Fly ash -limestone ternary composite cements: synergetic effect at 28 days

摘要: During cement production large amounts of CO2 are emitted, about 1 tonne per clinker, if no measures taken. About 40% originates from fuel combustion, grinding and other operations, 60% the de-carbonation limestone to form clinker phases. One way reduce these emissions on short term is by replacing part with materials such as slag, powder, fly ash, silica fume natural pozzolans. The type replacement used depends their availability (e.g. amount available, price transportation) therefore dependent geographical location plant. aim this study contribute development a novel all-round Portland composite for Norwegian market. When was started, cements produced at plants were: CEM I containing up 5% powder II/A-V ash 18% but powder. In study, effect increasing levels ordinary (OPC) (up 35% replacement), combining siliceous (FA) (L) replace OPC investigated. Using combination seems be better than using only one them. Limestone accelerates early hydration more contributes strength later ages due its pozzolanic reaction. Additionally chemical interaction between has been observed, first in simplified cementitious system also cement. interacts AFm AFt phases formed during OPC. At first, ettringite forms all gypsum consumed, will react remaining aluminates monosulphate. presence limestone, hemi- monocarboaluminate instead does, therefore, not decompose. This leads higher volume hydrates, which turn might porosity enhance compressive strength. limited low aluminate content. However, when replaced introduce additional it reacts. lower SO3/Al2O3 increase AFm/AFt ratio thereby amplify impact These changes have experimentally observed TGA, XRD EDX, predicted thermodynamic modelling. Only few percent required prevent decomposing products resulting small contents coincides an Replacement 65%OPC+35%FA resulted ranging 8 13% after 28 days curing. decreases again mainly serves inert filler. Replacing resulted, hand, reduction or slight 4% beneficial maximal days, reduces slightly upon further It furthermore valid 5, 20 40°C. 40°C reaction accelerated over time content important synergetic effect. partly described above filler (crystalline quartz) similar psd does same limestone. Additionally, seem affect reactivity significantly. enables them used. applicability demonstrated fact that optimal composition found (65%OPC+30%FA+5%L) recently construction Meteorological Centre Oslo Science county Ostfold