Silica Reaction In Concrete Research Articles

Historical defects in buildings – No. 3: Alkali–silica reaction in concrete

Hugh Docherty continues this series by examining the potential damage caused by alkalis and silica reacting in concrete, and offering brief advice on identification and remediation.

Development of a Screening Tool for Rapid Fly Ash Evaluation for Mitigating Alkali Silica Reaction in Concrete

Performance-based approaches to evaluate fly ash effectiveness in suppressing alkali silica reaction (ASR) require testing for a range of replacement levels to determine optimum fly ash dosage. Current approaches of ASR evaluation, that is, determining optimum fly ash dosage for ASR mitigation, are impractical as a mix design tool for new concrete construction. Therefore, in the present work a screening tool is developed to predict optimum fly ash dosage to suppress ASR in concrete mixes. The screening tool uses water-soluble (readily available) alkali from fly ash and cement to determine pore solution alkalinity (PSA) of concrete mixes for different fly ash replacement levels. The optimum fly ash dosage in concrete to mitigate ASR is estimated based on the PSA and aggregate threshold alkalinity (THA) relationship, that is, PSA should be ≤THA to make the mix ASR mitigated. Results from the screening tool demonstrate an 82% reliability in predicting fly ash dosage necessary to keep expansions below 0.04% based on AASHTO TP 142 tests for ASR expansion. In addition, a multiple non-linear regression model was developed to predict water-soluble alkali from fly ashes in place of testing using 50 experimental data points from laboratory measurements and literature studies. Overall, the screening tool presents a rapid and reliable approach to determine the optimum fly ash content required for ASR mitigation based on pore solution composition of mixes and aggregate reactivity.

Recycling Untreated Coal Bottom Ash with Added Value for Mitigating Alkali–Silica Reaction in Concrete: A Sustainable Approach

Each year, about 730 million tons of bottom ash is generated in coal fired power plants worldwide. This by-product can be used as partial replacement for Portland cement, favoring resource conservation and sustainability. Substantial research has explored treated and processed coal bottom ash (CBA) for possible use in the construction industry. The present research explores using local untreated and raw CBA in mitigating the alkali–silica reaction (ASR) of reactive aggregates in concrete. Mortar bar specimens incorporating various proportions of untreated CBA were tested in accordance with ASTM C1260 up to 150 days. Strength activity index (SAI) and thermal analysis were used to assess the pozzolanic activity of CBA. Specimens incorporating 20% CBA achieved SAI greater than 75%, indicating pozzolanic activity. Mixtures incorporating CBA had decreased ASR expansion. Incorporating 20% CBA in mixtures yielded 28-day ASR expansion of less than the ASTM C1260 limit value of 0.20%. Scanning electron microscopy depicted ASR induced microcracks in control specimens, while specimens incorporating CBA exhibited no microcracking. Moreover, low calcium-to-silica ratio and reduced alkali content were observed in specimens incorporating CBA owing to alkali dilution and absorption, consequently decreasing ASR expansion. The toxicity characteristics of CBA indicated the presence of heavy metals below the US-EPA limits. Therefore, using local untreated CBA in concrete as partial replacement for Portland cement can be a non-hazardous alternative for reducing the environmental overburden of cement production and CBA disposal, with the added benefit of mitigating ASR expansion and its associated costly damage, leading to sustainable infrastructure.

The Attack of Alkali Silica Reaction on The Strength of Sea Water Resistance Concrete Pavement

Aggregate is the main material in concrete slab for rigid pavement. Quality of the aggregate should be eligible for the rigid pavement. Roads with rigid pavement structure can be damaged by non-technical factors including the effect of tidal flood. That damage due to the attack of alkali silica reaction in concrete. So, it required a research to select the type of aggregate that is more resistant to alkali silica reaction that will produce concrete more resistant to sea water. The method used is this research is experimental one, some sample in alkali silica reaction test using mortar bar of (25x25x285) mm dimensions. For the testing compressive strength and flexural strength of concrete using a cube-shaped test specimens of 150mm x 150 mm and a beam shape (150x160x600)mm. For testing performed after the age of concrete 28 days for normal conditions and after a concrete immersed fresh water 28 days, then soaked in seawater 13 days, and 26 days for testing the effect of sea water on the concrete strength. The test was performed using aggregates from PT. Armada Hada Graha, Magelang and PT. Panca Dharma Puspawira, Surakarta. The conclusion at this experiment is aggregate basalt (Surakarta) is more resistant to alkali silica reaction that caused by sea water than the aggregate andesite (Magelang).

