【作者】 石从黎；

【导师】 王智；

【作者基本信息】 重庆大学 ， 材料科学与工程， 2009， 硕士

【摘要】 淀粉由脱氧葡萄糖单元组成,是自然界中储量最丰富的天然高分子聚合物之一,通过对淀粉结构的化学改性,可以使淀粉具备阴离子表面活性剂的性质,从而开辟天然高分子在水泥基材料中的应用领域,因此,本项研究具有重要的现实意义和广阔的发展前景。本论文从高效减水剂的化学结构、作用机理出发,根据分子结构设计的原理,用玉米淀粉制备出一种以脱氧葡萄糖长链为憎水基,羟基和磺酸基为亲水基的缓凝减水剂(ST),并进行了性能测试。ST的制备过程分两步:第一步,极限糊精的制备,其制备的方法是以玉米淀粉为原料,95%乙醇为分散剂,浓盐酸为催化剂进行水解反应,反应温度为60～70℃,反应时间为8h;第二步,淀粉基缓凝减水剂的制备,即极限糊精的硫酸酯化反应,采用氨基磺酸-甲酰胺酯化体系,其最佳工艺参数为:极限糊精∶N,N-二甲基甲酰胺∶氨基磺酸质量比等于1∶2∶0.5,反应温度90℃,反应时间1h。采用红外光谱、粘均分子量和取代度来表征ST分子结构,采用净浆流动度、凝结时间、减水率及强度等方法研究了ST性能。结果表明,ST的分子结构中有羟基和磺酸基两种阴离子作用基团,粘均分子量在30×104～40×104之间,磺酸基取代度DS为0.32; ST对不同的普通硅酸盐水泥都有很好的适应性,分散效果介于ASP和FDN之间,最大净浆流动度达到260mm,饱和点在0.6~0.8%范围内;ST有一定的缓释效果,能使水泥净浆流动度在30min时有大幅增加,在120min后损失较小,分散性保持能力优于FND和ASP等常用高效减水剂; ST能够使水泥净浆的初凝和终凝时间延长,尤其对终凝时间影响显著,随掺量增加,且终凝与初凝的间隔时间呈增大趋势;ST具有较高的减水率,砂浆和混凝土的减水率都可达到25%以上;ST掺量较高时,对砂浆和混凝土的早期强度有一定影响,但都能显著提高砂浆和混凝土的28d强度。更多还原

【Abstract】 Starch consisted of Anhydroglucose was one of the most abundant natural polymers in nature. The starch had property of anionic surfactants by chemical modification, which unfolded a new applied field for natural polymer-starch. Accordingly, the project shows great significance and broad prosperity.According to the chemical structure and effective mechanism of high-efficiency water-reducing agent, and principles of molecular structure design, a new-type water-reducing retarder ST contained hydrophobic groups of deoxyglucose chain and hydrophilic groups of hydroxy groups and sulphonic groups was prepared by cornstarch, and then the prepared product’s was tested. ST was prepared by two step reaction. Firstly, limit-dextrin was prepared by cornstarch, dispersing agent (ethanol 95%) and catalyst (concentrated hydrochloric acid) at 60~70℃for 8 h. Secondly, Water-reducing retarder based on starch was prepared by sulfating limit-dextrin in sulfamic acid-formamide esterification system. The optimum technological parameters was that the mass ratio of limit-dextrin, N,N-dimethylformamide and sulfamic acid was 1∶2∶0.5, the reaction temperature was 90℃, and the reaction time was 1h.The molecular structure of ST was shown by means of IR, viscosity average molecular weight and degree of substitution. The property of ST was studied by methods of fluidity of cement paste,setting-time, water reducing ratio and strength. Experimental results showed that molecular Structure of ST had two anionic groups which were hydroxy groups and sulphonic groups, viscosity average molecular weight range was 30×104～40×104, and degree of substitution (DS) was 0.32. ST had a good adaptability with various cements. Dispersing property of ST was higher than FDN and lower than ASP. The highest fluidity of cement paste reached 260mm, when the dosage reached saturation point(0.6~0.8%). Because of a little slow-release action, fluidity of cement paste with ST increased obviously after 30min, and fluidity loss was small after 120min. So the dispersing retention property of ST was superior to FDN and ASP. The initial and final setting time of cement were significantly increased by ST. Especially, time interval between initial and final setting gradually increased with dosage increasing. Water reducing ratio of ST was higher, which water reducing ratio both motar and concrete were more than 25%. Although higher dosage had no benefit for early strength of motar and concrete, 28d strength of motar and concrete were increased obviously.更多还原