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原文传递 Investigation of Differences in Deterioration of Two North Carolina Bridges Due to Alkali-Silica Reactivity (ASR); Final rept. 1 Jul 96-30 Jun 97

题名：	Investigation of Differences in Deterioration of Two North Carolina Bridges Due to Alkali-Silica Reactivity (ASR); Final rept. 1 Jul 96-30 Jun 97
作者：	Leming, M. L.; Nguyen, B. Q.
关键词：	Highway bridges; Cement aggregate reactions; Alkali aggregate reactions; Sea water; North Carolina; Cracking(Fracturing); Concrete durability; Portland cements; Microstructure; Expansion
摘要：	A previous investigation of the extent of alkali silica reactivity (ASR) in North Carolina highway structures found a distinct difference in the extent of ASR in cores from different parts of two separate bridges which contained reactive aggregates. In one bridge, differences were found to be directly related to the alkali content of the concrete. When the total equivalent alkali content of the cement was greateer than 0.6%, deleterious expansion and significant cracking occurred. When the alkali content was less than 0.55%, no deleterious cracking occurred even though ASR was present. When the alkali content of the cement was less than 0.4%, essentially no ASR was found. More ettringite was found than expected in one location in concrete with very low alkali content (less than 0.4%). In the other bridge, along the coast, the differences were due to the use of different coarse aggregates in the concrete, including a mixture of reactive and non-reactive aggregates along or in combination in varying amounts. An additional finding is that, due to the seawater exposure, the alkali content of the concrete is so high that ASR cannot be mitigated by controlling the alkali content of the cement. Ettringite, due to the seawater exposure, was found to have caused some cracking, but the damage was secondary in many cases and considerably less severe than that due to ASR.
总页数：	132p
报告类型：	科技报告