Pumice Aggregates for Internal Water Curing.
Pumice Aggregates for Internal Water Curing.
(3746 K)
Lura, P.; Bentz, D. P.; Lange, D. A.; Kovler, K.;
Bentur, A.
Concrete Science and Engienering: A Tribute to Arnon
Bentur. Proceedings. International RILEM Symposium.
March 22-24, 2004, Evanston, IL, 137-151 pp, 2004.
Keywords:
water curing; pumice; aggregates; internal curing;
saturated lightweight aggregates; self-desiccation; pore
structure; autogenous shrinkage
Abstract:
A novel concept in internal curing of High Performance
Concrete is based on dispersing very small, saturated
lightweight aggregates (LWA) in the concrete, containing
sufficient water to counteract self-desiccation. The
amount of water in the LWA can be minimized this way,
thus economizing on the amount of the LWA. In this
study, the pore structure of different size fractions of
pumice aggregates was characterized by various
techniques. The fractions show differences in porosity,
sorption behavior, and pore-size distribution. The
smaller fractions have lower water absorption, but they
release a greater percentage of the absorbed water at
the relative humidity of practical interest in early-age
concrete, above 90%. Additionally, early-age properties
of mortars with different contents of saturated pumice
were investigated: a reference mix without pumice and
mixes with 4% and 8% pumice by volume of mortar. By
addition of pumice, mortars with improved strength,
enhanced degree of hydration and reduced autogenous
shrinkage were obtained. An important obstacle to the
application of this kind of pumice for actual concrete
production is the difficult saturation of the particles,
which can be achieved only by immersion in boiling water
or by vacuum saturation.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899