THE EFFECT OF MICRO-FILLERS ON THE EFFECTIVENESS OF SUPERPLASTICIZERS AND THE STRENGTH OF LOW-CEMENT CONCRETES

In concretes of ordinary grades with a cement consumption of 180–250 kg/m3, the reduction in the water demand of the concrete mixture, even with the maximum consumption of superplasticizers, does not exceed 10 %. In this regard, the influence of micro-fillers with various electrosurface properties on the effectiveness of the superplasticizer and the strength of low-cement concrete is investigated. It is shown that in the concrete mixture of the control composition, achieving a normal consistency (PK = 106–115 mm) is possible only due to high water consumption, the water-reducing efficiency of the joint venture was only 4,5 %. It was found that with the addition of fine quartz from 20 to 70 %, the consumption of the powder part increased from 230 to 452 kg/m3, while there was a decrease in W / C from 0,68 to 0,51 (33 %), as well as an increase in strength by 40,5 % (R7comp) and 30,6 % (R28 comp). With an increase in the dosage of limestone microfillers from 20 to 70 % W / C decreased from 0,66 to 0,5 (32 %), the strength increased by 145 % (R7 comp) and 74% (R28 comp). Thus, the use of fine-dispersed fillers in low-cement concretes makes it possible to achieve a significant reduction in W/C by 23,6–43,8 % in equally mobile mixtures (GOST 310.4), depending on the dosage of the powder filler (20–70 %), while the type of filler does not have a noticeable effect on the water-reducing ability of the superplasticizer, but plays a significant role in the processes of structure formation of cement concrete matrices, due to the influence of their electrosurface properties on the adhesion between filler particles and cement stone. In low-cement concretes, with the growth of fine fillers from 20 to 70 %, the strength of concrete increases.