EFFECT OF WETTING OF COARSE AGGREGATES ON THE PROPERTIES OF CEMENT CONCRETE

Abstract

The article analyzes the literature on the effect of filler wetting on the processes of structure formation and physical and mechanical properties of concrete. It is shown that the weakest element of the concrete structure is the interphase transit zone (ITZ) between the hardened cement stone and the filler. The quality of this zone largely depends from the wetting of fillers with water or aqueous solutions of chemical additives. It is known that the wetting efficiency is affected by the quality of the filler surface, its porosity and W/C. However, there is no correlation between the wetting of the filler surface and the strength and durability of concrete. There are also no data on the effect of the mineral composition of fillers and the type of wetting liquid on the nature of wetting. Therefore, the article presents the experimental results of determining the contact angle of wetting of fillers by different mineral composition with water and aqueous solutions with superplasticizers of different concentrations. In addition, the wettability of fillers with cement - water suspensions of different concentrations with and without superplasticizers was studied. One of the criteria for good wetting of aggregates is the formation of high-quality ITZ. This leads to an increase in the strength of concrete. The article presents data on the effect of the wetting angle of aggregates on the strength of concrete. The relationship between wetting and mixing time of concrete mixture is established. This allowed us to establish that by improving wetting, the time of concrete mix preparation can be reduced. The conducted studies showed that in order to increase the strength of concrete and the efficiency of its preparation technology, it is necessary to select a specific type of wetting liquid for each type of filler.