Concrete Pavement Construction Aspects of Internally Cured Concrete

The production of internally cured concrete is similar to that of conventional concrete, but understanding and controlling the aggregate moisture is more critical in internally cured concrete in order to have a consistent mixture due to the higher absorption values in the fine lightweight aggregate. The lightweight aggregate is pre-wetted in a stockpile prior to batching with a sprinkler or soaker hose for 48 hours before allowing a drain-down period of at least 12 hours, which enables the reduction of surface moisture and greater uniformity throughout the stockpile.

The process for batching internally cured concrete is similar to that for conventional concrete. An extensive study noted that batching was performed easily, with no problems being reported due to the addition of the lightweight aggregate other than the need for an additional bin for the pre-wetted lightweight aggregate.

The absorbed moisture and surface moisture in the lightweight aggregate should be carefully measured and controlled to reduce the amount of variability from batch to batch. Two methods are commonly used to determine the aggregate absorption and surface moisture: the paper towel method and the centrifuge method. The centrifuge has been shown to be faster and more accurate than the paper towel method.

Most conventional quality control tools used for conventional concrete apply to internally cured concrete as well. It has also been noted that entrained air content can be measured using either ASTM C173 (the pressure method) or ASTM C231 (the volumetric method) when fine lightweight aggregate is used. This is an important finding, as it indicates that the more rapid, conventional pressure method can be used even though fine lightweight aggregate is being used, presumably due to the lightweight aggregate being well saturated before testing.