【作者】 徐超；

【导师】 李好新；

【作者基本信息】 同济大学 ， 材料科学与工程， 2023， 博士

【摘要】 全球气候变暖是本世纪人类面临的最大挑战,加快混凝土强度发展提升施工效率、降低成本是建筑工业低碳化的重要途径。有别于其它促进水化并加快强度发展的物质,水化硅酸钙（C-S-H）纳米颗粒因其可加速硅酸盐（占水泥质量75%左右）水化,促进早期强度发展,且不影响后期强度,而受到广泛关注。同时,水泥中还存在铝酸盐等其它矿物相,且为了改善水泥混凝土防水性能、韧性等,其它外加剂常用于水泥基材料中。然而,当前有关C-S-Hs-PCE与其它外加剂在硅酸盐水泥体系中的相互作用规律与机理尚不清楚。因此,开展C-S-Hs-PCE耦合典型外加剂对水泥水化/反应促进行为及其机理的研究具有十分重要的意义。针对单组份外加剂的局限性,本文系统研究了C-S-Hs-PCE耦合典型外加剂对水泥水化/反应促进行为及其机理,取得三个方面的创新结果:（1）分析了C-S-Hs-PCE的物理和水化特性,厘清了其促进硅酸三钙（C₃S）/铝酸三钙（C₃A）水化的微观机理;（2）探讨了C-S-Hs-PCE与不同种类、掺量的典型外加剂复合使用对硅酸盐水泥性能的影响规律与机理,发展了改善水泥基材料性能的系列方法;（3）探索了C-S-Hs-PCE激发矿粉和粉煤灰活性的可能性,为提高其活性提供了潜在思路。取得的主要研究结果如下:一、C-S-Hs-PCE的物理特性与水化加速特性典型C-S-Hs-PCE平均粒径小于50 nm,呈箔/褶皱状;2%C-S-Hs-PCE可显著促进C₃S与C₃A水化,12 h龄期C₃S水化产物可增加88%,C₃A水化效率可提高33%;水化促进作用与C-S-Hs-PCE的成核和核生长作用相关;水化产物沉淀具有取向特征。二、C-S-Hs-PCE耦合典型外加剂对水泥水化/反应促进行为及其机理1.C-S-Hs-PCE不仅可促进掺有Ca Cl₂、Na₂SO₄、TEA、TIPA、Al₂（SO₄）₃、硬脂酸钙（CS）等具早强、速凝、防水等功能水泥浆体的凝结,还可显著改善掺有硅烷粉和EVA-DP具缓凝作用浆体的凝结行为;C-S-Hs-PCE与Ca Cl₂、TEA、Al₂（SO₄）₃复合可将凝结时间缩短100 min以上,其中与Ca Cl₂复合可将初凝时间降低至15 min;与Al₂（SO₄）₃复合浆体具有最短凝结时间,可将初凝、终凝分别缩短至6与12 min;即使将其引入10%EVA-DP掺量的浆体中,仍可将初凝时间缩短11 min。2.C-S-Hs-PCE与Ca Cl₂、Na₂SO₄、TEA、TIPA、Al₂（SO₄）₃、硅烷粉、EVA-DP复合可改善硬化浆体的物理性能,提高早期强度,增加凝胶微孔体积,减少大毛细孔体积;与Al₂（SO₄）₃复合不仅可将6 h强度提升182%,还可提高13%的28 d强度;与TIPA复合可增加159%的12 h强度,小于100 nm的总孔隙率从0.135 ml/g降低至0.099 ml/g;与0.02%TEA共同使用可将1 d强度从11 MPa提高至19 MPa;与Na₂SO₄复合可将3 d强度提升57%;即使引入10%EVA-DP掺量的浆体中,仍可提升32%的3 d强度。3.C-S-Hs-PCE与Ca Cl₂、Na₂SO₄、TEA、TIPA、Al₂（SO₄）₃、硅烷粉、CS、EVA-DP复合可改变水泥水化历程,表现为水化速率的提高与水化阶段的提早;不仅可显著促进掺有Ca Cl₂、Na₂SO₄、TEA、TIPA、Al₂（SO₄）₃、CS水泥浆体的水化,且可改善掺有硅烷粉、EVA-DP浆体的水化行为;与Al₂（SO₄）₃复合可将加速期最大放热速率提升43%,相界相互作用控制的过程消失;与Ca Cl₂复合可将诱导期最低放热速率从1.02 m W/g提高至3.76 m W/g;与TIPA复合可将7d的化学收缩增大33%。这些变化主要原因:水化过程中物相溶解与产物沉淀的共促进作用。4.C-S-Hs-PCE与Ca Cl₂、Na₂SO₄、TEA、TIPA、Al₂（SO₄）₃、CS、硅烷粉、EVA-DP复合可提高水泥组成矿物反应效率、增加水化产物;与Ca Cl₂复合可促进Friedel’s盐形成,快速化学固化水泥基材料中的内源Cl^-;与TIPA复合1 d水泥硬化浆体中的CH相对含量可提高21%,仍可保证C₄AF的持续水化;与0.02%TEA复合可将1 d硬化浆体中的CH相对含量增加16%;建立了C-S-Hs-PCE与Ca Cl₂、Na₂SO₄、TEA、TIPA、Al₂（SO₄）₃、CS、硅烷粉、EVA-DP复合的反应模型,关联了凝结行为、强度与孔结构、水化反应等间的相互作用。三、C-S-Hs-PCE对辅助胶凝材料活性激发的探索C-S-Hs-PCE可显著提高水泥-矿粉砂浆的1 d、3 d、7 d、28 d强度与矿粉的反应程度;2%的C-S-Hs-PCE使其反应程度分别增加134%、94%、200%和46.1%;C-S-Hs-PCE在水泥-矿粉体系仍具有显著的成核效应,可显著促进CH形成,同时可为矿粉的反应提供碱性环境,并通过自身的成核效应加速矿粉的火山灰反应,为矿粉反应活性与力学性能提供物质基础;但对水泥-粉煤灰体系反应活性与力学性能的提升收效甚微。更多还原

【Abstract】 Global climate warming is the greatest challenge facing humanity in this century.Accelerating the development of concrete strength to enhance construction efficiency and reduce costs is a crucial pathway towards achieving low-carbon transformation in the construction industry.Differing from other substances that promote hydration and accelerate strength development,hydrated calcium silicate（C-S-H）nanoparticles have received widespread attention due to their ability to accelerate the hydration of silicates（accounting for about 75%of cement mass）,promote early strength development,and do not affect later strength.Meanwhile,other mineral phases like aluminates exist within cement.Additionally,other additives are commonly used in cement-based materials