The Workability Of Alkali-activated Slag Cementitious Material

Alkali-activated slag cementitious material(called AASCM) is a new type of cementitious materials, which is based on industrial waste ground blast furnace slag as the main raw material, alkali compounds or alkali industrial waste(sodium silicate, known as water glass) is prepared by the hydraulic binder.For construction the building materials should obtain the strength and the workability, otherwise the construction procedure of the building materials was unable to complete. The setting time plays an important role in workability. If the concrete setting time is too fast, the concrete don’t have enough time to cast for molding. And if the condense process of the concrete was slow, the construction progress was affected as delaying the schedule of construction. The setting time conclude the initial and the final setting time. The initial setting time is the time of the cement from adding the water to the paste beginning to loss of plastic. The final setting time, which was the time of cement from adding the water to the paste losing the plasticity completely and beginning to have the strength. The setting time was very important in the construction, the initial setting time should not be too short or the final setting time should not be too long. The initial setting time of Portland cement cannot be earlier than 45 min and the final setting time cannot be later than 390 min. At the same time, the initial setting time of ordinary Portland cement cannot be earlier than 45 min and the final setting time cannot be later than 600 min. Fast-setting is a major feature of alkali slag cementing material, alkali slag cement setting time is generally less than 30 min. Alkali slag cementing material to promote the use of the same as Portland cement, setting time must be controlled within a reasonable range. We must be sure that the alkali-activated slag cementitious material has the appropriate setting time for the application of AASCM masonry unit. For realizing the batch production of AASCM masonry unit in the application, the masonry unit should have enough initial setting time and then the final setting time was not too long to enhance the productivity.Fluidity is a measure of paste liquidity. In a certain amount of water, the degree of fluidity depends on the water content of the material. Suitable plasticity and liquidity assurance test molding and construction operations. AASCM is made into a forming blocks, needs to have an appropriate operational paste fluidity, which is convenient for processing.This paper aims to investigate the work properties of alkali activated slag cementitious material, which conclude only slag activation, activation by sodium silicate and sodium hydroxide. The modulus of sodium silicate is 2.4 and the Baume degree is 40, and the different concentrations of sodium hydroxide solution used to be adjust the modulus of sodium silicate in the experiment. This thesis mainly studies the effect of sodium silicate modulus; sodium hydroxide content, temperature on AASCM setting time and its fluidity.At laboratory temperature 15 ℃, while sodium silicate modulus is 3% and 6%, with the increase of sodium silicate modulus, AASCM setting time gradually becomes shorter; while sodium oxide content is 8% and 10%, with the increased sodium silicate modulus, AASCM setting time gradually becomes longer. When sodium silicate modulus is 1.5 AASCM, with the increase of sodium oxide content setting time decreased first and increased later; when sodium silicate modulus is 2.0 AASCM, with the increase of sodium oxide content it extend the setting time. When the temperature is 3 ℃, initial setting time and final setting time were significantly longer than at 15 ℃; when the temperature is 30 ℃, AASCM initial setting time and final setting time is not shortened, but with the 15 ℃ basically the same.The fluidity of AASCM first increased and then decreased with the increase of the sodium silicate modulus; then the fluidity of AASCM first increased and then decreased with the increase of sodium hydroxide modulus. There is an optimal range of sodium silicate modulus and sodium oxide content, maximum fluidity within range. Optimal range at M = 1.8, Na2O% = about 8%.Fitting the corresponding parameters under the influence of the initial setting time and final setting time, fluidity, and the prediction formula and preparation of suitable fluidity and suitable setting time of AASCM paste provides theoretical significance of quantified expressions.