Packing density of concrete mix under dry and wet conditions

• Fresh concrete is wet but most packing tests are conducted under dry condition.
• A recently developed wet packing test is extended for application to concrete.
• The results show that the filling effects are better revealed under wet condition.

It is well known that the packing of particles in concrete has great effects on the performance of concrete, but existing codified methods for packing density measurement are all carried out under dry condition and do not account for the effect of water in the concrete mix. In recent studies by the authors, a wet packing method has been developed and the packing densities of cementitious materials, fine aggregate and blended fine plus coarse aggregate were found to be higher under wet condition than dry condition. In this study, both the dry and wet packing methods were applied to concrete mixes containing cementitious materials, fine aggregate and coarse aggregate. It was found that for the entire particle system in a concrete mix, the packing density is higher, the voids ratio is smaller and the filling effects of ultrafine supplementary cementitious materials are better revealed under wet condition than dry condition. Therefore, when measuring the packing density of a concrete mix, the wet packing method should always be used.

The packing density of particles is dependent on whether the condition is dry or wet, as shown in the following diagram. Since fresh concrete is actually wet, its packing density should be measured under wet condition.Figure optionsDownload as PowerPoint slide