Paper by KORSHUNOV BASURMANOVA LANGE YUMASHEV from ISCR 11th 2010 Seville Spain
Worlds and domestic experiences in constructing cement concrete pavements confirm that the concrete resistance to the action of frost and de-icing agents depends on the content of the conventially-closed air voids in hardened concrete. In Russia the requirements for the content of the air voids in hardened concrete based on high-slump concrete mixes have been developed and introduced since July 1, 2008: no less than 3.5% for one-course concrete pavements and a top layer of the two-course ones. Before that time the State Standard (GOST) 26633-91 Heavy-weight and sand concretes. Specifications specified only the content of the entrained air in concrete mixes: from 5 to 7% by volume. It has been found that, irrespective of all technological factors, the air void quantity and their configuration in the finally compacted concrete mixes (of structures, specimens) conform to the air void quantity in hardened concrete. The procedure for determining the void contents in core specimens, drilled from the pavement, using the equipment common with construction laboratories (scales, thermo-chambers) has been developed. Knowing the air void content in concrete and the average void size depending on the sand size, the space factor can be easily calculated. The procedure in question makes it possible to evaluate the quality of the pavement concrete more objectively and promptly to intervene in the technology of work performance, and thus to insure the concrete pavement durability. In Standard (GOST) 26633-91, new requirements for roller compacted concrete (RCC) have been also introduced: the cement-water ratio is no more than 0.35 and the use of plasticized admixtures is obligatory. As for high-slump concrete mixes, the cement-water ratio should not exceed 0.45.