Alkali-silica Reaction Mitigation Research Articles

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.

Effect of fineness of high lime fly ash on pozzolanic reactivity and ASR mitigation

Typically, high lime fly ash (Class C) has been characterized as a fly ash, which at lower replacement levels is not as effective as the low lime (Class F) fly ash, in mitigating alkali-silica reaction (ASR) in portland cement concrete. The influence of fineness of Class C, obtained by grinding virgin fly ash into finer particles, on its pozzolanic reactivity and ASR mitigation performance was investigated in this study. In order to assess the pozzolanic reactivity of mortar mixtures containing virgin or ground fly ashes, the strength activity index (SAI) test and thermo-gravimetric analysis (TGA) were conducted on the mortar cubes and paste samples, respectively, containing virgin fly ash or two ground fly ashes. In addition, to evaluate any improvement in the ASR mitigation of ground fly ashes compared to that of the virgin fly ash, the accelerated mortar bar test (AMBT) was conducted on the mortar mixtures containing different dosages of either virgin or ground fly ashes. In all tests crushed glass aggregate was used as a highly reactive aggregate. Results from this study showed that the finest fly ash (i.e., with an average particle size of 3.1 microns) could increase the flow ability along with the pozzolanic reactivity of the mortar mixture. However, results from this study suggested that the fineness of high lime fly ash does not seem to have any significant effect on ASR mitigation.

Use of binary and ternary cementitious blends of F-Class fly-ash and limestone powder to mitigate alkali-silica reaction risk

The aim of this paper was to investigate the effects of binary and ternary cementitious systems including Portland Cement (PC), F-Class fly ash (FA) and limestone powder (LSP) to suppress expansion caused by alkali-silica reaction (ASR). Mortar prisms were prepared with potentially deleterious aggregates and tested by using Mortar-Bar Method according to ASTM C 1260. To evaluate the effect of FA and LSP on the suppression of ASR in mortar, ten different types of mortar were cast with combination of different dosages of FA and LSP as binary and ternary blend systems (partial replacement of PC) while the control mortar consisted of only PC as binder. Moreover, the Scanning Electron Microscopy (SEM) was carried out to interpret the microstructure. It was found that the reduction of ASR expansion rate due to increase in LSP content was more prominent compared to the increase of FA content in the binary blends system. Finally, the mixture containing ternary blends of 20% FA/LSP were in general more effective to mitigate the ASR risk for 14days compared to all mortars.

ASR Potential and Mitigation Measures for Wyoming Aggregates

AbstractDiscovered in the 1940s, alkali-silica reaction (ASR) causes undesired expansions in concrete. If unmitigated, ASR may cause premature deterioration. Since its discovery, researchers have s...

Mitigation of Alkali-Silica Reaction and Freezing and Thawing through Surface Treatment

Mitigation of Alkali-Silica Reaction and Freezing and Thawing through Surface Treatment

Mitigation of Alkali–Silica Reaction by Hydrated Alumina

Recent trends and forecasts on the availability of fly ash, slag, and lithium admixtures for use in concrete suggest a need to seek reliable alternatives for the mitigation of alkali–silica reaction (ASR). One such option may be aluminum-based admixtures. Past studies have shown that supplementary cementitious materials that contain alumina (Al2O3) are more effective at mitigating ASR than are supplementary cementitious materials purely rich in silica (SiO2). To establish the effectiveness and mechanisms of ASR mitigation by alumina, this research used pure hydrated alumina, Al(OH)3, as a cement replacement. The objectives of the study were to determine if Al(OH)3 can successfully mitigate ASR and to investigate five hypothesized mechanisms by which Al(OH)3 may mitigate ASR. The hypothesized mechanisms are ( a) reducing pH and alkalis in concrete pore solution, ( b) consuming and reducing portlandite and dissolved calcium in the pore solution, ( c) reducing silica dissolution and damage to aggregates at high pH, ( d) altering the composition of ASR gel and creating innocuous gels, and ( e) reducing water and ion transport by reducing the porosity and pore size of cement paste. The results show that Al(OH)3 can effectively mitigate ASR through mechanisms ( a), ( b), and primarily ( c).

