Industrial Production Practice Of Low Alkali Cement

The alkali existing in cement concrete and its harm have been fully recognized.Alkali aggregate reaction has become one of the most serious causes of damage to cement concrete buildings and components and affecting their durability.With the further improvement of the durability requirements of concrete structures,new requirements are put forward for the performance of cement which plays a cementing role in cement concrete.How to reduce alkali content in cement?How to improve the performance of cement?It has become a common concern to alleviate the harm of alkali in cement,to restrain the damage of alkali aggregate reaction to concrete,to improve the durability of buildings and to reduce the enviroumental load at the same time.In this paper,the production of low alkali cement clinker and the preparation of high performance composite low alkali cement from industrial waste slag are studied.The experimental results show that the f-CaO in clinker is less than 1.0%after the raw meal of high silica and low alkali sandstone and high alkali clay is calcined at 1400 C,and is much lower than that.The optimum control parameters of high silicon and low alkali sandstone mixing scheme are as follows:adopting "three high" formula,the saturation ratio of clinker is 0.9,the silicic acid ratio of clinker is 2.6,the aluminium oxide ratio of clinker is 1.6,and the fineness of raw material is controlled at 280 m2/kg.The effects of fineness of each component of low alkali cement on its physical and mechanical properties are different.For its early(3d)strength,clinker,fly ash and phosphorus slag are the influencing factors in turn.In the later stage(28d),the factors affecting the strength are phosphorus slag,clinker and fly ash.The optimum control parameters of the fineness of the three main components of composite cement are:clinker 420 m2/kg,fly ash 450 m2/kg and phosphorus slag 500 m2/kg.The addition of modified additives such as high-temperature calcined phosphatite and high-calcium fly ash has different effects on the properties of composite cement.Especially the addition of high calcium fly ash can obviously improve the early strength of composite cement mixed with phosphorus slag under the condition of fine grinding.By comparing with ordinary Portland cement in terms of hydration heat,initial hydration products,alkali aggregate reaction and durability,it is proved that composite low alkali cement has superiority in performance.The addition of industrial waste residue such as phosphorus slag and fly ash has positive significance in restraining alkali aggregate reaction,improving the durability of concrete and reducing the environmental load of cement products.