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1、南京航空航天大学 硕士学位论文 新型生态混凝土膨胀剂的制备及性能表征 姓名:骆菁菁 申请学位级别:硕士 专业:道路与铁道工程 指导教师:高培伟 2011-03 南京航空航天大学硕士学位论文 i 摘 要 本研究以工业尾矿为原料,经矿物组成设计、配料计算、粉磨和适宜的煅烧工艺,制备膨 胀剂。首先通过分析精矿与尾矿之间的成份探讨利用尾矿制备膨胀剂的可行性;其次通过确定 菱镁矿尾矿和白云石尾矿的比例制备具有早期膨胀、 又具有后期膨胀的新型生态混凝土膨胀剂, 以补偿不同类型混凝土结构中的收缩;最后采用 TG-DSC、SEM、XRD 及液相电导率法等测试 方法来表征新型膨胀剂性能,并针对水泥净浆、砂浆和混
2、凝土三种不同的基体,研究膨胀剂煅 烧制度、品种、掺量、掺合料和养护条件等因素对掺膨胀剂试体力学性能及变形性能的影响。 研究结果如下: (1)根据 XRD 及原材料化学成分分析得知,预处理后的尾矿成份含量接近尾矿,利用尾 矿制备新型生态混凝土膨胀剂是可行的。 (2)生料经 T1 煅烧、保温 90 min 以后,分解完全;经 T2煅烧、保温 60 min 以后, 分解完全,已无菱镁矿存在。在保证菱镁矿尾矿分解的前提下,随煅烧温度的升高和保温时间 的延长,轻烧氧化镁的活性降低。MgO 颗粒细度越小,MgO 的活性越好。根据差热图谱分析, 并考虑到工业化生产的需要以及煅烧设备的热量损失,确定最低煅烧温
3、度为 T1。 (3)随着膨胀剂掺量的增加,砂浆强度逐渐增加,比未掺膨胀剂水泥胶砂基体在 28d 强度 提高了 2%-15%。 (4) 与A膨胀剂相比, 掺膨胀剂B和F的水泥净浆和砂浆自由膨胀率能达到前者的8090% 左右。掺加煅烧温度在 T1T2之间膨胀剂的水泥净浆和砂浆早期膨胀快,后期膨胀趋缓; 掺煅烧温度 T3膨胀剂的水泥净浆和砂浆早期膨胀缓慢,后期膨胀相对加快。膨胀率随着膨胀 剂掺量的增大而增大;随着养护温度的升高而加快。粉煤灰可以有效地抑制 CaO 和 MgO 的膨 胀。CaO 水化快,膨胀主要发生在早期;MgO 水化,膨胀主要发生在后期。可根据实际需求选 取合适配比的膨胀剂。 关键词
4、:关键词:混凝土膨胀剂;尾矿;生态;氧化镁;氧化钙;制备;双膨胀 新型生态混凝土膨胀剂的制备及性能表征 ii ABSTRACT The tailings were used to produce expansion agents by mineral composition design, ingredients calculation, grinding and appropriate calcining process in this paper. Disscuss the feasibility of using tailings to prepare expansion materia
5、l by analysising composition of concentrates and tailings firstly, and prepare the novel ecological expansion agents with early expansive behaviour and delayed expansive behaviour to compensate the shrinkage of different kinds of concrete structures by determine the proportion of magenisit tailings
6、and dolomite taiings, TG-DSC, SEM, XRD and the liquid conductivity method were applied to measure performance of the novel ecological expansion agents lastly. The influence of calcining system of expansion agents, variety, dosage, admixture, and curing condition on mechanical properties and deformat
7、ion properties of paste, mortar and concrete was researched. The experimental results are shown following: 1 According to XRD and chemical analysis of raw materials, tailings after pretreatment and concentrates were close in content, Which proved that it was feasible to use tailings to produce the n
8、ovle eclogical expansion material. 2 Magnesite completely was decomposed respectively calcined at T1 under 90 min holding time, T2 under 60 min holding tim. Based on the complete decomposition fo Magnesite tailings, the higher the calcinations temperature, the longer the holding time, the worse the
9、activity of MgO. The smaller the particle fineness of MgO it was, the better the activity of MgO. According to TG-DSC and taking into account the needs of industrial production and heat loss of burning equipment, the lowest calcination temperature was T1. 3 With the amount increase of expansion agen
10、ts, the strength increased gradually. Compared with the strength of mortar without any expansion agents, the strength of mortar with expansion agents increased by 2% and 15%. 4 Expansion of paste and mortar added with B and F expansion agents can reach 80%-90% of that with A. The expansive propertie
11、s of expansion agent are greatly affected by many factors. The paste and mortar added with expansion agent calcined between T1 and T2 , expansion at the early stage are faster, and it is slower at the later stage; the paste and mortar added expansion agent calcineda at T3, expansion at the early sta
12、ge are slower, it is faster at later stage. With the amount increase of expansion agent, the expansion increased correspondingly. The higher the curing 南京航空航天大学硕士学位论文 iii temperature it is, the faster the expansion.it is. Fly ash restrains expansion caused by CaO and MgO. Hydration of CaO fasters an
13、d expansion is mainly at early stage while hydration of MgO slows and expansion is mainly at later stage. Key words: concrete expansion agent, tailings, ecology, MgO, CaO, preparation, double expansion 南京航空航天大学硕士学位论文 ix 注释表 LA 水泥净浆试件在龄期 t 时的自由变形; LB 水泥砂浆试件在龄期 t 时的自由变形; LC 水泥砂浆试件在龄期 t 时的限制变形; Lt 试件在龄
14、期 t 时的长度; L0 试件脱模后的初始长度; St 水泥砂浆试件在龄期 t 时的干缩变形; Ht 混凝土试件在龄期 t 时的自由变形; P(t) 砂浆变形。 承诺书 本人郑重声明:所呈交的学位论文,是本人在导师指导下,独立进 行研究工作所取得的成果。尽我所知,除文中已经注明引用的内容外, 本学位论文的研究成果不包含任何他人享有著作权的内容。 对本论文所 涉及的研究工作做出贡献的其他个人和集体, 均已在文中以明确方式标 明。 本人授权南京航空航天大学可以有权保留送交论文的复印件, 允许 论文被查阅和借阅,可以将学位论文的全部或部分内容编入有关数据库 进行检索,可以采用影印、缩印或其他复制手段
15、保存论文。 (保密的学位论文在解密后适用本承诺书) 作者签名: 日 期: 南京航空航天大学硕士学位论文 1 第一章 绪论 1.1 研究背景和意义 1.1.1 大体积混凝土裂缝的形成及危害 随着国民经济发展,我国公路建设正在以前所未有的速度发展。大体积水泥混凝土施工操 作方便、结构强度稳定、施工程序可控制,因此在西部交通、机场跑道和桥梁结构中的应用越 来越广泛。但由于混凝土抗拉能力差,会出现不同形式的裂缝,影响了水泥混凝土的美观、性 能及使用寿命1,2。 混凝土是一种非均质脆性材料,浇筑后,水泥在水化过程中要散发大量的水化热,由于热 量不能快速散发,在表面和内部将引起拉应力,当这些拉应力超出混凝土的极限抗拉强度时, 即会出现裂缝3。例如 1995 年,美国有 10 万座混凝土桥面板载浇注后一个月内就出现了间隔 13m 贯穿性裂缝,修补这些裂缝的费用高达 10 亿美元4。我国某市地铁建成不久混凝土结构 就出现严重开裂5。 抑制大体积混凝土开裂问题已成为目前工程界十分关注的热点和难点问题。 1.1