Effect of diethanolisopropanolamine and ethyldiisopropylamine on hydration and strength development of cement-fly ash-limestone ternary blend

Effect of diethanolisopropanolamine (DEIPA) and ethyldiisopropylamine (EDIPA) at dosages of 0.02 % and 0.05 % on hydration and strength development of cement-fly ash-limestone ternary blend is investigated. Results indicate that both dosages of DEIPA or EDIPA promote the chemical effect of limestone and the hydration of aluminates from cement and fly ash to form carboaluminates due to their complexation effect, especially 0.05 % of EDIPA. For silicates hydration, 0.02 % of DEIPA or EDIPA accelerate it with more C-S-H gel formation while 0.05 % of DEIPA or EDIPA retard it due to the excessive aluminates hydration and carboaluminates formation at 3 d. However, both dosages of DEIPA and EDIPA promote silicates hydration at 28 d. Besides, DEIPA or EDIPA at both dosages can refine the pore structure with decreased porosity due to the promoted hydration of aluminates and/or silicates and formation of hydration products, although DEIPA and EDIPA exhibit air entraining effect to cause larger pores (>1000 nm). As a result, 0.02 % of DEIPA or EDIPA increase compressive strength of the blend mortar at both 3 and 28 d while 0.05 % of DEIPA or EDIPA slightly decrease it at 3 d but increase it at 28 d. It can be concluded that DEIPA contributes to higher early strength while EDIPA contributes to higher later strength of the ternary blend at both dosages.