ASR Degradation and Expansion of Plain and Reinforced Concrete

Abstract

Alkali-silica reaction (ASR) occurs when the reactive siliceous aggregates (coarse or fine) are used in concrete with a high alkali content and exposed to high levels of moisture. In the long-term, ASR exhibits itself in the form of expansion, cracking, and ensuing degradation in mechanical properties, which may affect the functionality of structures. ASR has been extensively observed in dams, bridges, and power plants. In this study two mixes of concrete were prepared using fine aggregates from one of the most reactive siliceous aggerate sources in the United States located in El Paso, Texas. One of the concrete mixes was dosed with additional alkali content to bring the total alkalinity level to 1.25% by weight of cement to accelerate the ASR (compared to 0.1% in the other concrete mixture due to alkalinity from the cement only). Over a period of 18 months concrete cylinders, and plain and reinforced concrete prism samples from these two concretes were conditioned in different environments: indoor laboratory, outdoor in Los Angeles, and in an environmental chamber at 50°C and 90% relative humidity (RH). The ASR expansions and the corresponding changes in the compressive and tensile strength, modulus of rupture, and modulus of elasticity were monitored. Results showed that concrete tensile strength is more susceptible to degradation due to ASR. Additionally, the expansion caused by ASR in the prism samples reduces as the ratio of reinforcement increases. The results were used to develop relationships between ASR expansion and reinforcement ratio in a one-dimensional problem with an internal restraint.