Materials Science Forum Vol. 984

Abstract: Chemical admixtures are frequently used to regulate the setting and strength development of concrete materials. In this study, tricalcium silicate (C₃S) was used as a model of the cement system, and the influence of calcium chloride, an extremely useful accelerator, on C₃S hydration and the pore structure of hardened C₃S paste were investigated by the combination of the techniques of differential scanning calorimetry (DSC) and the N₂ adsorption (BET). The results indicated that the addition of calcium chloride would significantly shorten the pre-induction and induction periods and enhance the specific surface area and porosity of hardened C₃S paste. However, the presence of CaCl₂ has little effect on the pores, with a width ranging from 2.5 nm to 5 nm. DSC technique has an advantage of measuring continuously the process of C₃S hydration by changes of free water in hydrated C₃S.

Abstract: In order to explore the flexural behavior of CFRP reinforced pre-stressed concrete (PC) beams with initial cracks, 6 pre-tensioned beams were manufactured. Then the beams were pre-loaded to crack with 40% and 60% ultimate load respectively, and the beams were strengthened by CFRP under the conditions of load holding and fully unloaded. After that, the four-points bending tests were performed, and beam section strains, flexural capacities and cracks were analyzed. The results demonstrate that the ultimate load of CFRP reinforced beams increased by 10%~18%, and the ultimate loads of CFRP reinforced load holding beams were 3% and 6% lower than that of CFRP reinforced non-destructive beam, and the inhibiting effect of CFRP on cracks was weakened, the hysteresis strains should be considered for them. In this paper, the fiber hysteresis strains were calculated by the method of full section decompression moment, and the flexural capacities of CFRP reinforced PC beams were calculated, which are in good agreement with the test results.

Abstract: In order to study the stress-strain relationship of basalt fiber reactive powder concrete (RPC), the compressive stress-strain curve test of four groups of basalt fiber RPC was carried out. The test parameters including two kinds of basalt fiber length and three fiber volume fractions showed that the deformability of the test piece was improved and the failure process was delayed after incorporating basalt fiber. The optimum fiber fraction of the test piece with 12 mm long fiber was 0.10%. According to the experimental data, the stress-strain of the basalt fiber RPC was drawn. For the curve, the constitutive relation is fitted by the piecewise equation, and compared with the experimental curve, the fitting result is better.

Abstract: In this paper, finite element model of reactive powder concrete (RPC) pole was established by using finite element analysis software ABAQUS, and the strength of RPC pole was checked. The results of finite element analysis and theoretical calculation are compared to provide a basis for determining the parameters used in finite element modeling and revising the theoretical calculation formula.