纳米C-S-H对水泥水化、硬化浆体孔结构及混凝土强度的影响
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摘要
通过水化热测试、化学结合水含量测试、X射线衍射分析、压汞测试及强度测试研究了合成的纳米水化硅酸钙(n-C-S-H)对水泥水化过程、硬化水泥浆孔结构及混凝土强度的影响。结果表明:n-C-S-H显著加速了水泥早期水化,提升了水泥在12～24 h龄期的水化程度,从而显著提高混凝土12～24 h龄期的抗压强度,24 h以后对强度提升效果逐渐减小。3 d以后n-C-S-H对混凝土强度发展没有明显的促进作用,1.5%掺量下混凝土强度反而较空白样有所降低;加入n-C-S-H的硬化水泥浆在12 h～3 d龄期内相比空白水泥浆临界孔径降低,凝胶孔孔隙率提高,毛细孔孔隙率降低。n-C-S-H改变了C-S-H凝胶的生成方式,使其原本从水泥颗粒表面析出变为了从孔溶液中析出,显著减小了毛细孔孔隙率,同时增加了凝胶间孔的体积。这种多核生长的方式导致水化产物结构疏松,从而导致基体强度略微降低。因此,在相同水化程度时,掺有n-C-S-H的混凝土抗压强度略低于空白混凝土。
Effects of synthesized nano hydrated calcium silicate(n-C-S-H) on cement hydration, pore structure of hardened cement pastes and concrete strength were investigated using isothermal calorimetry, non-evaporative water test, X-ray diffraction,mercury intrusion test and compressive strength tests. The results show that n-C-S-H accelerates the early hydration of cement,significantly increases the hydration degree of cement in the age of 12–24 h, and thereby significantly enhances the compressive strength of concrete in the age of 12–24 h. The strength enhancement effect gradually reduces after 24 h. After 3 days, the acceleration effect on cement hydration and the enhancement effect on compressive strength of concrete become unobvious and the addition of 1.5% n-C-S-H even leads to lower compressive strength in comparison with the blank concrete sample. Compared with blank cement paste, the capillary porosity and the threshold pore size of the hardened cement pastes with addition of n-C-S-H decreases in the age of 12 h–3 d, while the gel porosity increases. Meanwhile, the incorporation of n-C-S-H in cement pastes changes the generation mode of C-S-H gel, which makes a large amount of the hydration product of C-S-H growing from the added n-C-S-H particles, instead of the typical growth from the surface of cement grains due to the so-called heterogeneous nucleation. The massive growth of C-S-H from the added n-C-S-H nuclei leads to the decrease of capillary porosity and the increase of inter-gel porosity. This multi-cores growth model causes a looser structure of hydration product and, thus reduces the strength of the C-S-H matrix. Because of this reason, at the same hydration degree, the compressive strength of concrete mixed with n-C-S-H is slightly lower than that of the blank concrete.
Effects of synthesized nano hydrated calcium silicate(n-C-S-H) on cement hydration, pore structure of hardened cement pastes and concrete strength were investigated using isothermal calorimetry, non-evaporative water test, X-ray diffraction,mercury intrusion test and compressive strength tests. The results show that n-C-S-H accelerates the early hydration of cement,significantly increases the hydration degree of cement in the age of 12–24 h, and thereby significantly enhances the compressive strength of concrete in the age of 12–24 h. The strength enhancement effect gradually reduces after 24 h. After 3 days, the acceleration effect on cement hydration and the enhancement effect on compressive strength of concrete become unobvious and the addition of 1.5% n-C-S-H even leads to lower compressive strength in comparison with the blank concrete sample. Compared with blank cement paste, the capillary porosity and the threshold pore size of the hardened cement pastes with addition of n-C-S-H decreases in the age of 12 h–3 d, while the gel porosity increases. Meanwhile, the incorporation of n-C-S-H in cement pastes changes the generation mode of C-S-H gel, which makes a large amount of the hydration product of C-S-H growing from the added n-C-S-H particles, instead of the typical growth from the surface of cement grains due to the so-called heterogeneous nucleation. The massive growth of C-S-H from the added n-C-S-H nuclei leads to the decrease of capillary porosity and the increase of inter-gel porosity. This multi-cores growth model causes a looser structure of hydration product and, thus reduces the strength of the C-S-H matrix. Because of this reason, at the same hydration degree, the compressive strength of concrete mixed with n-C-S-H is slightly lower than that of the blank concrete.
