不同配比和养护条件对超高性能混凝土微观结构的影响
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摘要
为了优化超高性能混凝土(Ultra High Performance Concrete,UHPC)制备方法,采用宏观力学试验与微观电镜技术相结合的方法,探讨不同配合比和养护条件对UHPC内部微观结构的影响。基于硅砂骨料的致密堆积级配,设计21个变量组,共制作了63个立方体试件,开展UHPC流动度试验、轴压试验和扫描电镜试验,分析水胶比、砂胶率、钢纤维掺量、消泡剂掺量、养护方法、龄期等因素对UHPC工作性能、抗压性能及其微观结构的影响规律以揭示UHPC的增强机制。研究结果表明:凝胶与骨料界面过渡区(ITZ)是UHPC内部的薄弱环节,提高ITZ的密实度和强度是增强UHPC的关键;UHPC的流动度随着水胶比的提高显著增大,但其抗压强度随着水胶比的提高先增大后降低;过高的砂胶率不利于UHPC工作性能,同时会造成其抗压强度下降;掺入消泡剂可以有效提高UHPC的表观质量,但可能会降低UHPC的工作性能和抗压强度;掺入2.5%的钢纤维能大幅提高UHPC的抗压强度,并明显改善其脆性特征,但会降低工作性能;高温养护能显著激发微硅粉和矿渣的火山灰效应,使UHPC的4 d抗压强度比常温养护提高约50%,有明显的早强优势,但存在后期强度下降的可能。
The aim of this study is to optimize the mix design and preparation method of ultra-high performance concrete(UHPC). By combining the macro-mechanical and scan electron microscopy(SEM) tests, the effects of mix proportion and curing condition on the microstructure of UHPC was investigated. A total of 21 groups of UHPC mixtures were developed, and 63 cubic specimens were fabricated based on the dense packing gradation of a silica sand aggregate. A series of UHPC fluidity, axial compression, and SEM tests were then conducted. The effects of water-binder ratio, sand-binder ratio, steel-fiber content, defoamer content, curing method, and curing age on the workability, compressive performance, and microstructure of UHPC were analyzed. The reinforcement mechanism of UHPC was revealed, and the results show that the interfacial transition zone(ITZ) between the gel and aggregate is a weak link in UHPC. Improving the density and strength of ITZ is the key to enhancing UHPC. With an increase in the water-binder ratio, the flowability of UHPC increases significantly, but its compressive strength increases first and then decreases. An excessively high sand-binder ratio is detrimental to the workability and compressive strength of UHPC. Adding a defoamer can effectively improve the apparent quality of UHPC, but may reduce the workability and compressive strength of UHPC. The compressive strength and brittleness of UHPC can be greatly improved by adding 2.5% steel fiber. However, the addition of steel fiber reduces the workability of UHPC. High-temperature curing can considerably stimulate the pozzolanic effect of silica fume and slag, resulting in that the four-day compressive strength of UHPC increases by approximately 50% as compared with that under normal temperature curing. This finding indicates that UHPC under high-temperature curing has the character of early strength. However, high-temperature curing may cause a reduction in the long-term strength of UHPC.
The aim of this study is to optimize the mix design and preparation method of ultra-high performance concrete(UHPC). By combining the macro-mechanical and scan electron microscopy(SEM) tests, the effects of mix proportion and curing condition on the microstructure of UHPC was investigated. A total of 21 groups of UHPC mixtures were developed, and 63 cubic specimens were fabricated based on the dense packing gradation of a silica sand aggregate. A series of UHPC fluidity, axial compression, and SEM tests were then conducted. The effects of water-binder ratio, sand-binder ratio, steel-fiber content, defoamer content, curing method, and curing age on the workability, compressive performance, and microstructure of UHPC were analyzed. The reinforcement mechanism of UHPC was revealed, and the results show that the interfacial transition zone(ITZ) between the gel and aggregate is a weak link in UHPC. Improving the density and strength of ITZ is the key to enhancing UHPC. With an increase in the water-binder ratio, the flowability of UHPC increases significantly, but its compressive strength increases first and then decreases. An excessively high sand-binder ratio is detrimental to the workability and compressive strength of UHPC. Adding a defoamer can effectively improve the apparent quality of UHPC, but may reduce the workability and compressive strength of UHPC. The compressive strength and brittleness of UHPC can be greatly improved by adding 2.5% steel fiber. However, the addition of steel fiber reduces the workability of UHPC. High-temperature curing can considerably stimulate the pozzolanic effect of silica fume and slag, resulting in that the four-day compressive strength of UHPC increases by approximately 50% as compared with that under normal temperature curing. This finding indicates that UHPC under high-temperature curing has the character of early strength. However, high-temperature curing may cause a reduction in the long-term strength of UHPC.
