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.Structures Congress 2020 Downloaded from ascelibrary.org by 44.224.250.200 on 08/02/20.

Impact of Laboratory-Accelerated Aging Methods to Study Alkali–Silica Reaction and Reinforcement Corrosion on the Properties of Concrete

“…The swelling is known to occur at a relative humidity (RH) higher than 80% [ 21 ]. To study ASR in a short period of time in a laboratory environment, two methods have commonly been used: (i) immersion in an alkaline solution [ 22 ] (simultaneously using high-alkali content cement in some references [ 23 , 24 ]); and (ii) adding alkali hydroxide to the fresh concrete [ 25 , 26 , 27 , 28 , 29 ]. Elevated temperatures were also adopted in these two methods to further accelerate the ASR deterioration.…”