INFLUENCE OF CURING REGIMES ON THE COMPRESSIVE STRENGTH OF THE REACTIVE POWDER CONCRETE (RPC) USED IN RIGID PAVEMENTS

Abstract

Experimental and analytical works were done in order to study the effect of different curing methods and determine the best curing method which characterize the mechanical properties (compressive strength) of Reactive Powder Concrete (RPCs), in order to use it in rigid pavements (Airport Pavements) in Iraq. RPCs specimens were subjected to five types of curing regimes, Modified Curing (C1), specimens are immersed in hot water at 60oC for 7 days starting at one day after cast, specimens are then stored at 23oC & 100% RH until testing, Normal Curing (C2), specimens are allowed to remain in a standard environment conditions (23oC & 95% RH) starting at one day after cast until testing, Delayed Curing (C3), specimens are subjected to Normal Curing (C2) for 10 days after casting then specimens are subjected to Steam Curing (C4) for 48 hours, Steam Curing (C4), specimens are subjected to thermal steam treatment for 48 hrs at 90oC & 100% RH starting at one day after cast, specimens are then stored at 23oC & 100% RH until testing, and the Steam Pressure Curing (C5), specimens are autoclaved at 120oC & 1.0 MPa for 3 hours starting at one day after cast, specimens are then stored at 23 oC & 100% RH until testing. Test results show that the highest compressive strength were obtained by both the C1 and C3 curing methods. Depending upon mix proportions and age of test, the percentages of increasing in the compressive strength of RPCs specimens with respect to curing types were as follows: (a) For mixes without polymers: C1 recorded (59.03, 14.69, 32.16, and 14.67)% higher 28-day compressive strength than (C2, C3, C4, and C5) respectively; and C3 recorded (39.42, 20.70, and 23.38)% higher 28-day compressive strength than (C2, C4, and C5) respectively. (b) For mixes with polymers: C1 recorded (20.99, 5.83, 30.59, and 26.07)% higher 28-day compressive strength than (C2, C3, C4, and C5) respectively; and C3 recorded (28.59, 38.78, and 57.34)% higher 28-day compressive strength than (C2, C4, and C5) respectively.