热处理对聚合物改性硬化水泥浆孔结构的影响
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摘要
硬化水泥浆体(HCP)的孔结构是影响混凝土耐久性的决定性因素,也是影响水泥基材料力学强度、收缩和开裂的关键因素之一。聚合物乳液常用做水泥基材料添加剂以提高其抗拉、抗折强度和韧性等。环境温度变化会影响聚合物相在硬化水泥浆中的成膜状态,进而影响聚合物改性硬化水泥浆孔结构。制备了玻璃化温度分别为–5℃(L1)和53℃(L2)的两种聚合物乳液,使用氮气吸附法、X射线衍射和扫描电子显微镜等手段研究了65℃和90℃高温热处理对两种聚合物改性硬化水泥浆孔结构的影响。结果表明,常温养护后,非成膜型聚合物(L2)的掺入会略增加硬化水泥浆的总孔体积,成膜型聚合物(L1)的掺入则会大幅降低硬化水泥浆的孔体积。此外,成膜型聚合物(L1)对水化过程中钙矾石(AFt)向单硫型水化硫铝酸钙(AFm)的转化过程起到抑制作用,以至于养护至28d及90d的净浆中仍有明显的AFt结晶相存在。65℃和90℃的热处理会导致硬化水泥浆失水或水化产物的分解,从而增加空白组水泥浆和成膜型聚合物改性水泥浆的总孔体积。对于非成膜型聚合物改性水泥浆,由于高温热处理过程中聚合物颗粒的融合成膜,导致其总孔体积在热处理后大幅降低。
Pore structure of hardened cement paste(HCP) is a decisive factor for the durability of concrete as well as one of the critical factors for mechanical strength, shrinkage and cracking of cementitious materials. Polymer latex is usually used as an additive of cementitious materials to improve their flexural strength, tension strength and toughness. Temperature variation was supposed to affect the pore structure of polymer modified hardened cement paste by changing the state of the polymer phase. In this paper, the influence of heat treatment on the pore structure of polymer modified hardened cement paste was investigated by nitrogen adsorption,X-ray diffraction and scanning electron microscopy. The addition of non-film-forming polymer(L2) increases the pore volume of HCP, while the addition of film-forming polymer(L1) decreases the pore volume of HCP after curing at normal temperature. Also, the addition of film-forming polymer(L1) depresses the conversion of ettringite(AFt) to calcium monosulfoaluminate hydrate(AFm)during cement hydration, so that AFt phase appears in the L1 modified HCP at 28 d and 90 d, whereas it is absent in the blank HCP and the L2 modified HCP. Heat treatments at 65 °C and 90 °C lead to the water loss of HCP and partly decomposition of hydration products, resulting in the increase of total pore volume of the blank HCP and the film-forming polymer modified HCP(PL1). For non-film-forming polymer modified HCP, heat treatment causes the fusion of polymer particles and film formation, resulting in a decrease of the total pore volume.
Pore structure of hardened cement paste(HCP) is a decisive factor for the durability of concrete as well as one of the critical factors for mechanical strength, shrinkage and cracking of cementitious materials. Polymer latex is usually used as an additive of cementitious materials to improve their flexural strength, tension strength and toughness. Temperature variation was supposed to affect the pore structure of polymer modified hardened cement paste by changing the state of the polymer phase. In this paper, the influence of heat treatment on the pore structure of polymer modified hardened cement paste was investigated by nitrogen adsorption,X-ray diffraction and scanning electron microscopy. The addition of non-film-forming polymer(L2) increases the pore volume of HCP, while the addition of film-forming polymer(L1) decreases the pore volume of HCP after curing at normal temperature. Also, the addition of film-forming polymer(L1) depresses the conversion of ettringite(AFt) to calcium monosulfoaluminate hydrate(AFm)during cement hydration, so that AFt phase appears in the L1 modified HCP at 28 d and 90 d, whereas it is absent in the blank HCP and the L2 modified HCP. Heat treatments at 65 °C and 90 °C lead to the water loss of HCP and partly decomposition of hydration products, resulting in the increase of total pore volume of the blank HCP and the film-forming polymer modified HCP(PL1). For non-film-forming polymer modified HCP, heat treatment causes the fusion of polymer particles and film formation, resulting in a decrease of the total pore volume.
