EVALUATION OF COLD IN-PLACE RECYCLING IN KANSAS

Kansas has many miles of thermally cracked roads, primarily in the western half of the state. Rehabilitation with conventional hot-mix asphalt overlays and hot recycling have not yielded the expected service life before existing cracks reflect through the pavement. Since 1986, the Kansas Department of Transportation has used cold in-place recycling (CIR) with an additive of emulsified asphalt as a cost-effective option for rehabilitating thermally cracked low-volume pavements. Field performance of the final product appears to have more variation than desirable, with an expected life of 3 to 5 years. The results of a 2-year study indicate that the material properties of locally available aggregates are poor, which results in the low strength of CIR mixes. In addition, the in-place air voids of the wearing surface were high and had an adverse effect on the performance of CIR mixes. Improvement of aggregate angularity and gradation with additional new aggregates or chemical stabilization of the materials is necessary to markedly improve CIR performance.