自密实混凝土浇筑成型方向对新老混凝土界面黏结抗剪强度的影响
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摘要
针对自密实混凝土加固既有混凝土结构时存在不同方位的黏结界面,为研究其对新老混凝土界面剪切强度的影响,设计具有不同混凝土浇筑成型方向的Z型黏结试件进行直剪试验,探究自密实混凝土浇筑成型方向、混凝土强度和界面处理方式等对黏结试件破坏形式和抗剪强度的影响,并探讨不同浇筑成型方向影响下新老混凝土黏结界面抗剪强度计算方法。研究结果表明:混凝土浇筑成型方向对界面抗剪强度影响显著,新混凝土从老混凝土顶面浇筑的效果最好,侧面浇筑次之,底面浇筑最差,差值最大多达到顶面浇筑试件抗剪强度的50%。一定范围内增大新混凝土强度能有效提高黏结界面抗剪强度,底面浇筑时效果尤为明显;当新老混凝土强度相差较大时,继续提高新混凝土强度作用不大。基于本试验结果,建议新老混凝土强度差宜控制在2个标号以内。界面处理方式对其抗剪强度的影响依赖于新老混凝土强度和新混凝土浇筑成型方向。本试验中,II类界面对于强度相同的新老混凝土界面抗剪强度影响不大,但能提高不同强度的新老混凝土界面抗剪强度,尤其是底面浇筑和侧面浇筑的界面。
There are different types of interfaces between the self-compacting concrete and the existed concrete because of their different directions. A direct shear test is performed on the Z Type specimens with different compacting directions to investigate the effects of concrete casting direction on the shear behavior between the new and old concrete interface. The influence of new concrete casting direction, concrete strength and the interfacial treatment modes on the failure mode and the ultimate shear strength of the tested specimens are clarified. A model is developed to consider the effects of concrete casting direction into the prediction of ultimate shear strength between the new and old interface. Results show that the concrete casting direction significantly affects the shear behavior. Concrete casting from the top face to the old concrete has the highest shear strength,followed by the side face and the bottom face. The maximum difference is about 50% of the shear strength of the specimen with top face casting. The increase of new concrete strength in a certain range can effectively improve the shear strength, especially when the concrete is casted form bottom face to old concrete. The further increase of the new concrete strength as it exceeds the critical value has little effects of the improvement of shear strength.Based on the present tested results, the compressive strength of the new and old concrete should not exceed two marked value. The effects of interfacial treatment mode on the shear strength also depends on the concrete strength and the casting direction. In the present test, Type II interface mode has little influence on the interface shear strength between the new and old concrete with the similar compressive strength, but it can increase the shear strength as the new and old concrete with different compressive strength, especially for the specimens with the concrete compacting direction from the side face and the bottom face.
There are different types of interfaces between the self-compacting concrete and the existed concrete because of their different directions. A direct shear test is performed on the Z Type specimens with different compacting directions to investigate the effects of concrete casting direction on the shear behavior between the new and old concrete interface. The influence of new concrete casting direction, concrete strength and the interfacial treatment modes on the failure mode and the ultimate shear strength of the tested specimens are clarified. A model is developed to consider the effects of concrete casting direction into the prediction of ultimate shear strength between the new and old interface. Results show that the concrete casting direction significantly affects the shear behavior. Concrete casting from the top face to the old concrete has the highest shear strength,followed by the side face and the bottom face. The maximum difference is about 50% of the shear strength of the specimen with top face casting. The increase of new concrete strength in a certain range can effectively improve the shear strength, especially when the concrete is casted form bottom face to old concrete. The further increase of the new concrete strength as it exceeds the critical value has little effects of the improvement of shear strength.Based on the present tested results, the compressive strength of the new and old concrete should not exceed two marked value. The effects of interfacial treatment mode on the shear strength also depends on the concrete strength and the casting direction. In the present test, Type II interface mode has little influence on the interface shear strength between the new and old concrete with the similar compressive strength, but it can increase the shear strength as the new and old concrete with different compressive strength, especially for the specimens with the concrete compacting direction from the side face and the bottom face.
