Study Of Properties Of Composite Cement With Multiple And High Content Of Mineral Admixtures

The research focused on rational utilization of industrial waste residue, improving theamount of doped mixing materials，reducing the use amount of cement clinker, reducing theproduction cost, under ensuring the property of cement. The experiments used industrialwastes such as granulated blast furnace slag, ferroalloy slag, fly ash, burnt shale, slag, FGDgypsum and other low grade natural resources as raw materials to study the performances ofcomposite cement with multiple and high content of mineral admixtures.The activity index, hydraulicity and alkali activation can provide the oretical foundationand system supporter for reasonable selection of admixtures. Combined with practicalapplication, we built granulated blast furnace slag-fly ash-slag system, granulated blastfurnace slag-fly ash-ferroalloy slag system and granulated blast furnace slag-fly ash-burntshale system to prepare composite cement with multiple and high content of mineraladmixtures. The experiments selected orthogonal experiment method, according toperformance test data of composite cement to optimize proportioning, and then verified theoptimization. Finally, we can conclude the best proportioning. In order to probe the hydrationmechanism of the mixture cement, the XRD and SEM was used to analyse the microcosmicstructure of the cement.The main conclusions and results of this paper are as follows:1．Granulated blast furnace slag has no apparent peak and the main minerals is glassyphase. The ferroalloy slag’s main mineral is gehlenite which has well crystalline and fullcrystalline form. Fly ash contains quartz, mullite, Fe₂O₃, Al₂O₃and glassy phase. Shalecontains SiO₂, calcite,[KAl₂Si₃AlO₁₀（OH）₂],（Na,K,Ca）₂（SiAl）₉O₁₈7H₂O and other clayminerals. Slag contains mullite, crystobolite and glassy phase. The main mineral of FGDgypsum is CaSO₄2H₂O.2．The activity index of granulated blast furnace slag is95%, the activity index of flyash is73%, the activity index of fly ash is81%, the activity index of burnt shale is66%, theactivity index of ferroalloy slag is70%. The activity index of all admixtures conform to thenational standards. The hydraulicity of ferroalloy slag was superior to granulated blast furnaceslag, and the growth rate was decreased with the increase of curing age. 3．The granulated blast furnace slag-fly ash-slag composite cement, the granulated blastfurnace slag-fly ash-ferroalloy slag composite cement and the granulated blast furnaceslag-fly ash-burnt shale composite cement with50%clinker can be achieved respectively thenational standards of P C42.5MPa.The granulated blast furnace slag-fly ash-slag compositecement with35%clinker can be achieved respectively the national standards of P C32.5MPa.4．The composite cement had been prepared by FGD gypsum instead of gypsum, whosesetting time and soundness can meet the national standards. Furthermore, FGD gypsum isbeneficial to improve of the strength of composite cement.5．Doping amount of clinker and the type of admixture affect composition effect amongdifferent mixture. Doping amount of clinker and the type of admixture affect the type ofhydration products lightly, and major hydration products are Calcium Silicate Hydrate,Ca（OH）₂, Calcium Aluminum Oxide Hydrate, Calcium Aluminum Sulfate Hydrate, etc.