Temperature correction protocol for in-situ monitoring of concrete during the curing and post-curing periods: application to low carbon concrete

The long-term performance of concrete depends primarily on the exposure and prevailing climatic conditions, with temperature during the initial curing period playing an important role in determining concrete strength development and durability characteristics. This paper presents the use of electrical property measurements as a potential testing methodology for assessing the relative performance of concrete subjected to varying field temperature conditions and constant laboratory temperatures. It introduces a new temperature correction procedure to facilitate such assessments to be conducted both during and beyond the standard curing period, building upon earlier work that focused on mature concrete. To this end, test data are presented for low-carbon concrete mixes incorporating binary and ternary binders, including Portland cement, ground granulated blast-furnace slag, and limestone powder. The parameter normalized resistivity is presented to highlight the influence of temperature on hydration and microstructural development across a range of low-carbon concrete mixes. The work presented reveals that the activation energy of electrical conduction is binder specific and increases with time during the initial five months after casting, with values ranging from 13 to 31 kJ/mol (0.14–0.32 eV/ion). Concrete with high levels of cement replacement exhibits a gradual increase in activation energy, eventually achieving higher values than plain Portland cement concrete. This indicates a more disconnected and tortuous pore network. However, when subjected to temperatures below 20^oC, the progression of pore structure development in such concrete is notably much slower. The work presented also shows that electrical measurements are technically straightforward to undertake and ideally suited for in-situ monitoring of concrete.