Preparation Of Concrete Using Hydrated Silicate Produced From Hydration Reaction

Slag,also named as blast furnace slag powder,is a residue during the ore smelting;while silica fume is produced by the rapid solidification of massive discharged silica and silicon dioxide gas.Present studies about solid waste like slag and silica fume tend to use solid waste as additions for portland cement,but few studies focus on hydration reactions between solid waste and other industrial materials.While this project studied physical and chemical properties of hydration products from the reaction of cement mixture that consists of calcium hydroxide,calcined kaolin,slag and silica fume.Thus this study has a certain degree of innovativeness and positive effect on resource reuse.The study of synthesizing hydrated silicate by hydration reaction started with cement mixture.All the formulas of cement mixture were decided by the predicted possible hydration reactions between this four raw materials;Meanwhile,cement mixture's pozzolanic activity was activated by the ball crusher mill,and cement mixture's powders'size distribution,specific surface area and X ray diffraction pattern by which whether cement mixture underwent physical or chemical changes can be analyzed and judged were measured;the extent of hydration reactions were judged by the results of compressive strength and rupture strength test;the ways to improve cement mixture's pozzolanic activity to guarantee an adequate hydration reaction were explored by trying different ways of concrete curing.The results of the studies tells that the concrete test briquette gains relatively the highest strength when using the cement mixture with the molar ratio of CSH and CAH of predicted hydration products is 9 to 1 and the molar ratio of calcium and silica is 5 to 6 in CSH;thus after 8 hours'1.0MPa steam pressure curing the compressive strength of the test briquettes that were made from this cement mixture reached 45.3MPa,and the rupture strength reached 5.7MPa,and the main hydration product is hydrated calcium silicate.This project also used the cement mixture to make concrete using the closest packing curve of cement and sand mixture.By changing the biggest particle size in the closest packing curve,the mechanical pressure during the process of compressing the materials,the way of making the test briquettes and the dosage of fiber to discuss the changes of test briquettes'compressive strength and rupture strength,the variation range of porosity pre and post steam pressure curing,three kinds of porosities after steam pressure curing and the pore size distribution.The results of the studies tells that smaller biggest particle size in the closest packing curve,higher mechanical pressure during compressing the materials without vibrating the material before,the absence of fiber in the mixture are the factors that gave the test briquettes higher strength,lower porosity and greater drop in porosity after steam pressure curing;when the D_PL is0.6mm,the mechanical pressure during compressing is 13.9MPa,the raw materials to be compressed are not vibrated,and when there is no fiber in the cement and sand mixture,the compressive strength and rupture strength of the test briquettes using the cement mixture can reach 92 per cents of that of the test briquettes using the 42.5portland cement as a substitution for vacuity contrast,after 1.0MPa steam pressure curing.The concrete test pieces using the same cement mixture has a good impermeability judged by pore size distribution test results,and more than 90 per cents of the pore size are smaller than 10nm.