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Wu H.,PLA University of Science and Technology | Fang Q.,PLA University of Science and Technology | Chen X.W.,China Academy of Engineering Physics | Gong Z.M.,PLA University of Science and Technology | Liu J.Z.,Jiangsu Research Institute of Building Science
Construction and Building Materials | Year: 2015

The ultra-high performance cement based composites (UHPCC) with the additions of steel fibers and basalt coarse aggregates was prepared under ambient temperature and pressure. In order to apply the UHPCC in the constructions of anti-strike protective structures, the impact resistance of UHPCC was investigated experimentally by conducting the high-speed projectile penetration tests with the broad striking velocities from 510 m/s to 1320 m/s. The rigid and mass abrasive penetration regimes are observed when the projectile striking velocity was lower than 1 km/s and increased up to 1-1.5 km/s, respectively. The experiments validated that UHPCC material has excellent projectile impact resistance, such as reducing the depth of penetration (DOP) and the crater dimensions of the rigid projectile, as well as defeating the structure and deviating the terminal ballistic trajectory of the abrasive projectile. The previously proposed models for rigid penetration depth on fiber reinforced high strength concrete as well as the limit striking velocity causing the structural destruction of mass abrasive projectile are both well validated. The parameters influential analyses further indicate that UHPCC with the compressive strength of 90 MPa and steel fiber mixing ratio of 1.5% is the most efficient and economical choice for protective structure constructions. In details, within the discussed ranges: (i) the projectile impact crater dimensions enlarges with the increase of the compressive strength of the target and the projectile striking kinetic energy, and which was reduced with the increase of fiber mixing fraction and the mixed coarse aggregate. The influential degree of mixing fibers on reducing the cratering dimensions is much greater than which of compressive strength on enlarging the cratering dimensions; (ii) both of the compressive strength, the fiber mixing fraction as well as coarse aggregates can help decreasing the DOP of the projectile so as to enhance the impact resistance of the target, while the contribution of fibers is very limited for the relatively low addition ratio (63%). The DOP of the projectiles are no longer decreasing obviously when the compressive strength of the target is larger than nearly 90 MPa. © 2014 Elsevier Ltd. All rights reserved.

Shi L.,Jiangsu Research Institute of Building Science | Liu J.,State Key Laboratory of High Performance Civil Engineering Materials
Procedia Engineering | Year: 2012

Polymer coating is progressively being used in fields of concrete curing and concrete surface strengthening. However, only very few researches have been reported to investigate the effect of polymer coating on the properties of surface layer concrete. The effects of polymer coating on shrinkage, mechanical property, carbonation, capillary absorption and chloride ion diffusion of surface layer concrete were studied in the present investigation. The experimental results showed that polymer coating could obviously reduce the mortar shrinkage of the concrete surface, and the thicker the polymer coating, the greater shrinkage reducing ratio at early ages. It has been found that the polymer coating enhanced the mortar early age strength of the concrete surface. Meanwhile, the carbonation resistance of surface layer concrete, as well as the mortar infiltration resistance on the surface of concrete was improved by polymer coating. The results also demonstrated that the capillary absorption ratio of mortar in the surface layer of concrete cured under the polymer coating condition could be reduced by 87% and 78%, respectively compared with dry and standard curing conditions. In the same way, polymer coating had an improvement effect on chloride ion diffusion resistance of surface layer concrete. © 2011 Published by Elsevier Ltd.

Yao F.,Hohai University | Shang S.,Hunan University | Liu K.,Jiangsu Research Institute of Building Science
Soil Dynamics and Earthquake Engineering | Year: 2014

Base isolation is an effective way to reduce earthquake energy transfer from ground to structure, but existing seismic isolation systems are not very suitable for rural buildings for some reasons. A new steel-asphalt composite layer for the seismic base isolation of housing units is present in this paper. Its dynamic characteristics and isolation effect are studied by shake table tests of two full-scale specimens. Different earthquake waves with different peak ground accelerations (PGA, from 0.1. g to 0.4. g) are input. Test results show that the isolation layer could efficiently reduce the input acceleration. Moreover, as the PGA increase, the isolation layer shows good function of the displacement limit. © 2014 Elsevier Ltd.

Zhao H.,Nanjing University of Technology | Zhou W.,Jiangsu Research Institute of Building Science | Gao B.,Nanjing University of Technology
Advances in Cement Research | Year: 2012

The water-soluble hydroxyl carboxyl sulfonated aminophenol (AH) polymers were synthesised by the reaction between phenol, soldium sulfanilate, salicylic acid and formaldehyde. The effect of monomer ratios, pH value, reaction time and temperature on the dispersing properties of cement particles was analysed, the optimum reaction conditions were investigated. The molecular structure of AH polymers was characterised by infrared spectroscopy and gel permeation chromatography. A study was made of the surface properties of cement particles with AH polymers, such as surface tension, foaming properties and -potential. The test results show that the surface tension of the solution decreases as AH polymers and aminosulfonate phenol formaldehyde condensate (AS) superplasticiser concentration increases. The solution with AH polymers has a lower surface tension than the solution with AS superplasticiser at the same concentration. The foaming capacity of AH polymers and AS superplasticiser, however, has a better foam stability than the solution with AS superplasticiser. The-potential of cement particles with AH, AS polymers and AS superplasticiser increase as AH polymers and AS superplasticiser concentration and time are increased. The excellent dispersing properties of AH polymers on cement particles are attributed to the combination effect of adsorbing lubricate, electrostatic repulsive force and steric hindrance. © 2012 Thomas Telford Ltd.

Liu H.-Q.,Jiangsu Research Institute of Building Science | Yin Z.-Z.,Hohai University
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

The strength parameters are obtained with consideration of influence of wetting and drying cycles by an experiment based on laboratory direct shear test. The test basically reflects the phenomenon of crack evolution with wetting and drying cycles and reveals that crack evolution results in strength degradation. The results show that both cohesion and internal friction angle will attenuate along with crack evolution. Comparatively, cohesion index will be affected more obviously by crack and its determination should be more cautious. The law of attenuation accords with hyperbola; and the empirical expressions are proposed, which show that the relationship between attenuation of shear strength with increase of wetting and drying times is in fact with crack evolution. The expansive soil in engineering practice includes all kinds of cracks; therefore, in the design, the selection of strength parameters should consider the crack in the expansive soils. As the same time, the test method proposed makes the research of influence of crack evolution on the strength characteristics relatively simple and feasible.

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