Central composite design-based development of eco-efficient high-volume fly ash mortar

Abstract

High-volume fly ash (HVFA) mixtures that contain a large amount of fly ash have been widely investigated as sustainable materials with desirable mechanical properties and durability performances at mature ages. However, the low strength at early ages is the main obstacle that limits their wider applications in the practice. This work presents the development of the HVFA mortar with high early-age strength as well as low environmental impact with the help of central composite design-based statistical model. Besides, the effects of fly ash, limestone powder, asphalt emulsion content and water-to-cementitious material ratio (w/cm) as four main variables of HVFA mortar on the compressive strength and splitting tensile strength at curing ages ranging from 7 days to 28 days as the responses of this environmentally friendly material were investigated. Moreover, the multi-objective optimization was conducted to achieve the eco-efficiency of HVFA mortar. In this study, HVFA mortar with fly ash content of 67%, limestone powder content of 5%, no asphalt emulsion and w/cm of 0.25 exhibited 28-d compressive strength of 39.2 MPa and 28-d splitting tensile strength of 3.3 MPa. The optimized mix design of HVFA mortar can ensure the equivalent strength while noticeably reducing the CO2 intensity (CO2 emission per compressive strength) by 17.57%.