Beneficial Role of the Industrial Wastes to Combat Adiabatic Temperature Rise in Massive Concrete
ABSTRACT An evaluation was made on the mutual beneficial role of fly ash and ground granulated blast furnace slag in combating adiabatic temperature rise. The experimental program was designed in two stages; the main experiment consisted of two massive concrete specimens with dimensions (50x50x50) cm. In first stage of experiment, an adiabatic rise in temperature of specimens was measured. In second stage, the mechanical properties of massive concrete specimens were measured at the ages of 8, 14, 28, 56 and 91 days. At the age of 91 days, surface core and central cores were extracted from the surface and the central part of massive concrete specimens to determine compressive strength and dynamic modulus of elasticity. In the massive concrete specimen without any additive, the peak temperature noted was 64.5Ã‚Â°C at 7th h after casting. While in mineral substituted concrete the maximum adiabatic temperature was 49.6Ã‚Â°C at 19th h after casting. Lower rate of temperature rise in mineral substituted concrete has resulted in higher value of ultrasonic pulse velocity and ultimate compressive strength of concrete.
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Article: Hydration of fly ash cement[Show abstract] [Hide abstract]
ABSTRACT: It is necessary to establish the material design system for the utilization of large amounts of fly ash as blended cement instead of disposing of it as a waste. Cement blended with fly ash is also required as a countermeasure to reduce the amount of CO 2 generation. In this study, the influences of the glass content and the basicity of glass phase on the hydration of fly ash cement were clarified and hydration over a long curing time was characterized. Two kinds of fly ash with different glass content, one with 38.2% and another with 76.6%, were used. The hydration ratio of fly ash was increased by increasing the glass content in fly ash in the specimens cured for 270 days. When the glass content of fly ash is low, the basicity of glass phase tends to decrease. Reactivity of fly ash is controlled by the basicity of the glass phase in fly ash during a period from 28 to 270 days. However, at an age of 360 days, the reaction ratios of fly ash show almost identical values with different glass contents. Fly ash also affected the hydration of cement clinker minerals in fly ash cement. While the hydration of alite was accelerated, that of belite was retarded at a late stage.Cement and Concrete Research - CEM CONCR RES. 01/2005; 35(6).
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ABSTRACT: In this paper, the results of a laboratory investigation conducted with heat evolution of high-volume fly ash (HVFA) concrete are presented. Heat evolution of concrete was studied by measuring the temperature increase in concrete under adiabatic curing condition. Characteristic of heat evolution of fly ash concrete was found to be strongly dependent on the replacement level of fly ash and dosage of superplasticizer used to maintain workability. It was also found that using fly ash as cement replacement resulted in a reduction on the maximum temperature rise. Increasing the replacement level of fly ash caused lower temperature rise in concrete. Superplasticizer caused a delay in peak temperature rise time; this is taken as an indicator that high-dosage superplasticizer used in concrete caused retardation in hydration of cement. Concretes having similar ingredients showed similar peak temperature rise whether they are superplasticized or not.Cement and Concrete Research 01/2002; · 3.11 Impact Factor
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ABSTRACT: The paper examines the role of different size fractions of ponded ash, characterised in terms of their physical nature and chemical composition, on the lime-reactivity strength of ash-lime-sand mortars. The paper also presents SEM and MIP characterisation of different size fractions. The results of the investigation show the strong influence of the fine particles on their physical properties and lime-reactivity strength of mortars. Ponded ash contains both reactive, small particles and non-reactive or poorly reactive large particles,due to which it loses its overall pozzolanicity. Its use as a pozzolan in cement concrete will only be possible if the non-reactive large sized particles are separated from it. The paper concludes that the practice of wet disposal of fly ash adopted mostly in India is detrimental to the pozzolanic activity of the ash.Cement and Concrete Research 05/1998; 28(5). · 3.11 Impact Factor