Using by-product industrial materials to replace all cement in construction products

摘要

At present, cementitious binders are used extensively in the construction industry andprincipally in concretes. They are also used in some applications like groundimprovement. 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 tothe financial cost there is also the environmental impact of quarrying and processing ofraw materials to produce Portland cements.Gypsum waste, by-pass dust and fly ash by-products have been identified as thealternative 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 theneed for expensive disposal.This thesis describes a programme of laboratory testing and study on the possible fieldtrials to investigate the possibility of using mentioned by-product materials asconstruction materials.Laboratory trials carried out to investigate the properties of waste materials in differentcombinations; binary and ternary using the same water content.Specimens were evaluated on the basis of Unconfined Compressive Strength at 3,7 and28 days curing. It was found that pastes containing waste gypsums, Basic oxygen Slagand Run of station ash achieved the highest unconfined compressive strengths (up to 20MPa) 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 differentmethods, i.e. Response Surface method and Artificial Neural Network.Two prediction models were created using MINITAB and MATLAB software and thepredicted results were compared. It was concluded that the Artificial Neural Networkhad fewer errors than the response surface model.The feasibility of using by-product materials in two field trials was also studied and thepossibility of 100% cement replacement in low strength concrete used in subwaybackfilling (using 80%BOS-15% Plasterboard Gypsum-5%bypass dust) and light weightblocks (60% run of station ash-20%plaster board gypsum-20% bypass dust) wasinvestigated.It was found that waste gypsum could be used in both trials and the basic oxygen slagcould be used for subway backfilling because it improved the flow. However it was nota 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 wastegypsums in combination with other waste materials in the construction industry butfurther work is required before it can be used commercially. However the sources anddiffering chemical contents of the by-product materials may have significant impact onthe cementitious behaviour of by product materials.