VERY HIGH EARLY STRENGTH OF MICROWAVE CURED CONCRETE

A high rate of strength development in concrete can benefit a number o f important operations in the construction industry, including concret e precasting and pavement repair. In this study, the acceleration of c oncrete curing with microwave energy is investigated. Type III Portlan d cement is employed and both mortar and concrete specimens are made a nd tested. By applying the microwave energy for only 45 minutes, the c ompressive 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 reach es 37.4 MPa (5,417 psi), which is higher than that of conventionally c ured specimens. Such performance compares favorably with commercially available rapid hardening concrete as well as concrete containing acce lerators, showing microwave curing to be a promising technique for pra ctical applications.