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Pumice Aggregates for Internal Water Curing.


pdf icon 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.