Combined Action of Mechanical Pre-Cracks and ASR Strain in Concrete

Abstract

An experimental study was undertaken to investigate aspects of durability of reinforced concrete elements subjected to the combined action of mechanical pre-cracking and alkali-silica reaction (ASR). Concrete beams with a high alkali content were pre-cracked in cyclic loading and subsequently submerged partially in water, or exposed to high humidity according to ASTM C1293-07 conditions (long-term method). Aggregates of relatively high, and aggregates of low reactivity were used. Reference beams with both reactive and less reactive aggregate were placed in the ASR chambers to compare the responses of specimens exposed to the combined action and specimens subjected to the ASR action only. The crack widths were monitored in pre-cracked specimens under both conditions (humidity, partially submerged). The test results indicate that the expansion due to the combined action at the middle of samples (mechanical crack zone) was significantly different in specimens exposed only to a high alkaline environment. The micro and macro cracks, induced by cyclic load, form ingress paths leading to increased ASR rate, while the macro-mechanical cracks provide regions of relatively free expansion, as deduced from decreasing crack widths.

Structural assessment of an ASR-affected reinforced concrete bridge

“…The sigmoid-shaped curve is corroborated by experimental data regression, from the relatively low initial expansion rate characterised by τ l to the reduced strain rate beyond the inflection point captured by the characteristic time. Both latent and characteristic times are functions of temperature, incorporating increased ASR reaction rate at elevated temperatures (Ulm et al 2000;Pourbehi et al 2019;Alaud & Van Zijl 2017). Jones and Poole (1986) reported that high moisture levels are required within the concrete for alkali-silica gel to absorb water and expand.…”

Seismic Analysis of the Kleinplaas Dam Affected by Alkali-Silica Reaction Using a Chemo-Thermo-Mechanical Finite Element Numerical Model Considering Fluid Structure Interaction

“…Note that permission to extract core samples from the actual dam was not obtained. The material model parameters in Table 1 are based on the specified compressive strength for the concrete used in the dam, and knowledge of the local aggregate type reportedly used in the concrete (Alaud and van Zijl 2017). Figure 6 illustrates the temperature history that is used in the transient heat-diffusion analysis of the dam.…”

“…Two main categories of aggregates are found, namely early reactive and late reactive, manufactured from rocks that contain specific types of minerals. Alaud and van Zijl (2017) studied the ASR effects on two types of aggregates that are widely used in South African construction namely Granite and Greywacke. They pointed out that concrete samples made using the Greywacke aggregates show late expansive behaviour, but the ultimate expansion was significantly more than that of the samples made using Granite aggregates.…”