氧化石墨烯對水泥基材料結(jié)構(gòu)與性能的影響
發(fā)布時間：2018-08-09 18:37
【摘要】：混凝土是應用最為廣泛的水泥基復合材料,目前存在抗折強度低、韌性差、易裂縫等主要問題,影響了水泥基復合材料的使用性能和耐久性。針對這一問題,目前主要通過添加纖維增強材料來提高混凝土的整體強度和韌性,但是易裂縫問題依然存在,其原因是裂縫主要產(chǎn)生于混凝土中的硬化水泥石,添加纖維增強材料不能改變混凝土中起黏結(jié)作用的水泥石的結(jié)構(gòu)和性能。前期研究發(fā)現(xiàn)氧化石墨烯(grahene oxide,簡稱GO)的高比表面積以及豐富官能團能夠調(diào)控水泥水化產(chǎn)物形成規(guī)整性晶體,并使水泥石的力學性能特別是抗折強度有顯著的提高,有助于從微觀結(jié)構(gòu)上解決水泥基復合材料的易裂縫問題。研究中也發(fā)現(xiàn)了GO的摻入使得水泥凈漿流動性顯著下降,并且GO在水泥漿體中存在著分散不均勻的問題,因此本論文針對GO摻入水泥基材料中存在的這些問題進行了研究,為GO在水泥基材料中的應用奠定基礎(chǔ)。(1)采用對石墨進行氧化及超聲波分散的方法制備了GO納米片層分散液,并對GO納米片層的含氧量、化學結(jié)構(gòu)和納米尺寸進行了檢測與表征。石墨與氧化劑KMn O4質(zhì)量比為1:6,氧化反應時間為12 h時,GO含氧量可達到31%左右,GO結(jié)構(gòu)中含有羧基-COOH、羥基-OH以及環(huán)氧基-O-等基團;在固體狀態(tài)下GO片層間距由0.35 nm擴大至0.84 nm;分散狀態(tài)的GO納米片層厚度為1.23 nm,片層大小為200 nm至500 nm。(2)系統(tǒng)地研究了GO摻量對水泥凈漿流動度、硬化水泥石力學性能以及硬化水泥石微觀結(jié)構(gòu)的影響。研究結(jié)果表明隨著GO摻量從0.01%增加到0.09%,水泥凈漿流動度依次下降。GO摻量增加至0.03%時,水泥凈漿流動度下降至160 mm以下;GO摻量增加至0.09%時,水泥凈漿處于完全不流動狀態(tài)。GO納米片層分散液對水泥凈漿流動性影響的規(guī)律為GO摻量每增加0.01%時,保持水泥漿體流動度在200 mm以上所需的聚羧酸系減水劑(polycarboxylate superplasticizer,簡稱PCs)摻量按照0.02%的比例增加。GO對水泥石力學性能的影響規(guī)律是隨著GO摻量的增加,硬化水泥石的抗折強度與抗壓強度均呈現(xiàn)先增加后下降的趨勢,其最大抗壓強度和抗折強度出現(xiàn)在GO摻量為0.01%時,在水化齡期為28天時的抗折強度、抗壓強度分別為8.4 MPa和73 MPa。(3)采用分散劑對GO進行了分散并研究了分散劑對GO納米片層分散液分散性的影響。發(fā)現(xiàn)PCs與十二烷基苯磺酸鈉(sodium dodecyl benzene sulfonate,簡稱SDBS)復配分散GO的效果最好且最佳復配分散的固含量比為1:1:1。復合物GO/PCs/SDBS的吸光度值為0.62,均高于GO與PCs直接混合的吸光度(0.56)和GO與SDBS直接混合的吸光度(0.55)。GO/PCs/SDBS摻入水泥漿中可使GO納米片層均勻分散,促使水泥水化產(chǎn)物形成密實規(guī)整的水化晶體,并優(yōu)先出現(xiàn)在水泥石中的孔洞、裂縫、結(jié)構(gòu)疏松等缺陷部分,使水泥石形成了密實的結(jié)構(gòu),GO/PCs/SDBS的摻量從0.01%增加至0.09%,微觀結(jié)構(gòu)中水泥水化產(chǎn)物越密實規(guī)整,并且使硬化水泥石的孔隙率下降、抗壓強度和抗折強度顯著提高,其中最大抗壓強度和抗折強度出現(xiàn)在GO/PCs/SDBS摻量為0.07%時,在水化齡期為28天時的抗折強度、抗壓強度分別為13.5 MPa和79 MPa。(4)提出GO納米片層調(diào)控水泥水化產(chǎn)物的作用機理,GO納米片層主要是通過調(diào)控水泥水化晶體的生長及形狀達到對水泥石微觀結(jié)構(gòu)的控制,最終達到增強增韌水泥基材料的作用。本論文的創(chuàng)新之處在于得到了GO納米片層對于水泥基材料流動性影響的規(guī)律以及制備了GO/PCs/SDBS復合材料,實現(xiàn)了GO納米片層在水泥基材料中的均勻分散。研究結(jié)果對于提高水泥基材料的抗折強度及抵抗裂縫和延長使用壽命具有重要意義。
[Abstract]:Concrete is the most widely used cement based composite material. At present, there are many problems, such as low flexural strength, poor toughness, easy crack and so on. It affects the performance and durability of cement based composites. At present, the strength and toughness of high concrete are raised mainly by adding fiber reinforced material, but it is easy to crack. The reason is that the crack is mainly caused by the hardened cement stone in the concrete. Adding fiber reinforced material can not change the structure and performance of the cement stone in the concrete. The high specific surface area of grahene oxide (GO) and the rich functional groups can regulate the hydration production of cement. The mechanical properties, especially the flexural strength of the cement stone are greatly improved, which helps to solve the fracture problem of cement based composites from the micro structure. It is also found that the mixing of GO makes the cement paste fluidity significantly decrease, and the dispersion of GO in cement paste is not uniform. Therefore, this paper studies the problems existing in the GO doped cement based materials and lays the foundation for the application of GO in the cement-based materials. (1) the GO nanoscale dispersions are prepared by oxidation and ultrasonic dispersion of graphite, and the oxygen content, chemical structure and nano size of the GO nanoscale layer are detected. And characterization. When the mass ratio of graphite and oxidizing agent KMn O4 is 1:6, the oxidation