Papers by Keyword: Heat Evolution

Abstract: With the development of concrete industry, the necessity for utilizing waste materials and decreasing overall energy consumption is becoming increasingly obvious. Fly ash and granulated blast-furnace slag, which are used as blends of Portland cement, are waste materials produced in electric and energy industry, and concretes made with them can have properties similar to ones made with pure Portland cement at lower cost per unit volume. By using blended Portland cement, both ecology benefit and economic benefit can be achieved. Due to the pozzolanic reaction between calcium hydroxide and blended components, compared with ordinary Portland cement, hydration process of blended Portland cement is more complex. In this paper, based on a multi-component hydration model, a numerical model which can simulate heat evolution process of blended Portland cements is built. The influence of water to cement ratio, curing temperature, particle size distribution of cement paste and blended Portland material, and cement mineral components on heat evolution process is considered. The prediction result agrees well with experiment result.

Abstract: Identification of precipitates appearing during DSC scan of Al-2.1Li-2.9Cu-0.12Zr(wt. pct) alloy has been conducted as a function of temperature by using a differential scanning calorimetry (DSC) and transmission electron microscopy(TEM). In the as-quenched specimen from 540°C, three couples of heat evolution and absorption peaks are observed during the heating period of DSC experiments. It is found from TEM works that these peaks are associated with the formation and dissolution of GP zone, δ‘, and T1(+θ') phases. The heat evolution peak appearing in the temperature range over 36~78°C is due to the formation of GP zone. Heat absorption peak appearing in 78~140°C is associated with the dissolution of GP zone. Heat evolution peaking at 166°C in the temperature range over 140~190°C and next heat absorption peak are attributed to the formation and dissolution of δ‘ phase. Heat evolution peaking at 288°C in the temperature range of 254~332°C and heat absorption at high temperature are attributed to the formation and dissolution of T1(+θ'). The hump in DSC curve at the temperature of 425°C is considered as the formation of hexagonal structure T2 phase.