State-of-the-Art Report on Alkali Silica Reactivity Mitigation Effectiveness Using Different Types of Fly Ashes

Use of fly ash by percent replacement of cement is considered as one of the most economical and effective methods for mitigating alkali-silica reaction (ASR) related distress in the concrete. However, fly ash has been proven to be somewhat variable in its effectiveness in inhibiting alkali-silica reactivity, principally because its composition depends on the coal properties from which it is derived. Typically class C fly ashes are not as efficient as class F ashes due to their higher calcium oxide content. Nevertheless, it is important to find out whether the lime content in the fly ash has linear effect on ASR distress mitigation and if the dosage of fly ash is more influential than type of fly ash. This research conducted extensive testing with nine different types of fly ashes with three in each category of fly ashes, class C, class F, and intermediate class. The results indicated that the effect of increased dosage of fly ash on ASR mitigation is linear for both low-lime and high-lime fly ashes and the dosage effect is more significant with rapid effect with high-lime fly ashes compared to low-lime fly ashes.

Effect of colloidal nano-silica on alkali–silica mitigation

Alkali–aggregate reaction was first observed in the US during 1920s. In the last decades, several studies investigated the mechanisms of alkali–silica reaction in concrete and the extent of damage it may cause to the cementitious matrix. Research on alkali–silica reaction mitigation covers mainly the use of supplementary cementitious materials and lithium compounds. However, with possible change in coal burning regulations and fly ash shortages in some areas, it is important to investigate approaches to mitigate ASR that involves lower amounts of supplementary cementitious materials. Furthermore, current research has shown the potential enhancements to concrete microstructure through the use of nano-silica. In the current study, the effect of using nano-silica on the alkali–silica reaction will be investigated. Preliminary results show that nano-silica can help mitigate the effect of alkali–silica reaction.

Factorial Design Method for Designing Ternary Composite Cements to Mitigate ASR Expansion

AbstractSupplementary cementitious materials (SCMs) have been successfully employed in binary or ternary cement blends to mitigate alkali-silica reaction (ASR). The determination of composition of binary or ternary composite cement to avoid deleterious expansion of concrete is usually based on a wide range of experiments, and it is time-consuming and costly. This paper introduces a factorial design method, combined with a ternary contour diagram, to correlate the compositions of ternary composite cements with ASR expansions with only seven batches of experiments. Based on the ternary contours, a safe composition range and dangerous composition range can be obtained. Moreover, the ternary contour diagram can also be used to analyze synergetic effects between any two components in the ternary composite cements. Finally, the efficiency of the factorial design method was verified by comparing the experimental and predicted expansions, and the results correlated very well.

Alkali Silica Reaction Mitigation and Prevention Measures for Arkansas Local Aggregates

Alkali Silica Reaction Mitigation and Prevention Measures for Arkansas Local Aggregates

An Experimental Study on Mitigating Alkali Silica Reaction by Using Fly Ash (FA) in Combination with Silica Fume and Expanded Perlite Powder (EPP)

ASR suppression by FA, SF, EPP, FA in combination with SF and EPP were evaluated by both mortar bar and concrete prism test. Mortar bars were made based on JIS A 1146, meanwhile concrete prism bars were casted in accordance with Rilem AAR-3. Both specimens were stored in 40°C 100% R.H. controlled room. Mortar and concrete mixtures used reactive aggregate in pessimum proportion. The results indicated that FA in combination with SF and EPP showed smaller expansion compared to FA. The best of concrete mixtures in reducing expansion is combination of FA with SF (FA15SF10).

