National Concrete Pavement Technology Center

Project description

The objective of this study was to evaluate the influence of internal curing and coarse aggregate type on concrete’s 28-day strength, as well as surface resistivity over time (at days 7, 14, 28, 56, 90, and 180). A total of 96 concrete mixtures were prepared to identify the effects of three coarse aggregate types, two water-to-cementitious (w/cm) ratios, three fine lightweight aggregate (LWA) sources, and four variations of supplementary cementitious materials (SCMs). The compressive strength tests showed that in most cases, the presence of lightweight aggregate had a positive effect on strength (i.e., either had equal or better strength). Concerning surface resistivity, the statistical analyses determined that the use of SCMs, w/cm ratio, coarse aggregate type, and presence of LWAs had significant effects. The use of SCMs caused significant increases in surface resistivity for all groups due to their pozzolanic activity, and significantly outperformed the specimens prepared with only portland cement. The w/cm ratio had a high impact on resistivity as expected, where the lower w/cm ratio consistently produced higher resistivity values over time for all specimen groups. The presence of LWAs had an overall positive effect on resistivity, where each of the LWA sources had an equal or better performance than the control specimens based on the findings from the statistical analyses. Lastly, the coarse aggregate type affected resistivity, albeit predominantly based on the porosity of the aggregate itself rather than the mineralogy.