to enhance properties such as waterproofing and toughness.However,the interaction rules and mechanisms between C-S-Hs-PCE and other admixtures in Portland cement systems are currently unclear.Therefore,it is of great significance to conduct research on the promoting behavior and mechanism of C-S-Hs-PCE coupled typical admixtures on cement hydration/reaction.Considering the limitations of single component admixtures,this article systematically investigated the promoting behavior and mechanism of C-S-Hs-PCE coupled typical admixtures on cement hydration/reaction,and achieved three innovative results:（1）Analyzed the physical and hydration characteristics of C-S-Hs-PCE,and clarified its micro mechanism of promoting tricalcium silicate（C₃S）/tricalcium aluminate（C₃A）hydration;（2）Explored the influence and mechanism of the composite use of C-S-Hs-PCE with different types and dosages of typical admixtures on the performance of Portland cement,and developed a series of methods to improve the performance of cement-based materials;（3）Investigated the possibility of C-S-Hs-PCE stimulating the activity of mineral powder and fly ash,providing potential ideas for improving their activity.The main research results obtained are as follows:1.Physical and hydration acceleration characteristics of C-S-Hs-PCEThe average particle size of typical C-S-Hs-PCE is less than 50 nm,appearing in a foil/fold shape;2%C-S-Hs-PCE can significantly promote the hydration of C₃S and C₃A,with an increase of 88%in C₃S hydration products and a 33%improvement in C₃A hydration efficiency at the age of 12 h;The hydration promoting effect is related to the nucleation and growth of C-S-Hs-PCE;The precipitation of hydration products exhibits orientation characteristics.2.Promoting behavior and mechanism of C-S-Hs-PCE coupled typical admixtures on cement hydration/reaction（1）C-S-Hs-PCE can not only promote the setting of cement pastes mixed with Ca Cl₂,Na₂SO_4,TEA,TIPA,Al₂（SO₄）₃,calcium stearate（CS）with early strength,rapid setting,waterproof and other functions,but also significantly improve the setting behavior of pastes mixed with silane powder and EVA-DP with retarding effect.The combination of C-S-Hs-PCE with Ca Cl₂,TEA,Al₂（SO₄）₃ can shorten the setting time by more than 100 min,and the combination with Ca Cl₂ can reduce the initial setting time to 15 min;The pastes composed of C-S-Hs-PCE and Al₂（SO₄）₃display the shortest setting time,which can shorten the initial and final setting to 6and 12 minutes,respectively;Even if it is introduced into the pastes with 10%EVA DP,the initial setting time can still be shortened by 11 min.