引文
[1] HE Y, ZHANG X, Hooton R D, et al. Effects of interface roughness and interface adhesion on new-to-old concrete bonding[J]. Construction and Building Materials,2017(151):582-590.
[2] Van Der Vurst F, Grünewald S, Feys D, et al. Effect of the mix design on the robustness of fresh self-compacting concrete[J]. Cement and Concrete Composites, 2017(82):190-201.
[3] Kaffetzakis M I, Papanicolaou C G. Bond behavior of reinforcement in lightweight aggregate self-compacting concrete[J]. Construction and Building Materials,2016(113):641-652.
[4] Karamloo M, Mazloom M, Payganeh G. Effects of maximum aggregate size on fracture behaviors of self-compacting lightweight concrete[J]. Construction and Building Materials, 2016(123):508-515.
[5] ZHANG J, DING X, ZHAO Q. Experimental and numerical investigation of scattering gravels on the surface bond strength of self-compacting concrete[J].Construction and Building Materials, 2017(145):11-19.
[6]郑建岚,庄金平.自密实混凝土与钢筋的粘结性能试验研究[J].工程力学, 2013, 30(2):112-117.ZHENG Jianlan, ZHUANG Jinping. Experiment research on bond properties between self-compacting concrete and reinforcement[J]. Engineering Mechanics, 2013, 30(2):112-117.
[7] López-Carre?o R D, Pujadas P, Cavalaro S H P, et al.Bond strength of whitetoppings and bonded overlays constructed with self-compacting high-performance concrete[J]. Construction and Building Materials,2017(153):835-845.
[8] Rahal K N, Khaleefi A L, Al-Sanee A. An experimental investigation of shear-transfer strength of normal and high strength self compacting concrete[J]. Engineering Structures, 2016(109):16-25.
[9]陈峰,郑建岚.自密实混凝土与老混凝土粘结强度的直剪试验研究[J].建筑结构学报, 2007, 28(1):59-63.CHEN Feng, ZHENG Jianlan. Experimental research on direct shear behavior of adhesion of self-compacting concrete on existing concrete[J]. Journal of Building Structures, 2007, 28(1):59-63.
[10] Diab A M, Abd Elmoaty A E M, Tag Eldin M R. Slant shear bond strength between self compacting concrete and old concrete[J]. Construction and Building Materials,2017(130):73-82.
[11]柴敏,罗素蓉.自密实混凝土与老混凝土黏结抗剪性能试验研究[J].福州大学学报(自然科学版), 2013,41(5):922-927.CHAI Min, LUO Surong. Experimental reserch on shear properties of selt-compating concrete on existing concrete[J]. Journal of Fuzhou University(Natural Science Edition), 2013, 41(5):922-927.
[12]陈峰,郑建岚.自密实混凝土与老混凝土黏结滑移关系的有限元分析[J].武汉大学学报(工学版), 2014,47(6):774-778.CHEN Feng, ZHENG Jianlan. Finite element analysis of bonding-slip relationship between old concrete and freshly cured self-compacting concrete[J]. Journal of Wuhan University Engineering, 2014, 47(6):774-778.
[13]郑建岚,陈峰.自密实混凝土与老混凝土黏结剪切强度的塑性极限分析[J].工程力学, 2008, 25(8):164-168.ZHENG Jianlan, CHEN Feng. The plastic limit analysis of adhesive shear strength between self-compacting concrete and old concrete[J]. Engineering Mechanics,2008, 25(8):164-168.
[14] Conforti A, Minelli F, Plizzari G A. Shear behaviour of prestressed double tees in self-compacting polypropylene fibre reinforced concrete[J]. Engineering Structures,2017(146):93-104.
[15] Mohamad M E, Ibrahim I S, Abdullah R, et al. Friction and cohesion coefficients of composite concrete-toconcrete bond[J]. Cement and Concrete Composites,2015(56):1-14.
[16]何薇.混凝土碳化及其对地下结构力学性能的影响研究[D].成都:西南交通大学, 2013.HE Wei. Research on concrete carbonization and its influence on the mechanical behavior of underground structurs[D]. Chengdu:Southwest Jiaotong University,2013.
