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Zhao X.-M.,University of Science and Technology Beijing | Wang C.-L.,Shangluo University | Wang C.-L.,Hebei University of Engineering | Zheng Y.-C.,State Key Laboratory of Solid Waste Reuse for Building Materials | And 2 more authors.
Meitan Xuebao/Journal of the China Coal Society | Year: 2016

To study the effect of mineral admixtures on the hydration and hardening of composite binders, different cement mortars and concrete were prepared using fly ash and iron ore tailings powder whose fineness are similar with cements as active or inert mineral admixtures. The influences of different adding ratios and types of mineral admixtures on the compressive strength development as well as the 7 d-age autogenous shrinkage development were investigated under the same curing schedule and different water binder ratios. The test results show that during the initial period of the hydration process of composite binder, the fly ash and iron ore tailings powder participations have physical filling effects. The pozzolanic reactivity of fly ash increases gradually with age. In the early hydration period, the physical properties of mineral admixtures (such as the particle shape, etc.), other than its chemical properties (such as degree of reaction, etc.) have an overwhelming effect on the compressive strength of mortar samples. The autogenous shrinkages of concrete with different admixtures show similar changing trends, which both decrease with the increasing adding ratios. © 2016, Editorial Office of Journal of China Coal Society. All right reserved. Source


Cheng H.,North China University of Technology | Yang F.,State Key Laboratory of Solid Waste Reuse for Building Materials | Zhang J.,North China University of Technology
Advanced Materials Research | Year: 2012

In this paper, the heat-activated conditions of Neimenggu high aluminum coal gangue were studied, and then, the activated coal gangue as a supplementary cementitious material was used in concrete to investigate the application effect. The result shows that the optimal calcining temperature of high aluminum coal gangue is 800°C, the setting time of concrete was postponed, the slump was reduced and the resistance of concrete to chloride ion penetration was improved for the use of activated coal gangue. The compressive strength of concrete was enhanced when cement was replaced by 20%∼30% activated coal gangue powder. Pozzolanic effect of activated coal gangue in the early age (7d) is higher and it can promote the hydration of cement with each other. © (2012) Trans Tech Publications, Switzerland. Source


Chen Y.,State Key Laboratory of Solid Waste Reuse for Building Materials | Bloomquist D.,University of Florida | Crowley R.,University of Florida
Applied Mechanics and Materials | Year: 2013

ASTM C78, the Flexural Strength tests were conducted on Cellulose Fiber Reinforced Concrete (CFRC) samples subjected to difference moisture-levels to quantify the effect of moisture on them. Results indicated that modulus elasticity did not change along the increase in moisture. However, flexural strength and yield strength appeared to be affected under certain conditions. © (2013) Trans Tech Publications, Switzerland. Source


Chen Y.,State Key Laboratory of Solid Waste Reuse for Building Materials | Bloomquist D.,University of Florida | Crowley R.,University of Florida
Applied Mechanics and Materials | Year: 2013

ASTM C78 standard tests for flexural strength of concrete were conducted on cellulose fiber reinforced concrete (CFRC) specimens using varying percentages of ultimate load. During testing, Acoustic Emission (AE) signals were recorded while after testing, a scanning electron microscope (SEM) was used to visually observe surface features. SEM results appear to illustrate three important stages of the fracture process: cement cracking, fiber-cement debonding, and fiber breakage/pullout. AE results were used to bound ranges for a relationship between AE amplitude and CFRC fracture mechanisms. © (2013) Trans Tech Publications, Switzerland. Source


Liu X.,Beijing University of Technology | Wang Z.,Beijing University of Technology | Zhu J.,Beijing University of Technology | Zheng Y.,State Key Laboratory of Solid Waste Reuse for Building Materials | And 4 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2014

The amide-structural polycarboxylate superplasticizers (amide-PCEs) were synthesized by amidation reaction between polyacrylic acid (PAA) and amino-terminated methoxy polyethylene glycol (amino-PEG) under different conditions, and the effects of amide-PCE's synthesis on amidation rate and flow performance of cement paste were investigated. Fourier Transform Infrared Spectroscopy (FTIR), 1H Nuclear Magnetic Resonance (1H NMR), and molecular-weight measurements were used for structural characterization, and the results confirmed ideal amide structure and sufficient amidation reaction. Amide-PCE with the carboxyl-amino ratio of 4:1 exhibited the lowest surface tension, highest adsorption percentage, and the best paste fluidity results. Based on the above results, the dispersion and adsorption mechanisms of amide-PCE in cement-water system were discussed. The application performances in concrete showed that amide-PCE had similar slump to that of conventional PCE, but also had better air-entraining ability, bubble retention and concrete frost-resistance than those of conventional PCE. Depending on this amide structure and good performances, amide-PCE shows broad application prospects. © 2014 Elsevier B.V. Source

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