本文選題：高強(qiáng)混凝土 + 高吸水性樹脂�。� 參考：《清華大學(xué)》2013年碩士論文

【摘要】：混凝土的收縮開裂嚴(yán)重危害了結(jié)構(gòu)物的安全性和耐久性。對高強(qiáng)混凝土（HSC）來說，早期的濕度收縮（包括自收縮和干燥收縮）是造成其開裂的主要原因。利用高吸水性樹脂（SAP）內(nèi)養(yǎng)護(hù)的方法可以有效減小HSC的濕度變形，對HSC的早期防裂有很好的效果。但是，SAP的減縮機(jī)理至今尚未完全揭示。 本文全面研究了摻入SAP對水泥水化、水泥石微觀結(jié)構(gòu)及混凝土力學(xué)性能等的影響規(guī)律，重點(diǎn)研究了摻入SAP后HSC早期自收縮和干燥收縮的減縮效果。結(jié)果表明：有效水灰比相同時，加入預(yù)吸水SAP可以明顯減小HSC的早期自收縮和干燥條件下的總收縮，適宜摻量下14d的自收縮減縮率可達(dá)90%以上，，干燥條件下總收縮可減少75%；SAP一定程度上延緩了HSC的早期水化放熱，但提高其28天水化度；改變水泥石的孔隙分布，使其大孔和小毛細(xì)孔含量提高，中間孔含量降低；延后相對濕度從100%下降的時間，使同齡期混凝土內(nèi)部濕度大幅升高；SAP對混凝土的強(qiáng)度有不利作用，但對后期強(qiáng)度的影響要小于早期。與簡單增加拌合水量相比，加入預(yù)吸水SAP對HSC水化進(jìn)程、孔隙結(jié)構(gòu)、力學(xué)性能、收縮變形等各項(xiàng)性能的影響都有很大的差異，這些差異與自由拌合水與內(nèi)養(yǎng)護(hù)水在混凝土中不同的空間分布狀態(tài)有關(guān)。 根據(jù)所獲的實(shí)驗(yàn)結(jié)論并結(jié)合已有的自身-干燥收縮一體化計算模型對SAP的減縮機(jī)理進(jìn)行了討論。模型計算結(jié)果表明，該模型很好地適用于HSC早期濕度變形的擬合和預(yù)測；相同齡期時遠(yuǎn)高于空白混凝土的內(nèi)部濕度是摻有SAP高強(qiáng)混凝土大幅減縮的主要原因之一；SAP會大幅減小相對濕度維持在100%階段內(nèi)化學(xué)減縮轉(zhuǎn)化為宏觀變形的比率，這對減縮也有重要的貢獻(xiàn)。 根據(jù)模型擬合的結(jié)果對混凝土早期總變形進(jìn)行了分離，獲得了混凝土早期的自膨脹曲線。結(jié)果表明，采用冀東水泥制得的混凝土，在開始變形測試后不久都出現(xiàn)了明顯的膨脹現(xiàn)象；增大水灰比及摻入預(yù)吸水SAP都可以顯著提高混凝土的早期膨脹量；混凝土化學(xué)外加劑（減水劑、緩凝劑等）通過影響混凝土工作性、水泥水化進(jìn)程、凝結(jié)時間及力學(xué)性能發(fā)展等因素，對混凝土早期變形性能造成重要影響；水泥種類及組成對混凝土的早期膨脹變形有決定性的影響；大體積的Ca(OH)2和鈣礬石晶體在水化早期大量生成是引起混凝土早期膨脹變形的主要原因，高堿含量下生成的C-K-S-H凝膠也是早期膨脹的來源之一。
[Abstract]:Shrinkage and cracking of concrete seriously harm the safety and durability of structures. For high strength concrete (HSC), early moisture shrinkage (including autogenous shrinkage and drying shrinkage) is the main cause of its cracking. The method of using high water absorbent resin (SAP) can effectively reduce the moisture deformation of HSC and prevent early cracking of HSC. Good results. However, the mechanism of SAP reduction has not yet been fully revealed.
The effects of SAP on cement hydration, microstructure of cement stone and mechanical properties of concrete are studied in this paper, and the shrinkage effect of autogenous shrinkage and drying shrinkage in early HSC after adding SAP is studied. The results show that the effective water cement ratio is at the same time, and the early self shrinkage and drying conditions of HSC can be obviously reduced by adding the pre absorbent SAP. Under the total shrinkage, the autogenous shrinkage and reduction rate of 14d can be over 90%, and the total shrinkage can be reduced by 75% under dry conditions; SAP to a certain extent postpones the early hydration heat of HSC, but improves the hydration degree of 28 days; it changes the pore distribution of the cement stone, increases the content of the pores and small capillary holes, and reduces the content of the middle hole; and the delayed relative content is reduced. The humidity of the concrete in the same age is greatly increased from 100% to 100%, and the strength of concrete has a negative effect on the strength of concrete, but the effect on the later strength is less than that in the early stage. Compared with the simple adding amount of water, the effects of adding pre absorbent SAP on the properties of HSC hydration process, pore structure, mechanical properties, shrinkage deformation and other properties are all affected. These differences are related to the different spatial distribution of free mixed water and internal curing water in concrete.
Based on the experimental conclusions obtained and combined with the existing self drying shrinkage calculation model, the shrinkage mechanism of SAP is discussed. The model calculation results show that the model is well suited to the fitting and prediction of the early humidity deformation of HSC, and the internal humidity of the same age is far higher than that of the blank coagulant soil with SAP high strength concrete. One of the main reasons for a large reduction is that SAP will significantly reduce the ratio of chemical shrinkage to macro deformation in the 100% stage of relative humidity, which also contributes greatly to the reduction.
According to the results of the model fitting, the early total concrete deformation was separated and the early self expansion curve of concrete was obtained. The results show that the concrete produced by Jidong Cement has obvious expansion phenomenon after the initial deformation test, and the concrete can be significantly increased by increasing the water cement ratio and adding the pre absorbent SAP. Early expansion of concrete, concrete chemical admixtures (water reducer, retarder and so on) have an important influence on the early deformation performance of concrete by influencing the workability of concrete, the process of cement hydration, the setting time and the development of mechanical properties, and the cement type and composition have a decisive influence on the early expansion and deformation of concrete; large volume of concrete. The formation of Ca (OH) 2 and Ettringite crystals at the early stage of hydration is the main cause of the early expansion and deformation of concrete. The C-K-S-H gel formed under high alkali content is also one of the sources of early expansion.

【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2013
【分類號】：TU528.31

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