Dongmin Wang

Characteristics and mechanism of modified triethanolamine as cement grinding aids

Effects of modified triethanolamine as cement grinding aids on particles characteristics and mechanical property of cement were studied, and its reaction mechanism was analyzed by IR, Zeta potential, SEM, XRD and TG-DTA. The results show that the content of 3–32 μm particles for cement with 0.015% modified triethanolamine(M-TEA) is increased by 12.4%, and the compressive strengths of cement with 0.03% M-TEA are increased by 5.5 and 8.2 MPa at 3 and 28 days, respectively. And both the grinding and enhancement effects of M-TEA on cement are better than triethanolamine. The mechanism analysis shows that M-TEA not only has the amino and hydroxyl groups of TEA, but also has the ester, carbonyl, carboxyl groups which easily combine with metal ions of cement minerals, resulting in that M-TEA can promote surface adsorption and shield the unsaturated charges in the surface and crack section of particles, thus particles reunion is prevented and grinding efficiency is improved. Enhancement of M-TEA on cement mainly lies in that it can promote or induce hydration reaction of cement mineral with gypsum and water, which accelerates formation of hydration products, and then improves the structure and morphology of cement hydration products, thus the uniformity and compactness of product structure is increased.

Influence of Organic Esters on Portland Cement Hydration and Hardening

This paper investigated the effect of organic compounds with ester groups on the hydration and hardening of cement. The effects of five kinds of organic compounds with ester groups (ethyl acetate, dimethyl oxalate, glyceryl triacetate, trimethyl phosphate, and triethanolamine borate) on hydration heat, hydration degree, setting time, mechanical properties, microstructure, and pore structure of hardened cement slurry were studied. The test results showed that esters can make the end time of cement hydration induction longer and delay the occurrence of the second exothermic peak. Also, the effect of five kinds of esters on the hydration and hardening of cement was basically followed by TG> TB> DMO> EAC> TMP. In terms of molecular structure, for organic compounds containing only ester groups, the higher the number of ester groups, the greater the effect on the hydration of cement. The introduction of other functional groups (such as phosphate or borate) will influence the effect of the esters.

Effect of contact load on fretting fatigue behaviour of steel wires

Abstract The tension–tension fretting fatigue tests of steel wires were performed on a self-made fretting fatigue test equipment under contact loads ranging from 40 to 70 N and a strain ratio of 0·8. The results showed that when the contact load increased, the fretting regime of steel wires transformed from gross slip regime to mixed fretting regime. The fretting fatigue life in the mixed fretting regime was significantly lower than that in the gross slip regime. The main fretting wear mechanisms in the gross slip regime, where there were serious fretting damage and a lot of wear debris, were abrasive wear and fatigue wear. Microcracks were observed in the fretting scar of the mixed fretting regime, and the main fretting wear mechanisms were adhesive and fatigue wears. The fretting wear scar was the fatigue source region, and the fatigue fracture surface could be divided into three regions.