引文
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[16]阎培渝,覃肖,杨文言.大体积补偿收缩混凝土中钙矾石的分解与二次生成[J].硅酸盐学报,2000,28(4):319-324.Yan Peiyu,QIN Xiao,YANG Wenyan.J Chin Ceram Soc,2000,28(4):319-324.
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[18]ALHOZAIMY A,JAAFAR M S,NEGHEIMISH A.Properties of high strength concrete using white and dune sands under normal and autoclaved curing[J].Constr Build Mater,2012,27(1):218-222.
[19]RAMLI M,AKHAVAN A.Effects of polymer modification on the permeability of cement mortars under different curing conditions:A correlational study that includes pore distributions,water absorption and compressive strength[J].Constr Build Mater,2012,28:561-570.
[20]OHAMA Y,MIYAKE M,NOTOYA K.Proceedings of the Second International Conference on Concrete Technology for Developing Countires[C].El-Fateh University,Tripoli,1986.
[21]SILVA D,JOHN V M,RIBEIRO J L D,et al.Pore size distribution of hydrated cement pastes modified with polymers[J].Cem Concr Res,2001,31(8):1177-1184.
[22]ALIGIZAKI K.Pore structure of cement-based materials:Testing,interpretation and requirements(Modern concrete technology series(E.&F.N.Spon)),Abingdon[England];New York:Taylor&Francis,2006.
[23]BAZANT Z P,KAPLAN M F.Concrete at High Temperatures[M].Longman-Addison-Wesley,London,1996.
[24]NAUS N J.A Compilation of Elevated Temperature Concrete Material Property Data and Information for Use in Assessments of Nuclear Power Plant Reinforced Concrete Structures[S].NUREG/CR-7031ORNL/TM-2009/175,Nuclear Regulatory Commission,U.S,2010.
[25]MA S W,YU T,WANG Y B,et al.Phase Evolution of Oil Well Cements with Nano-Additive at Elevated Temperature/Pressure[J].Aci Mater J,2016,113(5):571-578.
[26]VYDRA V,VODAK F,KAPICKOVA O.Effect of temperature on porosity of concrete for nuclear-safety structures[J].Cem Concr Res,2001,31(7):1023-1026.
[27]WANG R,WANG P M.Formation of hydrates of calcium aluminates in cement pastes with different dosages of SBR powder[J].Constr Build Mater,2011,25(2):736-741.
[2]OHAMA Y.Handbook of Polymer-Modified Concrete and Mortars:Properties and Process Technology[M].Noyes Publications,1995.
[3]WAGNER H B.Polymer-modified hydraulic cements[J].Ind Eng Chem Prod Res Dev,1965,4(3):191-6.
[4]MA H Y,LI Z J.Microstructures and mechanical properties of polymer modified mortars under distinct mechanisms[J].Constr Build Mater,2013,47:579-587.
[5]OHAMA Y.Polymer-based admixture[J].Cem Concr Compos,1998,20(2):189-212.
[6]OHAMA Y.Principle of latex modification and some typical properties of latex modified mortars and concretes[J].ACI Mater J,1987,84(6):511-518.
[7]SAKAI E,SUGITA J.Composite mechanism of polymer modified cement[J].Cem Concr Res,1995,25(1):127-135.
[8]URBAN D,TAKAMURA K.Polymer Dispersions and Their Industrial Applications[M].Weinheim:Wiley-VCH Verlag GmbH,2002.
[9]ZHANG Y R,KONG X M.Influences of superplasticizer,polymer latexes and asphalt emulsions on the pore structure and impermeability of hardened cementitious materials[J].Constr Build Mater,2014,53:392-402.