Single-Impact Nonlinear Resonant Acoustic Spectroscopy for Monitoring the Progressive Alkali–Silica Reaction in Concrete

Alkali–silica reaction (ASR) is a ubiquitous cause of concrete degradation. The reaction produces an expandable gel that may cause internal over-stressing and cracking. This paper demonstrates the utility of single-impact nonlinear resonant acoustic spectroscopy (SINRAS) for monitoring the progress of ASR over the course of a standard ASR-susceptibility test. In SINRAS, the transient softening and subsequent recovery of resonance frequency due to one strong impact are analyzed. The performance of SINRAS in monitoring ASR is compared to that of multi-impact nonlinear resonant acoustic spectroscopy (MINRAS), where the gradual resonance frequency shifts caused by impacts of increasing intensity is measured. The changes in standard linear expansion and linear resonance frequency are recorded in parallel. Finally, the sensitivity of measured parameters to sample temperature is investigated. Our findings indicate that SINRAS, while being much simpler and faster to conduct, yields results that strongly correlate to those from MINRAS and even gives an additional parameter describing the rate of recovery. The extracted nonlinearity parameters exhibit good sensitivity and clearly differentiate between concrete with reactive and non-reactive aggregates. Further, this study suggests that the influence of sample temperature on the nonlinearity parameters depends on the level of ASR progression and has to be taken account.

The use of calcium sulfoaluminate cement to mitigate the alkali silica reaction in mortars

The mitigation of the alkali silica reaction in concrete has been the interest of many studies by using low-alkali cement or supplementary cementitious materials. In this paper, calcium sulfoaluminate cement, characterized by its low alkali content and low pH, is used as a mean to reach this goal.Therefore, the main objective is to verify if the composition of a sulfoaluminate cement paste can mitigate the alkali silica reaction compared to that of a Portland cement. The reactive flint aggregate from north of France was used to initiate the alkali silica reaction phenomena with two types of cements: Portland cement CEMI 52.5 N from Holcim, and calcium sulfoaluminate cement Alpenat from Vicat. Alkalis were added by introducing NaOH or NaCl in the mortar mixing solution; six mortars were made. Two references – with Portland or sulfoaluminate cement – without addition of extra amount of alkali, and the four other mortars with either NaOH or NaCl. The results show that, for the reference mortars non expansion/alteration has been detected during the test duration of 140 days. For Portland cement mortar, with same alkali content but coming from two different sources (NaOH or NaCl), the expansion is almost the same. The expansion measurements show that the using of calcium sulfoaluminate cement can mitigate the alkali silica reaction in mortars by reducing its expansion 7 times compared to that of Portland cement mortars. This result was confirmed by the microstructural observations, where the frequency of the alterations – due to the alkali silica reaction – is much less in sulfoaluminate based mortars than the one of the alterations in Portland based mortars.

Effect of Lithium Based Admixtures on Alkali Silica Reaction in Concrete and Flexural Behavior of Reinforced Concrete Rectangular Beams

In recycling of lithium-ion batteries, lithium is a challenging element, which possesses great threat to the environment. The disposal of electronic waste is a major problem, which our country is currently facing, whereas, the lithium is one of the compound in electronic waste which challenges the recycling of lithium-ion batteries. If lithium is properly extracted, it can be used for structural engineering purpose. Lithium, if used in concrete, it controls the cracks due to alkali silica reaction (ASR), resulting in increased strength and durability of the concrete. Lithium based admixtures are effective in suppression of alkali silica reaction and delayed ettringite formation, if the dosage added in concrete is appropriate. The main objective of this paper is to assess the effectiveness of LiNO3 at various dosage levels in concrete. In this paper, the effect of LiNO3 on the mechanical properties of concrete, ASR gel formation and the flexural behavior of reinforced concrete rectangular beams are studied. The mechanical properties of concrete was investigated for six mix proportions comprising of control mix, lithium nitrate at 0.6M, 0.65M, 0.7M, 0.75M, 0.8M. LiNO3 not only prevents the ASR gel formation, but also it has great influence on mechanical properties of concrete. The results indicate that the concrete with 0.75M LiNO3 has higher strength values. SEM analysis has been performed for 0.75M and control mix to study the micro characteristics of concrete. The ASR gel formed in 0.75M has been suppressed as compared to that of concrete without lithium nitrate as an admixture. The durability studies are performed in concrete for water permeability, water absorption and rapid chloride penetration characteristics. The analytical study of flexural behavior of reinforced concrete rectangular beam is done using the software ANSYS 16.0.

