Thermal Expansion of Aggregates and Concrete Durablity
Edwin J. Callan
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Differences in durability of concretes containing aggregates from the same source and similar concretes containing different 6ne and coarse aggregates are explained partially by differences in thermal expansion of the coarse aggregate and the mortar. Methods were developed to obtain simply the thermal coefficients for numerous aggregates. Concretes were tested in accel-erated freezing and thawing, yielding durability factors, DFE, for each combination. The DFEs were statistically analyzed with the difference between the thermal coe5cients of coarse aggregates and mortars, AC, and coarse aggregate absorption, A, as variables. For 78 concrete combinations a relation DFE = 109.65 - 8.76 AC - 15.22 A was developed with a correlation coeffcient of 0.719, which is highly significant. Thus, the durability of these con-cretes was reduced when the differential expansion of mortar and coarse aggre-. gate increased. Stresses set up by such differential expansion and their effects on concrete durability are discussed briefly. It is concluded that thermal effects of this type should be considered in choosing aggregates for highly durable concretes. The methods developed for determining coefficients of thermal expansion of coarse aggregate and mortar are described.