Comparison Between D crit Considering the Abrupt Variation and Inflexion in the Concrete Mercury Intrusion Porosimetry Curve

Mercury intrusion porosimetry (MIP) has been widely used to evaluate the quality of concrete through the pore size distribution parameters. Two of these parameters are the critical pore diameter ( D crit ) and the percentage of the most interconnected net of pores compared to the total volume of pores. Some researchers consider D crit as the diameter obtained from the inexion point of the cumulative mercury intrusion curve while others consider D crit as the diameter obtained from the point of abrupt variation in the same curve. This study aims to analyze two groups of concretes of varying w/c ratios, one cast with pozzolanic cement and another with high initial strength cement, in order to determine which of these diameters feature a better correlation with the quality parameters of the concretes. The concrete quality parameters used for the evaluations were (1) the w/c ratios and (2) chloride diffusion coecients measured at approximately 90 days. MIP cumulative distributions of the same concretes were also measured at about 90 days, and D crit values were determined (1) from the point of abrupt variation and alternatively, (2) from the inexion point of each of these plots. It was found that D crit values measured from the point of abrupt variation were useful indicators of the quality of the concrete, but the D crit values based on the inexion points were not. Hence, it is recommended that D crit and the percentage of the most interconnected volume of pores should be obtained considering the point of abrupt variation of the cumulative curve of pore size distribution.