引文
[1] LIN W,ROMAN W,GIANLUCA C.Age-dependent Size Effect and Fracture Characteristics of Ultra-high Performance Concrete [J].Cement and Concrete Composites,2018 (85):67-82.
[2] 陈宝春,季韬,黄卿维,等.超高性能混凝土研究综述[J].建筑科学与工程学报,2014,31(3):1-24.CHEN Bao-chun,JI Tao,HUANG Qing-wei,et al.Review of Research on Ultra-high Performance Concrete [J].Journal of Architecture and Civil Engineering,2014,31 (3):1-24.
[3] HU A X,YU J,LIANG X W,et al.Tensile Characteristics of Ultra-high-performance Concrete [J].Magazine of Concrete Research,2018,70 (6):314-324.
[4] KIM M K,KIM D J,AN Y K.Electro-mechanical Self-sensing Response of Ultrahigh Performance Fiber-reinforced Concrete in Tension [J].Composites Part B - Engineering,2018,134:254-264.
[5] 邓宗才,肖锐,申臣良.超细水泥活性粉末混凝土的配合比设计[J].建筑材料学报,2014,17(4):659-665.DENG Zong-cai,XIAO Rui,SHEN Chen-liang.Mix Proportion Design of Reactive Powder Concrete with Superfine Cement [J].Journal of Building Materials,2014,17 (4):659-665.
[6] 《中国公路学报》编辑部.中国桥梁工程学术研究综述·2014[J].中国公路学报,2014,27(5):1-96.Editorial Department of China Journal of Highway and Transport.Review on China's Bridge Engineering Research:2014 [J].China Journal of Highway and Transport,2014,27 (5):1-96.
[7] 邵旭东,管亚萍,晏班夫.预制超高性能混凝土π形梁桥的设计与初步试验[J].中国公路学报,2018,31(1):46-56.SHAO Xu-dong,GUAN Ya-ping,YAN Ban-fu.Design and Preliminary Experiments of UHPC π-shaped Girder Bridge [J].China Journal of Highway and Transport,2018,31 (1):46-56.
[8] 刘诚,樊健生,聂建国,等.钢-超高性能混凝土组合桥面系中栓钉连接件的疲劳性能研究[J].中国公路学报,2017,30(3):139-146.LIU Cheng,FAN Jian-sheng,NIE Jian-guo,et al.Fatigue Performance Research of Headed Studs in Steel and Ultra-high Performance Concrete Composite Deck [J].China Journal of Highway and Transport,2017,30 (3):139-146.
[9] 杨剑,方志.预应力超高性能混凝土梁的受弯性能研究[J].中国公路学报,2009,22(1):39-46.YANG Jian,FANG Zhi.Research on Flexural Behaviors of Prestressed Ultra High Performance Concrete Beams [J].China Journal of Highway and Transport,2009,22 (1):39-46.
[10] SHI C,WU Z,XIAO J,WANG D,et al.A Review on Ultra High Performance Concrete:Part Ⅰ.Raw Materials and Mixture Design [J].Construction and Building Materials,2015 (101):741-751.
[11] YU R,SPIESZ P,BROUWERS H.Development of an Eco-friendly Ultra-high Performance Concrete (UHPC) with Efficient Cement and Mineral Admixtures Uses [J].Cement and Concrete Composites,2015 (55):383-394.
