Use of Soft Limestone for Road-Base Construction in Belize

The results of a highway experiment, constructed in May 1978 in northern Belize, designed to investigate the suitability of locally occurring calcareous materials, known as marls, for road bases are discussed. The marls comprise high-purity carbonate materials containing mainly siltsized particles and fall outside the grading, plasticity, and strength specifications normally required for road bases. Three marls, each with slightly different characteristics, were substituted as road base for crushed stone. One of the marls was also stabilized with ordinary portland cement. Detailed monitoring was then undertaken periodically to determine their performance. The road pavement was constructed on an embankment to ensure good drainage. A good quality surface dressing seal has been maintained. After 19 years of traffic, measured at 1.3 million equivalent standard axles, the marl road bases have performed at least as well as the crushed stone. The cement-stabilized marl road base performed exceptionally well. Stabilization would enable the use of more plastic marls.