Study On Optimizate The Mix Ratio Of And Modification The Toughous And Retardation Of Alkali-activated Slag Cementitious Material

Alkali-activated slag cementitious material（AASCM）is beening widely studied because of its many significant advantages including simple preparation technology,high strength,high temperature resistance,corrosion resistance.Large number of research results show that AASCM increases the comprehensive utilization of industrial wastes such as slag as a new type of green environmental building material,but it also has obvious defects,such as fast setting,high brittleness and poor toughness.In order to guarantee the safety of the building structure,the building materials is supposed to be enough toughness and excellent mechanical properties.At the same time,it has excellent working performance to meet the demance such as casting and vibrating in engineering applications.Therefore,this paper uses sodium silicate and slag powder to prepare AASCM.By adjusting the modulus and dosage of sodium silicate to optimize the ratio,and aiming at the defects of cementitious materials.The research contents were as follows:（1）Studying on mixture ratio optimization and basic properties of AASCM.The influence of modulus and dosage of sodium silicate on the compressive strength is studied.With the increase of sodium silicate modulus and content,the compressive strength of AASCM raise in early and then decline.When the sodium silicate modulus is 1.2 and the content is 16%,the compressive strength is the highest.The basic properties of alkali-activated slag cementification materials is tested.The results showed that the material had fast setting and hardening,short initial and final setting time,the initial setting time was17min,the final setting time was 21min and the fluidity was 205.2mm.The early compressive strength of the specimen is high,brittleness,poor toughness and brittle failure modes.（2）Modification of alkali-activated slag cementitious materials for retarding setting.The retarder effects of different dosage of retarder Ba Cl₂,Zn SO₄ and boric acid on alkali-activated slag cementitious materials is studied respectively.With the increase of the dosage of retarder Ba Cl₂,Zn SO₄ and boric acid,the initial and final setting time of cementitious materials is continuously extended.The initial setting time and final setting time of single dosage of retarder Ba Cl₂ is up to 182min and 192min respectively.The initial setting time and final setting time of Zn SO₄ with single dosage of retarder can reach53min and 59min respectively.The initial setting time can reach 83min and the final setting time can reach 91min with the single admixture of boric acid and Ba Cl₂.The retarding effect of the complex admixture of boric acid and Ba Cl₂ is studied.（3）Modification of alkali-activated slag cementitious material for flexural toughening.The toughening effect of PVA fiber,basalt fiber and glass fiber with different content is studied.With the increase of fiber content,the mechanical properties of the specimens is improved,the flexural strength and toughness is increased.Compared with the specimens without fiber,the flexural strength of the specimens mixed with 2%glass fiber,2%basalt fiber and 2%PVA fiber increased by 63.5%,140.4%and 178.8%,respectively.The failure mode of the specimen also changes from brittle failure to plastic failure.According to the load-deflection curve,the failure process of the specimen is divided into three stages:elastic stage,yield stage and damage stage,and the toughening mechanism is analyzed.