[12] RICHARD P,CHEYREZY M.Composition of Reactive Powder Concrete [J].Cement and Concrete Research,1995,25 (7):1501-1511.
[13] 黄伟,孙伟.石灰石粉掺量对超高性能混凝土水化演变的影响[J].东南大学学报:自然科学版,2017,47(4):751-759.HUANG Wei,SUN Wei.Effects of Limestone Addition on Hydration Development of Ultra-high Performance Concrete [J].Journal of Southeast University:Natural Science Edition,2017,47 (4):751-759.
[14] 韩松,刘丹,张戈,等.超低水胶比复合胶凝材料孔结构随养护制度和龄期的变化机理[J].硅酸盐学报,2017,45(11):1594-1604.HAN Song,LIU Dan,ZHANG Ge,et al.Mechanism of Curing Effect on Pore Structure of Hardened Cementitious Composites with Ultra-low Water to Binder Ratio [J].Journal of the Chinese Ceramic Society,2017,45 (11):1594-1604.
[15] 陈宝春,李聪,黄伟,等.超高性能混凝土收缩综述[J].交通运输工程学报,2018,18(1):13-28.CHEN Bao-chun,LI Cong,HUANG Wei,et al.Review of Ultra-high Performance Concrete Shrinkage [J].Journal of Traffic and Transportation Engineering,2018,18 (1):13-28.
[16] 王卫中,冯忠绪.二次搅拌工艺对混凝土性能影响的试验研究[J].混凝土,2006(4):40-42.WANG Wei-zhong,FENG Zhong-xu.Test Research on Concrete Performance by Secondary Mixing Processes [J].Concrete,2006 (4):40-42.
[17] MOSTOFINEJAD D,NIKOO M R,HOSSEINI S A.Determination of Optimized Mix Design and Curing Conditions of Reactive Powder Concrete (RPC) [J].Construction and Building Materials,2016,123:754-767.
[18] WILLE K,NAAMAN A E,PARRA G J.Ultra-high Performance Concrete with Compressive Strength Exceeding 150 MPa (22 ksi):A Simpler Way [J].ACI Materials Journal,2011,108 (1):46-54.
[19] AFROUGHSABET V,BIOLZI L,OZBAKKALOGLU T.High-performance Fiber-reinforced Concrete:A Review [J].Journal of Materials Science,2016,5:6517-6551.
[20] BUTTIGNOL T,SOUSA J,BITTENCOURT T N.Ultra High-performance Fiber-reinforced Concrete (UHPFRC):A Review of Material Properties and Design Procedures [J].Revista IBRACON Structures and Materials Journal,2017,10 (4):957-971.
[21] 陆加越,赵爽,刘红,等.消泡剂对聚羧酸系减水剂配制混凝土气泡结构的影响[J].混凝土与水泥制品,2014(增):57-60.LU Jia-yue,ZHAO Shuang,LIU Hong,et al.Effect of Air Structure on the Concrete Which Mixed with Polycarboxylate Water Reducer Admixture by Deformer [J].China Concrete and Cement Products,2014 (S):57-60.
[22] YAZICI H,YARDIMCI M Y,AYDIN S,et al.Mechanical Properties of Reactive Powder Concrete Containing Mineral Admixtures Under Different Curing Regimes [J].Construction and Building Materials,2009,23:1223-1231.
[23] 吴炎海,何雁斌,杨幼华,等.养护制度对活性粉末混凝土(RPC)强度的影响[J].福州大学学报:自然科学版,2003,31(5):593-597.WU Yan-hai,HE Yan-bin,YANG You-hua,et al.The Influence of Curing System on RPC Strength [J].Journal of Fuzhou University:Natural Science Edition,2003,31 (5):593-597.
[24] 何峰,黄政宇.养护制度对活性粉末混凝土(RPC)强度的影响研究[J].混凝土,2000(2):31-34.HE Feng,HUANG Zheng-yu.Study on Effect of Curing Schedule on the Strength of RPC [J].Concrete,2000 (2):31-34.
