Multifactorial experimental analysis of concrete compressive strength as a function of time and water-to-cement ratio

Concrete compressive strength is typically tested for fixed nominal values of curing age. Corresponding measurements, even if performed by multiple specimens testing, cannot figure the dispersion of the result attributed to all the significant effective error parameters.

This study is a step that aims at the creation of a function that correlates the expected testing result on the compressive strength of concrete specimens to all parameters that will be finally assessed as significant to incorporate. Based on the use of such a multifactorial function, results retrieved from testing procedures that are more loosely defined could be corrected accordingly, in order to be compatible with the strict definition of the testing procedure.

Also, the integration of various similar experiments of such a protocol could lead to the standardization of a semi-empirical model on the relation of concrete compressive strength as a function of a large number of testing parameters and mix materials characteristics. This study specifically aims at the experimental investigation a) of the correlation of compressive strength testing results with the parameters of curing age and water to cement ratio through sensitivity analysis and b) of the significance of the cross-correlation between these two parameters.

The experimental results were used into a multifactorial regression analysis procedure leading to a sigmoidal – by time – equation. The basic outcome of this study is a multifactorial regression function incorporating both the parameters of the curing age and the water to cement ratio for given qualitative characteristics of the constituents. Although this function corresponds to these qualitative characteristics of the constituents, the sensitivity analysis of this study is expected to have a more global validity.

Such semi-empirical models, especially if completed with all the significant parameters, are expected to be useful, among others, for accredited testing laboratories in order to perform their internal quality control program.