Packing density of cementitious materials : Part 1 - measurement using a wet packing method

The packing characteristics of the cementitious materials have great influence on the performance of a concrete mix, but there is so far no generally accepted method of measurement. Herein, a new method, called the wet packing method, is developed. It mixes the cementitious materials with water and then measures the apparent density and voids content of the resulting mixture at varying water/cementitious materials ratio to characterise the packing behaviour of the cementitious materials. Trial mixing and testing revealed that the mixing procedure is crucial to the success of the test method. To ensure thorough mixing within a reasonable time, a special mixing procedure is adopted. Using this method, the packing characteristics of pure cement and blended cementitious materials under different conditions have been measured. Based on the results so obtained, it is advocated that the packing density and water demand should be measured directly using a wet packing method rather than indirectly by any consistence test because the water content at any preset consistence is not necessarily the same as the minimum water content needed to fill up the voids. Some useful applications of the new method are illustrated in Part 2 of this paper.