File Name: mineral admixtures in cement and concrete .zip
Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement cement paste that hardens cures over time. In the past, lime based cement binders, such as lime putty, were often used but sometimes with other hydraulic cements , such as a calcium aluminate cement or with Portland cement to form Portland cement concrete named for its visual resemblance to Portland stone. When aggregate is mixed with dry Portland cement and water , the mixture forms a fluid slurry that is easily poured and molded into shape. The cement reacts with the water and other ingredients to form a hard matrix that binds the materials together into a durable stone-like material that has many uses.
The objective of this study is to investigate the effect of the mineral admixtures on pipe flow of pumped concrete through analyzing the properties of lubrication layer playing a dominant role to facilitate concrete pumping. Concrete mixtures incorporating blast furnace slag BFS , fly ash FA and silica fume SF were selected with three different replacement ratios for each case and pumped through m circuit. The rheological properties were measured before pumping and the thickness of lubrication layer was also experimentally observed with a special sensor, ultrasonic veloc-ity profiler UVP. An analytical equation considering the effect of the layer was adopted to calculate the thickness of the layer and to compare with full scale pumping results. Already have an account? Login in here. Journal of Advanced Concrete Technology.
Retarding admixtures , which slow the setting rate of concrete, are used to counteract the accelerating effect of hot weather on concrete setting. High temperatures often cause an increased rate of hardening which makes placing and finishing difficult. Retarders keep concrete workable during placement and delay the initial set of concrete. Most retarders also function as water reducers and may entrain some air in concrete. Accelerating admixtures are especially useful for modifying the properties of concrete in cold weather.
The influence of mineral admixtures on bending strength of mortar on the premise of equal compressive strength was investigated. Three mineral admixtures fly ash, ground granulated blast-furnace slag and steel slag were used. The adding amount of mineral admixture in this study ranges from With equal compressive strength, different mortars can be arranged in such a descending order with their bending strength: cement-fly ash mortar, cement mortar, cement-GGBS mortar, and cement-steel slag mortar. With the same compressive strength, the higher the steel slag content and water-to-binder ratio, the lower the bending strength of mortars. However, the effect of mineral mixture content and water-to-binder ratio on the bending strength of cement-fly ash mortar and cement-GGBS mortar is far inconspicuous.
Effects of superfine slag powder, fly ash and ultra-fine CaCO3 on compressive strength of sulphoaluminate cement were investigated. Cement hydration products were analyzed by using scanning electron microscopy SEM. The results show that different fineness and additions of mineral admixture differ in compressive strength. Meanwhile, it is concluded that the additions of superfine slag powder and ultra-fine CaCO3 facilitates hydration at early ages, while fly ash could accelerate hydration at later ages. Request Permissions.
The research assesses the effect of selected type II additives on concrete carbonation.
Effect of a combination of alkali ions, sulfate ion and chloride ion on durability of concrete structures was analyzed, and the effect of different mineral admixtures on deterioration caused by Cl- penetration, sulfate attack and alkali-silica reaction was investigated. It is shown from wetting-drying test that sulfate attack on concrete was greatly relieved in high Cl- concentration solution, but diffusion test showed that Cl- diffusion was accelerated by SO4 2- ion existence as SO4 2- may incorporate with aluminum phase prior to Cl- ion. Request Permissions. Vol 22 , pp. All Rights Reserved. Registration Log In.
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Fly ashes (FA) used as a mineral admixture in cement and concrete, is a product of the pulverized coal firing system, through conventional boilers, mostly used in.
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