NIST Time|NIST Home|About NIST|Contact NIST

HomeAll Years:AuthorKeywordTitle2005-2010:AuthorKeywordTitle

Capillary Transport in Mortars and Concrete.

pdf icon Capillary Transport in Mortars and Concrete. (951 K)
Martys, N. S.; Ferraris, C. F.

Cement and Concrete Research, Vol. 27, No. 5, 747-760, 1997.


mortar; cements; experimental design; sand


Results are presented of a study concerning capillary transport of water in concretes and mortars as a function of water/cement ratio, sand size distribution, and curing. Our studies indicate that the capillary sorption (1) of water in concrete exhibits a complex time dependence. At early times, of the order of one hour, the total water uptake increased with the t1/2 behavior of typical capillary sorption theories. At longer times, of the order of tens of days, a slow crossover regime is seen as the rate of capillary suction decreases. At very long times, of order hundreds of days, a slower uptake which may be driven by the capillary forces in the smaller gel pores is found. Again the t1/2 behavior is recovered but with a much smaller sorptivity coefficient. We describe an empirical fitting form for data which describes capillary suction at both short and long times. Aspects of the experimental design including sample drying and exposure to air are discussed. The utility of service life predictions from such measurements is discussed.