Research On The Effect Of Four Alkanolamines On Cement Hydration And Mortar Strength

The grinding aids are admixtures to improve grinding aid effect in the cement powdergrinding process without compromising the human health and the performance of cement andconcrete. Alkanolamine is the main component of cement grinding aids at the moment and thestrength-enhanced effects of alkanolamine to cement mainly reflect in two aspects: one isphysical strength-enhanced effect, which means the change of strength because of the changeof cement particle size distribution influenced by the alkanolamine in the cement powdergrinding process. For example, under the same surface area of cement, adding thealkanolamine can increase the concentration of particles, thereby improving the cementmortar strength. The other is chemical strength-enhanced effect that is the promotion effect ofthe alkanolamine on the process of cement clinker mineral hydration. The currentunderstanding on the action mechanism of the chemical strength-enhanced effect in practicalproduction is not thorough, there is little previous research on adjusting the combination ofthe alkanolamine in grinding aids based on clinker mineral or cement strength, which leadingto the instability of grinding aids’ strength-enhanced effect. Therefore, it is urgent to dodeeply research about the influence of various alkanolamine on the action mechanisms andstrength of different mineral combination.Through the analysis of the bound water, hydration heat, the change of CH amount, thispaper studies the influence of different alkanolamine on the rate of cement hydration, theresults indicate that: TEA can accelerate the1d,3d and28d hydration rate; TIPA reduce the1dand3d the hydration rate and obviously accelerate28d hydration rate; DEIPA and EDIPAhave little influence on the hydration rate at early age, but obviously accelerate28d hydrationrate. TIPA, EDIPA and DEIPA increase bond water of completely hydrated samples, decreasethe proportion of CH in hydration products and change the composition of cement hydrationproducts.This paper analyzes the morphology of28d hydration products by scanning electronmicroscope, we find that the CH is large in the blank sample and the cement pastes with TIPA,the C-S-H shows needle clavate shape and its structure is relatively loose. However, thecrystals of hydration products are less in the cement pastes with TIPA, DEIPA and EDIPA, theC-S-H shows honeycombed network structure and the total cement pastes’ structure looksmore compact. In addition, this paper confirms that adding TIPA, DEIPA and EDIPA makes the C-S-H composition change and produces more C-S-H with high Ca/Si by the continuousacid extraction method and scanning energy-spectrum.This paper studies four kinds of alkanolamine’ effects on mortar strength of differentmineral composition cement, the results show that: TEA mainly enhances the early cementmortar strength and the enhancement by TEA is much more significant in the cement with lessC3S and lower mortar strength at early age; TIPA mainly enhances the later cement mortarstrength and decrease the early cement mortar strength of the cement with less C3S and lowermortar strength at early age; DEIPA enhances the strength of cement at both early and laterages and the enhancement is much more significant in the cement with more C4AF at later age;EDIPA enhances the L cement mortar strength at early age while decreases the F cementmortar strength at early age, it obviously enhances the cement mortar strength at later age.