Performance of Unconventional Soil Stabilizers in Stabilization of Substandard Materials for Road Subgrade & Subbase

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Addis Ababa University


Road connectivity is one of the key components for development, as it promotes access to economic and social services, generating increased income and employment. However, the construction of such economically vital sector is the most expensive of public works project undertaken by the society. Traditional pavement design and construction practices require high quality materials to fulfil minimum construction standards. In many of road projects it is very difficult to get standard materials with in economical haul distances. There is an increasing effort around the world towards introducing innovative and unconventional road construction approaches that aim at reducing costs of construction by enabling use of marginal materials found with in the road route. One of proven technologies in connection to this effort is stabilization of soil. Stabilization can be derived from thermal, electrical, mechanical or chemical means. Chemical stabilizers can generally be categorized in to two broad categories: conventional and unconventional stabilizers. Traditional stabilizers such as cement lime, fly ash, and bituminous products have been intensely researched, and their fundamental stabilization mechanisms have been identified. Unconventional soil stabilization additives consist of a variety of chemical agents that are diverse in their composition and in the way they interact with the soil. Unfortunately, relatively little is known about their interaction with geotechnical materials or their fundamental stabilization mechanisms due to proprietary nature of commercial stabilization additives, their exact chemical compositions are not disclosed. In this research two unconventional stabilizers were used for investigation of their effect on the engineering properties of soils that are deemed to be marginal for road subbase and subgrade. The two stabilizers used were: PURE CRETE and Anyway Natural Soil Stabilizer (ANSS). ANSS Natural Soil Stabilizer is claimed to be inorganic, hydration activated powderbased stabilizer that reacts with the soil particles to create layers that are interconnected through a complex inter-particle framework. The manufacturer claims PURE CRETE to be a complex non-bacterial concentrated multi-enzymatic formulation that alters the properties of earth materials, providing one of the most cost effective methods to stabilize roads and seal ponds and landfills. The stabilizers were combined with a total of five different soils with classifications according to AASHTO as A-7-5, A-7-6, A-2-7, A-2-4, and A-2-6. ANSS stabilization induced the most improvement on engineering properties of all soils tested at manufacturer recommended dosages and PURE CRETE failed to show any improvement at manufacturer recommended application rate. However, at very high application rates modest effects were noticed. It is recommended based on the results of this research that ANSS can be considered as a viable option for stabilization of subgrade soils after conducting durability tests. It will particularly help use of marginal materials where materials that met standard specifications are far away.



Unconventional ;Soil