【作者】 王雨利；

【导师】 周明凯；

【作者基本信息】 武汉理工大学 ， 材料学， 2007， 博士

【摘要】 配制低强度、泵送混凝土时，由于水灰比大，用水量高，导致混凝土易于离析、泌水，且存在抗渗性差、干缩开裂、耐久性低等问题。为了解决这些问题，通常需要通过提高胶凝材料用量降低水胶比来满足混凝土的性能；另一方面，机制砂生产过程中伴随产生10～15％的石粉。因此，如果能利用机制砂中的石粉降低水粉比，达到提高混凝土拌和物性能，改善混凝土的抗渗性及耐久性能，那么就可以充分发挥石粉和机制砂的长处，对有效利用石粉副产物资源和扩大机制砂的应用范围意义重大。本文以水灰比0.50的砂浆和混凝土为主要研究对象，采用宏观和微观手段相结合，试验与理论分析相结合技术路线，进行了以下几个方面的研究工作：①对比研究了四种不同类型砂的物理特性对砂浆和混凝土工作性和强度的影响；②重点研究了三种不同岩性的石粉的含量对砂浆和混凝土工作性和强度的影响，以及石粉含量对混凝土耐久性的影响；③以石灰岩石粉为例，研究了石粉作矿物掺合料对混凝土性能的影响；④分析了石粉在水泥浆体中的物理化学作用效应；⑤基于石灰岩机制砂和石粉对砂浆和混凝土性能的影响，探讨了低强度混凝土用机制砂最佳石粉含量的确定方法。试验结果表明：相比河砂而言，机制砂具有空隙率小、粒形粗糙等特点，因此它们对混凝土性能的影响也不同。在不掺减水剂时，综合石粉对水泥浆、砂浆、混凝土流动性试验结果，得出在水粉比不小于0.40时，增加石粉可以提高砂浆和混凝土的工作性能。石粉对水泥在湿润状态的密实度变化的规律，与石粉作矿物掺合料对混凝土抗渗性能的影响有一定的联系。适量的石粉填充了机制砂的空隙并降低了水粉比，提高了混凝土拌和物的密实性和稳定性，从而提高了混凝土抗压强度，改善了抗渗性能，并有利于浆体的体积稳定性。机制砂中的石粉含量超过10％时对混凝土抗冻性能产生了一定的不利影响，但机制砂中的石粉含量的增加对混凝土的抗硫酸盐侵蚀没有不利影响。掺入粉煤灰、引气剂、膨胀剂、防水剂、纤维虽然提高了混凝土的抗渗性能，但也会对混凝土的工作性能或抗压强度等造成不利的影响。结合试验结果和理论分析，可以将石粉在低强度混凝土中的作用机理概括为：减水效应、密实效应、水化效应。在普通混凝土配合比设计和高性能混凝土配合比设计的基础上，以石灰岩机制砂为例，提出了低强度机制砂混凝土高性能化的配合比设计方法，该方法可以灵活地确定机制砂的最佳石粉含量。以上部分研究成果不但对沪蓉西高速公路C30及以下混凝土的配制起到了良好的指导作用，而且对低强度、流态、抗渗性机制砂混凝土的配制具有较好的参考价值。建议在配制低强度机制砂混凝土时，将机制砂中的石粉含量放宽到10％～15％，以改善混凝土的工作性、强度和抗渗等性能。更多还原

【Abstract】 When prepare low-grade and high-fluid concrete, the high W/C ratio and water consumption are so great that it is reason for segregating and bleeding, and the concrete also has some problems such as bad impervious performance, easy shrinkage crack, and so on. The method of increasing the amount of bond materials to reduce water bond ratio is usually adopted to improve the performances of concrete. In other hand, the amount of aggregate micro fines (AMF) is up to 10 to 15 percent in manufacturing fine aggregate (MFA), and the AMF can be used to improve the performances of concrete mixture by reducing the water powder ratio, and so the performances of imperviousness and durability. The advantages of AMF and MFA can be fully exerted for the promotion and application of MFA concrete.Mortar and concrete with the 0.50 of w/c ratio are the main subjects investigated, and the technology line of macro and micro means, experimental and theoretical analysis, and laboratory and field tests combining has been adopted in this paper. Some aspects listed are studied as follows:①Effects of four kinds of sands on workability and compressive strength of mortar and concrete were comparatively studied;②Effects of contents of three kinds of rock AMF on workability of mortar and concrete were systematically studied, and effects on durability of concrete were also studied;③Take limestone powder for example, the effects of MFA as mineral admixtures on performances of concrete were studied;④Effects of limestone powder, quartzite powder, granitic powder on physical and chemical performances of cement were comparatively studied;⑤The mix proportion design method of low-grade MFA concrete were studied.It is showed that the void ratios of limestone, quartzite, granitic MFA are less than that of natural sand, so their influences on performances of concrete are different. With the influences of water powder ratio on the fluid performance of concrete, it is showed that when water powder ratio is less than 0.40, increasing the amount of aggregate micro fines can improve the working performance of concrete. The rule of AMF to the compactness of cement with water state, have certain relation to the influence of MAF as mineral admixtures on the impervious performance of concrete. Proper amount of AMF fills void of MAF and reduces water powder ratio, so stability and compactness of concrete mixture can be improved, and so the compressive strength, impervious performance and other performances of concrete. Contents of AMF with more than 10% have bad influences on frost-resistant performance, but it doesnot have bad influences on sulfate corrosion with increment of AMF content. Fly ash, chemical admixture, fiber can improve impervious performance; but it also have some bad effects on other performances of concrete. Combined with experiment results and theoretical analysis, the active mechanism of AMF in the low-grade concrete may be generalized as: water-reducing effect, compact effect, hydrated effect.The mix proportion design method of low-grade MFA concrete is presented in this paper based on the mix proportion design of ordinary concrete and high performance concrete with the example of limestone MFA. The optimization content of MFA can be identified flexibly according to the actual proportion by this method.Partly these research results are tested in the construction of equal and less than C30 concrete for the Hurongxi highway, which has not only good reference value, but also conference value for preparation of low strength, fluidity, impervious concrete with MFA. To improve workability, strength, impervious performances of concrete it is suggested that contents of MFA should be between 10 and 15 percent.更多还原