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Cai X.-R.,Building Science Research Institute of Liaoning Province | Xu S.-L.,Zhejiang University | Fu B.-Q.,Shenyang Jianzhu University
Engineering Fracture Mechanics | Year: 2011

A new statistical micromechanical model of multiple cracking is proposed in which a general expression of the fiber bridging stress laws in the crack plane is established. In this model, the random distribution properties of fibers are considered. And the Weibull function is adopted to represent the flaw size distribution. The relationships of stress versus strain and crack width versus strain are proposed. The formulas of the crack width, crack space, strain capacity and fracture energy density at the end of multiple cracking processes are also deduced. The validity of the proposed model was demonstrated by experimental results. © 2011 Elsevier Ltd.


Cheng Y.-H.,Northeastern University China | Chen D.-H.,Northeastern University China | Wang Y.,Building Science Research Institute of Liaoning Province
Jianzhu Cailiao Xuebao/Journal of Building Materials | Year: 2011

To identify the minimum cement content with the different frost resistance of concrete, 12 groups of concrete were prepared, that is, 6 groups of concrete without air entraining admixture, and 6 groups of concrete with air entraining admixture. The freeze-thaw tests have been carried out. Test results show that at the same mw/mb, with the increase in cement content, frost resistance of concrete improves, fly ash can improve the frost resistance of concrete obviously, and air entraining admixture can improve the frost resistance of concrete obviously too. For different situations, the minimum cement content in concrete is given respectively.


Fu B.-Q.,Shenyang University | Cai X.-R.,Building Science Research Institute of Liaoning Province
Gongcheng Lixue/Engineering Mechanics | Year: 2016

The model of multiple cracking of high toughness concrete is established by analyzing the interface stress of fiber in the cement matrix. Based on this model, the effects of friction bond strength, chemical bond strength, matrix cracking strength and elastic modulus of fiber on the strain and crack width at the end of multiple-cracking zone are analyzed. The analysis results show that the strain and the crack width decrease with the increase of the friction bond strength; the strain increases and the crack width decreases with the increase of the chemical bond strength; the strain and the crack width increase with the increase of the matrix cracking strength; the strain and the crack width decrease with the increase of the elastic modulus of fiber. The crack control ability of high toughness concrete with initial crack defects is researched through direct tensile test. The notched specimens are used in the research. The test results show that, when the initial crack-depth ratio is 0.2, the ultimate stress is 5.3MPa at the notch and is 4.3MPa at the non-cutting position, and the phenomenon of multiple cracking appears in the whole specimen, and the crack width is controlled in less than 0.1mm. When the initial crack-depth ratio is 0.4, the ultimate stress is 5.8MPa at the notch and is 3.5MPa at the non-cutting position, and the development of cracks is not controlled effectively by the fibers at the fracture plane. Therefore, only some similar arc cracks appear near the notch of the specimen. © 2016, Engineering Mechanics Press. All right reserved.


Cai X.-R.,Building Science Research Institute of Liaoning Province | Fu B.-Q.,Shenyang Jianzhu University | Xu S.-L.,Zhejiang University
Advanced Materials Research | Year: 2011

A new class of high performance fiber reinforced cementitious composites called Ultra High Toughness Cementitious Composites (UHTCC) is developed in the last few years. It is a pseudo strain hardening material with maximum tensile strain capacity more than 3%, yet the fiber volume fraction no more than 2%. The multiple cracking patterns accompanying pseudo strain hardening behavior are obtained which implies high ductility, energy absorption capacity, and toughness. A remarkable characteristic distinguish it from conventional high performance fiber reinforced concrete is the maximum crack width of multiple cracks which is about 60μm under ultimate tensile load. Such micro-cracks are often small enough to prevent the intrusion of aggressive agents. From a durability point of view this composite can be considered as an effectively uncracked material. The performances of this new material, including the apparent density, the uniaxial tensile property, and the drying shrinkage performance, are experimental studied in this paper. © (2011) Trans Tech Publications, Switzerland.


Cheng Y.-H.,Northeastern University China | Gou Z.-Z.,Northeastern University China | Wang Y.,Building Science Research Institute of Liaoning Province
Dongbei Daxue Xuebao/Journal of Northeastern University | Year: 2010

9 groups of high-performance concrete specimens were designed for orthogonal test where each of the 3 factors was at 3 levels with an L9(34) orthogonal table set out. The three factors/levels were the mixing at artificial, mechanical and overtime levels; the vibrating at artificial, mechanical and non-vibrating levels and the curing at natural, standard and humidity-insulated levels. The compressive strength tests for the 9 groups of high-performance concrete specimens were carried out for 14 days and 28 days separately, then the differential analysis and variance analysis were made for the orthogonal test results. The analyses indicated that among the three influencing factors on the compression strength of the high-performance concrete the mixing, curing and vibrating are ranked the first, second and third, respectively, and the optimal modes(levels) are the overtime mixing, non-vibrating and humidity-insulated curing.


Cheng Y.-H.,Northeastern University China | Wang H.-W.,Northeastern University China | Wang Y.,Building Science Research Institute of Liaoning Province
Jianzhu Cailiao Xuebao/Journal of Building Materials | Year: 2010

The carbonation test of a plain concrete and 3 kinds of fiber reinforced concretes i. e. steel fiber reinforced concrete, alkali-resistant glass fiber reinforced concrete, and polypropylene fiber reinforced concrete were carried out. Test results show that the carbonation resistance of fiber reinforced concretes in the test is all better than that of control concrete, and among the fiber reinforced concretes in the test, carbonation resistance of polypropylene fiber reinforced concrete is the best, carbonation resistance of alkali-resistant glass fiber reinforced concrete is better than that of steel fiber reinforced concrete.


Cai X.-R.,Building Science Research Institute of Liaoning Province | Fu B.-Q.,Shenyang Jianzhu University
Engineering Fracture Mechanics | Year: 2013

The ideal tensile stress-strain curve of ultra high toughness cementitious composites (UHTCC) shows trilinear stress-strain relationship. And its strain hardening process can be divided into multiple cracking zone and post multiple cracking zone. In this paper, the general expression of the fiber bridging stress laws in the crack plane is presented, and the stress-strain models are established for both zones based on the law. Furthermore, the critical fiber length between fiber pull-out and fiber rupture in the post multiple cracking zone are deduced. And the precondition to guarantee the post multiple cracking zone is deduced. © 2013 Elsevier Ltd.

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