The Performance Of High Alumina Cement, The Limestone Powder

High alumina cement is known to yield early strength, high temperature resistance and sulfate resistance qualities, but exhibits poor stability of later strength, which restricted its application range. Limestone has a rich resource and lower cost, which was widely applied to use as cement industry admixture and concrete mineral admixture. Limestone was used in high alumina cement scientifically and rationally, which can not merely improve the high alumina cement poor stability of later strength, but also make the concrete safer, greener by achieving the purpose with waste energy-conserving profit.The working performance and physical and mechanical properties of influence of limestone on high alumina cement is discussed in this paper based on experimental test and microcosmic study. The drying shrinkage of high alumina cement colloidal mortar and the resistance to chloride ion permeability of the concrete are also discussed.The research results can be concluded as following:1.Physical and mechanical properties of limestone powder-high alumina cement system1)The setting time of limestone powder-high alumina cement system paste increases first and decreases later with limestone powder content increasing(when limestone powder content is 3%, the setting time of cement paste is maximum), and decreases with limestone powder fineness increasing.2)The fluidity of limestone powder-high alumina cement system paste increases first and decreases later with limestone powder content increasing(when limestone powder content is 3%, the fluidity of cement paste is maximum, up to 118mm), and increases with limestone powder fineness or water-cement ratio increasing. The fluidity of Limestone powder—High alumina cement system fresh mixed mortars increases with limestone powder content, limestone powder fineness, water—cement ratio increasing.3)The strength of the paste and mortar of limestone powder-high alumina cement system can be improved when limestone powder content in a certain range; The strength of the paste and mortar of limestone powder-high alumina cement system descends when limestone powder content exceeds a certain range. The strength of the paste and mortar decreases with water-cement ratio increasing, and increases with the limestone power content increasing. 2.The hydration characteristics and pore structure of limestone powder-high alumina cement system1) The XRD and scanning electron microscope analyses of samples show that limestone has an influence on hydration products of the high alumina. C3A·CaCO3·11H2O are formed after the hydration reaction of the limestone and high alumina cement, which reduced the formulation amount of CAH10, C2AH8 and C3AH6.2)The experimental results indicate that chemically combined water of limestone-high alumina cement system first decreases and then increases with the increasing replacement levels of limestone filler(when limestone powder content is 3%,the hydration degree of hardened paste reaches the maximum). The finer of the limestone, the higher of the chemically combined water of limestone-high alumina cement system, which contributes to high hydration degree.3)The evaporated-water content method experience results show that the porosity of the cement paste and mortar first decreases and then increases with the increasing replacement levels of limestone filler (When the limestone filler content 3%, The cement paste is the most densest).The porosity ratio of the cement paste and mortar decreases with the decreases water-binder ratio. The cement paste and mortar presents small pore reduced, the macroporous increased and the total porosity increased.3. The drying shrinkage of limestone-high alumina cement systemThe results show that the drying shrinkage of the limestone-high alumina cement system mortar decreases firstly and then increases with the increasing replacement levels of limestone filler at 3,7 14 and 28 day ages. When the dry-shrinkage ratio was increases with the increasing water-binder ratio but decreases with the increasing fineness limestone.4. The resistance to chloride ion permeability of limestone-high alumina cement systemThe results show that the resistance to chloride ion permeability of the concrete increases firstly and then decreases with the increasing replacement levels of limestone filler (The resistance to chloride ion permeability of the concrete has the most powerful ability with the limestone filler content up to 4%).When fineness of limestone and water-binder ratio are increased, the resistance to chloride ion permeability of the concrete are both increased.