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This paper describes the findings of a study carried out for evaluating the performance of cast in situ concrete block pavements for low volume roads. Concrete is filled up into a formwork of cells 150 mm x 150 mm x 100 mm made tip of thin plastic sheets and compacted to form flexible interlocked concrete blocks. Details of a laboratory investigation on the proportioning of mixes and the evaluation of the strength of different mixes arc presented. Cast in situ block pavements were constructed and tested in an accelerated pavement test facility. It was found that the blocks became interlocked and thai the block pavement displayed a very little amount of rutting along the wheel path. A falling weight deflectometer test indicated that the equivalent elastic modulus of cast in situ concrete blocks was over 2,500 MPa. An example of pavement design using cast in situ concrete blocks is presented. DOI: 10.1061/(ASCE)0733-947X(2005)131:9(662) CE Database subject headings: Concrete blocks; Concrete pavements; Pavement design Tests; Elastic analysis.

The paper presents the details of various investigations conducted for the laboratory evaluation of the performance of crumb-rubber modified asphalt mixes. Crumb rubber (CR) obtained from discarded truck and bus tires was used to modify 80/100 penetration grade asphalt cement. Fatigue and permanent deformation characteristics, temperature and moisture susceptibility, and oxidative aging are some of the performance indicators of mixes evaluated. A static indentation test was adopted for assessing the relative permanent deformation characteristics of different mixes. Three aggregate gradations: (1) superpave; (2) gradation specified by the Ministry of Surface Transport, India for asphalt concrete; and (3) one gap gradation, were considered in the investigation. Compared to normal mixes, CR modified mixes were found to have improved fatigue and permanent deformation characteristics. They also showed lower temperature susceptibility and greater resistance to moisture damage compared to normal mixes. Superpave mixes gave better overall performance compared to the mixes having other aggregate gradations. CE Database subject headings: Rubber; Binders, materials; Asphalt mixes; Laboratory tests; Fatigue strength; Deformation.

The current practice in India for thickness design of roads with bituminous surfacing is based on limited experience of road performance in the late 1970s. Extrapolation of the design method to the present day heavy traffic is not valid because of the empiricism in the original method. This paper describes the details of an investigation undertaken by the writers to develop a mechanistic design method by correlating the performance data of bituminous pavements from different parts of India to the critical stress-strain parameters of the pavement composition leading to the failure of pavements. Also indicated are the evaluation of fatigue and elastic properties of pavement materials, analysis of field performance data, determination of fatigue and rutting criteria from laboratory and field data, and development of thickness design charts for bituminous pavements.

Low-grade laterite and pit-run gravel aggregates available in abundance in eastern India may be turned into a cost-effective base for low-volume roads when ordinary portland cement, river sand, and aggregates are mixed in a 1:6:12 proportion by weight. 152 x 152 x 152 [mm.sup.3] cubes were cast at several water-cement ratios and the mix was compacted by a vibratory plate compactor. The compressive strength test was determined for different water-cement ratios, and the one that gave the maximum strength was used to prepare 102 x 102 x 508 [mm.sup.3] beam specimens. A number of cubes and beams were kept inside airtight polyethylene bags for accelerated curing at a temperature of 50 [degrees] C. Modulus of rupture and flexural fatigue tests were carried for the evaluation of pavement design parameters. A methodology of design of a lightly cemented pavement along with an example are also presented.