This paper presents the effect of fly ash grain-size fractions on Portland-fly ash cement hydration and its properties. Siliceous fly ashes of size fraction of 0 - 16 and 16 - 32 μm, separated from initial fly ash sa...This paper presents the effect of fly ash grain-size fractions on Portland-fly ash cement hydration and its properties. Siliceous fly ashes of size fraction of 0 - 16 and 16 - 32 μm, separated from initial fly ash samples from 1st, 2nd and 3rd hopper in ESP system, were analysed. Cement hydration was investigated by determination of hydration heat and content of Ca(OH)2 and C3S in cement samples. Water to cement ratio and initial setting time of cement pastes as well as compressive strength and microstructure of cement mortars were also analyzed. Results showed that the same amount of the same size ash fraction can give cement of lower or higher early strength and its lower or higher increase with time. Incorporation of 20 wt% of ash fraction of 0 - 16 μm can produce Portland-fly ash cement CEM II/A-V of strength class 42.5R (from 2nd hopper) or 52.5N (from 3rd hopper). Cement containing 40 wt% of ash fraction of 0 - 16 μm from 2nd and 3rd hopper can be classified as pozzolanic cements CEM IV/A-V of strength class 42.5 and normal or rapid early strength, respectively. Different development of strength of cement with addition of the same size ash fraction separated from the initial ash sample from the next hopper in ESP system is connected with higher depolymerization degree of SiO4 units in ash glass, resulting from the greater amount of AlO4 units replacing SiO4 units. Ash fraction of 16 - 32 μm shows lower depolymerisation of glass network and as a consequence lower hydration degree of C3S to portlandite and calcium silicate hydrates (C-S-H).展开更多
Utilizing NIPGA,an experimental device for cement raw material analysis has been developed,with a 2.5 MeV D-D neutron generator,BGO detector and 2048 MCA.A linear regression was developed for calculating the data.A 6-...Utilizing NIPGA,an experimental device for cement raw material analysis has been developed,with a 2.5 MeV D-D neutron generator,BGO detector and 2048 MCA.A linear regression was developed for calculating the data.A 6-month on-site application of the system showed that the CaO,SiO2,Fe2O3 and Al2O3 analysis results agreed well with chemical analysis,within 0.40%,0.40%,0.50% and 0.50%,respectively.展开更多
水泥混凝土路面的破坏类型有多种 ,其中路面板底脱空是水泥混凝土路面板的主要破坏类型。利用 AL GORFEAS公司开发的 SAP 93软件 ,采用材料非线性的有限元模型 ,对路面板底脱空修补前后的受力情况进行了弹塑性分析。分析结果表明 ,修补...水泥混凝土路面的破坏类型有多种 ,其中路面板底脱空是水泥混凝土路面板的主要破坏类型。利用 AL GORFEAS公司开发的 SAP 93软件 ,采用材料非线性的有限元模型 ,对路面板底脱空修补前后的受力情况进行了弹塑性分析。分析结果表明 ,修补后路面板底的应力集中现象得到了明显的改善。展开更多
基金The paper is financed by the Polish State Committee for Scientific Research,project No.N N506 299139.
文摘This paper presents the effect of fly ash grain-size fractions on Portland-fly ash cement hydration and its properties. Siliceous fly ashes of size fraction of 0 - 16 and 16 - 32 μm, separated from initial fly ash samples from 1st, 2nd and 3rd hopper in ESP system, were analysed. Cement hydration was investigated by determination of hydration heat and content of Ca(OH)2 and C3S in cement samples. Water to cement ratio and initial setting time of cement pastes as well as compressive strength and microstructure of cement mortars were also analyzed. Results showed that the same amount of the same size ash fraction can give cement of lower or higher early strength and its lower or higher increase with time. Incorporation of 20 wt% of ash fraction of 0 - 16 μm can produce Portland-fly ash cement CEM II/A-V of strength class 42.5R (from 2nd hopper) or 52.5N (from 3rd hopper). Cement containing 40 wt% of ash fraction of 0 - 16 μm from 2nd and 3rd hopper can be classified as pozzolanic cements CEM IV/A-V of strength class 42.5 and normal or rapid early strength, respectively. Different development of strength of cement with addition of the same size ash fraction separated from the initial ash sample from the next hopper in ESP system is connected with higher depolymerization degree of SiO4 units in ash glass, resulting from the greater amount of AlO4 units replacing SiO4 units. Ash fraction of 16 - 32 μm shows lower depolymerisation of glass network and as a consequence lower hydration degree of C3S to portlandite and calcium silicate hydrates (C-S-H).
基金Supported by Science and Technology Development Fund of Jilin Province (No.20050323)
文摘Utilizing NIPGA,an experimental device for cement raw material analysis has been developed,with a 2.5 MeV D-D neutron generator,BGO detector and 2048 MCA.A linear regression was developed for calculating the data.A 6-month on-site application of the system showed that the CaO,SiO2,Fe2O3 and Al2O3 analysis results agreed well with chemical analysis,within 0.40%,0.40%,0.50% and 0.50%,respectively.