Influence of Exposure Conditions on the Efficacy of Lithium Nitrate in Mitigating Alkali Silica Reaction

Lithium nitrate is known to have the highest potential to inhibit alkali silica reaction in concrete. It is well soluble in water and does not increase the pH of concrete pore solution. The extent to which the alkali silica reaction is mitigated is affected by the amount of the applied lithium ions, exposure conditions and by the kind of reactive aggregate. It is known that some lithium compounds such as lithium carbonate or lithium fluoride, when used in insufficient amount, may increase expansion due to alkali silica reaction. This effect was not detected in the presence of lithium nitrate. The aim of this study was to determine the effect of lithium nitrate on alkali silica reaction in mortars exposed to different conditions. Expansion studies were conducted in accordance with the accelerated mortar bar test (ASTM C1260) and the standard mortar bar test (ASTM C227). It was observed that the long-term expansion results are different from the values obtained in the accelerated mortar bar test. Lithium nitrate does not reduce ASR-induced expansion when mortars are stored under conditions specified in ASTM C 227. The microstructure of the mortar samples exposed to different conditions was examined and X-ray microanalysis was performed. The microstructure and compositions of the alkali-silica reaction products varied. The amount of alkali silica gel in mortars with lithium nitrate in which the expansion was high was greater than that in the mortar bars tested by accelerated method.

Briefing: Low-alkali cements as inhibitors of alkali–silica reaction

In this study, a compositional parameter, such as the maximum allowable total alkali content of cement (Matac) is proposed to identify the non-CEM I cements for their use as inhibitors of alkali–silica reaction in concrete. The Matac values for different types of Italian non-CEM I cements (cement type CEM III and CEM IV) were calculated using the authors' previously published experimental results. The Matac value is found to change significantly with the type of cement considered (blast furnace cement, pozzolanic cement made from coal fly ash or natural pozzolana). For cements of the same type (pozzolanic cements made with different natural pozzolanas), very similar Matac values are obtained. It is also demonstrated that the Matac value calculated for a CEM I cement is congruent with the limit of 0·6% as Na2Oeq commonly specified for the total alkali content of low-alkali Portland cements.

Alkali release from aggregates: contribution to ASR

The alkali–silica reaction in concrete is normally associated with alkalis from cement. However, some aggregates have alkalis in their crystalline or amorphous phases that can be released during long-term exposure to the water in concrete structures. Previous research has demonstrated that alkaline feldspars in aggregates can supply a significant amount of alkalis when exposed to alkaline solutions. Other research indicates that micas can release alkalis and promote alkali–silicate reaction. The main problem is the evaluation of the potential contribution of the alkalis released by aggregates during the service life of a concrete structure. This paper describes accelerated tests that can determine the level of alkalis released from aggregates, but finds that the results are not representative of the long-term behaviour of concrete structures. Alternative tests are being developed, but these could take much longer, and it is concluded that numerical methods may be the most practical solution.

Mitigating Alkali–Silica Reaction in Concrete

This study investigated the effectiveness of using recycled waste glass in portland cement concrete, both as a finely ground powder and as a crushed granular material. For the potential of glass to undergo alkali–silica reactivity (ASR) distress to be assessed, mortar bar and miniature concrete prism tests were conducted with glass as both a powder and a crushed material. Parallel studies were conducted with a crushed natural aggregate. Simultaneously, strength activity index and thermogravimetric analysis tests were conducted on cementitious mixtures to evaluate pozzolanic reactivity of glass powder when used as cement replacement material. Results showed that when glass powder (70 μm average size) was used as cement replacement material, its pozzolanic behavior (measured by thermogravimetric analysis and strength activity index) was minimal. When glass powder was used as aggregate replacement material, the combination of glass powder and ASR-prone coarse aggregates showed significantly lower expansion than did control specimens in accelerated mortar bar and miniature concrete prism tests. This result indicates the beneficial effect of using glass powder in mitigating expansion induced by ASR. The mechanism by which the fine glass powder appeared to alleviate ASR in coarse aggregates, and therefore any significant distress in test specimens, was by rapidly undergoing its own ASR, which depleted alkalinity in the vicinity of reactive coarse aggregates. ASR associated with the fine glass particles was localized, and the reaction product did not appear to generate sufficient expansion to cause global distress. Additional field studies are required to validate study findings before waste glass can be used in concrete on a large scale.

