Study On The Application Of Limestone Ultrafine Powder Instead Of Fly-ash In Dry Mixing Mortar

Mortar in civil engineering in wide use,a large amount of building materials industry,is indispensable to the construction materials.The dry mixed mortar in building materials field is a new type of green environmental protection material,by virtue of its good performance,stable quality,easy to use,improve the construction environment and greatly save the material advantages gradually replace the traditional mortar,boarded construction stage.Sand is the main part of dry mixed mortar in fine aggregate,but the natural sand can be rational mining nearly exhausted,sand or partly replace natural sand mortar to represent the general trend,mineral admixture is no longer a single use of fly ash,waste residue and gradually to find new resources,more energy saving and environmental protection.Lime powder is mixed into dry mixed mortar,can not only improve the performance of mortar,but also waste to treasure,is conducive to coordinated development of economy and environment.In this paper,the effects of two kinds of materials on the properties of cement-based materials were studied,and the application of two kinds of materials in dry-mixed mortar was studied by taking limestone powder and fly ash as the research objects,and taking machine-made sand and natural sand as the innovation point.In this paper,the mechanism of adding limestone powder to improve the properties of mortar is discussed.The limestone powder is not a completely inert material,and limestone powder can promote the hydration of cement and participate in the hydration reaction.Calcium aluminate hydrate,the product of hydration reaction between CaCO₃ and C₃A in limestone powder,can enhance the hydration of cement.The physical and mechanical properties of limestone powder and fly ash were studied.The effects of limestone powder and fly ash on shrinkage,impermeability,water retention,water demand and cracking property of dry mixed mortar were studied.Limestone powder and fly ash can affect the working performance of dry mixing mortar,when the total amount of cement material is constant,only limestone powder8（mass ratio in this paper）or only fly ash 13%and the total amount of both of them are less than 13%.It can meet the strength design requirements of conventional plastering mortar M10.The shrinkage of dry mortar can be improved by the addition of limestone powder and fly ash,and the shrinkage rate is the lowest when the content of limestone powder is 4%and fly ash is 9%.When the content of machined sand and natural sand is 90%and 10%respectively,the properties of dry mixing mortar,such as strength,water requirement,loss of consistency for 2 hours,shrinkage and impermeability,are in the best condition.