矿井预拌料混凝土微观结构和力学性能研究及应用

发布时间：2018-05-15 18:51

本文选题：喷射混凝土 + 预拌干料　；参考：《安徽理工大学》2014年博士论文

【摘要】：矿山井巷喷射混凝土的人工现场拌料施工,存在原材料计量不准确、混凝土质量差、粉尘浓度大等问题。针对这一现状,提出了预拌干料和预拌料混凝土技术。预拌干料是指将水泥、砂子和石子等混凝土原材料,按照设计配合比拌合均匀、干燥贮存的散装混合料。预拌料混凝土是在预拌干料中加入水和外加剂,硬化后形成的一种混凝土。预拌料混凝土具有准确的配合比、良好的混凝土质量、较低的粉尘浓度等诸多优点。但预拌干料中的砂子含有的极少量水,与水泥发生水化反应,劣化了原材料性能,对预拌料混凝土性能产生影响。结合教育部博士点基金优先发展领域课题“预拌喷射补偿收缩混凝土微观结构与力学特性研究”,采用理论分析、室内试验和现场试验相结合的方法,对砂子含水率分别为0%、0.5%、1.0%、1.5%、2.0%和贮存期分别为0d、3d、7d、10d、15d、20d、30d的预拌干料和预拌料混凝土的微观结构进行分析,揭示微观结构对预拌料混凝土抗压强度、孔隙率等的影响机理。主要研究结论如下。 (1)预拌干料和预拌料混凝土的微观分析表明,砂子含水率越高、贮存期越长,预拌干料中失效的水泥量越多,原材料性能劣化越严重,混凝土微观结构越疏松。当预拌干料的砂子含水率在1.0%以下、贮存期在15d以内时,预拌干料的水化产物和微观结构变化较小、材料性能劣化程度低,预拌料混凝土的微观结构密实：当预拌干料的砂子含水率在1.5%以上时,贮存期的增加导致预拌干料中失效的水泥数量增多、材料性能劣化加剧。 (2)预拌料混凝土抗压强度试验表明,预拌干料的砂子含水率小于1.0%、贮存期在15d以内时,水胶比为0.45的预拌料混凝土强度损失率不超过8.64%,抗压强度达到42.3MPa,满足要求；当砂子含水率增加到1.5%以上时,贮存期对预拌料混凝土强度的影响较大。结果表明,砂子含水率为1.0%的预拌干料有效贮存期为15d。 (3)建立了不同砂子含水率和贮存期条件下的预拌料混凝土抗压强度与孔隙率之间的定量关系。预拌干料的砂子含水率越小、贮存期越短,预拌料混凝土孔隙数量越少、孔径越小、微观结构越密实,预拌料混凝土的抗压强度越高。随预拌干料贮存期延长,砂子含水率在1.0%以下时,预拌料混凝土孔隙率增加较慢,对混凝土的强度影响较小；而砂子含水率为1.5%和2.0%时,预拌料混凝土孔隙率增加相对较快,对混凝土的强度影响较大。 (4)通过分析,得出预拌干料的砂子含水率和贮存期对预拌料混凝土强度的影响机理。预拌干料的砂子含水率和贮存期对预拌干料的水化程度产生影响,水化程度高时,预拌干料水化消耗的水泥量多,导致后期混凝土中水泥数量减少,同时,密实的预拌干料水化产物包裹部分水泥颗粒,阻止或延缓了这部分水泥在混凝土中继续水化；水化程度低时,预拌干料中的水化产物疏松,这些疏松的微观结构在混凝土中很难水化密实,成为预拌料混凝土的薄弱环节。预拌干料的水泥水化程度越高,失效水泥量越多,预拌干料性能劣化越严重,预拌料混凝土强度降低越多。 (5)工程应用表明,预拌料喷射混凝土具有良好的力学性能、较好的变形性能、较小的回弹率和较低的粉尘浓度。
[Abstract]:The construction of artificial site mixing for Shotcrete in mine shaft and roadway has problems of inaccurate raw material measurement, poor quality of concrete and large dust concentration. In view of this situation, the concrete technology of premixed dry material and premixed material is put forward. The premixed dry material is the concrete raw material such as cement, sand and stone, and it is evenly mixed according to the design mix ratio. Dry stored bulk mixture. Premixed concrete is a concrete formed after adding water and admixture into the premixed dry material and hardened. The premixed concrete has an accurate mix ratio, good concrete quality, low dust concentration and so on. But the sand in the premixed dry material contains a very small amount of water and water with cement. The reaction deteriorates the properties of raw materials and affects the performance of ready mixed concrete.
Combined with the theoretical analysis, indoor test and field test, the moisture content of the sand is 0%, 0.5%, 1%, 1.5%, 2% and the storage period of 0d, 3D, 7d, 10d, 15d, 20d, 30d, respectively. The microstructure of material and premixed concrete is analyzed, and the influence mechanism of microstructure on the compressive strength and porosity of premixed concrete is revealed. The main conclusions are as follows.
(1) the microanalysis of the premixed and premixed concrete shows that the higher the water content of the sand, the longer the storage period is, the more invalid cement in the premixed material, the worse the properties of the raw materials, the more loose the microstructure of the concrete. The hydration products of the premixed dry material when the moisture content of the premixed dry material is under 1% and the storage period is within 15d. The microstructure of the premixed concrete is low, the microstructure of the premixed concrete is low, and the microstructure of the premixed concrete is dense. When the moisture content of the sand of the premixed material is above 1.5%, the increase of the storage period leads to the increase of the number of invalid cement in the premixed dry material and the deterioration of the material performance.
(2) the compressive strength test of premixed concrete shows that the moisture content of the premixed material is less than 1% and the storage time is less than 15d, the concrete strength loss rate is not more than 8.64% and the compressive strength is up to 8.64%, and the compressive strength is up to 42.3MPa. When the water content of the sand is increased to more than 1.5%, the storage period can be used for the concrete strength of the premixed material. The results showed that the effective storage period of ready mixed dry matter with sand content of 1% was 15d.
(3) the quantitative relationship between the compressive strength and porosity of the premixed concrete under the conditions of water content and storage period is established. The smaller the water content of the sand of the premixed material is, the shorter the storage period, the less the pore size of the concrete, the smaller the pore size, the more dense the microstructure, the higher the compressive strength of the premixed concrete. With the premixed drying, the higher the compressive strength of the premixed concrete. When the storage period is prolonged and the water content of the sand is below 1%, the porosity of the premixed concrete increases slowly and has little effect on the strength of the concrete. When the water content of the sand is 1.5% and 2%, the porosity of the premixed concrete is relatively fast, and the strength of the concrete is greatly affected.
(4) through the analysis, the influence mechanism of the moisture content and storage period of the premixed dry material on the strength of the premixed concrete is obtained. The water content and storage period of the premixed dry aggregate have an effect on the hydration degree of the premixed dry material. When the hydration degree is high, the amount of cement consumed by the premixed dry material is more, resulting in the decrease of the cement quantity in the later concrete. The hydration products of dense premixed dry material encapsulate some cement particles, which prevent or delay the hydration of this part of the cement in concrete; when the degree of hydration is low, the hydration products of the premixed dry material are loose. These loose microstructure is difficult to be hydrated and dense in concrete, which is the weak link of the premixed concrete. The higher the degree of hydration of cement, the more failure of cement, the worse the performance of ready mixed dry matter, the more the strength of ready mixed concrete will decrease.
(5) engineering application shows that the sprayed concrete with ready mixed materials has good mechanical properties, better deformation performance, smaller rebound rate and lower dust concentration.

【学位授予单位】：安徽理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU528

【参考文献】