引文
[1]葛兆明.混凝土外加剂[M].第2版.化学工业出版社,2012.
[2]李晓玲.早期高温水养护对矿物料混凝土力学性能影响的研究[D].中国矿业大学,2014.LL Xiaoling.Research of Initial High Temperature Water Curing Conditions on Mechanical Properties of Mineral Admixture Cement Concrete[D].China University of Mining and Technology,2014.
[3]PEREZ J P,NONAT A,POURCHET S,et al.Why TIPA leads to an increase in the mechanical properties of mortars whereas TEA does not[J].Aci Mater J,2003,217(38):583-594.
[4]RAMACHANDRAN V S.Action of triethanolamine on the hydration of tricalcium aluminate[J].Cem Concr Res,1973,3(1):41-54.
[5]RIDING K,SILVA D A,SCRIVENER K.Early age strength enhancement of blended cement systems by CaCl2 and diethanol-isopropanolamine[J].Cem Concr Res,2010,40(6):935-946.
[6]STARK J,M?SER B,BELLMANN F.Nucleation and Growth of C-S-H Phases on Mineral Admixtures[M].Advances in Construction Materials.Springer Berlin Heidelberg,2007:531-538.
[7]LAND G,STEPHAN D.The influence of nano-silica on the hydration of ordinary Portland cement[J].J Mater Sci,2012,47(2):1011-1017.
[8]LAND G,STEPHAN D.Controlling cement hydration with nanoparticles[J].Cem Concr Compos,2015,57:64-67.
[9]THOMAS J J,JENNINGS H M,CHEN J J.Influence of Nucleation Seeding on the Hydration Mechanisms of Tricalcium Silicate and Cement[J].J Phys Chem C,2009,113(11):4327-4334.
[10]ALIZADEH R,RAKI L,MAKAR J M,et al.Hydration of tricalcium silicate in the presence of synthetic calcium-silicate-hydrate[J].JMater Chem,2009,19(42):7937-7946.
[11]李遵云,杨林,屠柳青,等.纳米水化硅酸钙对混凝土耐久性的影响[J].混凝土,2013,10:112-118.LI Zunyun,YANG Lin,TU Liuqing,et al.Concrete(in Chinese),2013,10:112-118.
[12]段运,王起才,张戎令,等.低温(3℃)下高强混凝土强度增长及其水化程度研究[J].硅酸盐通报,2016,35(1):12-18.DUAN Yun,WANG Qicai,ZHANG Rongling et al.Bull Chin Ceram Soc(in Chinese),2016,35(1):12-18.
[13]KUMAR R,BHATTACHARJEE B.Porosity,pore size distribution and in situ strength of concrete[J].Cem Concr Res,2003,33:155-164.
[14]DAS B B,KONDRAIVENDHAN B.Implication of pore size distribution parameters on compressive strength,permeability and hydraulic diffusivity of concrete[J].Constr Build Mater,2012,28(1):382-386.
[15]MA H,XU B,LIU J,et al.Effects of water content,magnesia-to-phosphate molar ratio and age on pore structure,strength and permeability of magnesium potassium phosphate cement paste[J].Mater Design,2014,64(64):497-502.
[16]ALIGIZAKI K,Pore structure of cement-based materials:Testing,interpretation and requirements(Modern concrete technology series[M].New York:Taylor&Francis,2006.
[17]IGARASHI S,WATANABE A,KAWAMURA M.Evaluation of capillary pore size characteristics in high-strength concrete at early ages[J].Cem Concr Res,2005,35:513-519.
[18]RADIM V,CHRISTOPHE G,MARC D,et al.Mercury intrusion porosimetry and hierarchical structure of cement pastes:Theory and experiment[J].Cem Concr Res,2000,30(4):521-527.
