Effect Of Limestone Powder On Properties Of Concrete Mixture

With the acceleration of city development and the improvement in environment management, natural resources as the raw materials for concrete become scarce. Meanwhile, with the upgrade in design of concrete strength and reinforcement ratio, in order to reduce water to cement ratio (w/cm) of concrete as much as possible, dosage of water reducer in concrete have to increase. Moreover, the fluidity of concrete need to meet the requirements of construction, this will bring about the segregation and weeping phenomenon during the transportation, pumping, pouring and vibrating of concrete. The thesis is focused on limestone powder, which is the main byproduct of production process of machine-sand with limestone. In this study, the limestone powder was milled to superfine powder (SPL), and mixed with other mineral admixtures compound to concrete. Effects of SPL on the properties of fresh and hardened concrete were investigated, in order to drive the production of machine-sand and wide application of byproducts-fine stone powder. The results show that:1,SLP has significant plasticizing effect. By improving the particle size distribution and filling of powers, the unit consumption of water and cement are obviously decreased, thus, economic benefits are significant.2,Although different kinds of water reducer has different relations between dosage and water-reduce effect, the stability of mixtures decreases around the saturated dosage, saturated dosage of water reducer is related with the components of the mixtures. After adding the SLP, the saturated dosage is increased, and the stability of fresh mixture is raised.3,Compared with the mixtures without SLP, the mixtures with proper SLP has low viscosity and high fluidity retention. Besides, the local segregation, deriving from external force and bleeding, are improved. In the respect of improving workability, SLP has better effects than fly ash with the same fineness, which can substitute for the mineral admixture such as fly ash excellently. 4,SLP has good compatibility with the most widely used mineral admixtures today, such as I class fly ash, slag and so on. When combined with mineral admixtures, it can improve the workability of concrete.Concrete prepared with SLP, which have been applied in engineering, showed good results in application. Especially for the special performance concrete, such as mass concrete, high strength concrete and Self-compacting Concrete, the amount of cement used and the viscosity both reduce greatly while ensuring the workability of concrete.