Development of a design procedure for roller-compacted concrete (RCC) pavements

A design procedure was developed to determine the thickness and joint spacing for roller-compacted concrete (RCC) pavements used for airfields, roads, streets, open storage areas, and parking areas. The thickness design procedure was based upon the U.S. Army Corps of Engineers rigid pavement thickness design procedure and performance model. Improvements to the Corps procedure were made to consider a range of joint spacings for a given thickness, variable load transfer at joints, the effects of RCC tensile stresses resulting from the frictional restraint of the base course acting upon the RCC, and concepts of reliability. A mechanistic-based cracking model was developed to estimate RCC tensile restraint stresses as well as the crack width and natural crack spacing occurring in the RCC pavement with time. The cracking model was also used to determine several joint spacings which would result from sawing contraction joints in the RCC at various depths. The RCC drying shrinkage was determined from a series of laboratory tests in which the aggregate grading and moisture content of the RCC was varied. The load transfer of thirteen RCC joints and crack types was determined from an analysis of heavy-weight deflectometer joint efficiency tests conducted at twelve RCC pavement sites at different times and temperatures. A regression model was developed to relate the expected joint efficiency (ratio of joint deflections due to applied loads) to the crack width, the pavement temperature, and the maximum aggregate size. Reliability concepts were incorporated in the design model to determine the variability in the expected life of the pavement as a result of variability in the RCC flexural strength, the load transfer at RCC joints, the RCC thickness, and the modulus of subgrade reaction. A computer program incorporating these concepts was written to provide several combinations of RCC thickness and joint spacings which meet the criteria of minimum and maximum joint spacings, minimum life-cycle cost, and user-specified design reliability. The results of the thickness design and joint spacing program were verified by comparing them to existing pavement thicknesses and natural crack spacings, and to the results of other RCC and conventional concrete design procedures.