No abstract

In general, steam curing is applied to improve the productivity of precast concrete products. After steam curing, products are stored outdoors for secondary curing before shipment. However, drying shrinkage and microcrack expansion that occurs during steam curing may impede strength enhancement. On the other hand, water curing is also clearly effective as a secondary curing process. However, installing a water curing pool in a precast concrete plant is not easy due to limited space. Therefore, this study focused on water sprinkling curing, which is relatively easy to perform without such restrictions. In this study, the effects of water sprinkling curing on the physical properties of mortar at the initial age of steam curing were investigated from the aspects of materials, mix proportions, curing conditions, and test piece dimensions. The results showed that water sprinkling curing increased the compressive strength by about 10% compared to curing under air. The effect of water sprinkling curing increased as the specific surface area of the test piece increased.

No abstract

This paper proposed a fabrication method of steel fiber reinforced concrete (SFRC) piles without shear reinforcement using the centrifugal forming technique to reorient the fibers perpendicular to the pile’s longitudinal axis for resisting the shear stresses. Effects of rotation patterns and concrete mixes on the fiber dispersion were investigated experimentally to identify the optimum procedure providing both well-oriented and well-distributed steel fibers. Using the X-ray radiography to visualize steel fibers inside the piles, it is confirmed that the centrifugal forming technique can realign the fibers in favor of the shear stresses. The shear test results show the effectiveness of the steel fibers in improving the shear strength of the SFRC piles due to good fiber dispersion. Moreover, the SFRC piles without shear reinforcement exhibited more ductile behavior than the RC piles with shear reinforcements. Steel fibers can be used to replace the shear reinforcements and improve the demanding productivity in the pile construction industry by saving time and labor.