Drying shrinkage of cement treated paving materials

The occurrence of shrinkage cracks soon after construction in pavements with cement treated layers may pose several problems, especially when the prevailing conditions provide free surface water for injection into cracks under the action of traffic. Shrinkage cracking can usually be attributed to a combination of drying shrinkage and temperature differentials. The drying shrinkage results from the loss of water by evaporation and from self-dessication during the hydration of cement. The magnitude and rate of drying shrinkage is affected by several factors including cement content, moulding moisture content, clay content and type, cement/additive type, secondary additives, paving material characteristics and curing/drying conditions. To ensure satisfactory pavement performance, it is necessary to identify the relative influence of these factors on drying shrinkage. This information provides a basis for the preparation of appropriate specifications and recommended construction practices for cement treated pavements. A study has been carried out to assess the influence of cement content, moulding moisture content, cement/additive type, paving material characteristics and curing/drying conditions on drying shrinkage. This study involved the development of a technique for measuring drying shrinkage in the laboratory and the results of the laboratory tests have been related to the performance of recently constructed cement treated pavements in south-east Queensland. This survey has clearly revealed the significance of shrinkage cracking in the initiation of secondary cracking and pumping of fines in pavements with cement treated layers, leading to premature deterioration.