【作者】 于利刚；

【导师】 余其俊；

【作者基本信息】 华南理工大学 ， 材料学， 2010， 博士

【摘要】 随着汽车工业的发展,产生了大量的废弃橡胶轮胎。废橡胶的处理和资源化再利用引起了众多研究工作者的关注。其中,废橡胶粉在水泥基材料中的应用逐渐成为一个研究热点。该研究一方面可以减少废橡胶在堆积与处理时所产生的环境污染,另一方面,橡胶良好的弹性可以改善水泥基材料的抗冲击、抗冻、抗渗、吸声、保温、隔热等性能。但是,由于废橡胶粉的憎水性,使其与水泥基材料的相容性差,造成强度大幅下降,极大地限制了其应用。本研究通过对废橡胶粉进行杂化改性处理,改善橡胶粉与水泥基材料的相容性,进而减小其对水泥基材料强度等性能的不利影响,拓展掺橡胶粉水泥基材料的应用领域和范围,这对废橡胶的综合利用及特种水泥基材料的开发具有极其重要的意义。采用正硅酸乙酯(TEOS)或硅酸钠为反应前躯体,并引入含亲水基团的有机硅氧烷,通过溶胶-凝胶(sol-gel)法制备了杂化改性胶粉。运用红外光谱(FT-IR)、热重分析(TGA)、固体核磁共振(NMR)29Si谱分析、电子探针显微分析仪(EPMA)、扫描电子显微镜(SEM)等测试方法,对杂化改性胶粉表面结构、亲水性变化等进行了分析与表征。结果表明:通过杂化改性,在胶粉内部生成了Si-O-Si的杂化网络并与胶粉互穿,同时在其表面引入了大量的亲水羟基(-OH),杂化改性胶粉表面的接触角由94°降低至68°,亲水性提高。以掺杂化改性橡胶粉水泥砂浆为研究对象,分析了杂化改性橡胶粉对砂浆强度、弹性模量、干燥收缩、抗冲击、抗渗、吸声和保温隔热等性能的影响。试验结果表明:与目前国内外报道的掺氢氧化钠改性胶粉、偶联剂改性胶粉等砂浆强度相比,杂化改性胶粉砂浆强度提高幅度明显。杂化改性反应前驱体的种类和掺量对掺改性胶粉砂浆的强度影响很大。当TEOS用量为5phr时,制得的杂化改性胶粉TRP掺入水泥砂浆后,砂浆28天抗压、抗折强度分别较对比样提高了51.4%和29.2%;当硅酸钠用量为6phr时,制得的杂化改性胶粉SRP掺入水泥砂浆后,砂浆的28天抗压、抗折强度分别提高了48.8%和17.2%。TEOS是sol-gel法中常用的反应前躯体,但其价格较高,且有一定的毒性;相比而言,硅酸钠也具有很好的改性效果,且价格便宜、安全环保,因此,选用硅酸钠来改性胶粉具有性价比优势,目前未见相关研究报道。对橡胶粉砂浆的性能研究发现,与未加入橡胶粉的砂浆相比,掺9%的SRP砂浆抗冲击性能提高了近7倍;掺7%的SRP砂浆平均吸声系数提高了17%,且导热系数降低了67%;掺0.8%的SRP砂浆抗渗压力提高了40%,而掺2%的SRP砂浆抗渗压力提高了180%。用SRP制得防水型砂浆稠化粉,配制了强度等级为M10、抗渗等级为P10的普通干混防水砂浆,其水泥用量仅为12.8%,砂浆性能完全符合国家标准要求。与常用的防水添加剂相比,添加剂成本可减少50%左右。这进一步说明,SRP可在砂浆中起到提高抗渗性能、增加保水性、提高粘结强度的作用。该研究为杂化改性橡胶粉作为水泥基材料的功能性改性剂的应用奠定了一定的理论和技术基础。XPS分析结果表明,杂化改性胶粉表面的Si-O-Si结构与水泥浆中的钙、硅在水化早期形成了Si-O-Ca结构。通过对橡胶-水泥浆体界面的微观形貌观察和界面粘结力分析发现,该产物与水泥的水化产物发生化学键合,从而使橡胶粉与水泥石紧密地结合在一起,杂化改性橡胶与水泥浆体的界面粘结强度提高了3倍。进一步分析表明,杂化改性胶粉与水泥浆体界面通过化学键结合,阻断了硬化水泥浆体毛细孔,从而提高了渗透压力。论文提出了杂化改性橡胶粉与水泥在各水化阶段的反应示意图,深入地分析了杂化改性橡胶粉对水泥砂浆性能的改善作用及其机理。更多还原

