THE USE OF GRANULAR VOLCANIC ASH IN ROADS CONSTRUCTION

摘要

Granular volcanic ash material is spread over considerable parts of Yemen including urban and suburban areas. Due to the inferior properties of this material, in its natural state, it can not be used as a foundation either for roads or buildings. It is common practice, when faced with such material, to replace it with superior filling material. Excavated volcanic ash is disposed off by transporting it to landfill sites. Such practice is becoming increasingly costly coupled with the problem of the fast growing volume of disposed volcanic ash which continuously necessitates allocation of new landfill sites. Due to the massive amount of transported material, the problem in some urban areas is becoming an environmental issue. Clearly, a better management system of such materials is needed. One possible way to resolving this problem is to recycle this material by improving its physical properties and utilizing it in the construction industry. The main objectives of this study are twofold. One to investigate the merits of utilizing volcanic ash as a cheap alternative to aggregate for road construction and consequently this contributes towards an efficient management of this undesirable material and reduce its environmental impact. This study was conducted on natural volcanic ash in order to assess the performance of cement-stabilized mixture (cement-volcanic ash and fine materials). The volcanic ash was mixed with two different types of fine soils individually to improve the grading of the volcanic ash, cohesion properties and to reduce the amount of required cement. Different variables influencing the performances of ash-soil-cement mixture were studied. These variables included cement content, fine soil plasticity, soil content, and curing duration. The laboratory program adopted in this investigation includes material characterization, compaction, deformation properties and strength. Strength characteristics using unconfined compressive strength were studied and recommended values of cement content for specified conditions of road bases and sub-bases are presented in this paper.