The effect of mix proportions upon the ultimate air-drying shrinkage of mortars

Values are given for the ultimate air-drying shrinkage of 25 mm square mortar and paste prisms moist-cured for one week and dried at 65% R.H. and 20°C. The mortars, of water/cement ratios 0·35, 0·47, 0·59 and 0·71 and aggregate volume concentrations ranging from 40 to 70%, were made from one hatch of all ordinary Portland cement and Thames Valley flint aggregate of 5 mm maximum size. The ultimate shrinkages of the mortars are plotted as contours on a ternary diagram of mix proportions by weight and it is shown that ultimate shrinkage of the mortars is approximately proportional to water content by weight in the original mix. A comparison is made between theoretical predictions of shrinkage and the experimental values.