[25] 张胜,周锡玲,谢友均,等.养护制度对活性粉未混凝土强度及微观结构影响的研究[J].混凝土,2007(6):16-18.ZHANG Sheng,ZHOU Xi-ling,XIE You-jun,et al.Study on the Effect of Curing System on the Strength and Microstructure of Reactive Powder Concrete [J].Concrete,2007 (6):16-18.
[26] SOLIMAN A M,NEHDI M L.Effect of Drying Conditions on Autogenous Shrinkage in Ultra-high Performance Concrete at Early-age [J].Materials and Structures,2010,44 (5):879-899.
[2] 陈宝春,季韬,黄卿维,等.超高性能混凝土研究综述[J].建筑科学与工程学报,2014,31(3):1-24.CHEN Bao-chun,JI Tao,HUANG Qing-wei,et al.Review of Research on Ultra-high Performance Concrete [J].Journal of Architecture and Civil Engineering,2014,31 (3):1-24.
[3] HU A X,YU J,LIANG X W,et al.Tensile Characteristics of Ultra-high-performance Concrete [J].Magazine of Concrete Research,2018,70 (6):314-324.
[4] KIM M K,KIM D J,AN Y K.Electro-mechanical Self-sensing Response of Ultrahigh Performance Fiber-reinforced Concrete in Tension [J].Composites Part B - Engineering,2018,134:254-264.
[5] 邓宗才,肖锐,申臣良.超细水泥活性粉末混凝土的配合比设计[J].建筑材料学报,2014,17(4):659-665.DENG Zong-cai,XIAO Rui,SHEN Chen-liang.Mix Proportion Design of Reactive Powder Concrete with Superfine Cement [J].Journal of Building Materials,2014,17 (4):659-665.
[6] 《中国公路学报》编辑部.中国桥梁工程学术研究综述·2014[J].中国公路学报,2014,27(5):1-96.Editorial Department of China Journal of Highway and Transport.Review on China's Bridge Engineering Research:2014 [J].China Journal of Highway and Transport,2014,27 (5):1-96.
[7] 邵旭东,管亚萍,晏班夫.预制超高性能混凝土π形梁桥的设计与初步试验[J].中国公路学报,2018,31(1):46-56.SHAO Xu-dong,GUAN Ya-ping,YAN Ban-fu.Design and Preliminary Experiments of UHPC π-shaped Girder Bridge [J].China Journal of Highway and Transport,2018,31 (1):46-56.
[8] 刘诚,樊健生,聂建国,等.钢-超高性能混凝土组合桥面系中栓钉连接件的疲劳性能研究[J].中国公路学报,2017,30(3):139-146.LIU Cheng,FAN Jian-sheng,NIE Jian-guo,et al.Fatigue Performance Research of Headed Studs in Steel and Ultra-high Performance Concrete Composite Deck [J].China Journal of Highway and Transport,2017,30 (3):139-146.
[9] 杨剑,方志.预应力超高性能混凝土梁的受弯性能研究[J].中国公路学报,2009,22(1):39-46.YANG Jian,FANG Zhi.Research on Flexural Behaviors of Prestressed Ultra High Performance Concrete Beams [J].China Journal of Highway and Transport,2009,22 (1):39-46.
[10] SHI C,WU Z,XIAO J,WANG D,et al.A Review on Ultra High Performance Concrete:Part Ⅰ.Raw Materials and Mixture Design [J].Construction and Building Materials,2015 (101):741-751.
[11] YU R,SPIESZ P,BROUWERS H.Development of an Eco-friendly Ultra-high Performance Concrete (UHPC) with Efficient Cement and Mineral Admixtures Uses [J].Cement and Concrete Composites,2015 (55):383-394.
[12] RICHARD P,CHEYREZY M.Composition of Reactive Powder Concrete [J].Cement and Concrete Research,1995,25 (7):1501-1511.
[13] 黄伟,孙伟.石灰石粉掺量对超高性能混凝土水化演变的影响[J].东南大学学报:自然科学版,2017,47(4):751-759.HUANG Wei,SUN Wei.Effects of Limestone Addition on Hydration Development of Ultra-high Performance Concrete [J].Journal of Southeast University:Natural Science Edition,2017,47 (4):751-759.
