Performance evaluation of alkali-activated mortars containing industrial wastes as surface repair materials

Abstract

Nowadays, alkali-activated binders based industrial and agricultural wastes have been introduced as the environmental friendly materials with high durability performance. We evaluate the performance of alkali-activated mortars (AAMs) incorporated with fly ash (FA) and ground blast furnace slag (GBFS) as surface repair materials useful in construction sector. Various levels of GBFS replacing FA were blended and activated via low concentration of the alkaline activator solution. The fresh and hardened state properties of these AAMs including the flow and setting time, compressive, flexural and tensile strengths, abrasion resistance, bond strength and compatibility with the base concrete substrate (NC) tests were performed. The microstructures and related characteristics of such mortars were also examined. The bond strength and other mechanical properties of the AAMs were enhanced when FA was replaced by GBFS in the presence of low alkaline solution contents. The early bond strength after 24 h was increased from 1.8 MPa to 2.4 MPa when the GBFS level was raised from 30 to 70%, respectively. This increase in the AAMs bond strength and improvement in the compressive strength as well as microstructure were ascribed to the formation of more C-(A)-S-H due to the increase in the calcium content. The obtained excellent abrasion-erosion resistance, freeze-thaw cycling resistance and high compatibility with the concrete substrate confirmed the effectiveness of the proposed AAMs as high performance repair material effective for the damaged concrete surfaces.