本文選題：白炭黑　切入點(diǎn)：聚羧酸減水劑　出處：《西南科技大學(xué)》2017年碩士論文

【摘要】：減水劑是一種在維持混凝土坍落度不變的條件下,能減少拌合用水量的混凝土外加劑。其加入混凝土拌合物后對水泥顆粒有分散作用,減少單位用水量,改善混凝土拌合物的流動(dòng)性或減少單位水泥用量。隨著人們對工程質(zhì)量要求的不斷提高,減水劑已經(jīng)成為現(xiàn)代水泥基工程材料不可或缺的"第五組分"。聚羧酸減水劑(PC)因其摻量低、減水率高而受到建筑工程界的高度認(rèn)可,并已經(jīng)實(shí)現(xiàn)大規(guī)模的生產(chǎn)和工程應(yīng)用。盡管如此,PC的減水(分散)作用主要是靠堿性條件下水解出帶負(fù)電荷的PC分子與帶正電荷的水泥顆粒表面的物理吸附,這種物理吸附在高硫酸根、提高溫度和帶負(fù)電荷的硅酸根環(huán)境下作用較弱,這也使其應(yīng)用普適性和穩(wěn)定性受到限制;此外,PC的加入也會(huì)抑制水泥早期水化,對水泥基材料早期強(qiáng)度發(fā)展不利。近年來,納米技術(shù)的快速發(fā)展同樣引起了水泥基工程界的廣泛興趣,在較低的摻量范圍內(nèi),納米粒子可有效改善水泥基材料的工作性、力學(xué)性能和耐久性。特別是納米級Si02,其表面具有大量活性硅羥基,可與其他材料表面的羥基發(fā)生縮聚反應(yīng);更重要的是,納米級SiO2還具有誘導(dǎo)水泥水化和超級火山灰活性效應(yīng)。然而,納米粒子常以團(tuán)聚體形式存在,難于在水泥基材料中均勻分散,需要與減水劑預(yù)先混合解聚。目前,聚羧酸減水劑性能提升和納米粒子有效作用發(fā)揮同時(shí)成為水泥基工程材料領(lǐng)域需要重點(diǎn)解決的問題�；诎滋亢�(納米級Si02)的表面高活性硅羥基特性,其可能與PC分子鏈的羥基官能團(tuán)發(fā)生縮聚反應(yīng),從而將納米SiO2負(fù)載于PC分子鏈上(或?qū)C吸附于納米SiO2表面),一方面提高PC的吸附性能,從而改善PC減水性和適應(yīng)性;另一方面,能夠有效實(shí)現(xiàn)納米粒子的均勻分散,充分發(fā)揮其誘導(dǎo)水泥水化和超級火山灰活性效應(yīng)。因此,本課題提出利用白炭黑與PC進(jìn)行相互改性,并將其應(yīng)用于水泥凈漿和砂漿的制備,一方面保留PC的高效減水效應(yīng),提高水泥基材的工作性能;另一方面將白炭黑以較為均勻的方式引入到水泥基材料中,提高其物理力學(xué)性能。研究結(jié)果表明:相比于未改性PC,在一定條件下得到的白炭黑與PC改性產(chǎn)物,可以有效改善水泥凈漿和砂漿工作性和力學(xué)性能。
[Abstract]:Water reducing agent is a kind of concrete admixture which can reduce the water consumption of concrete under the condition of keeping the slump of concrete constant. Improving the fluidity of concrete mixtures or reducing the amount of cement per unit. Water reducer has become an indispensable "fifth component" of modern cement based engineering materials. Polycarboxylic acid water reducing agent (PCP) has been highly recognized by the construction engineering because of its low content and high water reducing rate. However, the water-reducing (dispersion) effect of PC mainly depends on the physical adsorption of negatively charged PC molecules to the surface of positively charged cement particles under alkaline conditions. The effect of this physical adsorption on high sulphate, increasing temperature and negative charge silicates is weak, which limits its applicability and stability. In addition, the addition of PC also inhibits the early hydration of cement. In recent years, the rapid development of nanotechnology has also aroused wide interest in cement based engineering, and in the range of low content, nanoparticles can effectively improve the workability of cement-based materials. Mechanical properties and durability. In particular, nanoscale Si02, which has a large number of active silica hydroxyl groups, can be polymerized with hydroxyl groups on the surfaces of other materials and, more importantly, Nano-scale SiO2 also has the effect of inducing cement hydration and super pozzolanic activity. However, nanoparticles often exist in the form of aggregates, which are difficult to disperse uniformly in cement-based materials and need to be pre-mixed and depolymerized with water reducers. The improvement of properties of polycarboxylic acid superplasticizer and the effective action of nanoparticles have become important problems in cement based engineering materials field. It may react with the hydroxyl functional group of PC molecular chain, and then load the nanometer SiO2 onto the PC molecular chain (or adsorb PC on the surface of nanometer SiO2). On the one hand, the adsorption property of PC can be improved, and the water reducing ability and adaptability of PC can be improved. On the other hand, it can effectively realize the homogeneous dispersion of nano-particles and give full play to the effect of inducing cement hydration and super pozzolanic activity. Therefore, this paper proposes to use silica and PC to modify each other. It is applied to the preparation of cement mortar and mortar. On the one hand, the high efficiency water reducing effect of PC is retained to improve the working performance of cement substrate; on the other hand, silica is introduced into cement based materials in a more uniform way. The results show that compared with the unmodified PCs, the modified products of silica and PC under certain conditions can effectively improve the workability and mechanical properties of cement mortar and mortar.
【學(xué)位授予單位】：西南科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU528

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