Papers by Author: Yue Bo Cai

Abstract: Influences of moisture content and loading rate on flexural toughness were experimentally studied for fiber reinforced shotcrete (FRSC) with steel fiber or macro synthetic polypropylene fiber. According to the four-point bending test method specified in ASTM C1609 and Chinese standard CECS 13, the flexural toughness of specimens after drying for 0h, 16h, 24h and 72h in condition of (20±2)°C and (60±5)% relative humidity was tested at a loading rate of 0.05 mm/min. For specimens after drying for 24h and 72h, flexural toughness was tested at loading rates of 0.05 mm/min, 0.10 mm/min, and 0.20 mm/min respectively. With the moisture content decreasing, the flexural toughness T100,2.0, first-peak flexural strength, and residual flexural strength at prescribed deflections of FRSC exhibited decreasing tendency. The specimens with 0.5 vol% of steel fiber showed higher T100,2.0 value than that with 0.9 vol% of macro synthetic fiber. The residual strength and flexural toughness of FRSC increased with the increase of loading rate.

Abstract: Sulfate attack of cementitious materials is closely related to the essential properties of cementitious materials and erosive environments. Therefore, the foundation of service life prediction model becomes very difficult and complicated. In this paper, the temperature and concentration of an erosive solution were taken into account in lab accelerating test, the service life prediction model of sulfate attack based on equivalent time and damage variable was founded by using Arrhenius equation, the concept of maturity, Fick’s law and the theory of damage mechanics. Dynamic elastic modulus value change, and/or mass change, and/or compressive or flexural strength change, et al. can be used as damage variable to show the evolving process of sulfate attack in concrete in this prediction model, and certain changed rate was considered as the damage critical value in concrete in terms of the standard or references or test results. To estimate the possible service life of concrete structures in sulfate attacking condition by lab accelerating test according to this prediction model, it will be benefit to guide the selection of raw materials and design of durability in concrete.