Introduction
Austroads Guide to Pavement Technology Part 4D: Stabilised Materials states:
Stabilisation may be defined as a process by which the intrinsic properties of pavement materials or earthworks materials are altered by the addition of a stabilisation binder or granular material to meet performance expectations in its operating, geological, and climatic environment.
The use of stabilisation technology for stabilising and recycling materials for pavement construction and maintenance is widely accepted as a cost-effective method of improving long-term performance and reducing whole-of-life costs of modern, heavily-trafficked pavements.
This part of the Guide to Pavement Technology discusses:
- the types of stabilised pavement and earthworks materials
- the binders associated with various types of stabilised pavement materials
- methodologies for the determination of the appropriate mix proportions in the manufacture of stabilised pavement materials
- specification considerations for manufacture and supply of stabilised materials.
What is Cementitious Stabilisation
Cementitious stabilisation involves using cement or supplementary cementitious materials like fly ash and ground granulated blast furnace slag (GGBFS) mixed with lime. These binders react with water in the host material to form cementitious compounds, enhancing moisture stability and providing tensile strength and high elastic modulus.
Key points on cementitious stabilisation include:
- Commonly Used Cements: General Purpose (GP) and General Purpose Blended (GB) cements are primarily used, conforming to standards like AS 3972-2010 and NZS 3122:1995.
- Supplementary Cementitious Binders: These include combinations of pozzolanic materials like fly ash and GGBFS with lime. They offer extended working times and reduced shrinkage cracking compared to GP cement.
- Properties of Cementitiously-modified Pavement Materials: These materials have small amounts of binders added to improve rut resistance and modulus without significant tensile strength increase. They are treated as unbound granular materials for design purposes.
- Properties of Lightly-bound Pavement Materials: Treated with higher binder contents than modified materials, they exhibit higher strength and modulus but may develop fine cracks.
- Properties of Cementitiously-bound Pavement Materials: These materials have significant tensile strength due to higher binder contents, acting like a ‘beam’ in the pavement structure. However, they are prone to shrinkage and fatigue cracking.
- Mix Design: The mix design process involves determining the appropriate binder type and content through laboratory testing, ensuring the desired structural characteristics are achieved. The Unconfined Compressive Strength (UCS) test is commonly used for this purpose.
- Deleterious Materials: Organic matter, sulphates, and ferrous oxide can interfere with the hydration process of cementitious binders, necessitating careful assessment of host material quality.
- Reaction with Binders: Primary reactions involve hydration between the binder and water, forming cementitious compounds. Secondary reactions occur with pozzolans in the host material, contributing to long-term strength gains.
- Laboratory Testing: Essential tests include UCS, California Bearing Ratio (CBR), flexural modulus, flexural strength, and fatigue life to ensure the mix design meets performance requirements.
Summary
Cementitious stabilisation is a widely accepted method for improving pavement performance by enhancing material properties through chemical reactions between binders and host materials. Pavement performance may be further improved, and the risk of cracking greatly reduced, through the use of Renolith 2.0 nanotechnology in conjunction with conventional cementitious stabilisation.
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