reaction time is 12 h, the oxygen content of GO can reach about 31%. The GO structure contains carboxyl -COOH, hydroxyl -OH and epoxy group -O- groups. In the solid state, the interval between the GO lamellae of GO expands from 0.35 nm to 0.84 nm; the thickness of the dispersed nanoscale layer is 1.23 and the size of the lamellar is 200. Nm to 500 nm. (2) systematically studied the effect of GO content on the flow degree of cement paste, the mechanical properties of hardened cement stone and the microstructure of hardened cement stone. The results showed that with the increase of GO content from 0.01% to 0.09%, the flow degree of cement paste decreased to 0.03%, and the cement paste fluidity decreased to less than 160 mm; GO admixture was added to the cement paste. When the amount of the cement is increased to 0.09%, the effect of the cement paste in the complete non flow state of the.GO nanoscale dispersions on the fluidity of the cement paste is that the Polycarboxylic Water reducing agent (polycarboxylate superplasticizer, abbreviated as PCs) required to maintain the cement slurry flow degree above 200 mm (polycarboxylate superplasticizer, abbreviated as PCs) is added to the cement paste fluidity. The effect of adding.GO on the mechanical properties of cement stone is that with the increase of GO content, the flexural strength and compressive strength of hardened cement show a trend of increasing and then decreasing, and the maximum compressive strength and flexural strength appear at the age of 28 days when the age of hydration is 0.01%, and the compressive strength is 8.4 MPa and 73 MPa., respectively. (3) the dispersing agent was used to disperse GO and to study the effect of dispersant on dispersion of GO nanoscale dispersions. It was found that PCs and twelve alkyl benzene sulfonate (sodium dodecyl benzene sulfonate, for short, SDBS) were best used to disperse GO and the best compound dispersive absorbance value of 1:1:1. compound GO/PCs/SDBS was 0.. 62, the absorbance (0.56) and the absorbance of direct mixture of GO and PCs and the absorbance of GO and SDBS directly mixed with SDBS can make the GO nanoscale evenly dispersed, and promote the cement hydration products to form dense and regular hydrated crystals, and give priority to the holes, cracks and loose structure in the cement stone and make the cement. The stone formed a dense structure, the amount of GO/PCs/SDBS added from 0.01% to 0.09%. The cement hydration products are more dense and regular in the microstructure, and the porosity of the hardened cement stone is reduced, the compressive strength and flexural strength are significantly improved. The maximum compressive strength and flexural strength are now 0.07%, and the age of hydration is 2 at the age of 2. The flexural strength and compressive strength of 8 days are 13.5 MPa and 79 MPa. (4). The mechanism of GO nanoscale regulation of cement hydration products is proposed. The GO nanoscale is mainly controlled by the growth and shape of cement hydration crystals and the effect of reinforced toughening cement-based materials. The innovation is to obtain the regularity of the influence of the GO nano layer on the fluidity of cement based materials and the preparation of GO/PCs/SDBS composites. The uniform dispersion of the GO nanoscale in the cement-based materials is realized. The results are of great significance to improve the flexural strength of the cement-based materials and to resist the crack and prolong the service life.
