Shock vibration effects on freshly placed concrete

Freshly placed (green) concrete is vulnerable to weakening of its properties if subjected to forces which disrupt the concrete matrix during the formative bond development process. Insufficient qualitative data, relating to the establishment of shock-type vibration limits for green concrete has been found in the engineering community. This shortage of substantiative information and a job schedule requiring concurrent concrete placement and excavation blasting dictated the need to obtain reliable data on the extent to which green concrete could be shock-vibrated without detrimental effects. An extensive laboratory and field test program provided conclusive information to support a significant increase in the commonly imposed green concrete shock-vibration limits. Although green concrete was subjected to very high vibration levels, no critical damage limit was ever reached. Associated reinforcement bond tests questions the ACI 318-77 application of' “Top Bar” factors to horizontal wall splices.