Christian Y. Agnew, P.E.1, Mark J. Farrow, P.E.2 & Michael D. Roland3

Most large cities are currently using pavement standards developed decades ago based on traffic projections that did not accurately predict the amount of heavy trucks and buses on our roadways today. Many pavement sections that once had a 20 to 30 year design life years ago now have a serviceable life of less than 10 years. This is typically confirmed when pavement design studies are performed for major municipal roadways receiving frequent heavy truck and/or bus traffic.

One factor contributing to reduced pavement lives involves deterioration of the pavement subbase resulting in base and subgrade failure under application of heavy truck or bus wheel loads. This paper presents some of the results of extensive field and laboratory studies performed for the City of Dallas at two paving projects during the development of their revised pavement standards. This paper also presents recommended in-place treatment of clay soils that will result in an effective subgrade modulus comparable to cement treated base (CTB) at almost half the cost.