On the role of compaction in disputes over the quality of the supplied concrete

This paper evaluates the effect of poor compaction on the compressive strength, sorptivity, gas permeability and accelerated carbonation resistance of bulk concrete in structures, framed in the scenario of disputes over the quality of the supplied concrete. For that purpose, several real-scale elements (beams, columns and slabs) were cast with concrete incorporating Portland-limestone cement and fly ash addition, covering a wide range of slumps (35–123 mm) and compressive strengths (25–65 MPa). The elements were then subjected to different compaction conditions (standard vibration and no vibration), and later cored for concrete testing. A new compaction indicator that overcomes the main practical limitations associated with the determination of the excess voidage of concrete is proposed, as well as new factors for correcting the effects of on-site compaction in the estimation of the potential carbonation resistance and the compressive strength of concrete. It is also shown that vibration no longer improves the quality of bulk concrete in structures for slumps above ~ 140 mm, which suggests that, in cases of dispute where greater slumps are specified, no correction for compaction should be needed in the estimation of the potential properties of concrete.