Stresses and creep relaxation induced in restrained autogenous shrinkage of Thigh-strength pastes and concretes

The development of internal stresses induced by restrained autogenous shrinkage Ain cement pastes and concretes with low water/hinder ratios was investigated. The restrained autogenous stress Adeveloped was smaller than that expected on the basis of consideration of the autogenous shrinkage strain only. AThis was accounted for by relaxation due to early age creep. Reduction of w/b and the addition of silica Afume led to stresses that could approach 50% of the strength. At such high stresses, the risk. of cracking was Asignificant. Development of the stress in high-strength concrete could not be directly related to the Aproperties of its cement paste matrix. The presence of aggregates reduced proportionally the autogenous shrinkage. AHowever, this was not accompanied by a similar proportional reduction in the induced stress, since the aggregate Aalso caused a reduction in the creep relaxation effect. The reduced creep in the concrete, compared with the paste, Awas not always proportional to the aggregate content.