Effects Of Alkali-silica Reaction Research Articles

Use of recycled glass in architectural mortars

In recent years,recycled glass has been widely used as aggregate replacements in concrete. Owing to the aesthetic potential of the coloured recycled glass,this research aims to fully utilize this advantage for their higher end uses,such as architectural mortar. In this study,architectural white cement mortar was produced with a self consolidating method using recycled glass as the aggregate. An adequate amount of Metakaolin was incorporated into the mortar to mitigate the adverse effect of alkali-silica reaction. The results show that the self-compacting method is suitable to produce architectural mortar containing up to 100% recycled glass. Overall,the performance of all the architectural mortar mixtures in terms of both fresh and hardened properties was good.

Effect of alkali-silica reaction and freezing and thawing action on concrete–steel bond

An experimental program was conducted to investigate the effect of stresses and cracks, caused by alkali-silica reaction (ASR) and freezing and thawing (F/T), on bond between reinforcing steel and concrete. Pullout test cylinders, reinforced with 18 mm steel bars, were used to evaluate bond behavior. Concrete prisms (50 × 50 × 300 mm) were also cast to evaluate expansion and reduction in ultrasonic velocity due to ASR and F/T cycles, respectively. Specimens were cured for 40 days before being either immersed in sodium hydroxide solution of 0.5 normality in order to accelerate ASR, or subjected to different cycles of F/T. Bond behavior, expansion, and ultrasonic pulse velocity tests were carried out as ASR progressed or under F/T cycles. The progress of ASR resulted in significant losses in critical bond stress and ultimate bond strength capacity reaching as high as 44% and 24%, respectively, accompanied by a significant increase in free-end slip at failure. The loss in bond due to ASR was higher for specimens prepared using concrete with lower concrete strength and higher percentage of reactive aggregate. F/T action caused a significant reduction in critical bond stress and ultimate bond strength that reached as high as 100% and 55%, respectively, and an increase in free-end slip at failure. Neither ASR nor F/T cycles affected trends in the behavior of bond stress versus free end slip curves.

The effect of alkali-silica-reaction on the fatigue behaviour of plain concrete tested in compression, indirect tension and flexure

The fatigue strength of concrete is an important factor in the design of many structures. However, the behaviour of concrete under indirect tensile repeated load has never been clarified to date by researchers. Therefore one of the objectives of this investigation was to study the effect of alkali-silica reaction (ASR) on the fatigue behaviour of concrete tested in flexure as well as under repeated indirect tensile load. The other objective of this investigation was to study the effect of ASR on the fatigue behaviour of plain concrete tested in compression. The latter is of particular importance to the structural engineer. Its importance lies in that it is a quality control test as well as a basic physical property for use in theoretical analysis of concrete structures. The lack of understanding of the basic nature of the fatigue behaviour of unreinforced alkali-silica-reacted concrete has led to this part of the investigation, which aims to relate the effect of the reaction not only to the performance of small specimens which are used to obtain basic design information but also to the lifetime of complete structures. The data obtained in relation to the fatigue performance of ASR-affected concrete could allow engineers to maintain and repair such structures with greater confidence. (A)

Unique response of LiNO 3 as an alkali silica reaction-preventive admixture

Lithium hydroxide and various lithium salts have been known to ameliorate the effects of alkali silica reaction for many years. The use of lithium hydroxide is not without risk. A significant increase in the pore solution OH − ion concentration (and pH) by lithium hydroxide and inadequate dosages are known to result in increased, rather than decreased expansion. Almost insoluble lithium salts (such as lithium fluoride and lithium carbonate) are effective at large dose levels, but generate lithium hydroxide in solution, and are thus subject to the same difficulty as LiOH. It is shown that lithium nitrate, a fully soluble neutral salt, does not generate significant increases in hydroxide ion concentration, and thus does not undergo the risk of accelerating the alkali silica reaction at the same time that it is attempting to ameliorate its effects. Lithium nitrate is, however, subject to the same extensive sorption by newly forming cement hydration products as other forms of lithium treatment, and a high dosage level is needed to indefinitely maintain the requisite concentration in solution.

Modeling of Thermomechanical Effects of Alkali-Silica Reaction

In this paper, a nonlinear continuum theory is applied to model the thermomechanical behavior of concrete subjected to alkali-silica reaction. The reaction results in formation of silica gel around the aggregate particles, which expands triggering a progressive damage of the material. The expansion rate is assumed to be controlled by the alkali content, the magnitude of confining stress as well as the evolution of the temperature. The progress in the reaction is assumed to be coupled with degradation of the mechanical properties of concrete. First, the constitutive model describing the thermomechanical effects of the reaction, as recently developed by the second writer, is presented. Subsequently, numerical examples are provided to assess the performance of the proposed formulation. In particular, the model is applied to analyze different structural elements of the Beauharnois power plant, situated in Quebec, Canada.

Effect of Alkali-Silica Reaction on Bearing Capacity of Plain and Reinforced Concrete

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Effect of Alkali-Silica Reaction on Tensile Bond Strength of Reinforcement in Concrete Tested under Static and Fatigue Loading

The effect of alkali-silica reaction (ASR) on bond strength in 26 reinforced concrete beams was studied. The reinforced beams were tested under static and cyclic loading. The test results showed that the reduction in bond strength caused by ASR are consistent with the lap length of the tensile reinforcement. ASR also caused a reduction in the fatigue life of the reinforced concrete beams with the tension reinforcement lapped in the bending zone.

Effect of Alkali-Silica Reaction on the Structural Behavior of Reinforced Concrete Beams

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