Quick Fix

To minimize traffic interruptions and speed construction on road and runway rehabilitation projects, Caltrans and other transportation agencies are using rapid-hardening-cement concrete (RHCC). Although similar to portland cement in many ways, rapid-hardening cement has a different chemistry, giving concrete significantly improved properties. RHCC with a 5-inch slump and 650 pounds of cement per cubic yard routinely achieves compressive strengths of 2500 to 3000 psi in 1 1/2 hours. Its shrinkage is about 25% that of portland-cement concrete (PCC) of the same slump, and its porosity is much lower, contributing to improved durability. In freeze/thaw tests (ASTM C 666), RHCC can withstand 1000 freeze/thaw cycles, compared with only 350 cycles for most PCCs. Generally, rapid-hardening cement can be substituted pound for pound for portland cement. Mixing and placing procedures for RHCC and PCC also are similar.

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