EFFECT OF BITUMINOUS MATERIALS ON SOIL AGGREGATION

Soil physical degradation is a progressive problem in most semiarid Me diterranean soils. The use of organic amendments is one of the most wi dely used remedial practices. Asphaltic emulsions are used to take adv antage of their binding properties and hydrophobic nature. Two soils, similar with regard to their degree of physical degradation, were stud ied Soil F was considered as a standard in terms of its physical chara cteristics, and soil D displayed an incipient state of degradation. Bo th soils were treated with an asphaltic emulsion as well as with a dis tillation residue and a series of organic materials prepared in the la boratory, consisting of composting asphaltic products with a mixture o f cereal straw and cattle manure. Both the asphaltic emulsion and the bituminous residue, as well as the composted mixtures resulting from t hese products with straw and cattle manure, had a favorable effect on the aggregate content of the soils, especially for soil D. In the degr aded soil this was due to the adherent properties of the materials and the formation of macroaggregates from microaggregates originally link ed to each other by Fe and Al bridges. In soil F the effect was due to physical adherence. Of the products tested, the asphaltic emulsion an d its mixture with fermented straw proved to be the most successful ma terials for Else in the regeneration of soils in an incipient conditio n of physical degradation.