An updated look at drying shrinkage of Portland and blended Portland cement concretes

摘要

National and overseas reports clearly show that a significant proportion of concrete construction problems are associated with drying shrinkage. These results could be a result of few available long-term drying shrinkage data and changes of the behaviour of concrete mixes used nowadays. Therefore, poor estimates of drying shrinkage strains from prediction models could impair the performance and service life of concrete structures. The objective of the current research was to analyse the effect of mix design parameters on drying shrinkage of concretes made with Portland and blended Portland cements, considering 30 mixes that are commonly used in local construction, tested up to 1350 days of drying. It was concluded that, when using rapid-hardening cement of any type, a larger maximum aggregate size and lower water content reduces drying shrinkage. Cement and aggregate type are shown to have a significant effect on drying shrinkage time function and magnitude. Experimental results were compared with calculated drying shrinkage strains estimated by ACI209, CEB MC90, B3, GL 2000, Sakata 1993 and Sakata 2001 models. It was concluded that none of the shrinkage prediction models adequately reproduced the observed shrinkage behaviour of concrete made with Chilean Portland and blended Portland cements, underestimating the actual long-term drying shrinkage strains.