Research of Alkali Silica Reaction in Concrete With Active Mineral Additives

This paper analyses the effect of mineral additives on alkali - silica reaction. Amorphous SiO2 contained in concrete aggregate is known for reactions with Na2O and K2O that cause concrete expansion and cracking. Concrete expansion is the result of silicates reaction (ASR). Alkali silica gel is a reaction product having expanding properties. Expanding silica gel creates stress that causes concrete cracking. The paper investigates the elimination of the negative effect of ASR by using fly ash as active mineral additive. In the tests active mineral additive (fly ash) is expected to reduce the effect of alkali - silica reaction and volumetric strain. DOI: http://dx.doi.org/10.5755/j01.sace.6.1.6354

Alkali silica reaction in concrete induced by mortar adhered to recycled aggregate

The durability of recycled concrete must be determined before this material can be used in construction. In this paper the alkali-silica reaction in recycled concrete is analyzed. The recycled concrete is made with recycled aggregates, composed by original limestone aggregates and adhered mortar with reactive silica sand, and high alkali content cement. Due to the manufacturing process used for concrete production and the high water absorption capacity of recycled aggregates, cement accumulation happens in the interface (ITZ). The concentration of alkalis on the surface of recycled aggregates- ITZ and the presence of reactive sand in the mortar adhering to the recycled aggregate induce an alkali-silica reaction in 6-month concrete. The existence of this reaction is confirmed by environmental scanning electron microscopy (ESEM) and EDX analysis. The mechanical properties of 6-month recycled concrete were similar to those values at 28-days of curing.

Effectiveness of nondestructive testing for the evaluation of alkali–silica reaction in concrete

This paper deals with the application of various test methods for monitoring the progression of alkali–silica reaction (ASR) in laboratory concrete mixtures. The effectiveness of each method is reported. Concrete specimens were stored at 38 °C in high humidity environment according to the Canadian CSA A23.2-14A standard. Mechanical properties were assessed with conventional destructive test and with nondestructive tests (ultrasonic pulse velocity, dynamic modulus of elasticity and nonlinear acoustics). Petrographic examination was performed to confirm damage associated with ASR. Compressive strength and ultrasonic pulse velocity were slightly affected by ASR expansion. Both static and dynamic moduli of elasticity were significantly affected by ASR expansion. Nonlinear acoustics yielded the best correlation with expansion. The ultimate goal of such study would contribute to develop a universal procedure for the evaluation of the state of ASR in a structure. This paper does not answer this issue but is a first step toward that goal.

Test methods for evaluating preventive measures for controlling expansion due to alkali–silica reaction in concrete

This paper provides a critical evaluation of the various methods available for testing the efficacy of measures for preventing expansion due to alkali–silica reaction (ASR) in concrete containing deleteriously reactive aggregate. The ideal test method should be rapid, reliable and capable of determining the influence of aggregate reactivity, alkali availability and exposure conditions. None of the currently available or commonly used methods meet all of these criteria. The shortcomings of the different test methods are discussed and suggestions are made for modifying the concrete prism test and accelerated mortar bar test to make these tests more acceptable.

Role of PFA quality and conditioning in minimising alkali–silica reaction in concrete

This paper describes the work of a study carried out to assess the effect of pulverised full ash (PFA) quality (including conditioned (moistened) PFA) on its ability to minimise the risk of alkali–silica reaction (ASR) in concrete and thereby, whether the wider range of materials covered in BS 3892-1, BS 3892-2 and BS EN 450 can be used in this role. A total of 11 PFAs (within and between sources) and three types of aggregate combination, covering materials used in the UK, were examined. Two series of tests were carried out, which used concrete mixes proportioned to (a) the BS 812-123 standard method (alkali content 7·0 kg/m3) and (b) the BRE method (alkali content from 3·6 to 6·0 kg/m3), using the BS 812-123 test procedure (38°C, above water). The results obtained over three years, established that the physical and chemical properties of PFA (fineness and alkali content (Na2Oeq)) had only a minor influence on its ability to minimise ASR risk. Conditioning of PFA and its loss on ignition appeared to have no effect. Overall, the results suggest that PFA to BS 3892-2 and to BS EN 450, may be considered to be equally as effective as BS 3892-1 PFA in minimising ASR in concrete, containing potentially reactive aggregates available in the UK. The outcomes of this and other work have been considered by the ASI concrete committee and this has led to a change in BS 8500, which now permits the use of BS EN 450 PFA.

