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dc.contributor.supervisorSiddique, Rafat-
dc.contributor.authorMehta, Ankur-
dc.description.abstractWith the fast growing infrastructure development, the demand of cement is bound to increase. But in producing 1 tonne of cement, around 1 tonne of carbon dioxide is released. For the changing environment, green house gases such as carbon dioxide, carbon monoxide, etc have been considered as responsible which also enhance the most hazardous environmental problem of global warming. This clearly reflects the inability of cement concrete to fit in the contemporary picture of sustainable development. On the other hand, various industrial by-products such as fly ash, metakaolin, slags, etc have prompted their use as supplementary cementitious material due to their cement like physical and chemical properties. Geopolymer technology utilizes these industrial by-products having high silica and alumina in the production of binders by polymerization reaction. The reaction is activated by hydroxides and silicates of alkalis such as sodium or potassium. The present research work involves the development of low-calcium fly ash based geopolymer concrete. Control geopolymer concrete with 3-day compressive strength of 41.3MPa was developed with fly ash content of 310 kg/m3, alkali solution-to-fly ash ratio of 0.55, sodium silicate-to-sodium hydroxide ratio of 2.5, total aggregate content of 70%, molarity of sodium hydroxide as 10M,fine aggregates-to-total aggregates ratio of 0.35and temperature curingat 80 ̊C for 24 hours. Further, additional geopolymer concretes were made by partially replacing fly ash with Ordinary Portland cement (OPC) (5-30%). Workability properties such as slump and compaction factor, strength properties such as compressive strength and split tensile strength, and durability properties such as water absorption, porosity sorptivity, chloride permeability and resistance to sulphuric acid solution were performed up to the age of 365 days. For reference, conventional cement concrete of similar 28-day compressive strength was also developed and properties were evaluated. Workability test results showed decrease in slump and compaction factor with the increase of OPC content in geopolymer concrete. The decrease in trend was found to be linear as high value of coefficient of determination was obtained. Compressive strength and split tensile strength increased with the increase in OPC up to 20%, and beyond that they decreased. The maximum compressive and split tensile strength of 66.81 and 5.35 MPa, respectively was obtained for geopolymer concrete with 20% OPC at 365 days. Also, for geopolymer concrete mixtures, high 3-day compressive strength and split tensile strength was obtained of around 92-98% and 91-95% of their 28-day values, respectively. For reference, 3-day values of compressive strength and split tensile strength for conventional cement concrete were found to be 38 and 55% of their 28-day values, respectively. Microstructural analysis of geopolymer concrete mixtures with inclusion of OPC as partial replacement of fly ash showed the coexistence of additional calcium based compounds (calcium-silicate hydrate and calcium alumino-silicate hydrate) with polymerization product (sodium-alumino-silicate hydrates). Water absorption, porosity and sorptivity decreased with the increase in OPC up to 20%, and beyond that they increased. The minimum values of water absorption, porosity and sorptivity were observed to be 1.1%, 6.1% and 2.54µmm/s1/2, respectively for geopolymer concrete mixture with 20% OPC at 365 days. Also, with the increase in OPC content up to 20%, reduction inchloride permeability in terms of total charge passed was observed. Beyond 20% OPC, thetotal charge passed values increased slightly.With reference to permeability range as specified in ASTM C1202, geopolymer concrete with OPC content from 10-30% exhibited the chloride permeability of “very low” category at all ages. The geopolymer concrete mixtures with OPC ranging from 0-30% showed better sulphuric acid resistance in comparison to conventional cement concrete at all ages. Also, with the increase in OPC in geopolymer concrete, the loss of compressive strength for sulphuric acid exposed geopolymer concrete decreased with the increase in OPC content up to 10%, and beyond that, it increased i.e. maximum compressive strength after sulphuric acid exposure was retained by geopolymer concrete with 10% OPC.en_US
dc.subjectFly Ash, Concrete, Geopolymer, Strength, Durabilityen_US
dc.titleStrength and Durability Properties of Low-Calcium Fly Ash Based Geopolymer Concreteen_US
Appears in Collections:Doctoral Theses@CED

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