（2）The combination of C-S-Hs-PCE with Ca Cl₂,Na₂SO₄,TEA,TIPA,Al₂（SO₄）₃,silane powder and EVA-DP can improve the physical properties of hardened pastes,enhance the early strength,increase the micropore volume of gel,and reduce the volume of large capillary pores;Composite with Al₂（SO₄）₃ not only increases the 6 h strength by 182%,but also increases the 28 d strength by 13%;Composite with TIPA can increase the 12 h strength by 159%,and the total porosity below 100 nm decreases from 0.135 ml/g to 0.099 ml/g;When used together with 0.02%TEA,the 1d strength can be increased from 11 MPa to 19 MPa;Composite with Na₂SO₄ can increase the 3 d strength by 57%;Even with the introduction of 10%EVA DP content in the pastes,it can still improve the 3 d strength by 32%.（3）The combination of C-S-Hs-PCE with Ca Cl₂,Na₂SO₄,TEA,TIPA,Al₂（SO₄）₃,silane powder,CS,and EVA-DP can alter the hydration process of cement,manifested by an increase in hydration rate and an earlier hydration stage;Not only significantly promote the hydration of cement pastes containing Ca Cl₂,Na₂SO₄,TEA,TIPA,Al₂（SO₄）₃,CS,but also improve the hydration behavior of pastes with silane powder and EVA-DP;Combining with Al₂（SO₄）₃ can increase the maximum heat release rate during the acceleration period by 43%,and the phase boundary interaction controlled process disappears;Combining with Ca Cl₂ can increase the minimum heat release rate during the induction period from 1.02 m W/g to 3.76 m W/g;Combining with TIPA can increase the chemical shrinkage of 7 d by 33%.The main reason for these changes is the co-promotion effect of phase dissolution and product precipitation during the hydration process.（4）The combination of C-S-Hs-PCE with Ca Cl₂,Na₂SO₄,TEA,TIPA,Al₂（SO₄）₃,CS,silane powder,and EVA-DP can improve the mineral reaction efficiency of cement composition and increase hydration products;Composite with Ca Cl₂ can promote the formation of Friedel’s salts and quickly chemically solidify endogenous Cl^-in cementitious materials;The relative content of CH in the 1 d hardened cement pastes compounded with TIPA can be increased by 21%,which can still ensure the continuous hydration of C₄AF;Composite with 0.02%TEA can increase the relative content of CH in 1 d hardened pastes by 16%;A reaction model was established for the composite reaction of C-S-Hs-PCE with Ca Cl₂,Na₂SO₄,TEA,TIPA,Al₂（SO₄）₃,CS,silane powder,EVA-DP,and the interactions between setting behavior,strength and pore structure,hydration reaction were correlated.3.Exploration of C-S-Hs-PCE for activation of supplementary cementitious materialsC-S-Hs-PCE can significantly improve the 1 d,3 d,7 d,and 28 d strength of cement-mineral powder mortar and the reaction degree of mineral powder;2%C-S-Hs-PCE increases the reaction degree by 134%,94%,200%,and 46.1%,respectively;C-S-Hs-PCE still displays a significant nucleation effect in the cement-mineral powder system,which can significantly promote the formation of CH,provide an alkaline environment for the reaction of mineral powder,and accelerate the pozzolanic reaction of mineral powder through its nucleation effect,providing a material basis for the reaction activity and mechanical properties of mineral powder;However,it exhibits little effect on improving the reactivity and mechanical properties of the cement-fly ash system.更多还原