Efficiency of ternary blends containing fine glass powder in mitigating alkali–silica reaction

In this study potential synergistic role of a finely ground glass powder in binary and ternary cementitious blends with conventional SCMs such as meta-kaolin, fly ash and slag was evaluated. Strength activity index, thermo-gravimetric analysis (TGA) and mortar bar tests were conducted to study the pozzolanic behavior and ASR mitigation ability. The results from this study showed that ternary mixtures consisting of finely ground soda glass with either slag or Class C fly ash out-performed binary mixtures consisting of each of these SCMs at an equivalent dosage level. Binary mixtures consisting of meta-kaolin out-performed ternary mixtures consisting of ground glass powder with meta-kaolin at equivalent dosage level. Among all the binary and ternary mixtures that contained 30% level of SCMs, the maximum strength activity index and the most efficient ASR mitigation was obtained in ternary mixtures consisting of at least 10% glass powder. The results from TGA studies supported these findings.

The Effectiveness of High Quality Supplementary Cementitious Materials for Mitigating ASR Expansion in Concrete with High Alkali Content

Alkali silica reaction (ASR) is influenced by external factors such as the surrounding environment of high alkalinity. Countries with cold climate have a high probability to be exposed to high concentrations of NaCl solution by the deicing salt. This condition will lead to serious ASR problems in concrete, if the aggregates contain reactive silica. The main research work in this paper is to investigate the effect of 15% replacement ratio of high quality fine fly ash (FA15%) and 42% replacement ratio of blast furnace slag (BFS42%) on the ASR mitigation in concrete with different alkali amount inside the pore solution. The experiments were conducted according to the accelerated mortar bars experiment following the JIS A1146 mortar bar test method. In addition, post-analysis such as observation of ASR gel formation by the Uranyl Acetate Fluorescence Method and observation of thin sections using a Polarizing Microscope were also conducted. The mortar bar tests show a very good mitigation effect of supplementary cementitious materials (SCMs). The results show that only small ASR expansions, which can be categorized as “innocuous”, occurred for specimens with 1.2% Na2Oeq using FA15% and BFS42%. However, larger alkali amount inside the system will require more SCMs amount.

The Effectiveness of High Quality Supplementary Cementitious Materials for Mitigating ASR Expansion in Concrete with High Alkali Content

Alkali silica reaction (ASR) is influenced by external factors such as the surrounding environment of high alkalinity. Countries with cold climate have a high probability to be exposed to high concentrations of NaCl solution by the deicing salt. This condition will lead to serious ASR problems in concrete, if the aggregates contain reactive silica. The main research work in this paper is to investigate the effect of 15% replacement ratio of high quality fine fly ash (FA15%) and 42% replacement ratio of blast furnace slag (BFS42%) on the ASR mitigation in concrete with different alkali amount inside the pore solution. The experiments were conducted according to the accelerated mortar bars experiment following the JIS A1146 mortar bar test method. In addition, post-analysis such as observation of ASR gel formation by the Uranyl Acetate Fluorescence Method and observation of thin sections using a Polarizing Microscope were also conducted. The mortar bar tests show a very good mitigation effect of supplementary cementitious materials (SCMs). The results show that only small ASR expansions, which can be categorized as “innocuous”, occurred for specimens with 1.2% Na2Oeq using FA15% and BFS42%. However, larger alkali amount inside the system will require more SCMs amount.

Effectiveness of Natural Zeolite in Mitigating Alkali Silica Reaction Expansions

Effectiveness of Natural Zeolite in Mitigating Alkali Silica Reaction Expansions

The potential of ground clay brick to mitigate Alkali–Silica Reaction in mortar prepared with highly reactive aggregate