【Abstract】 With the development of automobile industry large amounts of waste rubber tires are produced all around the world. More and more researchers have concerned on the application of crumb rubber powder in cement-based materials. This is of great interest because it can reduce the environment pollution caused by waste rubber. Besides, cement-based materials containing rubber is superior to conventional ones with following advantages, such as lower density, higher toughness and impact resistance, enhanced ductility and better sound insulation and so on. But it is also found a fatal weakness that is a sharp decline in the strength of cement-based materials incorporating rubber powder, because the surface of rubber is hydrophobic and is not compatible with cement-based materials. This greatly limits the application of waste rubber in cement-based materials. Therefore, the modification of rubber powder is one of the key techniques associated with its application in cement-based materials. With improved performance, modified rubber powder may serve as a functional additive of cement-based materials. Thus, it is of prime importance for comprehensive utilization of rubber powder and preparation of functional cement-based materials.In this study, rubber powder (RP) as a cross-linked elastomer was hybrid modified by sol-gel method under swelling condition with reactive precursor tetraethyl orthosilicate (TEOS) or sodium silicate, respectively, and also inducting organic siloxane with hydrophilic groups. Then the hydrolysis and condensation reactions took place in situ and the hybrid modified rubber powder TRP (modified with TEOS) and SRP (modified with sodium silicate) were produced. The structures of the obtained products were investigated with Fourier Transform Infrared Spectroscopy (FTIR), Thermalgravimetric Anylsis (TGA), Nuclear Magnetic Resonance (NMR) of 29Si, Electron Probe Microanalysis (EPMA), Scaning Electron Microscope (SEM) and so on. The results show that Si-O-Si hybrid network has interpenetrated through the network of RP and a lot of hydrophilic groups–OH have also inducted onto the surface of RP at the same time. Contact angle of water on the surface of modified rubber powder is decreased by 26o (from initial 94o to 68o). The surface of RP has been turned from hydrophobic to hydrophilic. Cement mortar specimens with hybrid modified rubber powder addition were prepared and cured to definite ages, thereafter their strength, elastic modulus, shrinkage, impact toughness, impermeability, sound absorption and thermal insulation properties were tested. Compared to the mortars with RP, NaOH modified rubber powder (HRP) and coupling agent modified rubber powder (CRP), the mortar with hybrid modified rubber powder has the highest compressive and flexural strength. It is found that the type and content of precursor of hybrid modified rubber powder have greatly effect on the strength of cement mortar. When TEOS addition is 5phr, the 28day compressive and flexural strength of TRP-cement mortar is increased by 51.5% and 29.0% respectively, compared with that of RP-mortar. On the same way, the 28day compressive and flexural strength of SRP-cement mortar is enhanced by 48.8% and 17.2% respectively with 6phr sodium silicate. In comparison to TEOS, sodium silicate is cheaper, more safety and environment friendly. So in this study researches were mainly performed on cement mortars with SRP addition in the subsequent experiments.In addition, the results show the anti-impact performance of SRP-cement mortar with 9% SRP addition is increased by 7times, while the average sound absorption coefficient of SRP-cement mortar with 7% SRP addition is improved by 17%, at the same time, its thermal conductivity is decreased by 67%. Furthermore, compared with the reference specimens the anti-permeability pressure of the mortar with 0.8% SRP addition is increased by 40% and that of mortar with 2% SRP addition is improved by 180%.It is expected that the hybrid modified rubber powder can be used as a new additive in the production of functional cement-based materials. Using SRP one kind of thickening powder applied for making waterproof mortar was prepared, with it and only 12.8% cement addition, dry-mixed waterproof mortar with strength grade of M10 and impermeability level of P10 was prepared. Compared to using common waterproof additive, production cost of the dry-mixed waterproof mortar is reduced by about 50%. This shows SRP can also find its application in the production of dry-mixed waterproof mortar by increasing impermeability, water retention and adhesive strength and reducing production cost as well.The result shows that the interfacial adhesive strength between SRP and cement mortar is increased by 3 times in comparison to that of reference specimens. Morpological observations confirm that the hydration product between SPR and cement mortar is C-S-H gel, thus, interpenetrating networks structure of C-S-H gels is formed, leading to improvement of interfacial adhesive strength. The results of XPS indicate that the O-Si-OH group on SRP’s surface can react with Ca and Si in hydrating cement paste and generate Si-O-Si and Si-O-Ca group, which makes the rubber powder and the cement paste combine closely together by chemical bonds. To sum up, SRP itself and the bond between SRP and cement paste block the capillary pores of hardened cement paste so as to improve impermeability of cement mortar. As a result, it has been originally put forwarded that the reaction model of hybrid modified rubber powder with hydrating cement during different hydration stages, and the effect and mechanism of SRP on cement mortar performance.更多还原