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Although the machine-made sand was widely used for concrete in recent years in China, it was short of studies on the relations among the basic mechanical properties of fly-ash concrete with machine-made sand (MSFAC). However, these relations such as the compressive strength, the tensile strength and the elastic modulus with the cubic compressive strength (i.e. strength grade) are the basis of design for concrete structures. This paper summarizes the test data from the published references, and discusses the relations among these properties by statistical analyses compared with those of ordinary concrete. The results show that only the tensile strength of MSFAC can be safely forecasted by the same formula of ordinary concrete specified in current Chinese design code. When the strength grade is higher than C45, the axial compressive strength of MSFAC is largely forecasted by the formula of ordinary concrete. The elastic modulus of MSFAC is larger than that of ordinary concrete, which should be prospect by the formula in this paper. This work gives out some cautions for the proper use of the MSFAC in concrete structures.

As part of the studies on the durability of concrete with machine-made sand, this paper introduces the test results and the forecast model of time-dependent chloride penetration of this kind of concrete. Three strength grades of concrete C30, C40 and C50, and the contents of stone powder in machine-made sand of 5%, 9% and 13% in mass were considered in the mix proportion of concrete with machine-made sand. The ordinary concrete with natural river sand in the same strength grade was tested at the same time for comparison. The test was conducted for 360 days, the results showed that the effect of the content of stone powder on the chloride penetration of concrete was obvious at early curing time of 7 days, and tended to be lower with the increase of curing time. When the curing time was longer than 90 days, this effect could be neglected, and the resistance to chloride penetration of concrete with machine-made sand was almost equal to or larger than that of ordinary concrete. The decrement of chloride diffusion coefficient varied from sharp to gentle with the curing time, the resistance of concrete to chloride penetration increased with the increase of concrete strength. Meanwhile, to facilitate the calculation in practice, the forecast model of chloride diffusion coefficient of concrete is proposed.

Combined with the application of high-performance concrete in bridge engineering, the construction technics of pretensioned prestressed high-strength concrete (PPHC) hollow slabs with new section is summarized. The qualities of concrete in C80 strength grade are statistically analyzed based on the precast of 75 PPHC hollow slabs for two bridges. The results show that it is reliable to precast PPHC hollow slabs for bridge construction.

For the micro torsion bar used in inertial navigation, the torsional stiffness should be evaluated precisely. A computer-controlled instrument for stiffness measurement based on static measuring principle was introduced for variant section micro bars, The main hardware of the system includes a precision motorized rotary stage and a torsion sensor. The stepping resolution of angular displacement is 0.00250, the measurement accuracy of moment is 0.05mN•m. The measurement software was programmed on the LabVIEW platform for virtual instrument. The measuring experiments indicate the device can be used for automatic testing of stiffness of the torsion bars with high accuracy and efficiency.