Use of coal chemical industry by-product coal gasification fine ash as supplementary cementitious materials in cement: Chemical excitation, hydration and hardening characteristics

Abstract

In order to realize the resource utilization of coal gasification fine ash (CGFA) in cement fields, a key is to solve the problem of low activity of CGFA. This paper studied the performance of CGFA as supplementary cementitious materials in cement. Furthermore, to enhance the activity of CGFA, targeted chemical activators were employed, with triethanolamine (TEA) and simulated high salinity wastewater (SHSW) chosen as representatives of organic and inorganic agents, respectively. It was found that CGFA had a synergistic effect with cement at a low dosage, while the inhibition effect on cement hydration was dominant at a high dosage. TEA promotes the strength development of the CGFA-cement system by promoting early hydration of cement and dissolution of active minerals in CGFA. However, the promoting effect of TEA on cement hydration will change to an inhibiting effect with the development of time, which will have an adverse effect on the development of strength. In general, the optimal dosage of TEA is 0.03 %, which can increase the 28-day activity index of CGFA from 69.1 % to 75.6 %. SHSW accelerates the strength development of the CGFA-cement system by promoting the hydration of cement and facilitating the dissolution and hydration of active minerals in CGFA. In addition, X-ray diffraction results show that a new hydration product, Friedel’s salt, is formed under the excitation of SHSW. But this new hydration product will gradually dissolve as the pH decreases. The 28-day activity index of CGFA can be increased to a maximum of 83.3 % under the excitation of 2 % SHSW.