The Restraining influence of unhydrated cement on the creep and shrinkage of cement paste

The investigation consists of a study of the restraining influence of unhydrated cement on the creep and shrinkage of cement paste. The effect of the aggregate-like behaviour of unhydrated cement on the rheological properties of hydrated cement paste is known. Tests were carried out on specimens containing cement paste of two water-cement ratios (Oo35 and 0.45 by weight) and different volumetric percentages of cement clinker. Type I nonnal Portland cement manufactured from the same batch as the clinker was used. The time-dependent deformation of hydrated cement paste is analysed as that of a composite material consisting of hard grains of unhydrated cement embedded in a continuous soft component of cement gel and pores. The observed values are shown to be more close to those calculated by using a series model of composite material. Under simultaneous drying conditions, loaded creep specimens were found to lose more moisture than companion shrinkage specimens . The creep recovery was greater at 95 percent relative humidity than at lower humidities.