DEVELOPMENT
OF ALTERNATIVE MATERIALS
- Given the fact that good quality aggregates are depleting and cost of material extraction is increasing, researchers are looking for suitable alternative materials.
- The tests and specifications, which are applicable for conventional materials, may be inappropriate for evaluation of non-conventional materials ( i.e. alternative materials).
- This is because the material properties, for example, particle sizes, grading and chemical structure, may differ substantially from those of the conventional materials.
- Thus, for an appropriate assessment of these materials, new tests are to be devised and new acceptability criteria are to be formed.
- However, with the advent of performance-based tests, it is expected that the performances of the conventional as well as new materials can be tested on a same set-up and be compared.
Industrial
and Domestic Wastes
- Industrial and domestic waste products provide a prospective source of alternative materials.
- These materials are cheaply available.
- Also, their use in road construction provides an efficient solution to the associated problems of pollution and disposal of these wastes.
Table 2 presents a partial list of industrial waste materials that can be used in road construction. Table 3 summarizes the advantages and disadvantages of using specific industrial wastes in road construction.
Table 2. Industrial waste
product usage in road construction (TFHRC
2004; Hamad
et al., 2003; Hawkins
et al., 2003; Mroueh
et al., 2002; Okagbue
et al. , 1999; Sherwood
1995; Javed
et al., 1994)
Waste product |
Source |
Possible usage |
Fly ash |
Thermal power station |
Bulk fill, filler in bituminous mix, artificial aggregates |
Blast furnace slag |
Steel industry |
Base/ Sub-base material, Binder in soil stabilization (ground slag) |
Construction and demolition waste |
Construction industry |
Base/ Sub-base material, bulk-fill, recycling |
Colliery spoil |
Coal mining |
Bulk-fill |
Spent oil shale |
Petrochemical industry |
Bulk-fill |
Foundry sands |
Foundry industry |
Bulk-fill, filler for concrete, crack-relief layer |
Mill tailings |
Mineral processing industry |
Granular base/sub-base, aggregates in bituminous mix, bulk fill |
Cement kiln dust |
Cement industry |
Stabilization of base, binder in bituminous mix |
Used engine oil |
Automobile industry |
Air entraining of concrete |
Marble dust |
Marble industry |
Filler in bituminous mix |
Waste tyres |
Automobile industry |
Rubber modfied bitumen, aggregate |
Glass waste |
Glass industry |
Glass-fibre reinforcement, bulk fill |
Nonferrous slags |
Mineral processing industry |
Bulk-fill, aggregates in bituminous mix |
China clay |
Bricks and tile industry |
Bulk-fill, aggregates in bituminous mix |
Table 3. Suitability of using industrial waste products in road construction
(TFHRC 2004; Hamad et al., 2003; Hawk ins et al., 2003; Nunes et al. 1996; Sherwood 1995; Javed et al., 1994)
Material |
Advantages |
Disadvantages |
Fly ash |
Lightweight, used as binder in stabilized base/ sub-base due to pozzolanic properties |
Lack of homogeneity,
presence of sulphates, slow strength development
|
Metallic slag
- Steel slag
- Nonferrous slag |
Higher skid resistance
Light weight ( phosphorus slag) |
Unsuitable for concrete
and fill work beneath slabs.
May show inconsistent properties |
Construction and
demolition waste |
More strength, can be used as aggregates granular base |
May show inconsistent properties |
Blast furnace slag |
Used in production of cement, granular fill |
Ground water pollution due to leachate formation, used as unbound aggregates |
Colliery spoil |
- |
Combustion of unburnt coal, sulphate attack in case of concrete roads |
Spent oil shale |
- |
Burning of combustible materials |
Foundry sands |
Substitute for fine aggregate in bituminous mixes |
Presence of heavy metals in non ferrous foundry origin, less affinity to bitumen |
Mill tailings |
Some are pozzolanic in nature |
Presence of poisonous materials (e.g., cyanide from gold extraction) |
Cement kiln dust |
Hardens when exposed to moisture, can be used in soil stabilization |
Corrosion of metals (used in concrete roads) in contact because of significant alkali percentage |
Used engine oil |
Good air entertainer, can be used in
concrete works |
Requires well organized
used oil collection system |
Rubber tires |
Enhances fatigue
life |
Requires special techniques for fine grinding and mixing with bitumen, sometimes segregation occurs |
|
