For utilization of flyash which is one of byproducts, authors focus on flyash cement having relative lower consumption, even specified in JIS. One of the reasons for lower consumption is slower early strength development than ordinary Portland cement (OPC) in case of much replacing ratio of flyash in flyash cement. Therefore in this study, strength enhancers as cement additives are studied on the effect of strength development, especially for early age. Firstly, the compressive strength of mixtures using OPC and flyash corresponding to JIS Type-B and Type-C are measured to confirm the effect of the strength enhancers. Additionally, the heat of hydration by isothermal calorimeter of cement paste using amines as strength enhancers are measured for discussion of the effect of the strength enhancer for cement hydration and the hydration mechanism for early strength enhancement. The conclusions are as followings;
1) Two different strength enhancers Triisopropanolamine (TIPA) and Alkanolamine are evaluated for FA Type-B-mixture and FA Type-C-mixture replacing flyash to a part of the OPC. Alkanolamine shows higher strength than TIPA by FA Type-B-mixture and FA Type-C-mixture. Besides, Alkanolamine shows higher strength than OPC from 1day to 7days. This result shows the effect of strength enhancer differs for mixtures, and it suggests that TIPA and Alkanolamine have different hydration mechanism.
2) As a result of heat of hydration, Alkanolamine generates highest heat of FA Type-B-mixture and FA Type-C-mixture. The strength enhancers are considered to have acceleration effect for this heat of hydration.
3) In dissolution test using flyash and the strength enhancers, TIPA shows high elution amount of Fe2O3 from flyash. In contrast, Alkanolamine shows no effect for dissolution of Fe2O3. But when using TIPA and Alkanolamine for flyash, it was confirmed that the amount of effusion of the metal-ion was different than only flyash mixed.
4) C3S or C4AF is used for heat of hydration measurement to determine the hydration mechanism of the strength enhancers. Alkanolamine shows acceleration effect for C3S. However, TIPA shows the retarding effect constantly. For C4AF, Alkanolamine shows higher acceleration effect than TIPA.
5) As for estimated hydration mechanism for early strength enhancement, the strength enhancers would accelerate C3S and C4AF in OPC.
