Research determination of autogenous shrinkage of cement pastes at very early age

Abstract

   The early volume change of concrete is the result of a complex physico-chemical process, the volume change of hydraulic cement paste is usually expressed by a shrinkage phenomena. This volume reduction is called autogenous shrinkage, it is correlated to chemical shrinkage and internal structural changes. For conventional concrete, autogenous shrinkage strain is generally negligible, but in concrete with low water-cementitious materials ratio or with silica fume it may be considerable. Restraint of the autogenous shringkage by aggregates or adjoining structural members may result in formation of micro and macro cracks that impair strength, durability and aesthetics. In practice, actual measurements of this early age (first 24 hours) shrinkage are rarely obtained due to difficulty in measuring and lack of standardization. This work aimed at developing a test apparatus to assess the autogenous shrinkage values occurring immediately after mixing the paste and continuing for the first 24 hours.