Clay aggregates for road asphalt

Clay Technology magazine
1 Apr 2008

Aggregates for asphalt made from granulated clay have been developed by researchers at the Amazon Federal University in Manhaus, Brazil. The aggregate could replace stone used for paving in areas of the Amazon poorly supplied with suitable rocks but richly covered with clay.

Scientists have produced synthetic calcinated clay aggregates (SCCA) from soil that shows good resistance to manual mechanical compression. Water was added to the material at a humidity greater than the limit of plasticity. ‘This phase is important since inadequate homogenisation of the soil can generate brittle aggregates that are more prone to cracks,’ explains Professor Consuelo Alves da Frota of the Amazon University.

The material was then shaped in to aggregates 6.3-19mm in height. After drying in the shade for four days, they were heated in an oven at temperatures up to 950ºC, before cooling for six hours.
Tests of an asphalt mixture containing 41% SCCA has shown a tensile strength of 940kPa and a resilient modulus of 1,528MPa. This compares well to the strength and resilience of asphalt mixtures made from local pebbles, which tested at 600kPa and 991MPa, respectively. The SCCA mixture also shows good elastic recovery and is less susceptible to deformation.

The mixture is expected to be used on Brazil’s BR-319 highway connecting Manhaus to Porto Velho, which is in serious need of repair.