VERY HIGH EARLY STRENGTH OF MICROWAVE CURED CONCRETE

A high rate of strength development in concrete can benefit a number of important operations in the construction industry, including concrete precasting and pavement repair. In this study, the acceleration of concrete curing with microwave energy is investigated. Type III Portland cement is employed and both mortar and concrete specimens are made and tested. By applying the microwave energy for only 45 minutes, the compressive strength of concrete at an early age of 4.5 hours can reach 19.2 MPa (2,785 psi) for w/c=0.55 and 27.2 MPa (3,947 psi) for w/c=0.40. For the 0.55 w/c composition, the 7-day compressive strength reaches 37.4 MPa (5,417 psi), which is higher than that of conventionally cured specimens. Such performance compares favorably with commercially available rapid hardening concrete as well as concrete containing accelerators, showing microwave curing to be a promising technique for practical applications.