【學位授予單位】：陜西科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU528
本文編號：2174951
[Abstract]:Concrete is the most widely used cement based composite material. At present, there are many problems, such as low flexural strength, poor toughness, easy crack and so on. It affects the performance and durability of cement based composites. At present, the strength and toughness of high concrete are raised mainly by adding fiber reinforced material, but it is easy to crack. The reason is that the crack is mainly caused by the hardened cement stone in the concrete. Adding fiber reinforced material can not change the structure and performance of the cement stone in the concrete. The high specific surface area of grahene oxide (GO) and the rich functional groups can regulate the hydration production of cement. The mechanical properties, especially the flexural strength of the cement stone are greatly improved, which helps to solve the fracture problem of cement based composites from the micro structure. It is also found that the mixing of GO makes the cement paste fluidity significantly decrease, and the dispersion of GO in cement paste is not uniform. Therefore, this paper studies the problems existing in the GO doped cement based materials and lays the foundation for the application of GO in the cement-based materials. (1) the GO nanoscale dispersions are prepared by oxidation and ultrasonic dispersion of graphite, and the oxygen content, chemical structure and nano size of the GO nanoscale layer are detected. And characterization. When the mass ratio of graphite and oxidizing agent KMn O4 is 1:6, the oxidation reaction time is 12 h, the oxygen content of GO can reach about 31%. The GO structure contains carboxyl -COOH, hydroxyl -OH and epoxy group -O- groups. In the solid state, the interval between the GO lamellae of GO expands from 0.35 nm to 0.84 nm; the thickness of the dispersed nanoscale layer is 1.23 and the size of the lamellar is 200. Nm to 500 nm. (2) systematically studied the effect of GO content on the flow degree of cement paste, the mechanical properties of hardened cement stone and the microstructure of hardened cement stone. The results showed that with the increase of GO content from 0.01% to 0.09%, the flow degree of cement paste decreased to 0.03%, and the cement paste fluidity decreased to less than 160 mm; GO admixture was added to the cement paste. When the amount of the cement is increased to 0.09%, the effect of the cement paste in the complete non flow state of the.GO nanoscale dispersions on the fluidity of the cement paste is that the Polycarboxylic Water reducing agent (polycarboxylate superplasticizer, abbreviated as PCs) required to maintain the cement slurry flow degree above 200 mm (polycarboxylate superplasticizer, abbreviated as PCs) is added to the cement paste fluidity. The effect of adding.GO on the mechanical properties of cement stone is that with the increase of GO content, the flexural strength and compressive strength of hardened cement show a trend of increasing and then decreasing, and the maximum compressive strength and flexural strength appear at the age of 28 days when the age of hydration is 0.01%, and the compressive strength is 8.4 MPa and 73 MPa., respectively. (3) the dispersing agent was used to disperse GO and to study the effect of dispersant on dispersion of GO nanoscale dispersions. It was found that PCs and twelve alkyl benzene sulfonate (sodium dodecyl benzene sulfonate, for short, SDBS) were best used to disperse GO and the best compound dispersive absorbance value of 1:1:1. compound GO/PCs/SDBS was 0.. 62, the absorbance (0.56) and the absorbance of direct mixture of GO and PCs and the absorbance of GO and SDBS directly mixed with SDBS can make the GO nanoscale evenly dispersed, and promote the cement hydration products to form dense and regular hydrated crystals, and give priority to the holes, cracks and loose structure in the cement stone and make the cement. The stone formed a dense structure, the amount of GO/PCs/SDBS added from 0.01% to 0.09%. The cement hydration products are more dense and regular in the microstructure, and the porosity of the hardened cement stone is reduced, the compressive strength and flexural strength are significantly improved. The maximum compressive strength and flexural strength are now 0.07%, and the age of hydration is 2 at the age of 2. The flexural strength and compressive strength of 8 days are 13.5 MPa and 79 MPa. (4). The mechanism of GO nanoscale regulation of cement hydration products is proposed. The GO nanoscale is mainly controlled by the growth and shape of cement hydration crystals and the effect of reinforced toughening cement-based materials. The innovation is to obtain the regularity of the influence of the GO nano layer on the fluidity of cement based materials and the preparation of GO/PCs/SDBS composites. The uniform dispersion of the GO nanoscale in the cement-based materials is realized. The results are of great significance to improve the flexural strength of the cement-based materials and to resist the crack and prolong the service life.
【學位授予單位】：陜西科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU528
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