Alkali-activated binary mortar based on natural volcanic pozzolan for repair applications

Abstract

The goal of this investigation was evaluate the potential of an alkali-activated binary mortar (AABM), based on a natural volcanic pozzolan (70%) and granulated blast furnace slag (30%), as a repair material. This evaluation focused on its physico-mechanical characterisation (compressive, flexural and splitting tensile strengths; modulus of elasticity; capillary water absorption; and shrinkage) and the measurement of its adherence to three class of OPC concretes (substrates) using pull-off tests. A mixture of NaOH and Na2SiO3 was used as alkaline activator. The compressive and splitting tensile strength of AABM were 34.8 MPa and 2.13 MPa at 28 days of curing, respectively. Its capillary absorption coefficient and modulus of elasticity were 0.5088 kg/m2h0.5 and 8.66 GPa respectively. The results of the pull-off test demonstrate the adherent nature of the AABM, which was promoted by the strength (quality) of the OPC substrate, with pull-off adherences of 0.75 MPa, 1.14 MPa and 1.24 MPa for class C25/30, C35/45 and C50/60, respectively. According to the results obtained and standard specifications (EN 1504-3), this material can be classified as a class R2-repair mortar.