained using the aggregate model, as well as against experimental results. This comparison confirms equivalency between the concrete model and the aggregate model, opening the possibility of simulating ASR damage in RC structures in the future.

PVA fiber-reinforced geopolymer mortar made with hybrid recycled aggregates: Toward thermal insulation, lightweight and improved durability

Polyvinyl alcohol (PVA) fiber-reinforced geopolymer mortar minimizes the shortcomings of large drying shrinkage and high brittleness of conventional geopolymer mortar made with natural sand. Replacing natural sand with crushed glass (CG) and crumb rubber (CR) aggregates is a sustainable alternative. However, their collaborative role in the performance of PVA fiber-reinforced geopolymer mortar remains unclear. To fill this gap, this research investigated the performance of a novel geopolymer mortar reinforced with 0–0.6 vol% PVA fibers and made with CG and CR aggregates with a mix ratio of 10:0–0:10. Due to different physical properties, CG and CR aggregates worked together to control their respective disadvantages. Compared to 100% CG, incorporating 30%–100% CR reduced the hardened density by 8.33%–27.13% and the thermal conductivity coefficient by 44.37%–82.17%. For 0.6 vol% PVA fibers, the 28-d drying shrinkage and 364-d alkali-silica reaction expansion decreased by 10.24%–35.20% and 60.71%–72.50%, respectively.

A Locally Available Natural Pozzolan as a Supplementary Cementitious Material in Portland Cement Concrete

For several decades, class F fly ash has been an attractive supplementary cementitious material, at least in part, due to its ability to reduce Portland cement consumption and mitigate alkali-silica reactions in concrete. However, fly ash availability is becoming uncertain as the energy industry decommissions coal burning power plants as it transitions to renewable energy production. This situation creates a need to identify viable and sustainable alternative supplementary cementitious materials. There are several types of supplementary cementitious materials, such as natural pozzolans, metakaolin, or ground granulated blast-furnace slag, which appear to be potential alternatives to fly ash in concrete. In this research, a locally available natural pozzolan (pumicite) was selected to replace fly ash in concrete. After conducting alkali-silica reaction tests on mortar mixtures, rheological and strength properties, shrinkage, resistance to freezing and thawing, and chloride ion permeability of concrete mixtures containing different amounts of fly ash and natural pozzolan were evaluated. The results showed that pumicite was more effective than fly ash at mitigating the alkali-silica reaction, and a pumicite content of 20% was necessary to mitigate the alkali-silica reaction. Ternary mixtures containing both pumicite and fly ash were the most effective cementitious materials combinations for mitigating the alkali-silica reaction expansion. Additionally, pumicite provided acceptable compressive strength and modulus of rupture values (greater than 4.0 MPa) that exceeded the flexural strengths provided by established mixtures containing only fly ash. Shrinkage and durability factor values for all mixtures were less than 710 μstrain and greater than 75, which are generally considered acceptable. Additionally, all mixtures with acceptable alkali-silica reaction expansions had very low chloride permeability. These results indicate that pumicite can be a reliable alternative for fly ash.

Influence of the expansive sites distribution on alkali-silica reaction expansion under applied stress: Crack orientation as a key factor for expansion transfer

The influence of the expansive site distribution of the alkali-silica reaction (ASR) on the expansion behavior under applied stresses was numerically investigated to verify the mechanical factor of expansion transfer. In the analysis, the aggregate and mortar phases were individually modelled by mesoscale discrete analysis. To reproduce expansive site distribution and time-dependent behavior, expansive phase model, pressure development model, and creep model were developed. As a result, expansion transfer was observed for the model based on the reaction rim assumption and the crack effect model under applied stress of less than 10 MPa. A detailed numerical investigation identified that the cracks under applied stress in the reaction rim model are modified more easily than those in the gel pocket model, despite crack generation being inhibited. Consequently, expansion transfer was found to be significantly influenced by the crack orientation because of the mechanical interactions at the expansive sites under applied stress.

