INFLUENCE OF MECHANOCHEMICAL ACTIVATION OF MIXED PORTLAND CEMENT ON THE STRENGTH OF CEMENT STONE

Abstract

For the production of mortar mixtures and mortars based on them, mixed cements are used, including those with the use of ground quartz sand as a mineral additive. Technologically, such cements are obtained both by joint grinding of Portland cement clinker, dihydrate gypsum stone and quartz sand additive and by thorough mixing of Portland cement with ground quartz sand. A promising method for improving the mechanical characteristics of mortars using this type of binder is its mechanochemical activation in high-speed turbulent mixers. The issues considered in the article are related to determining the influence of the specific surface area of ​​ground sand (S = 200; 350; 500 m2/kg), as well as its amount in the mixed binder (from 0 to 60%) on the properties of both cement stone and mortar based on it. It was experimentally found that the specific surface area of ​​quartz sand used (in the specified range of its consumption) significantly affects both the strength of cement stone and the mortar based on it. Regarding the mechanochemical activation of the cement-water composition, it should be noted that high-speed processing contributes to both an increase in the kinetics of its exothermic heating and an increase in its maximum temperature, reaching a value of 68 ° C (compared to the control - 54 ° C - there is no activation of the binder).

Experimental data on determining the influence of mechanochemical activation on the strength of the mortar indicate that the cement-sand mixture activated for 2 minutes without the addition of the superplasticizer SP-5 provides an increase in the strength of the samples at 28 days of age from 30.0 MPa to 38.3 MPa - (27.7%), and in the presence of 1.0% of the superplasticizer - from 37.3 MPa to 46.2 MPa, i.e. almost by 24%. The results of experimental studies indicate that the combined use of mechanical activation in the presence of ground quartz sand and superplasticizer SP-5 is an effective technological method that successfully solves the issues of a technical and economic nature.