Papers by Author: Bo Chen

Abstract: In order to investigate influence of aggregates on cracking resistance of concrete at early age, four kinds of aggregates, i.e. syenite, basalt, marble and sandstone, were used for the test on cracking resistance of hydraulic concretes by the temperature stress testing machine. Analogy analysis was carried out with test results of concretes with two gradings of aggregates. The results show that aggregates affect elastic modulus, thermal expansion coefficients and tensile creep behavior of concrete at early age. However, the temperature rise of concrete was slightly affected by various types and gradings of aggregate. Moreover, the cracking temperature is reliably to be used to quantitatively evaluate the influence of aggregates on cracking resistance of concrete at early age.

Abstract: The temperature-stress testing machine can be adopted to evaluate the crack resistance of concrete, but because of the disadvantages of long time, costs much restrict the development of temperature-stress test method. Getting needed mechanical and thermal parameters by the test here, then be used in the temperature history calculated by simulation software to compare crack resistance of different concretes. By using the convenient method, we can compare crack resistance of different concretes under the actual condition through simulation. The results showed that: the B4Cast simulation software can be used to get different concrete internal temperature histories under different temperature control methods, using the temperature history close to the real condition can evaluate the crack resistance of concrete objectively; on the basis of the temperature-stress test results, via fitting obtained the rules of concrete coefficient of thermal expansion, contraction deformation, elastic modulus, tensile strength and other parameters with maturation changes, then be used in the temperature history calculated by B4Cast, the concrete cracking risk can be simulation analyzed; using this method to compare the same strength grade of normal and pump concrete, the result showed that crack resistance of normal concrete is better.

Abstract: In order to evaluate the thermal cracking resistance of shotcrete under the condition of practical temperature field and strong restrain, a proper test method is needed. Based on temperature matched curing and by applying temperature stress testing machine, a new test method has been provided. With the application of this test method, thermal cracking resistance of three shotcretes with different types of fiber were investigated. Test results show that the cracking tendency of different shotcretes can be distinguished with the parameter of the difference between the max temperature and the cracking temperature.

Abstract: In order to evaluate the crack resistance of high strength fly ash concrete, concretes with different contents of silica fume and fly ash were compared with same strength grade by adjusting water to binder ratio. Compared with the concrete with 5% silica fume plus 35% fly ash，concrete with 40% fly ash has same mechanical properties and tensile strain as well as lower drying shrinkage. Complex crack resistance of high strength fly ash concretes were evaluated by Temperature Stress Testing Machine (TSTM). The results show that fly ash concretes have outstanding crack resistance because of higher allowable temperature differential and lower cracking temperature.