The effects of restraint on ASR expansion of reinforced concrete

Abstract

This paper presents the results of tests relating the expansion of concrete specimens with alkali-silica reaction (ASR) to applied constant stresses, both tensile and compressive, and reinforcement ratio. The results were compared with those found by other researchers and to two proposed mathematical models. Additionally, the effects of rate of expansion, specimen size and shape, and orientation of restraint were investigated. It was concluded that size of specimen and orientation of restraint were important factors, and that the relationship between restraint and expansion could be modelled mathematically but the amount of data required restricted the model's practical use.

Development and multiaxial distribution of expansions in reinforced concrete elements affected by alkali–silica reaction

“…All expansion rates were reduced; however, the expansion rates for the unreinforced directions were slightly less affected than those for reinforced directions within the same specimens. Similar transitions in expansion rates have been evidenced in other studies and may be the result of a transition from internal to external moisture contribution to the reaction. Expansions in unreinforced specimen directions may have been more sensitive to variations in temperature and external relative humidity within the ECF.…”

“…A few specimens expanded the same or slightly more in more highly reinforced directions. These observations, to some degree, conflict with previously reported experimental data, which suggest that increased reinforcement levels result in lower expansion rates and reduced maximum element expansions . However, previous experimentation has often been conducted on uniaxially reinforced cylinders or prisms in which expansions were only monitored in the reinforced direction.…”

“…Distress originates from the formation of a chemically produced gel within hardened concrete and the subsequent swelling of the gel in the presence of a sufficient quantity of moisture supplied internally (i.e., within the pore structure for hydration) or externally (e.g., from the atmosphere or surrounding water). ASR expansion behavior in concrete elements is well known to be influenced by the presence of embedded, deformed reinforcement, which serves as a passive restraint to expansions . Understanding how different reinforcing details, such as reinforcement ratios, orientations, and layouts, influence the development and multiaxial distribution of ASR‐induced expansions is key in establishing the in‐service performance and functionality of ASR‐affected structures.…”

“…Several prior expansion monitoring studies have been conducted in an effort to understand the ASR‐induced expansion behaviors of RC specimens containing different quantities of deformed reinforcement. Many studies have examined the behavior of small‐scale cylindrical or prismatic specimens with deformed reinforcement in only one direction, occasionally with but most commonly without, nondeformed transverse reinforcement. Results from these studies have indicated that the presence of deformed reinforcement in one direction reduces the expansion rate and the maximum expansion developed in that direction.…”

“…Results from these studies have shown that expansions in restrained directions are less than those in the unreinforced directions comprising the same RC element. Other studies have examined the behavior of triaxially reinforced cubes, blocks, or beams with cross‐sectional dimensions ranging from 250 mm to beyond 1,000 mm. Various reinforcement ratio combinations have been incorporated in these specimens by way of individual straight bars for cubes and blocks or longitudinal bars and stirrups for beams.…”