Exploration of offsetting the negative effects of polyethylene glycol admixture on mortar performance: Using diethanol-isopropanolamine

Abstract

• The co-mixing accelerates the hydration of C 4 AF compared to samples added PEG alone. • The co-mixing can increase the microviscosity of the solution and the CBC. • The co-mixing of PEG and DEIPA increased susceptibility of leaching. • Leaching arises from the changes of pore structure, Ca/Si ratio, products morphology. Polyethylene glycol (PEG) is a viscosity modifying admixture that can effectively increase the viscosity of concrete pore solution and retard the diffusion of Cl - . However, to ensure excellent anti-chloride diffusion performance, the dosage of PEG is usually large enough to retard cement hydration and even to reduce the chloride chemical binding capacity of cement matrix due to the conversion inhibition from AFt to AFm. Diethanol-isopropanolamine (DEIPA), a commonly used alkanolamine grinding aid during cement production, seems to be a good candidate to offset these side effects introduced by PEG through promoting the conversion from AFt to AFm and refining the pore structure of cementitious materials. In this paper, we explored the possibility of using DEIPA to offset the negative effects of PEG. The cement hydration, mechanical strength, chloride diffusion capacity, pore structure, and micro-morphology of mortars containing both DEIPA and PEG are systematically investigated. The results indicated that the addition of DEIPA indeed reduces the porosity and increases the chloride binding capacity of mortars. Yet the coarsening of pore structure is still observed. Besides, the co-mixing of DEIPA can increase the mortar compressive strength at 90 d when the DEIPA dose is appropriate. Unfortunately, the co-mixing increased the susceptibility of the matrix to leaching, which reduces the resistance to chloride diffusion. The higher degree of leaching may arise from three reasons: the coarsening of the pore structure, the increase in the Ca/Si ratio of C-S-H, and the thinning of the hydration products morphology. This study draws attention to the durability issues when alkanolamine grinding aids and water-soluble viscosity modifying admixtures are coexisted in cementitious materials.