CONTROL OF ALKALI-ACTIVATED SLAG CEMENT FINE CONCRETES PROPER DEFORMATIONS BY COMPLEX MULTIFUNCTIONAL ADDITIVES BASED ON SALTS-ELECTOLYTES FOR PREVENTION OF STEEL REINFORCEMENT CORROSION

Abstract

The actuality of alkali-activated slag cements (AASC) implementation is due to their conformity with modern tendencies concerning efficient consumption of raw materials and energy, while ensuring high functionality of mortars and concretes. AASC concretes are characterized by increased strength, sulfate resistance, freeze-thaw resistance and weather resistance in comparison with analogues based on traditional clinker cements. The modern requirements to high consistency fresh concretes are governed by practice. This way the disturbance of reinforcement passive state can be caused by changes in hardened concrete structure. Shrinkage reduction of AASC concretes due to complex multifunctional additives (CA’s) based on salts-electrolytes is seen as a way to prevent corrosion of steel reinforcement. The aim of the paper is substantiation of CA’s presented by the system «ordinary portland cement clinker (OPC clinker) - salt-electrolyte - surfactant» for adjustment of proper deformations and strength of AASC fine concrete with increasing density to prevent corrosion of steel reinforcement. Modification of AASC by CA based on NaNO3 provides shrinkage reduction from 0,984 down to 0,560 - 0,605 mm/m (t=20 2 °С, R.H.=65 %). Unlike, CA based on Na2SO4 causes shrinkage mitigation down to 0,625 - 0,640 mm/m. CA based on Na3PO4 minimizes shrinkage to 0,713 - 0,700 mm/m. Shrinkage mitigation is explained by less water, higher crystallinity of hydrated phases as well as by formation of minamiit (Na,Ca0.5)Al3(SO4)2(OH)6, calcium hydronitroaluminate ess than the reference one.