Characteristics of early age shrinkages development of HPC containing mineral admixtures

Autogenous shrinkage under sealed condition and total shrinkage under single-faced dry condition of concrete with different mineral admixtures were measured from 6 hours to 3 days age by a new method, which adopted one type of untouched micro-displacement sensor controlled by a programmed computer automatically. The strength development and weight loss of every concrete were measured at the same time. Results shown that the addition of silica fume could increase the autogenous shrinkage a little and almost had no effect on the drying shrinkage. Fly ash could markedly decrease the autogenous shrinkage of concrete at early age, but the drying shrinkage may be increased due to lowering concrete strength development. The autogenous shrinkage of concrete could be evidently decreased at early ages only when high replacement of finely-pulverized blast slag was used, but the drying shrinkage would be increased in the case. The relationship between autogenous shrinkage and compressive strength of the same w/b concretes with mineral admixtures could be described as a linear equation. The drying shrinkages of the same w/b concretes at early ages could be approximately expressed as a logarithmic function of the water loss ratio.