【作者】 黄凤远；

【导师】 王立久； 马希晨；

【作者基本信息】 大连理工大学 ， 材料学， 2008， 博士

【摘要】 本文在材料过程工程学理论框架内,从可再生资源利用、环境保护等角度出发,选择可再生的天然高分子为主要原材料,通过化学合成制备新型混凝土减水剂/高效减水剂,系统的研究基于天然高分子的混凝土减水剂的合成条件与应用性能。根据分子设计理论,首先采用棉纤维素为原材料,制备水溶性丁基磺酸纤维素醚(SBC),探讨了反应物配比、反应温度、反应时间等因素对产物分子结构的影响。作为对比,探讨了硫酸酯化羟乙基纤维素(SHEC)、微波辐射方法制备淀粉顺丁烯二酸半酯(SMHE)的合成条件及作为减水剂应用的性能。采用傅立叶变换红外光谱、核磁共振光谱、扫描电镜、电感耦合等离子体发射光谱、凝胶渗透色谱等现代分析手段表征了分子结构。为研究减水剂性能,测定了水泥颗粒吸附减水剂后ζ—电位,水泥颗粒对减水剂的吸附特性,减水剂在水泥颗粒表面的吸附层厚度,减水剂对水泥水化的影响以及产物对水泥水化物形貌的影响。减水剂合成的研究结果表明:氢氧化钠与脱水葡萄糖单元及醚化试剂(1,4—丁基磺酸内酯)摩尔比为NaOH:AGU:BS=2.5:1:1.7,最佳反应温度为75℃,醚化反应时间为4.5h。得到的SBC特性粘度为35.3ml/g(粘均分子量约29,000g/mol),丁基磺酸基团取代度达到0.38,1%掺量下水泥净浆流动度可达182mm。分次加碱的方法可将产物的取代度从0.38提高到0.67,数均分子量为6177g/mol,1%掺量净浆流动度270mm以上。在试验范围内,SBC的取代度越高、分子量越低,越有利于减水分散作用的发挥;取代度越小缓凝现象越严重,取代度适中的减水剂不会影响水泥/混凝土水化后期强度的发展,而且表现出良好的流动度保持性,水泥颗粒表面ζ—电位(绝对值)随SBC掺量的提高而明显提高,且在120min内变化较小。因此,不同取代度的SBC可以用作缓凝减水剂、减水剂和高效减水剂。合成的SMHE取代度达0.49,数均分子量为7286g/mol;SHEC取代度达0.49,数均分子量为1978g/mol;二者均可提高水泥净浆流动度,但掺量过高缓凝现象严重,均可用作缓凝减水剂。水泥对SBC的吸附符合Langmuir型等温吸附,其极限吸附量在4.66mg/g～5.49mg/g范围;对SNF(商品萘系高效减水剂)和SMHE的吸附同样符合Langmuir型等温吸附,前者极限吸附量为11.23mg/g,后者的极限吸附量是9.73mg/g。SNF、SBC和SMHE的吸附层厚度分别是0.82nm、3.72nm和6.82nm,SBC约是SNF的4倍,SMHE约是SNF的8.3倍。吸附减水剂后,Ca2p结合能发生不同程度位移,表明SNF、SBC、SMHE等三种减水剂在水泥颗粒上均发生化学吸附。为解释SBC减水作用机理,采用经验公式计算水泥悬浮体系中水泥颗粒受力情况。计算结果表明,水泥颗粒表面吸附SBC形成3.72nm的吸附层后,消弱了水泥颗粒间的范德华引力,在水泥颗粒靠近到吸附层可以相互压缩时,产生的空间位阻作用力远大于静电斥力和范德华引力,对水泥颗粒的分散起主导作用;而吸附层未相互压缩时,水泥颗粒的分散主要依赖于静电斥力作用。因此,SBC减水分散作用是空间位阻作用和静电斥力协同作用的结果。水泥浆中高效减水剂掺量与水泥絮凝颗粒分形维数间有关,当高效减水剂掺加到一定量时,水泥絮凝颗粒分形维数D_f突变,该突变对应的减水剂掺量与净浆流动度法测定的高效减水剂饱和掺量吻合良好,因此将D_f突变对应的减水剂掺量视为饱和掺量,从而建立了以分形维数确定高效减水剂饱和掺量的新方法,该方法与Marsh筒及净浆流动度法相比具有方便、快捷、节约试验材料等优点。在水泥絮凝理论的基础上,研究了掺加减水剂前后水泥净浆絮凝体积的变化规律,提出减水因子概念,它涵盖了减水剂、水泥和混凝土的特性。不同减水剂的减水因子在0～1范围内,且趋于某定值。研究结果表明,不论哪种减水剂,减水因子越大则减水剂的减水分散效果越明显,减水因子与水泥水化以及减水剂与水泥的相容性有一定关系。在相同工作性条件下,混凝土用水量随而减水因子的增大而减小,并且基于减水因子计算的用水量与实际试配用水量非常接近。可见,减水因子对混凝土配合比设计有指导作用,完善了混凝土配合比相关理论。SBC减水率与其分子结构有关,1%掺量下砂浆减水率为11.2%～16.5%,混凝土减水率为9%～19%;掺加SBC8的水泥砂浆抗折强度与抗压强度提高明显。掺加SBC8的混凝土和易性良好,泌水率比小,保水性能优于SNF。为测试SBC8实际应用性能,配制了C40混凝土,其各龄期强度提高明显,干缩率在混凝土性能范围内。说明SBC具有实际应用价值。更多还原

