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Description: Two phase research about (1) effect of high-temperature curing (65ºC to 95ºC ) on concrete durability and (2) the effects of lithium admixtures, alkali-silica reaction and freeze-thaw microcracks, and chloride ingress on the potential for DEF. This report is also found on DVD021.
Delayed ettringite formation (DEF) is a deterioration phenomenon attributed to high temperature curing. This research was conducted in two phases using concretes and mortars heat cured at temperatures in the range of 65ºC to 95ºC. Phase I of the investigation was conducted to determine the effect of high-temperature curing on the physical properties of concrete. Phase II of the investigation examined the influence of other deterioration processes on the potential for DEF. The effects of lithium admixtures, alkali-silica reaction and freeze-thaw microcracks, and chloride ingress were investigated. Most adverse effects of heat curing were significantly mitigated by using ternary cement concrete except in the case of compressive strength. It was found that the use of lithium admixture in cementitious systems controls DEF. Also, externally applied chlorides have a pessimum effect on expansion due to DEF. This deviates from the commonly held view that chlorides mitigate sulphate attack in concretes. A mechanism describing the pessimum effect of chlorides on DEF expansion has been proposed.
This thesis was developed as part of the educational requirements under a fellowship grant from PCA.
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