Measuring the influence of Pre-Wetted Lightweight aggregates on concrete's surface resistivity

Abstract This study evaluated the influence of pre-wetted lightweight aggregates (LWAs) typically used for internal curing applications on concrete’s 28-day strength and surface resistivity over time. Ninety-six concrete mixtures were prepared to identify the effects of three coarse aggregate types, two water-to-cementitious (w/cm) ratios, three LWA sources, and four variations of supplementary cementitious materials (SCMs). The compressive strength tests showed that LWAs generally had a positive effect on strength. While some exceptions were observed where LWAs had lower strengths than the controls, all LWA specimens met the 27.6 MPa strength requirements for structural concrete in Louisiana. Concerning surface resistivity, a statistical analysis determined that the use of SCMs, w/cm ratio, coarse aggregate type, and LWAs all had significant effects. The samples containing SCMs significantly outperformed the specimens prepared with only portland cement. The w/cm ratio had a high impact in resistivity. The coarse aggregate type also had an effect on resistivity based on the porosity of the aggregate itself, rather than the mineralogy. Lastly, LWAs had an overall positive effect on resistivity, performing similarly or better than the control specimens in most cases. Based on these results, internal curing through pre-wetted LWAs is expected to be compatible with specifications from state highway agencies (SHAs) that have a performance requirement with surface resistivity.