[17] ACI 318-08, American concrete institute building code requirements for structural concrete and commentary[S].
[2] Van Der Vurst F, Grünewald S, Feys D, et al. Effect of the mix design on the robustness of fresh self-compacting concrete[J]. Cement and Concrete Composites, 2017(82):190-201.
[3] Kaffetzakis M I, Papanicolaou C G. Bond behavior of reinforcement in lightweight aggregate self-compacting concrete[J]. Construction and Building Materials,2016(113):641-652.
[4] Karamloo M, Mazloom M, Payganeh G. Effects of maximum aggregate size on fracture behaviors of self-compacting lightweight concrete[J]. Construction and Building Materials, 2016(123):508-515.
[5] ZHANG J, DING X, ZHAO Q. Experimental and numerical investigation of scattering gravels on the surface bond strength of self-compacting concrete[J].Construction and Building Materials, 2017(145):11-19.
[6]郑建岚,庄金平.自密实混凝土与钢筋的粘结性能试验研究[J].工程力学, 2013, 30(2):112-117.ZHENG Jianlan, ZHUANG Jinping. Experiment research on bond properties between self-compacting concrete and reinforcement[J]. Engineering Mechanics, 2013, 30(2):112-117.
[7] López-Carre?o R D, Pujadas P, Cavalaro S H P, et al.Bond strength of whitetoppings and bonded overlays constructed with self-compacting high-performance concrete[J]. Construction and Building Materials,2017(153):835-845.
[8] Rahal K N, Khaleefi A L, Al-Sanee A. An experimental investigation of shear-transfer strength of normal and high strength self compacting concrete[J]. Engineering Structures, 2016(109):16-25.
[9]陈峰,郑建岚.自密实混凝土与老混凝土粘结强度的直剪试验研究[J].建筑结构学报, 2007, 28(1):59-63.CHEN Feng, ZHENG Jianlan. Experimental research on direct shear behavior of adhesion of self-compacting concrete on existing concrete[J]. Journal of Building Structures, 2007, 28(1):59-63.
[10] Diab A M, Abd Elmoaty A E M, Tag Eldin M R. Slant shear bond strength between self compacting concrete and old concrete[J]. Construction and Building Materials,2017(130):73-82.
[11]柴敏,罗素蓉.自密实混凝土与老混凝土黏结抗剪性能试验研究[J].福州大学学报(自然科学版), 2013,41(5):922-927.CHAI Min, LUO Surong. Experimental reserch on shear properties of selt-compating concrete on existing concrete[J]. Journal of Fuzhou University(Natural Science Edition), 2013, 41(5):922-927.
[12]陈峰,郑建岚.自密实混凝土与老混凝土黏结滑移关系的有限元分析[J].武汉大学学报(工学版), 2014,47(6):774-778.CHEN Feng, ZHENG Jianlan. Finite element analysis of bonding-slip relationship between old concrete and freshly cured self-compacting concrete[J]. Journal of Wuhan University Engineering, 2014, 47(6):774-778.
[13]郑建岚,陈峰.自密实混凝土与老混凝土黏结剪切强度的塑性极限分析[J].工程力学, 2008, 25(8):164-168.ZHENG Jianlan, CHEN Feng. The plastic limit analysis of adhesive shear strength between self-compacting concrete and old concrete[J]. Engineering Mechanics,2008, 25(8):164-168.
[14] Conforti A, Minelli F, Plizzari G A. Shear behaviour of prestressed double tees in self-compacting polypropylene fibre reinforced concrete[J]. Engineering Structures,2017(146):93-104.
[15] Mohamad M E, Ibrahim I S, Abdullah R, et al. Friction and cohesion coefficients of composite concrete-toconcrete bond[J]. Cement and Concrete Composites,2015(56):1-14.
[16]何薇.混凝土碳化及其对地下结构力学性能的影响研究[D].成都:西南交通大学, 2013.HE Wei. Research on concrete carbonization and its influence on the mechanical behavior of underground structurs[D]. Chengdu:Southwest Jiaotong University,2013.
[17] ACI 318-08, American concrete institute building code requirements for structural concrete and commentary[S].
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