Capillary Transport in Mortars and Concrete.
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.
Keywords:
mortar; cements; experimental design; sand
Abstract:
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.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899