A NOVEL APPROACH TO FLY ASH IN ROADBED CONSTRUCTION

Abstract

Sand is commonly used in the construction of roads, however, sand resources are becoming depleted in many areas. The loose grain structure and low elastic modulus of most sand means it often cannot meet the technical requirements of road base construction. As a result, alternative materials such as soil reinforced with inorganic binders, natural aggregates, and macadam are often employed for constructing road embankments. The use of these alternative materials contributes to the increase in construction costs and potentially, in environmental pollution. Therefore, it is important to identify new types of materials that can be used for road construction. This study investigates the mechanical properties of fly ash–sand mixtures through various laboratory tests to identify the optimal composition for road construction applications. The test results show that the sand-fly ash mixture, which features an optimal ratio of 70% sand to 30% fly ash with a dry volume of 1.821 g/cm3, not only satisfies the requirements for road base materials but also increases the use of fly ash. By employing geopolymer technology and incorporating an alkaline solution to strengthen the sand-fly ash mixture with 70% to 30% sand-fly ash mixture, the fly ash is activated to produce a gelatinous material through a series of reactions. The gelatinous material exhibits high-strength and tightly linked molecular structures. In addition to being a suitable material for road construction, the sand-fly ash mixture can also be used as a foundation layer for pavement structures.