Report on Internally Cured Concrete Using Prewetted Absorptive Lightweight Aggregate

Description

Portland-cement concrete, including mixtures with supplementary cementitious materials, does not typically develop its durability, strength, and mechanical characteris-tics without adequate curing. This report on internally cured concrete (ICC) does not presume to change the require-ment for water retention at the curing-affected zone on the concrete surface.

The curing methods listed in ACI 308R-01 should be consulted for appropriate methods to prevent or mitigate moisture loss from the concrete surface.Test trial batches should be used during initial mixture proportioning to determine and verify those concrete prop-erties required for each project.Internally cured concrete uses prewetted absorptive mate-rials that contain moisture.

The absorbed moisture is released as the internal humidity of the concrete drops below 100 percent to enhance and maximize the hydration of cement.High-performance concrete typically has a low w/cm that may not supply enough water to hydrate all of the cement. Due to the reduction in permeability of high-performance concrete, even in the first 2 to 3 days, exterior water curing is limited in its ability to supply in-depth hydration to the cement as the products of hydration fill in and disconnect the capillary pore network (Powers et al. 1959).

In this case, the beneficial effect of external water curing is limited to the concrete surface. As a result, external water cannot penetrate the interior of the concrete to maintain a saturated capillary pore system thereby avoiding self-desiccation. One solution is to replace a portion of the normalweight aggregate with absorbent materials to desorb water to the hydrating cement. The principal improvements of supplying internal water are the maintenance of a saturated cement paste, which leads to greater hydration of the cement and more complete pozzo-lanic reactions