Two-lift concrete paving (2LCP) involves placing two layers of concrete (wet-on-wet) instead of a single homogeneous layer. The practice not only allows the use of local aggregates that might not be suitable for conventional pavement, but also provides opportunities for incorporating recycled materials and higher levels of supplemental cementitious materials (SCMs) to produce an economical and sustainable pavement. The practice can also produce durable pavements through the optimization of top lift mixture design with desirable surface characteristics including improved skid resistance and reduced noise. While 2LCP could become a viable and competitive alternative to conventional single-lift paving, challenges of 2LCP are to have the proper paving equipment and pavement construction management, the right mixture proportions to ensure the use of local materials in the bottom lift to result in an economical placement and to ensure a high quality top lift. Through information collected from an extensive literature review, surveys, interviews and a recently hosted 2LCP workshop, a summary of benefits of 2LCP from sustainability and cost effectiveness perspectives was provided. Four 2LCP projects recently constructed in the U.S. were summarized as case studies. This paper also discusses additional requirements in materials, equipment and construction, project scheduling and jobsite management, which will be beneficial in the implementation of 2LCP construction.
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