Ye Qing

Bio: Ye Qing is an academic researcher from Zhejiang University of Technology. The author has contributed to research in topics: Cement & Silica fume. The author has an hindex of 3, co-authored 4 publications receiving 1032 citations.

A comparative study on the pozzolanic activity between nano-SiO2 and silica fume

Abstract: The pozzolanic activity of nano-SiO2 and silica fume was comparatively studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and the compressive, bond and bending strengths of hardened paste and concrete were also measured. Results indicate that the compressive strength development of the paste made from Ca (OH)2 and nano-SiO2, the reaction rate of Ca (OH)2 with nano-SiO2 and the velocity of C−S−H gel formation from Ca(OH)2 with nano-SiO2 showed marked increases over those of Ca(OH)2 with silica fume. Furthermore, the bond strength at the interface between aggregate and hardened cement paste, and the bending strength of concrete incorporated with 3% NS increased more than those with SF, especially at early ages. To sum up, the pozzolanic activity of nano-SiO2 was much greater than that of silica fume. The results suggest that with a small amount of nano-SiO2, the Ca(OH)2 crystal at the interface between hardened cement paste and aggregate at early ages may be effectively absorbed in high performance concrete.

Effect of MgO and gypsum content on long-term expansion of low heat Portland slag cement with slight expansion

Abstract: The expansion of low heat Portland slag cement with slight expansion (LSE cement) was studied by XRD, SEM and test methods for strength and expansion. Results indicated that under the condition of 4.5–5.0% MgO in clinker and 2.8–3.4% SO 3 in cement, ettringite expansion and brucite expansion produced by periclase hydration in the paste had continuity, entirety and stability. Periclase hydration in the paste started at about 60 days and was completed up to 2000 days and ettringite was stable from 3 to 2000 days. At the ages of 28, 90, 365, 730 and 2000 days the expansion of the paste reached 0.08–0.13%, 0.09–0.14%, 0.12–0.17%, 0.13–0.18% and 0.15–0.21%, respectively. At the ages of 2, 28 and 180 days the autogenous volume deformation of mass concrete made out of LSE cement was positive and was 0.0042%, 0.0050% and 0.0066%, respectively and the prestress of the concrete with 2.0% steel bar content was 0.069, 0.060 and 0.082 MPa, respectively. The results suggest that using this cement in mass concrete may compensate for a part of its thermal shrinkage and autogenous shrinkage.

Effect of moist-curing time at early ages on carbonation resistance of pumping concrete incorporated with fly-ash

Abstract: Based on accelerated carbonation test, the variation of carbonation resistance of pumping concrete (C30 grade) with moist-curing time at early ages and fly ash content was studied in this paper. Results indicate that the carbonation resistance of the concrete decreased obviously with moist-curing time at early ages reducing and with the cement replacement by fly ash increasing. For example, under conditions of curing schedules with 28, 7, 3, 2 and 1 d moist-curing at early ages and then 0, 21, 25, 26 and 27 d air-curing at (60+5)% RH respectively, the 28-day accelerated carbonation depths of the concrete incorporated with 20% fly ash were 15.6, 20.5, 25.3, 31.5 and 45.9 mm respectively, and thus it can be seen the calculated times when concrete cover (25 mm) was completely carbonated naturally in the air were 98, 57, 38, 24 and 11 years respectively. The results suggest that for the carbonation resistance of the concrete incorporated with 20% fly ash, it is necessary that the moist-curing time at early ages should need 7 days.