CC2 Single Test Slab Test Objective
Construction cycle one (CC-1) included three Portland cement concrete (PCC) test pavement placed on stabilized base, one above low strength subgrade, one above medium strength subgrade, and one above high strength subgrade. During trafficking the rigid pavements developed top down corner cracking at the 28th loading pass. Upward curl had caused a separation of the slab corners with the pavement layer below resulting in a loss of support. It was of interest to build test pavements capable of enduring 20,000 passes prior to significant failure. Longitudinal and transverse cracking within the slabs would be the normal failure mechanisms typically experienced in rigid airport pavements and incorporated in theoretical predictive models, not the premature corner cracking observe in CC-1.
A single concrete slab with high flyash content, to reduce the flexural strength of the concrete, was placed on a rigid support in order to study the curling phenomenon within the indoor environment of the NAPTF. The slab would be instrumented to characterize curling, and the data obtained used to identify a method of minimizing it.
Additional objectives were to determine the adequacy of the instrumentation system, gather experience in placing concrete around the instruments, and to determine the effectiveness of the monitoring system. The entire effort would serve as the precursor in preparation for the design, placement, and monitoring of the actual CC-2 concrete test items.