Effect of thermally activated clay on corrosion and chloride resistivity of cement mortar

Corrosion and chloride attack are the two important issues of cement mortar and concrete. The aim of this study is to design corrosion and chloride resistive cement mortar, by incorporating thermally treated clay available at Khyber Pakhtunkhwa, Pakistan. The clay containing low kaolinite content was converted to metakaolinite and characterized by X-ray diffraction (XRD), Differential thermal analysis (DTA) and Scanning electron microscopy (SEM). Six types of mortars containing 5, 10, 15, 20, 25 and 30% of metakaolin were made and studied for different parameters including compressive strength, corrosion resistance and chloride diffusion coefficients for the evaluation of the performance of metakaolin. Mortar specimens were then exposed to the corrosive environment of 3% w/w NaCl solution. It is concluded that metakaolin improves the compressive strength and 20% w/w replacement of cement in mortars show optimum contribution to the strength development, corrosion resistance and chloride attack resistance. Excess amount of metakaolin in mortar has no positive effect.