AbstractAt present, cementitious binders are used extensively in the construction industry and principally in concretes. They are also used in some applications like ground improvement. In these applications the cost of the binder, typically Portland cement, accounts for a considerable proportion of the total cost of the technique. In addition to the financial cost there is also the environmental impact of quarrying and processing of raw materials to produce Portland cements.
Gypsum waste, by-pass dust and fly ash by-products have been identified as the alternative sources of cementitious binder. Using these materials has two advantages: they have little or no production cost; and the re-use of such material would negate the need for expensive disposal.
This thesis describes a programme of laboratory testing and study on the possible field trials to investigate the possibility of using mentioned by-product materials as construction materials.
Laboratory trials carried out to investigate the properties of waste materials in different combinations; binary and ternary using the same water content.
Specimens were evaluated on the basis of Unconfined Compressive Strength at 3,7 and 28 days curing. It was found that pastes containing waste gypsums, Basic oxygen Slag and Run of station ash achieved the highest unconfined compressive strengths (up to 20 MPa) and five mixes of these groups were selected for further tests such as viscosity, permeability, expansion, XRD and freeze and thaw.
Data obtained from the ternary combinations were analyzed using two different methods, i.e. Response Surface method and Artificial Neural Network.
Two prediction models were created using MINITAB and MATLAB software and the predicted results were compared. It was concluded that the Artificial Neural Network had fewer errors than the response surface model.
The feasibility of using by-product materials in two field trials was also studied and the possibility of 100% cement replacement in low strength concrete used in subway backfilling (using 80%BOS-15% Plasterboard Gypsum-5%bypass dust) and light weight blocks (60% run of station ash-20%plaster board gypsum-20% bypass dust) was investigated.
It was found that waste gypsum could be used in both trials and the basic oxygen slag could be used for subway backfilling because it improved the flow. However it was not a good idea to use the steel slag in light weight products because of its density.
The thesis concludes that there are several potential applications for the use of the waste gypsums in combination with other waste materials in the construction industry but further work is required before it can be used commercially. However the sources and differing chemical contents of the by-product materials may have significant impact on the cementitious behaviour of by product materials.
|Date of Award||2008|
|Sponsors||Engineering and Physical Sciences Research Council, Tioxide Europe & Lafarge Plasterboard|
|Supervisor||Eshmaiel Ganjian (Supervisor) & Peter Claisse (Supervisor)|
- construction industry
- by-product materials
- cementitious binders