Identification of various chemical phenomena in concrete using thermal analysis

Abstract

Chemical changes that occur in concrete at the microstructure level due to environmental effects are normally identified by SEM, XRD, thermal analysis and by chemical analysis. In the present investigation, the chemical compounds formed in various chemical reactions are quantified using thermal analysis. The concrete having characteristic compressive strength of 20 MPa was subjected to undergo various chemical reactions for a specified period. Three types of cements were used for casting the concrete specimens. The thermal analyses (DTA and TG) were carried out on powdered concrete samples passing through 75 μm sieve drawn from the concrete specimens which were subjected to various chemical phenomenon. Chemical compounds such as Ca(OH)₂, gypsum, ettringite, calcium chloroaluminate are estimated quantitatively. The type of fly ash blended with cement and complex amine salt in Migrating Corrosion Inhibitor (MCI) treated concrete are also identified. Each chemical compound is identified by a distinct endotherm present in the DTA (Differential Thermal Analysis) plot and quantitative estimation has been done using the TG (Thermo-gravimetric) curve.