Two-Lift Construction to Address Today’s Challenges

Two-lift concrete pavement construction is not new, especially in Europe. In the United States it was used in the mid-1900’s but fell out of favor. This technology is one being considered by the Federal Highway Administration’s “Every Day Counts” initiative to implement innovations to the public. This paper discusses the evolution of the two-lift concept in the United States and how it offers a method of construction that could help transform traditional designs and techniques to those that make the transportation industry better environmental stewards. Concrete used in the bottom lift provides numerous opportunities for incorporating recycled by-products and other materials. Utilization of materials not acceptable for a surface layer may now be possible, thereby reducing the need to import materials. They may include recycled concrete and aggregates prone to polishing, as well as the use of high volume fly ash or other supplemental cementitious materials. The concrete in the top lift can take advantage of mixture and material options that may be cost prohibitive or difficult to work with for full depth construction. Reducing the permeability of this concrete, increasing the wear resistance, and addressing the surface characteristics challenges of noise and skid resistance are all feasible options.