The impact of fly ash content on bond performance of steel bars and their surrounding concrete is studied by means of sticking strain gauges on steel bars. The average bond stress-slip curves, the steel strain-anchor ...The impact of fly ash content on bond performance of steel bars and their surrounding concrete is studied by means of sticking strain gauges on steel bars. The average bond stress-slip curves, the steel strain-anchor location curves, and the bond stress-anchor position curves of the pullout specimens with various fly ash contents are obtained. Results indicate that the bond performance of concrete and steel bars can be improved and the distribution of steel strain along the anchorage length tends to be more uniform by adding fly ash in concrete specimens, and both ultimate bond stress and ultimate slip deformation increase the most when 20% of specimens′ content is fly ash.展开更多
In this paper, different particle sizes of coal fly ash FA-R(D50= 15.75 μm), FA-A(D50= 3.61 μm) and FA-B(D50= 1.73 μm) were treated with Na OH solution to prepare the forming adsorbents FFA-R, FFA-A and FFA-B.The s...In this paper, different particle sizes of coal fly ash FA-R(D50= 15.75 μm), FA-A(D50= 3.61 μm) and FA-B(D50= 1.73 μm) were treated with Na OH solution to prepare the forming adsorbents FFA-R, FFA-A and FFA-B.The structure and adsorption properties of the forming adsorbents for methylene blue(MB) from aqueous solution were examined. The results showed that the specific surface areas and adsorption capacities of the forming adsorbent for MB increased with decreasing particle size of raw coal fly ashes. The adsorption kinetic data of MB on FFA-R, FFA-A and FFA-B fitted the second-order kinetic model very well with the rate constants(k2) of3.15 × 10-2, 3.84 × 10-2and 6.27 × 10-2g·mg-1·min-1, respectively. The adsorption process was not only controlled by intra-particle diffusion. The isotherms of MB on FFA-R, FFA-A and FFA-B can be described by the Langmuir isotherm and the Freundlich isotherm, and the adsorption processes were spontaneous and exothermic.展开更多
This paper is aimed at verifying utilization possibilities of alkaline modified coal fly ash as cement replacement in the concrete. The influence of alkaline activated coal fly ash originating from Slovakian power pla...This paper is aimed at verifying utilization possibilities of alkaline modified coal fly ash as cement replacement in the concrete. The influence of alkaline activated coal fly ash originating from Slovakian power plant in Novsky （Si/Al = 3,1） as a partial cement replacement in concrete on compressive strength of hardened composites after 28 and 90 days was investigated. Alkaline activation of coal fly ash was realized in an autoclave at 130 ℃ and pressure of 160 kPa during 5 hours and in a reactor under normal conditions （equal temperature during 36 hours） at solid/liquid ratio of 0.5. Coal fly ash/cement mixtures were prepared with 25 % cement replacement by starting and modified coal fly ash and given in forms. Compressive strengths of composites after 28 and 90 days of hardening were compared to referential composite without coal fly ash and evaluated according to the standard of STN EN 450 by the value of relative strength KR （compressive strength of coal fly ash/cement composite to compressive strength of comparative concrete）. The final compressive strengths of hardened composites based on alkaline activated coal fly ash reached values in the range of 6 up to 50 MPa. In the set of experimental composites based on alkaline activated coal fly ashes, the highest value of relative strength after 28- and 90- days of hardening reached composite with cement replacement by coal fly ash zeolitized in autoclave （105% of compressive strength of referential sample）, what is connected with formation of zeolitic phases on surface of coal fly ash particles. The achieved results confirm that alkaline activation of coal fly ash in an autoclave under observed conditions can be successfully used as a partial cement replacement in concrete of C20/25 and C25/30 in accordance with requirements of standards （STN EN 450 and STN EN 206）.展开更多
基金Supported by the Program of Excellent Talents in Six Fields of Jiangsu Province(2008183)~~
文摘The impact of fly ash content on bond performance of steel bars and their surrounding concrete is studied by means of sticking strain gauges on steel bars. The average bond stress-slip curves, the steel strain-anchor location curves, and the bond stress-anchor position curves of the pullout specimens with various fly ash contents are obtained. Results indicate that the bond performance of concrete and steel bars can be improved and the distribution of steel strain along the anchorage length tends to be more uniform by adding fly ash in concrete specimens, and both ultimate bond stress and ultimate slip deformation increase the most when 20% of specimens′ content is fly ash.
基金Supported by the National Natural Science Foundation of China(51278418)the Natural Science Basic Research Plan in Shaanxi Province of China(2013K11-10)
文摘In this paper, different particle sizes of coal fly ash FA-R(D50= 15.75 μm), FA-A(D50= 3.61 μm) and FA-B(D50= 1.73 μm) were treated with Na OH solution to prepare the forming adsorbents FFA-R, FFA-A and FFA-B.The structure and adsorption properties of the forming adsorbents for methylene blue(MB) from aqueous solution were examined. The results showed that the specific surface areas and adsorption capacities of the forming adsorbent for MB increased with decreasing particle size of raw coal fly ashes. The adsorption kinetic data of MB on FFA-R, FFA-A and FFA-B fitted the second-order kinetic model very well with the rate constants(k2) of3.15 × 10-2, 3.84 × 10-2and 6.27 × 10-2g·mg-1·min-1, respectively. The adsorption process was not only controlled by intra-particle diffusion. The isotherms of MB on FFA-R, FFA-A and FFA-B can be described by the Langmuir isotherm and the Freundlich isotherm, and the adsorption processes were spontaneous and exothermic.
文摘This paper is aimed at verifying utilization possibilities of alkaline modified coal fly ash as cement replacement in the concrete. The influence of alkaline activated coal fly ash originating from Slovakian power plant in Novsky （Si/Al = 3,1） as a partial cement replacement in concrete on compressive strength of hardened composites after 28 and 90 days was investigated. Alkaline activation of coal fly ash was realized in an autoclave at 130 ℃ and pressure of 160 kPa during 5 hours and in a reactor under normal conditions （equal temperature during 36 hours） at solid/liquid ratio of 0.5. Coal fly ash/cement mixtures were prepared with 25 % cement replacement by starting and modified coal fly ash and given in forms. Compressive strengths of composites after 28 and 90 days of hardening were compared to referential composite without coal fly ash and evaluated according to the standard of STN EN 450 by the value of relative strength KR （compressive strength of coal fly ash/cement composite to compressive strength of comparative concrete）. The final compressive strengths of hardened composites based on alkaline activated coal fly ash reached values in the range of 6 up to 50 MPa. In the set of experimental composites based on alkaline activated coal fly ashes, the highest value of relative strength after 28- and 90- days of hardening reached composite with cement replacement by coal fly ash zeolitized in autoclave （105% of compressive strength of referential sample）, what is connected with formation of zeolitic phases on surface of coal fly ash particles. The achieved results confirm that alkaline activation of coal fly ash in an autoclave under observed conditions can be successfully used as a partial cement replacement in concrete of C20/25 and C25/30 in accordance with requirements of standards （STN EN 450 and STN EN 206）.
