The expansion and micro-cracks of the mortar with composite mineral admixtures （fly ash, zeolite and slag） due to the alkali-silica reaction （ASR） are studied. Results show that composite mineral admixtures cannot...The expansion and micro-cracks of the mortar with composite mineral admixtures （fly ash, zeolite and slag） due to the alkali-silica reaction （ASR） are studied. Results show that composite mineral admixtures cannot absolutely diminish the ASR of mortar bars with the low-alkali cement and a highly reactive aggregate. But the expansion rate and the deleterious expansion of the mortar bar are mostly reduced with increasing composite mineral admixture. The influence of mineral admixtures on the fluidity of the paste and the strength of the mortar is also studied.展开更多
In Na_2O–CaO–SiO_2–H_2O system,systematic investigations of phase and morphology of calcium silicate in hydrothermal conditions were concisely conducted for high-value utilization of silicon resource in high-alumin...In Na_2O–CaO–SiO_2–H_2O system,systematic investigations of phase and morphology of calcium silicate in hydrothermal conditions were concisely conducted for high-value utilization of silicon resource in high-alumina fly ash(HAFA).The results show that crystal composition and phase may be affected by relatively low concentration of NaOH,and sodium ions are rearranged into the structure to form NaCaHSiO_4 and Na_2Ca_3H_8Si_2O_(12) with different C/S ratio at high concentration of Na OH.In addition,phases in wollastonite group possess the morphology of nano fiber.Formation of nano fiber is attributed to the difference of surface energies between axial and radial direction,and higher temperatures lead to easier growth along radial direction.The preparation of C–S–H with different phases and morphologies can guide for the application of silicate solution with high alkalinity with different purposes.展开更多
This paper studies the reaction between alkaline metal ions Li＋, Na＋ and K＋ and ASR （alkali-silica reaction） reactive aggregates to determine whether Li＋ can substitute Na＋ and K＋ that are unified in cement pa...This paper studies the reaction between alkaline metal ions Li＋, Na＋ and K＋ and ASR （alkali-silica reaction） reactive aggregates to determine whether Li＋ can substitute Na＋ and K＋ that are unified in cement paste. Reactive aggregates use meta-sandstone from eastern Taiwan and Pyrex glass. Non-reactive aggregates use siliceous sand. The results show that the dissolved amount of SiO2 is lower when the reactive aggregates are immersed in an 80 ℃1 N LiOH＇H20 solution than in NaOH and KOH solutions. The reduced amounts of OH and Li＋ in the solution are also higher than those in the NaOH and KOH solutions. These results reveal that reactive SiO2 can react with LiOH to form a reactant with low water solubility. When the powder of the cement paste is immersed in an 80 ℃ 1 N LiOH-H2O solution, the amounts of free Na＋ and K＋ in the solution are higher than those in water. The increased amount increases with the duration of immersion. The amount of Li＋ in the solution also decreases with the duration of immersion. These results reveal that Li＋ can substitute Na＋ and K＋ that are unified in cement paste, which indicates that ASR can be prevented with the existence of Li＋.展开更多
文摘The expansion and micro-cracks of the mortar with composite mineral admixtures （fly ash, zeolite and slag） due to the alkali-silica reaction （ASR） are studied. Results show that composite mineral admixtures cannot absolutely diminish the ASR of mortar bars with the low-alkali cement and a highly reactive aggregate. But the expansion rate and the deleterious expansion of the mortar bar are mostly reduced with increasing composite mineral admixture. The influence of mineral admixtures on the fluidity of the paste and the strength of the mortar is also studied.
基金Supported by the National Natural Science Foundation of China(51304184)the Coal Based Key Scientific and Technological Project of Shanxi Province(MC2014-06)
文摘In Na_2O–CaO–SiO_2–H_2O system,systematic investigations of phase and morphology of calcium silicate in hydrothermal conditions were concisely conducted for high-value utilization of silicon resource in high-alumina fly ash(HAFA).The results show that crystal composition and phase may be affected by relatively low concentration of NaOH,and sodium ions are rearranged into the structure to form NaCaHSiO_4 and Na_2Ca_3H_8Si_2O_(12) with different C/S ratio at high concentration of Na OH.In addition,phases in wollastonite group possess the morphology of nano fiber.Formation of nano fiber is attributed to the difference of surface energies between axial and radial direction,and higher temperatures lead to easier growth along radial direction.The preparation of C–S–H with different phases and morphologies can guide for the application of silicate solution with high alkalinity with different purposes.
文摘This paper studies the reaction between alkaline metal ions Li＋, Na＋ and K＋ and ASR （alkali-silica reaction） reactive aggregates to determine whether Li＋ can substitute Na＋ and K＋ that are unified in cement paste. Reactive aggregates use meta-sandstone from eastern Taiwan and Pyrex glass. Non-reactive aggregates use siliceous sand. The results show that the dissolved amount of SiO2 is lower when the reactive aggregates are immersed in an 80 ℃1 N LiOH＇H20 solution than in NaOH and KOH solutions. The reduced amounts of OH and Li＋ in the solution are also higher than those in the NaOH and KOH solutions. These results reveal that reactive SiO2 can react with LiOH to form a reactant with low water solubility. When the powder of the cement paste is immersed in an 80 ℃ 1 N LiOH-H2O solution, the amounts of free Na＋ and K＋ in the solution are higher than those in water. The increased amount increases with the duration of immersion. The amount of Li＋ in the solution also decreases with the duration of immersion. These results reveal that Li＋ can substitute Na＋ and K＋ that are unified in cement paste, which indicates that ASR can be prevented with the existence of Li＋.
基金致谢 本文所取得的成果属于欧盟资助的JNCO-DEV项目“SILIC-SALT”（ICA4-CT-2002-10107）.并对以下合作伙伴表示感谢：Technisches Zentrum an der HBLVA（奥地利）.Lederinstitut Gerberschule Reutlingen（德国）.Richard Daniels（英国）.中央皮革研究所（钦奈/印度）.孟加拉国皮革技术学校.皮革研究协会（达卡/孟加拉国）.VOGL股份有限公司（Mattighofen/奥地利）和B0EHME股份有限公司（Geretsried/德国）.
