Study on Preparation and Performance of Ceramic Fiber and Silica Fume Reinforced Alkali-activated Steel Slag-based Cementitious Material
|School||Xi'an University of Architecture and Technology|
|Keywords||Steel slag Silica fume Alkali-activated steel slag-based cementitiousmaterial Reinforced Durability|
Steel slag is a by-product produced in the conversion of iron ore or scrap iron tosteel. Steel slag is divided into three categories of electric furnace slag, open hearthslag and converter slag. Steel slag is emitted100million tons every year in China. Alarge number of steel slag stacking mountain, not only takes up a lot of land, but alsopollutes the environment. Reduction, resource and high-value utilization of steel slagare particularly important.Ceramic fiber and silica fume reinforced alkali-activated steel slag-basedcementitious material and concrete were prepared by curing different days. Mechanicalproperties, high temperature resistance and freezing-thawing performances of concretewere studied in the thesis. XRD, SEM, mercury intrusion porosimetry andthermochemistry analysis were employed to characterize ceramic fiber and silica fumereinforced alkali-activated steel slag-based cementitious material.Calcium silicate hydrate, portlandite, aegirine and metahalloysite are the mainhydration products of alkali-activated steel slag-based cementitious material, andportlandite continuously generates with the prolongation of the ages. Compressivestrength of alkali-activated steel slag-based cementitious material increases withincreasing of the dosage of sodium silicate. Compressive strength of alkali-activatedsteel slag-based cementitious material reached the maximum when the sodium silicatedosage is about11wt%, but the compressive strength decreased when the sodiumsilicate dosage is bigger than the quantity of11wt%. The early compressive strength ofalkali-activated steel slag-based cementitious material increases with increasing of the specific surface area of raw materials. Micropore volume increases and large porevolume decreases with the prolongation of the age for the alkali-activated steelslag-based cementitious material. There are three endothermic processes: the loss offree water, the removal of bound water and decomposition process of calciumhydroxide with the temperature increasing.As far as the ceramic fiber and silica fume reinforced alkali-activated steelslag-based cementitious material, silica fume could effectively inhibit the production ofcalcium hydroxide in the hydration process, and the main hydration products arehydrated calcium silicate and calcium hydrogen silicate, which matrix microstructure ismore dense which compare with alkali-activated steel slag-based cementitious material.When10wt%silica fume and0.2wt%ceramic fiber were incorporated, small porevolume percent increases, as well as the compressive strength and flexural strength wereimproved for the ceramic fiber and silica fume reinforced alkali-activated steelslag-based cementitious material. The mechanical properties remarkably increase withincreasing the specific surface area of steel slag raw material for the ceramic fiber andsilica fume reinforced alkali-activated steel slag-based cementitious material. It issuggested that silica fume is active agent to accelerate the formation of hydratedcalcium silicate, while ceramic fibers are bonded with CSH gel closely which play arole in reinforcement effect.The compressive strength developments of alkali-activated steel slag-basedcementitious materials, silica fume reinforced alkali-activated steel slag-basedcementitious materials, ceramic fiber and silica fume reinforced alkali-activated steelslag-based cementitious materials were studied after exposure to elevated temperatures.The compressive strength of specimens increases with the increasing temperature up to450℃. When the temperature is higher than450℃, some new phases are generated inthe binder and formed interfaces one another so as to lead low mechanical properties.The compressive strength of ceramic fiber and silica fume reinforcedalkali-activated steel slag-based concrete is52.2MPa and it could reach C40degree bywater to steel slag ratio of0.4. The freezing-thawing performance of alkali-activatedsteel slag-based concrete steel slag concrete is F50. However, the performance ofalkali-activated steel slag-based concrete resistance freezing-thawing which approaches to F150, can be drasticly improved by doping certain amount of ceramic fiber and silicafume.