[19]LAND G,STEPHAN D.The influence of nano-silica on the hydration of ordinary Portland cement[J].J Mater Sci,2012,47:1011-1017.
[20]NICOLEAU L.New calcium silicate hydrate network[J].Transport Res Rec,2010,2142:42-51.
[2]李晓玲.早期高温水养护对矿物料混凝土力学性能影响的研究[D].中国矿业大学,2014.LL Xiaoling.Research of Initial High Temperature Water Curing Conditions on Mechanical Properties of Mineral Admixture Cement Concrete[D].China University of Mining and Technology,2014.
[3]PEREZ J P,NONAT A,POURCHET S,et al.Why TIPA leads to an increase in the mechanical properties of mortars whereas TEA does not[J].Aci Mater J,2003,217(38):583-594.
[4]RAMACHANDRAN V S.Action of triethanolamine on the hydration of tricalcium aluminate[J].Cem Concr Res,1973,3(1):41-54.
[5]RIDING K,SILVA D A,SCRIVENER K.Early age strength enhancement of blended cement systems by CaCl2 and diethanol-isopropanolamine[J].Cem Concr Res,2010,40(6):935-946.
[6]STARK J,M?SER B,BELLMANN F.Nucleation and Growth of C-S-H Phases on Mineral Admixtures[M].Advances in Construction Materials.Springer Berlin Heidelberg,2007:531-538.
[7]LAND G,STEPHAN D.The influence of nano-silica on the hydration of ordinary Portland cement[J].J Mater Sci,2012,47(2):1011-1017.
[8]LAND G,STEPHAN D.Controlling cement hydration with nanoparticles[J].Cem Concr Compos,2015,57:64-67.
[9]THOMAS J J,JENNINGS H M,CHEN J J.Influence of Nucleation Seeding on the Hydration Mechanisms of Tricalcium Silicate and Cement[J].J Phys Chem C,2009,113(11):4327-4334.
[10]ALIZADEH R,RAKI L,MAKAR J M,et al.Hydration of tricalcium silicate in the presence of synthetic calcium-silicate-hydrate[J].JMater Chem,2009,19(42):7937-7946.
[11]李遵云,杨林,屠柳青,等.纳米水化硅酸钙对混凝土耐久性的影响[J].混凝土,2013,10:112-118.LI Zunyun,YANG Lin,TU Liuqing,et al.Concrete(in Chinese),2013,10:112-118.
[12]段运,王起才,张戎令,等.低温(3℃)下高强混凝土强度增长及其水化程度研究[J].硅酸盐通报,2016,35(1):12-18.DUAN Yun,WANG Qicai,ZHANG Rongling et al.Bull Chin Ceram Soc(in Chinese),2016,35(1):12-18.
[13]KUMAR R,BHATTACHARJEE B.Porosity,pore size distribution and in situ strength of concrete[J].Cem Concr Res,2003,33:155-164.
[14]DAS B B,KONDRAIVENDHAN B.Implication of pore size distribution parameters on compressive strength,permeability and hydraulic diffusivity of concrete[J].Constr Build Mater,2012,28(1):382-386.
[15]MA H,XU B,LIU J,et al.Effects of water content,magnesia-to-phosphate molar ratio and age on pore structure,strength and permeability of magnesium potassium phosphate cement paste[J].Mater Design,2014,64(64):497-502.
[16]ALIGIZAKI K,Pore structure of cement-based materials:Testing,interpretation and requirements(Modern concrete technology series[M].New York:Taylor&Francis,2006.
[17]IGARASHI S,WATANABE A,KAWAMURA M.Evaluation of capillary pore size characteristics in high-strength concrete at early ages[J].Cem Concr Res,2005,35:513-519.
[18]RADIM V,CHRISTOPHE G,MARC D,et al.Mercury intrusion porosimetry and hierarchical structure of cement pastes:Theory and experiment[J].Cem Concr Res,2000,30(4):521-527.
[19]LAND G,STEPHAN D.The influence of nano-silica on the hydration of ordinary Portland cement[J].J Mater Sci,2012,47:1011-1017.
[20]NICOLEAU L.New calcium silicate hydrate network[J].Transport Res Rec,2010,2142:42-51.