Dolomite refractories have a good production potential in Iran due to the existence of high-quality dolomite ore in many regions of the country, particularly in Isfahan and Hamedan. The basic problem associated with the production and use of this type of refractories is inherent tendency to hydration of calcined dolomite. One of the methods to overcome this problem is to increase the amount of Magnesia in doloma. This study focuses on the use of Iranian dolomite to produce Magnesia -doloma (mag-dol) refractory with high resistance to hydration and corrosion. It was found that addition of 20wt% magnesite to dolomite would result in capsulating of CaO by MgO that protects doloma from further hydration.

There have been lots of studies to control the poor hydration resistance of dolomite refractories, one of the most effective solutions has been the addition of Magnesia to doloma. Using a co-clinker of Magnesia-doloma as a starting material would provide more homogeneity in the properties of the product and has been published recently. On the other hand, addition of iron oxide to doloma has been found to increase the hydration resistance. In this paper, the effect of iron oxide addition on hydration phase analysis and microstructure of two different Magnesia-doloma samples, one with CaO content of 25 wt% and the other one with that of 35 wt% has been investigated. Ten samples were prepared by pressing followed by firing at 1750 oC for 3hrs. Results showed that the hydration resistance of the samples improved by decreasing the CaO content, because CaO is much more prone to hydration comparing to MgO. Besides, iron oxide addition lead to the formation of iron-containing phases which increased the hydration resistance of the samples both by capsulating the CaO and MgO grains and by promoting the liquid phase sintering.

In the persent work the effect of Al in Magnesia-graphite refractories(MGR) on phase transformation has been investigated. Small disc shape sample were prepared by using proper starting materials and different amounts of Al powder. Then the samples were heat treated in a carbon bed in temperature range of 600-1400°C DTA/TG, XRD and SEM were used to analyse the sequences of the thermal enents and microstructural characterization. Results show that at temperature around 800°C carbide and nitride of Al formed due to the reaction of Al melt with carbon and nitrogen in the media. Above 1000°C spinel formed. Around 1200°Cby decreasing amount of Al__4 C__3 spinel phase increased and at 1400°C the major formed phases are spinel and ALN. ALN phase and Al__4 C__3 had needle and platelet shape respectively

Magnesia-carbon refractory brick has attracted attention in steelmaking industry due to special properties of heat resistance and non wettability with steel melt. Hot corrosion of slag line and the need to repair and replace with the new brick is a problem. In this research the effect of different slag additions on corrosion of Magnesia-carbon refractories in ladle furnace is studied. Results show that the addition of dolomite powder, magnesite carbon used bricks (waste), sintered magnesium oxide and talc in proportions of 15% and 30% to be replaced with the amount of slag is beneficial. The most effective additive in corrosion resistance increase is dolomite.

The present study was undertaken to improve the quality and increase the life time of Magnesia-chromite refractory bricks used in the copper and lead industries. The results show that a decrease in the amount of large chromite particles in the formulation improves the thermomechanical properties and also reduces the slag penetration in the bricks. In addition, it was observed that the use of co-clinker decreases the open porosity in the bricks and thereby improves the mechanical properties. It was also shown that the use of around 4 percent iron oxide has beneficial effect on the bricks properties. Microstructural evaluation on the bricks shows increased formation of spinel phase and more direct bonding in the improved bricks.

Background and objectives: Solidification/stabilization is an effective technique for reducing the leachability of contaminants in soils. Magnesia phosphate cement and ordinary Portland cement can be used to remediate soils contaminated. In this study, the performance of the solidified/stabilized soil was compared for mixtures composed of Magnesia phosphate and ordinary Portland cement. Materials & Methods: In this study, the experimental soil were contaminated with 500, 1000 and 5000 mg/kg of lead. Lead-contaminated soils were stabilized by mixing Magnesia phosphate and Portland cement in proportions of 25% and 50% by weight. Cement and soil mortars were prepared with waterto-cement ratio 0. 5 of distilled water. The performance was assessed using unconfined compressive strength (UCS), toxicity characteristic leaching procedure (TCLP), initial and final setting and X-ray powder diffraction (XRD). Results: The results showed that use of Magnesia phosphate cement instead of Portland cement could significantly reduce the concentration of lead in TCLP leachate, the setting time and increase the buffer capacity and the formation of crystals in samples containing lead. In 28-day samples containing soil with 5000 mg Pb/kg, Pb concentration in TCLP leachate of samples stabilized with 50% and 25% cement had been determined as 0. 41 mg/L and 1. 15 mg/L for Magnesia phosphate cement and 4. 92 mg/L and 12. 04 mg/L for Portland cement, respectively. However, using this type of cement instead of Portland cement reduces the compressive strength of 7 and 28 days. Conclusion: The substitution of Portland cement with magnesium phosphate cement for stabilization and solidification of contaminated soil revealed a significant decrease in leachability of heavy metals, setting time, maintenance and equipment cost.