Experimental modeling of burnt oil shale impact towards ASR

The alkali-silica reaction (ASR) is a civil engineering issue that can be inhibited using supplementary cementitious materials such as burnt oil shale. Furthermore, these allow an improvement of the properties of the concrete as increasing density and compressive strength. Currently, the tests to characterize the development of the ASR in concrete are very long and can take more than a year. This paper proposes to model the impact of mineral addition towards ASR by short time laboratory testing via the model reactor in order to assess the inhibition. The study was conducted on fine flint aggregate, as a reactive aggregate, with burnt oil shale as supplementary cementitious material. At the end of the tests, a liquid phase and a solid phase are recovered. The liquid phase is analyzed by Inductively Coupled Plasma Emission Spectroscopy (ICP-OES) to follow the evolution of the chemical elements in solution. The solid phase was analyzed by BET/BJH method, thermogravimetric analysis (TGA) and helium pycnometry. Microscopic observations by Scanning Electron Microscope (SEM) were also carried out. The results show an increase of the absolute density whereas porosity and specific surface decrease by adding burnt oil shale. This addition yields less aggregate alteration. The observation by SEM shows less micro-cracks and a modification of reaction products in the presence of burnt oil shale. ICP-OES analyses are consistent with less dissolved silica in solution.