CHEMICALLY BOUND ROLLER COMPACTED SOIL TO CONTROL CORROSIVE DUST ON UN-SURFACED ROADS

Un-surfaced roads, especially those in arid regions, can produce large volumes of dust that, besides being a safety issue, cause corrosion and deterioration of vehicles traveling the roads.  At Pohakuloa Training Area (PTA), Hawaii, the unpaved roads are built on volcanic flows that weather to produce fine dust containing a high proportion of volcanic glass. In natural settings, alkaline conditions cause volcanic glasses to react and form complex calcium and sodium aluminum silicates that bond the particles together to form a rock-like material. Large parts of the ocean floor are paved with rock produced by the recrystallization of volcanic ash that was blown out to sea. Army researchers are investigating the use of similar reactions to stabilize the fine dust on un-surfaced roads.

Laboratory investigations using X-ray diffraction (XRD), uniaxial load frames, scanning electron microscopy (SEM), and nanoindentation indicate that suitable alkaline conditions can be produced by adding sodium carbonate and other soluble sodium compounds when lime-treating the glassy dust, causing the glass particles to self-cement. The addition of wastes such as pulverized fly ash or ground blast furnace slag can accelerate cementation. The stabilized volcanic material can be used as a traffic surface or a sub-grade material for a gravel top course. 

Test sections have been developed at the University of Hawai’i while a half mile of road is being constructed by roller compacted construction procedures at PTA. The construction of the road demonstrates how this unconventional system can produce dust control without using conventional Portland cement additions. This same technology can potentially be used with fine clays to produce “chemically bound roller compacted” traffic surfaces.