Study On The Performance Of Hydraulic Concrete Using High Titanium Slag As Additive And Aggregate

Resources of vanadium titano-magnetite are abundant in Southwest of China.With the development of metallurgical industry,the intensive increment in the amountof high titanium slag discharged as industrial byproduct, not only occupies a large ofland resources, but also endangers living beings in the soil, underground water,surface water and earth's surface seriously in case that the harmful substancescontained in the high titanium slag might permeate into the ground. With theincreased awareness of environmental protection, taking full advantage of wastematerials has been recognized as a new approach to protect environment and conserveenergy. Therefore, it is significant to find new ways to exploit high titanium slag.It has comprehensively analyzed chemical components, mineral compositions andphysical properties of high titanium slag. Results indicate that, in terms of chemicalcomponents, high titanium slag contains relatively few content of CaO and SiO2, onlyapproximately 50%, and high content of TiO2, more than 20%. In terms of mineralcomposition, it mainly contains titanaugite, perovskite, spinel and basnite, which arenot only difficult to dissolve and disaggregate in the condition of aqueous medium,but also are of obvious crystal characteristics which are typical of a large number ofcrystal precipitations and growth. With increment in content of high titanium slagincorporated into cement paste increases, normal consistency of cement pastedecreases and setting time extends a little. Water demand ratio of high titanium slagincreases slightly with its specific surface area increases. It fails to find dead burningphase in the high titanium slag and its soundness is qualified by autoclave inspection.It investigates influence of specific surface area and content of high titanium slagon mortar strength of composite cementitious system. Results show, mortar strengthof composite cementitious system made with cement and high titanium slag is slowerthan that without high titanium slag. What's more, mortar strength decreases with increment in content of high titanium slag. The optimum specific surface area of hightitanium slag is about 400m²/kg, less than which mortar strength of compositecementitious system increases with fineness while beyond which mortar strength yettends to decrease. Influence degree of fineness on mortar strength is diminishedgradually with high titanium slag content increases, which indicates that specificsurface area is not the major influencing factor on mortar strength of compositecementitious system. Potential activity of high titanium slag is so slow that it is notadvisable that its content by mass of cement should not exceed 30% when it is used ascement or concrete additive. The development trendency of mortar strength ofcement-based cementitious materials with high titanium slag is similar to that withgrade II fly ash, yet its final strength is slightly lower than the latter. When givenadditive content is 30%, mixing with grade II fly ash and high titanium slag canproduce a certain enhancement effect so that it is favorable to improve mortar strengthof composite cementitious system.In virtue of various measurements including scanning electron microscope, x-raydiffraction, thermal analysis and water-absorpting dynamics, it reveals the fulldevelopment of hydration process,hydration products and pore structure ofcement-high titanium slag cementitious with age in terms of fineness and content ofhigh titanium slag. Test results can be concluded as follows: Hydration products ofcement-based cementitious doped with high titanium slag mainly include C-S-H gel,Ca(OH)2 crystal and few AFt crystal. High titanium slag particles possess fillingeffects and micro-aggregate effects so that incorporating appropriate content of hightitanium slag into cement paste could enhance compact degree of hydration systemyet excessive high titanium slag may reduce hydration degree as a whole. Amount ofhydration products increases obviously with age, which enwrap high titanium slagparticles gradually and favor the development of mortar strength. However, as a resultof few active ingredients in the high titanium slag, C-S-H gel contents produced arequite few, correspondingly it fails to form compacted network structure, which resultin low final strength. High titanium slag will enhance pore average diameterparameter and aggravate pores distribution irregularity. By mechanical grinding and adding chemical reagents such as NaOH, Ca(OH)₂,Na₂CO₃, Na₂SiO₃, CaSO₄, Na₂SO₄ and gypsum, it investigates activation of hightitanium slag. Results show that, among the given ground fineness, when specificsurface area is around 400 m²/kg, hydration activity of high titanium slag ranks thehighest. It contributes little to mortar strength if continuing to increase groundfineness. Adding chemical reagents only improves early strength of cement-hightitanium slag cementitious slightly. At 90 days, mortar strength of compositecementitious system is lower than that without adding chemical reagents instead,which may be connected with stable crystal structure of high titanium slag. Furtherefforts are needed to confirm this point.It examines concrete performances made with high titanium slag as aggregate.Results indicate that, in terms of concrete strength, there is little difference betweenconcrete made with limestone aggregate and high titanium slag individually yetdrying shrinksge of the latter is obviously bigger, while its autogenous volumedeformation is relatively mocro expansive.