Investigation into Potential of Alkali–Acetate–Based Deicers to Cause Alkali–Silica Reaction in Concrete

Recent investigations by the FAA into the condition of airfield pavements have indicated increased occurrence of premature deterioration in concrete pavements, particularly caused by alkali–silica reaction (ASR). On the basis of the evidence, it was suspected that certain deicing chemicals used on the pavements may have been responsible for the distress. This paper presents the results from a study conducted to investigate the effect of potassium acetate–and sodium acetate–based deicers on causing ASR in test specimens. A modified ASTM C 1260 test procedure was used in this study, in which mortar bars prepared with reactive aggregates were soaked in deicer solutions, instead of 1 N sodium hydroxide solution as in the standard ASTM C 1260 test. Tests were conducted on four reactive aggregate sources and one nonreactive aggregate, using a low-alkali and a high-alkali cement. In addition, standard ASTM C 1260 tests were conducted on all aggregates considered in this study. The effect of concentration and temperature of soak solutions on the observed expansions of mortar bars was also investigated. Length-change measurements, dynamic modulus of elasticity, scanning electron microscopy, and energy dispersive X-ray analyses were conducted on test specimens. The pH values of the soak solution were monitored to observe any interactions between the soak solution and the mortar bars. On the basis of this research, it was found that the two common airfield deicing chemicals—potassium acetate–and sodium acetate–based deicer solutions—have a significant potential to cause ASR in test specimens containing reactive aggregates.

The effects of potassium and rubidium hydroxide on the alkali–silica reaction

Expansion of mortar specimens prepared with an aggregate of mylonite from the Santa Rosa mylonite zone in southern California was studied to investigate the effect of different alkali ions on the alkali–silica reaction in concrete. The expansion tests indicate that mortar has a greater expansion when subjected to a sodium hydroxide bath than in a sodium–potassium–rubidium hydroxide bath. Electron probe microanalysis (EPMA) of mortar bars at early ages show that rubidium ions, used as tracer, were present throughout the sample by the third day of exposure. The analysis also shows a high concentration of rubidium in silica gel from mortar bars exposed to bath solutions containing rubidium. The results suggest that expansion of mortar bars using ASTM C 1260 does not depend on the diffusion of alkali ions. The results indicate that the expansion of alkali–silica gel depends on the type of alkali ions present. Alkali–silica gel containing rubidium shows a lower concentration of calcium, suggesting competition for the same sites.

Use of ternary blends containing silica fume and fly ash to suppress expansion due to alkali–silica reaction in concrete

This paper investigates the effects of cementitious systems containing Portland cement (PC), silica fume (SF) and fly ash (FA) on the expansion due to alkali–silica reaction (ASR). Concrete prisms were prepared and tested in accordance with the Canadian Standards Association (CSA A23.2-14A). Paste samples were cast using the same or similar cementitious materials and proportions that were used in the concrete prism test. Pore solution chemistry and portlandite content of the paste samples are reported. It was found that practical levels of SF with low-, moderate- or high-calcium FA are effective in maintaining the expansion below 0.04% after 2 years. Pore solution chemistry shows that while pastes containing SF yield pore solutions of increasing alkalinity at ages beyond 28 days, pastes containing ternary blends maintain the low alkalinity of the pore solution throughout the testing period (3 years).

Mathematical model for kinetics of alkali–silica reaction in concrete

Vast though the literature on the chemistry of the alkali–silica reaction (ASR) in concrete has become, a comprehensive mathematical model allowing quantitative predictions seems lacking. The present study attempts a step toward this goal. While two distinct problems must be dealt with, namely, (1) the kinetics of the chemical reaction with the associated diffusion processes and (2) fracture mechanics of the damage process, only the former is addressed here. The analysis is focused on the recent attempts by C. Meyers and W. Jin to incorporate ground waste glass (mainly, bottle glass) into concrete. With minor adjustments, though, the model can be applied to ASR in natural aggregates as well. A characteristic unit cubic cell of concrete containing one spherical glass particle is analyzed. A spherical layer of basic ASR gel grows radially inward into the particle, controlled by diffusion of water toward the reaction front. Modification of the solution for the case of mineral aggregates with veins of silica is also indicated. Imbibition of additional water from the adjacent capillary pores, which causes swelling of the gel, is described as a second diffusion process, limited by the development of pressure due to resistance of concrete to expansion. The water used up to form the basic ASR gel and imbibed to cause its swelling appears as a sink term in the non-linear diffusion equation for the global water transport through a concrete structure. The differential equations are integrated numerically. The study of the effects of various parameters provides improved understanding of the ASR, and especially the effect of glass particle size. Full prediction will require measurements of some parameters of the reaction processes.