Mechanical Properties of Precast Concrete Pipe (PCP) Sheet Under Different Curing Conditions and Ages.

With the rapid development of underground rail transportation in China, the demand for precast concrete pipe sheets in metro construction continues to increase, and the quality and safety of precast concrete pipe sheets profoundly affect the safety of tunnels. The quality and safety of precast concrete pipe sheets have a profound impact on the safety of tunnels. The maintenance of pipe sheets plays an important role in ensuring the strength and durability of concrete pipe sheets. Therefore, it is important to study the maintenance methods of concrete pipe sheets. The method of substituting immersion curing with spray curing is proposed in this paper. It has been shown that spray curing can overcome the challenges of high pollution and high cost caused by the immersion curing of precast concrete pipe (PCP) sheets. Experimental tests investigate the influence of macro-mechanical properties and microstructure of pipe sheet materials under various ages of the two curing conditions. The results highlighted that the conventional methods of water immersion for PCP have minimal effect on concrete's macro-mechanical characteristics or microstructure after a certain curing age. The comparative studies on both curing processes showed that after seven days of curing, the degree of moisture attained by the spray-cured samples was relatively lower than that of the water immersion approach. In addition, samples with the water spray curing process had larger pore sizes (which could degrade faster) with lower mechanical strength. Interestingly, after 28 days of curing age, both approaches attained complete hydration levels, resulting in a dense pore structure with reduced median pore size and higher mechanical performance. Investigations on two distinct methods indicated that the early strength properties (after seven days of curing) acquired with water immersion curing were higher than the mechanical properties obtained with spray curing. This difference in mechanical properties, in addition, was not significant after 28 days of curing age. As a result, the suggested technique of water spray curing is an appropriate method with minimum water use to some extent. [ABSTRACT FROM AUTHOR]