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|Title:||Characteristics of Concrete Incorporating Waste Marble Powder|
|Abstract:||In the present study, the influence of using marble waste as fine aggregates in concrete is investigated. Seven mixes were prepared by varying the replacement levels of marble waste from 10 to 60%. The w/c ratio of the mixes was kept constant at 0.5. The effect of using marble waste aggregates is investigated in terms of workability, mechanical strength of concrete, permeation properties and durability properties of concrete. The various durability properties investigated in the study included abrasion resistance of concrete, drying shrinkage, resistance of concrete when subjected to external exposure to severe sulphuric acid and sodium sulphate exposure. All the studies are supported by micro-structural analysis of concrete. Test results indicate that marble waste can be incorporated into concrete to improve its strength and permeation properties, with the maximum improvement obtained at 40% replacement level. The improvement in properties of concrete with the incorporation of marble waste can be attributed to better filler effect provided by marble waste, due to presence of more fines in the particle size range of 1.18mm - 300μm, which led to refinement of pore structure. Along with this, the angular sizes of marble waste aggregates helped in better bonding and improvement in interstitial transition zone of the resultant mix. At the chemical level, marble waste improves the binding ability of the mix. The reaction between calcite present in marble with C3A of cement provides a compact structure and helps in improving binding capability of the concrete matrix. Micro-structural analysis also revealed densification of concrete matrix, which is attributed to refinement of pores because of both physical and chemical changes in the concrete matrix. The fact that marble is largely an inert material and has filler effect on the properties of the resultant mix, is confirmed from the SEM and XRD analysis which shows major phases formed in all mixes remained same, irrespective of the replacement levels of marble waste. Incorporation of marble waste as fine aggregates led to reduction in drying shrinkage strain of concrete mixes. During 270 days of drying duration, the ultimate shrinkage strain reduced gradually from 478×10─6 mm/mm to 332 ×10─6 mm/mm as the percentage of marble waste is increased from 10 to 60% of fine aggregates. A shrinkage prediction model incorporating 28-day compressive strength, drying duration and proportion of marble waste used, is proposed. The proposed model had high correlation coefficient (R2) which indicates its effectiveness in predicting drying shrinkage accurately. The mixes were subjected to 3% sulphuric acid solution for a period of 180 days. The mixes were continuously monitored in terms of visual appearance, weight loss and compressive strength loss. SEM images and XRD patterns were also analysed to understand the performance of various mixes in severe sulphuric acid exposure. The mixes with marble waste were observed to have better performance towards severe sulphuric acid exposure. It is due to the high acid solubility of marble waste, due to which it had greater acid neutralizing capacity locally. It helped in reducing the local acid concentration and hence the rate of acid attack on compounds of concrete. In mixes containing marble waste, calcium carbonate present in marble waste reacts with sulphuric acid to form gypsum. Since marble waste is available for reaction with acid, reaction of cement hydration products with sulphuric acid is delayed; thereby delaying the conversion of cement hydration products into gypsum and ettringite. The exposure to 5% sodium sulphate solution for 18 months indicated that the incorporation of marble waste helped in arresting the sodium sulphate attack. The mixes incorporating marble waste registered lower weight loss, lower compressive strength loss and expansion of the mixes reduced drastically. Lower expansion demonstrated that lesser amount of gypsum and ettringite were formed, which are mainly responsible for expansion and ultimate degradation of concrete under sodium sulphate exposure. Also, at the physical level, permeability of the mixes with marble powder decreased to the extent of exposure. Overall, the results confirm that marble waste has the potential to be used as an alternate fine aggregate to improve overall performance of concrete for sustainable development.|
|Appears in Collections:||Doctoral Theses@CED|
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