Influence of Coarse Aggregate on the Shrinkage of Normal and High-Strength Concretes

Inclusion of aggregates leads to a reduction in drying shrinkage of cement paste. This is due to the elastic deformation of the aggregates that partly restrains the shrinkage deformation of cement paste. Hence, concrete with higher aggregate content exhibits smaller shrinkage. In addition, concrete with aggregates of higher modulus of elasticity or of rougher surfaces is more resistant to shrinkage process. In this paper the effects of the type of coarse aggregate on the shrinkage of normal and high-strength concretes are investigated. Two different types of crushed stone were used as coarse aggregates to produce the concrete mixtures used in this study. For each coarse aggregate type, two normal-strength concrete (NSC) mixtures and two high-strength concrete (HSC) mixtures were prepared. The 28-day compressive strength values of NSC mixtures were about 35 and 50 MPa, while those of HSC mixtures were 70 and 100 MPa, respectively. All shrinkage specimens were cured in water for 14 days after casting, then exposed to drying under the conditions of constant temperature (20℃) and relative humidity (60%). It has been shown that the type of the coarse aggregate influences shrinkage behaviour of both normal and high-strength concretes.