基于颗粒特性的水泥基材料流变性能研究

发布时间：2018-04-20 04:08

本文选题：水泥净浆 + 砂浆　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：拌合物流变性能直接决定了混凝土的施工难易程度和施工质量,因而流变性能是现代混凝土配合比设计中最重要的技术指标之一。目前,国内外绝大多数研究和现行混凝土配合比设计规程中对于流变性能的设计和调整主要是基于经验公式,没有考虑到实际原材料颗粒特性不同而产生的重要影响,从而导致不同研究者的研究结果不一致和实际工程混凝土的配合比设计经济性差。因此,本课题基于颗粒堆积与悬浮液理论,从水泥净浆、水泥砂浆、混凝土拌合物三个层次分别研究胶凝材料、细骨料、粗骨料颗粒组成特性不同对拌合物流变性能的影响规律,通过确定颗粒特性与流变性能之间的对应关系,为实际混凝土配合比优化设计奠定理论基础。在水泥净浆体系中,通过不同掺量、不同细度的粉煤灰、矿渣粉代替水泥以改变胶凝材料体系的颗粒组成与特性,结果发现:在一定范围内,增加粉煤灰的掺量会降低水泥净浆粘度,提高水泥净浆流动度。当掺入过细粉煤灰时,对水泥浆体的流动性不利。随着矿渣掺量的不断增加,水泥净浆的流动度变大,粘度变小。复合胶凝材料颗粒与Fuller曲线之间相差的面积S1和S2与水泥净浆流变性能有较好的相关关系。S1越大,水泥净浆流动度越小,粘度越大;S2越大,水泥净浆流动度越大,粘度越小。当在较小范围内变化砂的细度模数时,水泥砂浆的流动性不是随着砂的细度模数的变大而变大。这就表明即使砂子的细度模数相同,如果各个粒级细颗粒的含量不同,水泥砂浆的流动性也会存在显著差异。所以在研究细集料砂子对水泥砂浆流变性能的影响时,不能只以砂的细度模数作为参考,还应该考虑砂的颗粒级配。水泥砂浆的屈服剪切应力和塑性粘度均随浆体富余系数增加而降低,流动度则随浆体富余系数增加而增大;增大浆体富余系数到一定值,其变化较平缓。骨料堆积空隙率和骨料总比表面积随着针片状含量增加而增大,从而导致相同配合比时混凝土的流动性变差;设计混凝土配合比应该控制针片状粗骨料含量在10%以内,挑选颗粒形态好的粗骨料颗粒,能显著改善混凝土拌合物流变性能。相同条件下,混凝土的坍落度和扩展度均随砂浆富余系数增加而增大,但在达到2.5~3.5以后,继续增加砂浆量对坍落度和扩展度的增加效果不明显。
[Abstract]:The rheological properties of the mixture directly determine the construction difficulty and the construction quality of concrete, so the rheological properties are one of the most important technical indexes in the design of modern concrete mix ratio. At present, the design and adjustment of the rheological properties in most of the research and current concrete mix design regulations at home and abroad is mainly based on the design and adjustment of the rheological properties. The experimental formula does not take into account the important effect of the different properties of the actual raw material, which leads to the difference of the research results of different researchers and the poor design economy of the actual engineering concrete. Therefore, this subject is based on the theory of particle accumulation and suspension, from three layers of cement paste, cement mortar and concrete mix. The effects of different properties of cementitious materials, fine aggregate and coarse aggregate particles on the rheological properties of the mixture are studied, and the theoretical basis for the optimization of concrete mix ratio is established by determining the corresponding relationship between the particle properties and rheological properties. In the cement slurry system, the fly ash with different quantities and different fineness is passed in the cement slurry system. Slag powder instead of cement is used to change the particle composition and characteristics of the cementitious material system. It is found that increasing the amount of fly ash in a certain range will reduce the viscosity of cement paste and increase the fluidity of cement paste. When adding fine fly ash, the fluidity of cement slurry is not good. With the increase of slag content, the flow of cement paste is increased. The area S1 and S2 difference between the particle size and the Fuller curve of the composite cementitious material has a better correlation with the rheological properties of cement paste, the greater the.S1, the smaller the flow degree of cement paste, the greater the viscosity; the larger the S2, the greater the cement paste fluidity and the smaller the viscosity. When the fineness modulus of the sand is changed in a small range, the water can be changed in a smaller range. The fluidity of the mortar is not larger than the size of the sand. This shows that if the fine modulus of the sand is the same, there is a significant difference in the fluidity of the cement mortar if the content of the fine particles is different. So, it is not only fine to study the effect of the fine aggregate sand on the rheological properties of the cement mortar. As a reference, the grain gradation of sand should be considered as a reference. The yield shear stress and plastic viscosity of the cement mortar are decreased with the increase of the slurry surplus coefficient, and the flow degree increases with the increase of the slurry surplus coefficient; the change of the slurry surplus coefficient to a certain value is slow. The porosity of aggregate accumulation and the aggregate surface area of aggregate The fluidity of the concrete increases with the increase of the needle sheet content, which leads to the poor fluidity of concrete in the same mix ratio. The design concrete mix ratio should control the content of the coarse aggregate of the needle like coarse aggregate within 10%, and select the coarse aggregate particles with good particle shape. The concrete slump and expansion can be improved significantly. The degree increases with the increase of mortar surplus coefficient, but after reaching 2.5~3.5, the effect of increasing mortar volume on slump and expansion is not obvious.

【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

【引证文献】