寒冷地区盐渍溶液环境下天然浮石混凝土耐久性研究

发布时间：2018-06-16 16:38

  本文选题：天然浮石混凝土 + 盐渍溶液　； 参考：《内蒙古农业大学》2015年博士论文

【摘要】：本文充分利用内蒙古地区丰富的浮石资源和工业废料,研究和开发水泥、浮石、砂子、粉煤灰等混合的新型轻质节能寒区材料——天然浮石混凝土。本文选定内蒙古河套灌区为研究区域,灌区用水主要来自黄河,呈碱性,pH值在7.7-8.2之间,主要含有Na+、Mg2+、Ca2+、Cl-、SO42-等侵蚀性介质,盐分随着水流在灌区中积累,必然会对水工建筑物造成严重侵蚀。本文依据内蒙古河套灌区盐渍水分的调查资料和灌区水工建筑物所处的自然环境特点(冬季时间长、昼夜温差大等),配制了五组不同配合比的天然浮石混凝土(LC20、LC25、LC30及两组引气天然浮石混凝土),并设计了四种工况组合：冻融(清水)与盐渍溶液-冻融循环、干湿循环(清水)与盐渍溶液-干湿循环、冻融-干湿(清水)与盐渍溶液-冻融-干湿、清水浸泡与盐浸试验。主要进行了以下几项内容的试验和模拟研究：1.通过对不同工况下的质量损失率和超声波波速的测试,可得到：相对动弹模量作为衡量天然浮石混凝土耐久性的评价指标更准确；天然浮石混凝土强度越大,则质量损失率和相对动弹模量的损伤越小,适量引气剂的加入也可以改善混凝土的耐久性。同时为了使研究更加深入,利用电镜照片和能谱成分图分析天然浮石混凝土破坏机理。2.在天然浮石混凝土研究中首次运用核磁共振测试方法,从孔隙度、核磁共振乃谱分布、孔径分布及核磁共振图像分析得到冻融前后的内部孔隙损伤扩展特征：天然浮石混凝土的核磁共振乃谱分布一般为4个峰,冻融循环使得天然浮石混凝土内部小孔隙逐渐向大孔隙扩展破坏,造成孔隙度、乃谱面积增大,并且在盐渍溶液中核磁共振信号较强,亮点区域较大。3.本文运用计算机X射线断层扫描(CT)、环境扫描电镜(ESEM)、超景深三维显微系统综合分析天然浮石混凝土的细观特征,并结合核磁共振成像,从不同角度分析了冻融前后内部孔隙的损伤扩展特征,最终得到一致结论：在盐渍溶液中的天然浮石混凝土内部损伤较严重。4.论文提出利用冻融核磁共振测试天然浮石混凝土孔溶液在冻融过程中的变化规律,得到了冷冻过程和融化过程中各个温度下天然浮石混凝土孔溶液的信号量、结冰量等相关指标,并由此得出天然浮石混凝土孔溶液结冰的一般规律：用冷冻过程中的含冰量来评价由孔溶液结冰引起的静水压比较符合实际情况：天然浮石混凝土发生冻害主要是-15℃以上。5.最后利用损伤力学的理论,结合静水压假说,根据天然浮石混凝士的孔结构、抗拉力学性能和冻融条件,建立了天然浮石混凝土的抗冻耐久性预测模型,对天然浮石混凝土冻害的全过程进行了定量描述。
[Abstract]:This paper makes full use of the abundant pumice resources and industrial wastes in Inner Mongolia to study and develop the natural pumice concrete, which is a new type of light energy saving cold zone material, such as cement, pumice, sand, fly ash and so on. In this paper, the Hetao Irrigation area of Inner Mongolia is selected as the study area. The water used in the irrigated area mainly comes from the Yellow River, and the pH value of the irrigated area is between 7.7-8.2, which mainly contains the erosive medium such as Na ~ (2 +) mg _ (2) Ca ~ (2 +) ~ (2 +) -Cl-so _ (4) _ (4-). It is bound to cause serious erosion of hydraulic structures. Based on the investigation data of salinized water in Hetao Irrigation District of Inner Mongolia and the characteristics of the natural environment of the hydraulic structures in the irrigated area, the winter time is long. Five groups of natural pumice concrete (LC20LC25LC30) and two groups of air-entrained natural pumice concrete (LC20LC25LC30) and two groups of air-entrained natural pumice concrete (LC20LC25LC30) were prepared, and four working conditions were designed: freeze-thaw (clear water) and salinized solution-freeze-thaw cycle. Dry and wet cycles (clear water) and salinized solution-dry and wet cycles, freeze-thawing (clear water) and salinized solutions-freeze-thawing, soaking and salt soaking tests. The following experiments and simulations were carried out: 1. Through the measurement of mass loss rate and ultrasonic wave velocity under different working conditions, it can be concluded that the relative dynamic modulus is more accurate as an evaluation index to evaluate the durability of natural pumice concrete, and the greater the strength of natural pumice concrete, the greater the strength of natural pumice concrete. The damage of mass loss rate and relative dynamic modulus is smaller and the durability of concrete can be improved by adding proper amount of air entraining agent. At the same time, the damage mechanism of natural pumice concrete was analyzed by means of electron microscope photos and energy dispersive composition diagram. In the study of natural pumice concrete, nuclear magnetic resonance (NMR) method is used for the first time. Pore size distribution and nuclear magnetic resonance (NMR) image analysis showed that the propagation characteristics of internal pore damage before and after freezing and thawing: the NMR spectrum distribution of natural pumice concrete was generally four peaks. The freeze-thaw cycle causes the small pores in the natural pumice concrete to expand and destroy to the macropores, resulting in the increase of the porosity and the increase of the spectral area, and the nuclear magnetic resonance signal is stronger in the saline solution, and the bright spot region is larger than that in the saline solution. In this paper, the microcosmic characteristics of natural pumice concrete are comprehensively analyzed by means of computer X ray tomography (CTT), environmental scanning electron microscopy (ESM) and superfine depth of field (depth of field) three dimensional microscopic system, and combined with nuclear magnetic resonance imaging (NMR). The damage and propagation characteristics of internal pores before and after freezing and thawing are analyzed from different angles, and a consistent conclusion is obtained: the internal damage of natural pumice concrete in salinized solution is more serious. In this paper, nuclear magnetic resonance spectroscopy (NMR) is used to test the variation of natural pumice concrete pore solution during freeze-thaw process, and the signal quantity of natural pumice concrete pore solution at different temperatures during freezing and thawing is obtained. Ice volume and other related indicators, From this, the general law of freezing in pore solution of natural pumice concrete is obtained: the hydrostatic pressure caused by freezing solution of natural pumice concrete is evaluated by the content of ice in freezing process. The freezing damage of natural pumice concrete is mainly above -15 鈩，

本文编号：2027384