[14] 韩松,刘丹,张戈,等.超低水胶比复合胶凝材料孔结构随养护制度和龄期的变化机理[J].硅酸盐学报,2017,45(11):1594-1604.HAN Song,LIU Dan,ZHANG Ge,et al.Mechanism of Curing Effect on Pore Structure of Hardened Cementitious Composites with Ultra-low Water to Binder Ratio [J].Journal of the Chinese Ceramic Society,2017,45 (11):1594-1604.
[15] 陈宝春,李聪,黄伟,等.超高性能混凝土收缩综述[J].交通运输工程学报,2018,18(1):13-28.CHEN Bao-chun,LI Cong,HUANG Wei,et al.Review of Ultra-high Performance Concrete Shrinkage [J].Journal of Traffic and Transportation Engineering,2018,18 (1):13-28.
[16] 王卫中,冯忠绪.二次搅拌工艺对混凝土性能影响的试验研究[J].混凝土,2006(4):40-42.WANG Wei-zhong,FENG Zhong-xu.Test Research on Concrete Performance by Secondary Mixing Processes [J].Concrete,2006 (4):40-42.
[17] MOSTOFINEJAD D,NIKOO M R,HOSSEINI S A.Determination of Optimized Mix Design and Curing Conditions of Reactive Powder Concrete (RPC) [J].Construction and Building Materials,2016,123:754-767.
[18] WILLE K,NAAMAN A E,PARRA G J.Ultra-high Performance Concrete with Compressive Strength Exceeding 150 MPa (22 ksi):A Simpler Way [J].ACI Materials Journal,2011,108 (1):46-54.
[19] AFROUGHSABET V,BIOLZI L,OZBAKKALOGLU T.High-performance Fiber-reinforced Concrete:A Review [J].Journal of Materials Science,2016,5:6517-6551.
[20] BUTTIGNOL T,SOUSA J,BITTENCOURT T N.Ultra High-performance Fiber-reinforced Concrete (UHPFRC):A Review of Material Properties and Design Procedures [J].Revista IBRACON Structures and Materials Journal,2017,10 (4):957-971.
[21] 陆加越,赵爽,刘红,等.消泡剂对聚羧酸系减水剂配制混凝土气泡结构的影响[J].混凝土与水泥制品,2014(增):57-60.LU Jia-yue,ZHAO Shuang,LIU Hong,et al.Effect of Air Structure on the Concrete Which Mixed with Polycarboxylate Water Reducer Admixture by Deformer [J].China Concrete and Cement Products,2014 (S):57-60.
[22] YAZICI H,YARDIMCI M Y,AYDIN S,et al.Mechanical Properties of Reactive Powder Concrete Containing Mineral Admixtures Under Different Curing Regimes [J].Construction and Building Materials,2009,23:1223-1231.
[23] 吴炎海,何雁斌,杨幼华,等.养护制度对活性粉末混凝土(RPC)强度的影响[J].福州大学学报:自然科学版,2003,31(5):593-597.WU Yan-hai,HE Yan-bin,YANG You-hua,et al.The Influence of Curing System on RPC Strength [J].Journal of Fuzhou University:Natural Science Edition,2003,31 (5):593-597.
[24] 何峰,黄政宇.养护制度对活性粉末混凝土(RPC)强度的影响研究[J].混凝土,2000(2):31-34.HE Feng,HUANG Zheng-yu.Study on Effect of Curing Schedule on the Strength of RPC [J].Concrete,2000 (2):31-34.
[25] 张胜,周锡玲,谢友均,等.养护制度对活性粉未混凝土强度及微观结构影响的研究[J].混凝土,2007(6):16-18.ZHANG Sheng,ZHOU Xi-ling,XIE You-jun,et al.Study on the Effect of Curing System on the Strength and Microstructure of Reactive Powder Concrete [J].Concrete,2007 (6):16-18.
[26] SOLIMAN A M,NEHDI M L.Effect of Drying Conditions on Autogenous Shrinkage in Ultra-high Performance Concrete at Early-age [J].Materials and Structures,2010,44 (5):879-899.