Evaluation of a Nuclear Gage for Controlling the Consolidation of Fresh Concrete

摘要

This study evaluated the use of a nuclear gage for controlling the consolidation of in-place, fresh portland cement concrete. The gage was used in the backscatter mode on low-slump concrete overlays and in both the backscatter and direct transmission modes on continuously reinforced concrete pavements. It was found that the nuclear gage gave readings comparable to the standard unit weight values. However, concretes from both the deck and the pavement indicated the presence of coarse voids in amounts exceeding those found in adequately consolidated concretes. Thus, it was concluded that because of the normal variability in density resulting from variations in the grading and amounts of individual ingredients of concrete mixtures, including the air content, the nuclear gage measurements cannot detect small but detrimental amounts of large voids resulting from inadequate consolidation. The presence of an appreciable amount of honeycombing or excessive air entrainment would be detected by nuclear density measurements however.