Effect of PVME on cement hydration and pore creation in mortar at elevated temperatures

Abstract

High strength concrete (HSC) has found significant applications in offshore structures, long-span bridges, and tall buildings due to its outstanding strength and durability. There have been concerns regarding the use of HSC in case of fire, especially due to explosive spalling. Polypropylene (PP) fiber has been demonstrated to reduce spalling in concrete. However, the addition of PP fibers adversely affects the concrete's workability and can lead to non-homogeneous mixes due to fiber agglomeration during compaction. Addition of water soluble polymers in HSC is an innovative approach to avoid spalling under fire circumstances. The present work investigates the influence of polyvinyl methyl ether (PVME) on the hydration of cement, and its pore creation ability in mortars at elevated temperature. PVME was found to reduce the initial rate of hydration of cement, which was confirmed by thermogravimetry analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), isothermal calorimetry and bound water calculations. The rate of hydration increased with time and became greater than that of control samples after 24 h. PVME showed pore creation ability in mortars at high temperatures, which was similar to that of PP-fiber-modified mortars. PVME enhanced the volume of inter-connected pores, which can provide an escape route for gases and moisture and potentially alleviate spalling. It is expected that the present work will form the basis for further assessment and adoption of PVME as an admixture to HSC mixes to reduce its susceptibility to spalling at elevated temperatures.