As a kind of monocrystal reinforcing material, CaCO3 whisker has good characteristics of high strength, high module and high thermal stability. This research aims to optimize the microscopic structure of fiber cement mortar by adding CaCO3 whiskers and improve the macroscopic mechanical properties. The results showed that CaCO3 whiskers increased the flexural and compressive strength of cement mortar at 3d age by 29.5% and 19.8% at maximum respectively, which fell to 7.2% and 13.0% at 28d age; when CaCO3 whiskers content was 10% and polypropylene fibers content was 0.05%, compared with the pure cement mortar, the flexural and compressive strength were increased by 32.4% and 29.4% at 3d age and 7.6% and 4.6% at 28d age respectively; when the fiber length was 9mm, the composite effect of whiskers and fibers was more ideal; through the SEM analysis, the reinforcing mechanisms of CaCO3 whiskers and polypropylene fibers in cement mortar were discussed.

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The fracture behavior of brittle materials under biaxial plane stress has been investigated by means of numerical simulation method with software MFPA2D (Material Failure Process Analysis). The aims of this study are to clarify the fracture dependence of brittle material on biaxial plane stress state. The observation of crack initiation and fracture behavior reveals that the biaxial stresses have strong influence on the fracture properties of glass. Thus, the fracture criterion by the stress intensity factor was questioned for the biaxial plane stress issues. It is confirmed that the tensile stress parallel to the crack plane is an important factor affecting crack arrest, while the compressive stress parallel to the crack plane contributes to crack opening.

The aim of this study is to demonstrate the influence of the stress parallel to the crack plane on subcritical crack growth in brittle materials by using a numerical code MFPA2D. The mechanism of this influence is also discussed. The curves of subcritical crack extension vs. strain of brittle materials under uniaxial and biaxial stress were obtained through numerical tests with acoustic emission consideration. The results showed that the tensile stress parallel to the crack plane has the effect on crack arrest, while the compressive stress parallel to the crack plane plays important role in crack opening process. The numerical results were consistent with experimental observed result, which shows the reliability of the numerical method, and provides theoretic foundation for failure analysis and life estimation of brittle materials.

The compactibility, mobility and segregation stability of self compacting concrete (SCC) is essential for its quality control. Completely and reasonably workability evaluation to SCC has an obviously influence in concrete engineering field. The paper introduced the rheology and workability mechanism of SCC. Ten workability assessment methods, such as Slump Flow test, U-box test, J-ring test, L-box test, VSI method, Oriment test, V-funnel test, Inverted Slump Cone test, were presented and the advantages and disadvantages of each appraisal procedure and the evaluation practice were analyzed. It also put forward the prospect direction of workability evaluation of SCC.