【Abstract】 Within the framework of the theory of Materials Process Engineering, kinds of novel concrete water reducers based on natural polymers were synthesized in present paper from the view of renewable materials and environmental protection. The optium conditions of these products and their properties were investigated systemically.According molecular design theory, cotton cellulose was hydrolysis to get Leveling-Off Degree of Polymerization (LODP) cellulose. After basification with 30% Sodium Hydroxide (NaOH), the LODP cellulose was suspended in Isopropanol aqueous solvent and reacted with 1,4-butanesultone(BS) under certain temperature. Finally, water soluble Sulfobutylated Cellulose ether (SBC) was synthesized. The factors which affected the properties of SBC, such as reactant ratio, reaction temperature, and reaction time, were discussed. Hydroxylethylcellulose sulfate was synthesized via Hydroxylethylcellulose (HEC) and-Chlorosulfonic Acid (CSA).In order to investigate the properties of starch derivatives, starch maleate half ester (SMHE) was obtained by microwave radiation. The molecular structure of these products were characterized with modern analysis methods, such as FT-IR, Nuclear Magnetic Resonance (NMR), Scanning Electronic Microscopy (SEM), Inductively-Coupled Plasma Spectrometer (ICP), and Gel Permeation Chromatography (GPC). The performances of SBC, SMHE and SHEC in cement suspension were investigated. The zeta—potential of cement particles adsorbed water reducers, the adsorbed amount of water reducers and the thickness adsorbed layer of water reducers on cement particles were determined. The hydration properties and the apparent pattern of hydrate were analyzed, also.The optimum conditions for SBC were obtained as followed: n(NaOH):n(AGU):n(BS) is 2.5:1:1.7, reaction temperature is 75℃, and reaction time is 4.5hr. The product had intrinsic viscosity of 35.3ml/g (Viscosity Average Molecular Weight, M_ηwas about 29,000g/mol), the Degree of Substitution (DS) of sulfobutyl group was 0.38, the fluidity of cement paste with 1% of the product reached 182mm. The DS was improved from 0.38 to 0.67 by the method of fractional basification; the number average molecular weight was 6177g/mol. And the fluidity with 1% SBC also improved, reached to 270mm. The DS of SMHE was 0.49, and M_ηwas 7286g/mol; the DS of SHEC was 0.49, and Mn was 1978g/mol. SMHE and SHE also could improve fluidity of cement paste in appropriate dosage with set retarding. In the present experiment, the higher the DS was, and the lower the M_ηwas, the better the fluidity of cement paste with SBC was. The zeta-potential of cement particles with SBC could be improved from +8.9mV to -31mV, and the value changed little in 120min. SBC also could improve the retainable fluidity of cement paste. Langmiur-type adsorption occurred during the process of adsorption of SBC, SMHE and SNF on cement particles. The maximum adsorption capacities of SBCs were from 4.66mg/g to 5.49mg/g, and that of SNF and SMHE was 11.23mg/g and 9.73mg/g, respectively. The adsorbed layer of SNF on cement particles was 0.82nm, that of SBC and SMHE was 3.72nm and 6.82nm, respectively, the former was about 4.5 times of that of SNF, and the latter was about 8.3 times of that of SNF. The results of XPS spectrum of Ca2p indicated that chemical adsorption occurred when SNF, SBC and SMHE was adsorbed on cement particles.In order to discuss the mechanism of SBC, the empirical formulas were applied to calculate the forces between cement particles in cement suspension system. The results indicated that the Van der Waals force was weaken for the formation of 3.72nm SBC layer on cement particles, thus when the adsorbed layers compressed each other, the steric force became stronger than electronic repulsive force and Van der Waals attractive force, and steric force was dominant force under this situation. While the adsorbed layer didn’t contact each other, the electronic static repulsive force could make cement particles dispersed. So we got the mechanism of SBC was synergism of steric force and electronic repulsive force.The saturated point of water reducers in concrete was an important parameter for the application of water reducers, and novel method to determine the parameter was developed in the paper. Firstly, the cement flocculation particle distribution after SPs added was tested; and then, fractal dimensions (Df) were counted; finally, the relationship between Df and dosage of SPs was discussed. The results indicated that the Df was affected greatly by the dosage of SP. When the dosage reaches certain range, a saltation of Df will occur. The dosage range corresponding to the saltation of SPs fitted well with the saturation point measured by cement paste fluidity. Thus the saturation point of SPs can be ascertained via Df. The method has some advantages, such as simple, convenient, and cement and water reducers saving.Based on flocculation theory of cement, the flocculated volumes of cement pastes with or without SPs were investigated, and the water-reducing factor (L) was educed. Ls trended to different constants in range from 0 to 1 for different SPs. The Ls had effect on the hydration of cements and the compatibility between SPs and cements. Water content of concrete decreased accompanying the L increasing, and approximately was equal to real water content in the same workability. The results indicated that L could guide concrete mix design.The water reducing ratio of SBC was affected by the structure of SBC. The ratio of mortar with 1% SBC ranged form 11.2% to 16.5%, and that of concrete ranged from 9% to 19.5%. The bending strength and compressive strength of mortar with SBC8 were improved obviously. The concrete with SBC8 could have good workability, lower bleeding ratio, lower slump loss and good water retention. The applications of SBC8 in C40 concrete indicated that SBCs have potential to be developed as high range water reducer.更多还原