Influence of various clay particles on effectiveness of polycarboxylate superplasticizer and properties of cement stone

Influence of impurities of clay minerals from sands on the efficiency of polycarboxylate superplasticizers, the properties of cement paste and stone was studied. For the study, the sands of various deposits of the Chelyabinsk region were taken, which contained various clay minerals: montmorillonite, hydromica and kaolin. Research results of phase composition of the clay are presented in this article. The study was performed using modeling cement stone of concrete and was carried out using mathematical planning of the experiment, where the main factors were: the amount of superplasticizer from 0 to 0.8% and the amount of clayey from 0 to 4 %. The effect of these factors on fluidity was assessed by slump test of the cement paste, and influence on strength and porosity by cubic samples of cement stone with an edge of 20 mm. The study of the phase composition of clay impurities from sands and the structural features of the obtained cement stone was carried out using derivatography, X-ray phase analysis and electron microscopy. It has been established that the strength of the cement stone and effectiveness of the polycarboxylate superplasticizer more reduce the clay mineral montmorillonite, and clay minerals containing hydromica or kaolinite do not significantly affect these parameters. Therefore, sands with clay impurities up to 2 % consisting of hydromica or kaolinite are permissible to be used in order to obtain even high-performance concrete. However, to ensure high efficiency of polycarboxylate superplasticizers, increased strength and durability of concrete on cement binders, it is recommended to use washed sands or sands with clay content less than 1 %. Additionally, it was revealed that the polycarboxylate superplasticizer contributes to the formation of the structure of cement stone from amorphous highly basic calcium hydrosilicates, which are characterized by increased durability and, consequently, durability.