Development of prediction models for evaluation of alkali-silica reaction in concrete

Alkali-silica reaction (ASR) and expansion induced are one of the major concerns over durability of concrete structures. It causes an increase in internal stresses and hence deteriorating mechanical properties, reducing load capacity, and compromising structures’ serviceability. Factors governing ASR include water-to-cement ratio, alkali content, the content of reactive aggregate, exposure temperature, relative humidity, etc. Previous prediction models for ASR expansion focus on the measurements under particular conditions and these models are suffering from the neglect of effects of some factors. This study aims to propose a back-propagation neural network (BPNN) model to predict ASR by considering both mix compositions and environmental conditions. In this paper, by adopting two different training functions, namely Levenberg-Marquardt function (LM) and Bayesian regularisation backpropagation (BR), two models of LM-BPNN and BR-BPNN were developed and proposed. To achieve this, a database containing 168 pairs of data from 25 studies was established, its data includes water-to-cement ratio, cement content, alkali fraction, content of non-reactive and reactive fine/coarse aggregate, temperature, and relative humidity. Results indicate that both LM-BPNN and BR-BPNN models can produce reasonable estimates for ASR expansion at 180 days with MSE and R of 0.00209%, 0.002753%, 0.926 and 0.912, respectively. Results reveal that fraction of reactive fine/coarse aggregate is dominant on ASR expansion while alkali content and humidity have a significant correlation with expansion. Water-to-cement ratio, cement content, and content of non-reactive fine/coarse aggregate have low impact on ASR expansion based on the results.

Expansion and Mitigation of Alkali-Silica Reaction in Binary Blended Concrete Confining Potentially Reactive Aggregates

Without a cure but preventable, Alkali-Silica Reaction (ASR), dubbed the “Concrete Cancer,” happens when alkali in cement bonds with silica in aggregates to form an expansive gel. This research aims to investigate expansion and influence mitigation of ASR in concrete by identifying potentially reactive aggregates causing its onset and using binary blended cement to slow down unwanted gel expansions through the mitigative ability found in its fly ash component. This research also observed variations in expansive behavior and the physical changes that arose after the experiments. Aggregate samples were collected from different quarries in Davao, Philippines, denoted as Deposit A, Deposit B, Deposit C, and Deposit D. These deposits were tested according to the ASTM C1260: Accelerated Mortar Bar Tests (AMBT) to identify a reactive group. Three aggregate groups, Deposit A, Deposit B, and Deposit C, were tagged as reactive due to exhibiting more than a 0.1% increase in lengths, indicating unideal expansion. Additional sets of AMBTs were done for the identified aggregates using blended cement as a binder to test the combinations' ability to minimize expansion. This resulted in an average expansion decrease per set of approximately 78%, 82%, and 85% for A, B, and C, respectively, further strengthening the reputation of fly ash as an effective mitigating SCM against ASR.

Characteristics of the alkali-silica reaction in seawater and sea sand concrete with different water-cement ratios

Research of seawater and sea sand concrete (SWSSC) is the current hot topic, but effects of water-cement ratios (W/C) on alkali-silica reaction (ASR) of SWSSC haven't been investigated. To solve this issue, the ASR products, pore structure and expansion rate of specimens with different W/C (0.35 ∼ 0.55) were measured. The study shows that pore structure and Na+ consumption are two key factors influencing ASR of SWSSC. When the W/C increases from 0.45 to 0.55, Na+ in specimen replaces K+ in ASR-P1(K0.52Ca1.16Si4O8(OH)2.84·1.5H2O), and ASR-P1 is converted into Na-shlykovite(NaCaSi4O8(OH)3·2.3H2O); the porosity is the dominant factor for the expansion rate of SWSSC. When the W/C increases from 0.35 to 0.45, the Na+ consumption is the dominant factor for the expansion rate of SWSSC. Magnesium element mainly coexists in Na-shlykovite and transition zone in SWSSC with W/C = 0.55. The research results are beneficial to inhibit ASR of SWSSC with different W/C and improve their durability.

ASR induced by chloride- and formate-based deicers in concrete with non-reactive aggregates

Despite ongoing efforts to prevent the damaging effects of alkali-silica reaction (ASR) in concrete structures, this phenomenon still exists and causes significant degradation. This study aims to investigate the role of various deicing agents in provoking ASR by examining volume expansion, cracks, and microstructure of mortar and concrete containing aggregates identified as non-reactive by standard ASR test methods. To achieve this, the concrete specimens undergo simulated operating conditions testing to induce ASR expansion, with an external supply of alkali from chloride- and formate-based deicers. The findings suggest that the configuration and concentration of the deicing agent used, as well as the mineral composition of the aggregate that was previously identified as non-reactive, can significantly impact the expansion and damage caused by ASR. The results indicate that existing methods for testing aggregates for ASR may have limitations when formate-based agents are used.