[10]KONG X M,WU C E,ZHANG Y R,et al.Polymer modified mortar with gradient polymer distribution:preparation,permeability,and mechanical behavior[J].Constr Build Mater,2013,38:195-203.
[11]BEELDENS A,VAN GEMERT D,SCHORN H,et al.From microstructure to macrostructure:an integrated model of structure formation in polymer-modified concrete[J].Mater Struct,2005,38:601-607.
[12]SU Z,SUJATA K,BIJEN J M,et al.The Evolution of the Microstructure in Styrene Acrylate Polymer-Modified Cement Pastes at the Early stage of Cement Hydration[J].Adv Cem Based Mater,1996,3:87-93.
[13]WANG R,MA D X,WANG P M,et al.Study on waterproof mechanism of polymer modified cement mortar[J].Mag Concr Res,2015,67(18):972-979.
[14]KEDDIE J L,MEREDITH P,JONES R A L,et al.Kinetics of film formation in acrylic latices studied with multiple-angle-of-incidence ellipsometry and environmental SEM[J].Macromolecules,1995,28(8):2673-2682.
[15]LU Z C,KONG X M,ZHANG C Y,et al.Effect of polymer latexes with varied glass transition temperature on cement hydration[J].J Appl Polym Sci,2017,134(36):45264.
[16]阎培渝,覃肖,杨文言.大体积补偿收缩混凝土中钙矾石的分解与二次生成[J].硅酸盐学报,2000,28(4):319-324.Yan Peiyu,QIN Xiao,YANG Wenyan.J Chin Ceram Soc,2000,28(4):319-324.
[17]马保国,温小栋,潘伟,等.蒸养温度与水化热协同下混凝土热稳定性研究[J].硅酸盐通报,2007,26(20):237-241.MA Baoguo,WEN Xiaodong,PAN Wei,et al.Bull Chin Ceram Soc(in Chinese),2007,26(20):237-241.
[18]ALHOZAIMY A,JAAFAR M S,NEGHEIMISH A.Properties of high strength concrete using white and dune sands under normal and autoclaved curing[J].Constr Build Mater,2012,27(1):218-222.
[19]RAMLI M,AKHAVAN A.Effects of polymer modification on the permeability of cement mortars under different curing conditions:A correlational study that includes pore distributions,water absorption and compressive strength[J].Constr Build Mater,2012,28:561-570.
[20]OHAMA Y,MIYAKE M,NOTOYA K.Proceedings of the Second International Conference on Concrete Technology for Developing Countires[C].El-Fateh University,Tripoli,1986.
[21]SILVA D,JOHN V M,RIBEIRO J L D,et al.Pore size distribution of hydrated cement pastes modified with polymers[J].Cem Concr Res,2001,31(8):1177-1184.
[22]ALIGIZAKI K.Pore structure of cement-based materials:Testing,interpretation and requirements(Modern concrete technology series(E.&F.N.Spon)),Abingdon[England];New York:Taylor&Francis,2006.
[23]BAZANT Z P,KAPLAN M F.Concrete at High Temperatures[M].Longman-Addison-Wesley,London,1996.
[24]NAUS N J.A Compilation of Elevated Temperature Concrete Material Property Data and Information for Use in Assessments of Nuclear Power Plant Reinforced Concrete Structures[S].NUREG/CR-7031ORNL/TM-2009/175,Nuclear Regulatory Commission,U.S,2010.
[25]MA S W,YU T,WANG Y B,et al.Phase Evolution of Oil Well Cements with Nano-Additive at Elevated Temperature/Pressure[J].Aci Mater J,2016,113(5):571-578.
[26]VYDRA V,VODAK F,KAPICKOVA O.Effect of temperature on porosity of concrete for nuclear-safety structures[J].Cem Concr Res,2001,31(7):1023-1026.
[27]WANG R,WANG P M.Formation of hydrates of calcium aluminates in cement pastes with different dosages of SBR powder[J].Constr Build Mater,2011,25(2):736-741.
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