Study on Performance and Preparation of Dry-Mixed Masonary Mortar with Red Mud from Bayer Process
|Course||Materials Science and Engineering|
|Keywords||Bayer red mud dry-mixed masonry mortar preparation performance|
Red mud is a high alkaline and fine solid waste generated during aluminum product raised from bauxite. It is reported that production of 1 tonne of metallic aluminum generates about 0.8-1.76 tonnes of red mud.With the increasing alumina production in China, annually there are about 10 million tonnes of red mud being disposed from alumina plants. It was estimated that the total amount of red mud was up to 200 million tones but only about 4% of the red mud is effective utilization. So taking full advantage and expanding application of red mud as a useful material is a exigent mission。Mortar is a high consumption building material in earth wood building and the requirement is approximately 1000 million tones a year. Application red mud to mortar production is a effective utilized method.The characterization of red mud-cement binder systems hydration and hardening was studied. Through it the dosage of red mud was determined. Based on the influence of mineral admixture and chemical additive on the workability and mechanical properties of mortar a kind of high performance and low cost dry-mixed masonry mortar with red mud was prepared. The absorbing property, efflorescence, carbonization resistance, dry-shrinkage, sulfate attack resistance of mortar were also investigated. The main conclusion as follows:(1) There is an increase in alkalinity of red mud-cement binder system pore solution with the increase dosage of Bayer red-mud. But red mud would not increase the late alkalinity of binder system pore solution. The analysis on X-ray differaction(XRD), chemical combined water, sterngth of red mud–cement binder system hydration product indicate that red mud can promote the ordinary portland cement early age hydration and strength development.(2)The optimum preparation parameters of red mud dry-mixed masonry mortar are that: the red mud content is 30%; excessive replacement coefficientβis 1.63;the water-binder ration is 0.6.The red mud mixed with phosphorous slag, blast furnace slag or fly ash can improve the workability and mechanical property of red mud mortar. The flexural strength and compressive strength of mortar are 7.5MPa and 26.4MPa respectively when mixed with 25% red mud and 25% blast furnace slag, which was obviously enhanced. The workability and mechanical property of red mud mortar can be improved with appropriate amount chemical additive as well. The optimum dosage of water reducer, defoaming agent, TEA accelerator and polymer dispersion powder are about 0.25%, 0.2%, 0.04%, 2.0% separately. This red mud dry-mixed masonry mortar has good performance and low cost.(3) The porosity and water absorption of mortar both increased with red mud. The red mud mortar efflorescence can be inhibited by mixing red mud with phosphorous slag, blast furnace slag or fly ash, especially when mixing red mud and fly ash.(4) The mortar carbonation resistance was decreased with red mud. However this can be modified by mixing red mud with phosphorous slag, blast furnace slag or fly ash. The mortar dry shrinkage mixed with red mud and fly ash, or red mud and blast furnace slag is obviously lower than reference mortar. The sulfate attack resistance of mortar with red mud and fly ash is superior to reference mortar. Although the corrosion resistance coefficient of mortar with red mud and phosphorous slag is less than reference mortar, its sulfate attack resistance property can be improved as age prolonged.