Applicability of the Modified Nurse-Saul (MNS) maturity function for estimating the effect of temperature on the compressive strength of GGBS concretes

The non-destructive real-time evaluation of compressive strength of concrete is of significant interest to the concrete industry as it can serve as a decision tool for performing critical operations on site. Maturity methods have traditionally been employed for such purpose; however, conventional maturity approaches encompass certain deficiencies. The Modified Nurse-Saul function is an improved maturity function for estimating the compressive strength development of concrete under non-isothermal curing histories. The function relies on a relationship between concrete compressive strength and the Nurse-Saul maturity index and makes use of: (a) an “acceleration” factor and (b) a “temperature efficiency” factor. The method has been previously validated under isothermal and non-isothermal conditions for neat Portland cement concrete mixes. It is however important to assess the applicability of the Modified Nurse-Saul function for concretes with varying levels of GGBS which are known to be more temperature sensitive when compared to Portland cement concretes. The procedures needed to determine the inputs for the Modified Nurse-Saul function for estimating the compressive strength of concrete under isothermal and non-isothermal (adiabatic) conditions are described herein. The predictions/estimates of compressive strength of GGBS concrete were shown to be significantly more accurate than those from the Nurse-Saul and Arrhenius maturity functions, which are the most frequently employed maturity functions in construction despite their known deficiencies/inaccuracies. The Modified Nurse-Saul function encompasses high potential for being used reliably to optimise construction processes relying on real-time strength development evaluation, such as precast concrete and fast-track construction applications.