纳米C-S-H-PCE对免蒸养高强混凝土性能的影响  

Effect of nano C-S-H-PCE on the properties of high-strength non-steam-cured concrete

作　　者：付华 王鹏刚[1] 田砾[1] 唐兴滨 赵铁军[1] FU Hua;WANG Penggang;TIAN Li;TANG Xingbin;ZHAO Tiejun(Department of Civil Engineering,Qingdao University of Technology,Qingdao 266520,China;Qingdao Municipal Group Concrete Engineering CO.,LTD.,Qingdao 266231,China)

机构地区：[1]青岛理工大学土木工程学院,青岛266520 [2]青岛市政集团砼业工程有限公司,青岛266231

出　　处：《复合材料学报》2024年第1期333-347,共15页Acta Materiae Compositae Sinica

基　　金：国家自然科学基金(52278263)。

摘　　要：针对蒸汽养护易引起混凝土初始损伤及耐久性差等问题。本文采用纳米水化硅酸钙-聚羧酸醚复合材料(n-C-S-H-PCE)制备免蒸养高强混凝土。通过水化热、低场核磁等试验研究了n-C-S-H-PCE对混凝土抗压强度、水化速率、孔径分布、自收缩及耐久性的影响。结果表明:纳米水化硅酸钙(C-S-H)晶核为水化产物提供了成核位点,降低了成核的临界离子浓度K_(sp),诱导期和加速期显著提前,显著提高了混凝土早期抗压强度,1天混凝土抗压强度提高64%,且28天以后混凝土没有发生强度倒缩。掺入n-C-S-H-PCE后,混凝土基体孔径细化,凝胶孔和毛细孔比例均增加,导致混凝土自干燥过程中毛细孔负压增大,增大混凝土自收缩;然而,混凝土基体的最可几孔径和50~100 nm孔隙累计体积降低,提高了混凝土的抗氯离子侵蚀性能;孔径大于14 nm(临界孔径)的孔隙含量降低(由0.0287 mL/g降低到0.0156 mL/g),从而提高了混凝土的抗冻性能;此外,掺入n-C-S-H-PCE后,混凝土孔隙率降低,且随着矿粉掺量的增加,铝酸钙相和Ca2+的浓度降低,混凝土抗硫酸盐侵蚀能力提高。该研究为免蒸养、低收缩、高耐久、高强混凝土制备与应用提供了理论依据。To solve the initial damage,poor durability,and other problems of concrete caused by steam curing,the nano-hydrated calcium silicate polycarboxylate ether composite(n-C-S-H-PCE)was used to prepare high-strength non-steam-cured concrete.The effects of n-C-S-H-PCE on the compressive strength,hydration rate,pore size distribution,autogenous shrinkage and durability of concrete were studied using hydration heat,low-field nuclear magnetic resonance and other methods.Results show that the crystal nucleus of nano-C-S-H provides nucleation sites for the hydration products of cement,reducing the critical ion concentration K_(sp) of nucleation.And the induction and acceleration periods are advanced significantly.Also,the early compressive strength of concrete is improved considerably.The compressive strength of concrete increases by 64%after 1 day of curing,and the strength of concrete has no regression after 28 days of curing.The addition of the n-C-S-H-PCE refines the pore size of concrete matrix and increases the proportion of gel pores and capillary pores.As a result,the negative capillary pressure increases during the auto-drying process of concrete.Thus,the autogenous shrinkage of concrete increases.However,the most probable pore size of the concrete matrix and the cumulative volume of pores with a diameter of 50-100 nm decrease.This improves the resistance to chloride migration into concrete.The content of pores with a pore diameter larger than 14 nm(the critical pore diameter)decreases(from 0.0287 mL/g to 0.0156 mL/g).As a result,the freeze-thaw resistance of concrete is improved.The addition of n-C-S-H-PCE can reduce the porosity of concrete.In addition,with the increase of slag content,the concentration of calcium aluminate phase and Ca2+decreases.In this way,the resistance to sulfate attack of concrete increases.The results provide a theoretical basis for the preparation of non-steam-cured,low shrinkage,high durability and high-strength concrete.

关 键 词：纳米早强剂 免蒸养混凝土 孔结构 自收缩 耐久性 C-S-H-PCE 

分 类 号：TU377.2[建筑科学—结构工程] TB332[一般工业技术—材料科学与工程]