The objective of this work was to study the effect of ground clay brick on mitigating the Alkali Silica Reaction (ASR) in mortar bars prepared with highly reactive aggregates. To evaluate the potential of ground crushed clay brick to mitigate ASR distress in mortar, mortar bars and mortar cubes were cast with combination of different dosages of ground clay brick (partial replacement of portland cement). The pozzolanic reactivity of ground clay brick was also evaluated using strength activity index test. In addition, the Scanning Electron Microscopy (SEM) and the Energy-Dispersive X-ray Spectroscopy (EDS) were conducted to evaluate the microstructure and location of the ASR gel and its chemical composition. The results from this study indicated satisfactory level of pozzolanic reactivity when cement was partially replacement by the ground clay brick. Also, it was found that replacing 25% of cement with ground clay brick (by weight) could significantly decrease the ASR expansion by 67% at the age of 14days. However, this study suggested that the compressive strength values of the specimens containing higher dosages of ground crushed brick (i.e. 50% replacement level) were significantly lower than that of the control specimens.

Influence of fineness of ground recycled glass on mitigation of alkali–silica reaction in mortars

The use of waste glass, both as a crushed glass aggregate and in a finely ground form, as a pozzolanic material in concrete has been extensively studied in the past. However, the combined use of finely ground glass powders with crushed glass aggregates has not been previously explored, as this presents a unique opportunity to not only maximize the use of waste glass in concrete but also potentially address the alkali–silica reaction issues, often associated with the use of crushed glass aggregates in concrete. This study focused on studying the influence of fineness of glass powder in mitigating alkali–silica reaction in mortar specimens containing crushed glass aggregate and a natural reactive aggregate. In these studies the glass powders were used both as a cement replacement material and as an aggregate replacement material. Two different fineness of glass powder were evaluated in this study, with an average particle size of 17 and 70microns. Mortar bars prepared with glass powder as aggregate replacement material at 10%, 20% and 30% replacement levels were evaluated in the standard ASTM C1260 test method. Mortar bars prepared with glass powder as cement replacement material at 10% and 20% were evaluated in the standard ASTM C1567 test method. The results from these studies showed that the finer glass powder showed significantly improved ability to mitigate ASR, particularly when used as an aggregate replacement material, both in the case of crushed glass and natural reactive aggregates. This study shows that an aggregate comprised of 100% glass material can be produced without any deleterious consequences of alkali–silica reaction, provided sufficient quantity of fine glass powder is used in the mixture.

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.

The resistance of mortars and concrete with calcareous fly ash on alkaline corrosion

Results of the research on alkali-silica reaction in the presence of calcareous fly ash are presented in the paper. Cements containing different calcareous fly ash quantity, including addition of other non-clinker cement constituents, i.e. siliceous fly ash, granulated blast furnace slag and ground limestone, were examined. Measurements of hardening mortars and concrete linear changes, performed according to ASTM standards, were used to evaluate the influence of calcareous fly ash on mitigation of alkali-silica reaction (ASR). The significance of chosen chemical and physical properties of calcareous fly ash in suppressing ASR expansion was also analyzed. Authors indicated that proper quantities of calcareous fly ash may improve the resistance of mortars and concrete to alkali-silica reaction.

New Considerations in Predicting Mitigation of Alkali-Silica Reaction Based on Fly Ash Chemistry

AbstractThe purpose of this study was to determine the ability of high CaO and/or high-alkali (Na2Oeq) fly ashes to control alkali-silica reaction (ASR) in mortar bars. The research focused on using an industry standard test method to validate if the chemical index characterization technique common in the literature could be used to accurately predict the replacement levels of investigated fly ashes to mitigate ASR. Results confirmed that low and moderate CaO content fly ashes (with both low and high Na2Oeq contents) were more effective in mitigating ASR compared to higher CaO and higher Na2Oeq ashes. A chemical index characterization technique was applied to calculate the required fly ash replacement based on the raw fly ash chemistries and 14-day industry standard results without fly ash (e.g., control). The index was shown to work well for low-CaO and low-alkali ashes; however, adjustments are necessary to use this methodology to predict replacement levels of moderate and high-alkali fly ashes. The ind...