High-strength development through accelerated curings of epoxy-modified mortars without hardener: Fid-Bau Portal

High-strength development through accelerated curings of epoxy-modified mortars without hardener

Ohama, Y. / Kumagai, S. / Miyamoto, Y.

The authors found the fact that, even without any hardener, epoxy resin had been able to harden in the presence of the hydroxide ions produced by the hydration of cement in epoxy-modified mortars and concretes at ambient temperature. However, the hardening rate of the hardener-free epoxy resin at ambient temperature is low, and the acceleration of the hardening reaction of the hardener-free epoxy resin is requested for the manufacture of precast products. The purpose of this investigation is to examine the application of the effective accelerated curings to the hardener-free epoxy-modified mortars for the accelerated hardening reaction of the epoxy resin. Epoxy-modified mortars without any hardener are prepared with polymer-cement ratios of 0 % to 20%, subjected to an autoclaving or steam curing after a 1 d moist curing, followed by a 1 d heat curing, and tested for flexural and compressive strengths, pore size distribution and microstructure aspects. As a result, the flexural and compressive strengths of autoclave and heat- or steam and heat-cured hardener-free epoxy-modified mortars with high polymer-cement ratio are about twice to three times higher than those before the heat curing, and tend to increase with an increase in the polymer-cement ratio. The strengths of the autoclave and heat-cured hardener-free epoxy-modified mortars are somewhat lower than those of the steam and heat-cured ones. The epoxy resin in the autoclave and heat- or steam and heat-cured hardener-free epoxy-modified mortars hardens completely by the heat curing after the autoclaving or steam curing. The microstructures of interfacial transition zones are improved by the epoxy resin modification and the heat curing after the autoclaving or steam curing. The morphological change of the hardener-free epoxy resin provides the high-strength development through the accelerated curings.