The aim of this project is to develop designs for a durable long-life continuously reinforced concrete pavement (CRCP) with a low-noise asphalt surfacing. This aims to meet the objectives of the Government’s white paper (“Transport 2010 – The Ten Year Plan”) of covering new and existing concrete pavement with a quiet surface. The combination of a concrete structural layer and an asphalt surfacing has great potential to provide long-life pavements with minimum maintenance. The concrete substrate is relatively strong, durable and provides a good load distribution to the underlying foundation, whereas the asphalt surfacing provides better performance in terms of reduced-noise, improved riding quality, and a protective layer to the concrete. The resulting pavement also has the ability to receive further applications of asphalt overlays at stages during the life of the pavement. To reduce the quantity of asphalt in overlays, a variety of proprietary thin surface course systems (TSCSs) have been used with some success in recent years, both in the UK and elsewhere. The performance of selected continuously reinforced concrete pavement (CRCP) slabs, with and without a thin asphalt overlay, was compared with a continuously reinforced concrete road base (CRCB) with a 100 mm asphalt overlay. Measurements were made on a number of full-scale road sites to determine the amount of reflection cracking in the main slab, and the amount of seasonal thermal movement experienced at the ends of the slabs and across the expansion joints in the terminations. These measurements showed that a TSCS is likely to be successful in bridging cracks in CRCP where the concrete is in a sound condition, but where special treatment to the overlay is required to prevent reflection cracks from the joints in CRCP terminations. The potential exists for an asphalt overlay to modify the temperature characteristics of the underlying concrete, and thus the amount of thermal movements of the cracks. Temperature measurements in continuously reinforced concrete (CRC) slabs have shown that an asphalt overlay has the potential to reduce the range of temperatures in an overlaid concrete, leading to a reduced seasonal thermal movement of the concrete surface cracks. The ability of various TSCSs to bridge cracks and to prevent reflection cracks from the underlying CRC slabs was undertaken on laboratory-produced specimens of pre-cracked reinforced slabs in tension, and uncracked reinforced slabs in flexure. The TSCS parameters included in the investigation were: the binder type, the aggregate size, the surfacing thickness and the use of a bond or tack coat. The largest influence for reducing reflection cracking came from the type of binder material with – in order of influence – the asphalt thickness, type of bond coat and the aggregate grading having least influence. A detailed analytical approach was undertaken to determine the reduction in CRCP slab thickness which can be achieved, for the same cumulative traffic loading, by the addition of an asphalt surfacing. The results from the study are presented as a simple equation which adjusts the thickness of the CRCP slab to compensate for the addition of a dense bitumen macadam (DBM) asphalt surfacing material. Other asphalt grades or types of surfacing have been considered by converting the thickness and type of surfacing into an equivalent thickness of a DBM, and then substituting this thickness in the CRCP slab thickness reduction equation. The results of this work have been used to develop a family of design curves for CRCP with an asphalt overlay curve for a range of concrete flexural strengths and foundation classes. (Author/publisher)
Samenvatting