Complex multifunctional additive for anchoring grout based on alkali-activated portland cement

Abstract

Complex multifunctional additive (further, CA) which consists of aluminum powder, surfactant, salt-electrolyte (NaNO3) and calcium sulfate hemihydrate (CaSO4∙0.5H2O) is proposed for ensuring necessary properties of anchoring grouts based on alkali-activated portland cement (further, AAPC) presented by the system «ordinary portland cement clinker - sodium metasilicate». Specified consistency of fresh AAPC mortar along with it strength after hardening are provided by water reducing due to application of modified polyethylene glycol characterized by stability of molecular structure in AAPC hydration medium. CA influence on shrinkage mitigation in AAPC mortar is explained both water-reducing effect and gas release with volume increasing during formation of dispersive-coagulation structure. Expansion of crystallization-condensation structure is ensured due to stress of calcium hydrosulfoaluminate 3CaO∙Al2O3∙3СаSО4∙32H2O and calcium hydronitroaluminate ЗСаО∙А12О3∙Са(NO3)2∙10Н2О which form due to presence of СаSО4∙0,5H2O and NaNO3 in CA. Time matching of gas release with structure formation insures dense microstructure due to filling of pores by hydrated phases that causes lower excess stress during crystallization. CA ensures necessary performances of AAPC anchoring grout: consistency 190 mm; workability retention time 15 min; tensile strength in bending / compressive strength 6.1 / 25.7 MPа and 12.9 / 68.5 MPa in 1 d and 28 d agreeably; adhesion 0.9 MPa; linear extension up to +0.37 mm/m.