The castables specimens were prepared using white fused alumina particle and powder, α-Al2O3 micropowder, hydrated alumina, nano calcium carbonate or calcium aluminate cement as starting materials. Effects of nano ca...The castables specimens were prepared using white fused alumina particle and powder, α-Al2O3 micropowder, hydrated alumina, nano calcium carbonate or calcium aluminate cement as starting materials. Effects of nano calcium carbonate addition on phase compositions, strength and microstructure of corundum based castables were studied. The calcium aluminate cement-containing corundum based castables with the same CaO amount was also tested for comparison. The results show that, when temperature is higher than 900 ℃ , the phase compositions of nano CaCO3-containing mixture and the calcium aluminate cement containing mixture are the same, but the forming mechanism, modality and distribution of new phases in the castables are different. With temperature rising, the hydration cement dehydrates and reacts inside cement forming calcium aluminate until the alumina in cement is not enough for the reaction （ternperature is 91 400 ℃ ） , then reacts with the surrounding alumina forming cluster CA6 in the castables. The change process of nano CaCO3 in corundum based enstables is that nano calcium carbonate decomposes to CaO after firing at 800℃ which reacts with Al2O3 forming amorphous calcium aluminate that causes an in-situ bonding. With temperature rising, the formed calcium aluminate reacts with Al2O3 in matrix and wholly forms tabular CA6 at 1 600 ℃ , which distributes uniformly in the castables. The cold and hot strength of the castables with nano calcium carbonate are obviously higher than those of the castables without nano calcium carbonate, especially at 800 -1 000 ℃ due to smaller size and higher dispersion of the nano calcium carbonate and its different reaction mechanism with Al2O3.展开更多
Using sintered corundum as aggregate, white fused corundum powder, fused spinel powder, ultra-fine a-A12 0 3, nano calcium carbonate and hydrated alumina as matrix, effects of nano calcium carbonate additions （0. 4%,...Using sintered corundum as aggregate, white fused corundum powder, fused spinel powder, ultra-fine a-A12 0 3, nano calcium carbonate and hydrated alumina as matrix, effects of nano calcium carbonate additions （0. 4%, O. 8%, 1.2%, 1.6% and 2. 0% in mass, the same hereinafter） on modulus of rupture, thermal shock resi.~tanee and slag resistance of corundum -spinel castables after treating at different temperatures were studied. The results show that nano calcium carbonate decomposes at high temperatures and in-situ forms ealci- ant aluminates, which can significantly increase the CMOR and HMOR of the castables after treating at 800 -1 400 ℃ ; adding nano calcium carbonate obviously improves the thermal shock resistance of the castables, and has little influence on the high basicity slag resist- ance, however, significantly decreases the corrosion and penetration resistance to low basicity slag.展开更多
Efforts have been made to evaluate the influences of the addition of nanoparticles on the strength,durability and mineralogical changes of high strength concrete(HSC).Therefore,mixes were prepared for conventional con...Efforts have been made to evaluate the influences of the addition of nanoparticles on the strength,durability and mineralogical changes of high strength concrete(HSC).Therefore,mixes were prepared for conventional concrete mix(CCM)of M80 grade.Further,various mixes were prepared by replacing cementitious materials initially with 1%Nano-CaCO_(3)(NC),2%NC,3%NC in the CCM,and then 1%NC and Nano-SiO_(2)(NS)NS,2%NC and NS,3%NC and NS(NC and NS were in equal proportion)in the CCM.The developed concretes were then evaluated for mechanical properties,permeation characteristics,and mineralogical studies.From the studies,it is found that the concrete at 2%NCS possesses superior mechanical and superior permeation characteristics of all the mixes.A clear variation in the mineralogical structure with the addition of nanoparticles has been observed.展开更多
文摘The castables specimens were prepared using white fused alumina particle and powder, α-Al2O3 micropowder, hydrated alumina, nano calcium carbonate or calcium aluminate cement as starting materials. Effects of nano calcium carbonate addition on phase compositions, strength and microstructure of corundum based castables were studied. The calcium aluminate cement-containing corundum based castables with the same CaO amount was also tested for comparison. The results show that, when temperature is higher than 900 ℃ , the phase compositions of nano CaCO3-containing mixture and the calcium aluminate cement containing mixture are the same, but the forming mechanism, modality and distribution of new phases in the castables are different. With temperature rising, the hydration cement dehydrates and reacts inside cement forming calcium aluminate until the alumina in cement is not enough for the reaction （ternperature is 91 400 ℃ ） , then reacts with the surrounding alumina forming cluster CA6 in the castables. The change process of nano CaCO3 in corundum based enstables is that nano calcium carbonate decomposes to CaO after firing at 800℃ which reacts with Al2O3 forming amorphous calcium aluminate that causes an in-situ bonding. With temperature rising, the formed calcium aluminate reacts with Al2O3 in matrix and wholly forms tabular CA6 at 1 600 ℃ , which distributes uniformly in the castables. The cold and hot strength of the castables with nano calcium carbonate are obviously higher than those of the castables without nano calcium carbonate, especially at 800 -1 000 ℃ due to smaller size and higher dispersion of the nano calcium carbonate and its different reaction mechanism with Al2O3.
文摘Using sintered corundum as aggregate, white fused corundum powder, fused spinel powder, ultra-fine a-A12 0 3, nano calcium carbonate and hydrated alumina as matrix, effects of nano calcium carbonate additions （0. 4%, O. 8%, 1.2%, 1.6% and 2. 0% in mass, the same hereinafter） on modulus of rupture, thermal shock resi.~tanee and slag resistance of corundum -spinel castables after treating at different temperatures were studied. The results show that nano calcium carbonate decomposes at high temperatures and in-situ forms ealci- ant aluminates, which can significantly increase the CMOR and HMOR of the castables after treating at 800 -1 400 ℃ ; adding nano calcium carbonate obviously improves the thermal shock resistance of the castables, and has little influence on the high basicity slag resist- ance, however, significantly decreases the corrosion and penetration resistance to low basicity slag.
文摘Efforts have been made to evaluate the influences of the addition of nanoparticles on the strength,durability and mineralogical changes of high strength concrete(HSC).Therefore,mixes were prepared for conventional concrete mix(CCM)of M80 grade.Further,various mixes were prepared by replacing cementitious materials initially with 1%Nano-CaCO_(3)(NC),2%NC,3%NC in the CCM,and then 1%NC and Nano-SiO_(2)(NS)NS,2%NC and NS,3%NC and NS(NC and NS were in equal proportion)in the CCM.The developed concretes were then evaluated for mechanical properties,permeation characteristics,and mineralogical studies.From the studies,it is found that the concrete at 2%NCS possesses superior mechanical and superior permeation characteristics of all the mixes.A clear variation in the mineralogical structure with the addition of nanoparticles has been observed.
