Performance of Unconventional Soil Stabilizers in Stabilization of Substandard Materials for Road Subgrade & Subbase
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Date
2010-06
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Addis Ababa University
Abstract
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.
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Keywords
Unconventional ;Soil