Enabling sustainable rapid construction with high volume GGBS concrete through elevated temperature curing and maturity testing

Abstract

Nowadays, low carbon footprint concrete for construction relies heavily on ground granulated blast-furnace slag (GGBS) as a partial cement replacement material (CRM) in places where other CRMs are in short supply. However, it is relatively well-known that the low early-age strengths of GGBS concretes discourage the maximisation of cement replacement in most applications; a constraint which can be potentially overcome through exploitation of hydration acceleration under elevated temperature curing. Concrete and mortar mixes of 47 MPa 28-day target mean cube strength were developed and investigated in this study with various percentages of GGBS (0, 20, 35, 50 and 70%) and cured under isothermal and non-isothermal regimes (20, 30, 40 and 50 °C and adiabatic). Higher temperatures appeared to significantly accelerate the strength gain of GGBS concretes, particularly those containing high GGBS percentages. In-situ strength development may be estimated through maturity functions which were initially developed for neat Portland cement concretes. The accuracy of several maturity functions, such as the Nurse-Saul, Arrhenius, Weighted Maturity, Weaver-Sadgrove and Rastrup ones, were examined together with two strength-maturity/time correlations. It was found that although maturity methods can be used to optimise a concrete mix in terms of GGBS content and depending on the application, it is not possible to obtain consistently reliable estimates for GGBS concretes from the current functions. Nonetheless, from the current models considered, the Arrhenius, Weighted Maturity and Rastrup functions appear as more appropriate for higher replacement levels of cement with GGBS. Overall, the present study highlighted a need for further improving maturity functions to account for the strength development of GGBS concrete.