高性能混凝土表层硬度与强度的相关性及其机理研究

发布时间：2018-03-20 13:41

本文选题：高性能混凝土　切入点：回弹法　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：混凝土是基建工程的主体,控制混凝土的强度能有效保证建筑物结构整体安全。由于回弹法具有使用方便、成本低廉、仪器携带方便,且不会造成检测结构的损坏等优点,因此被广泛应用于我国混凝土强度现场检测。然而,近些年来高性能混凝土迅速发展,因其高流动度,大掺量矿物掺合料等特点,导致使用国家统一测强曲线推定的混凝土强度与高性能混凝土的实际强度偏差较大。本文在详细调研的基础上,对影响高性能混凝土的表层因素进行了系统研究,建立了多重因素作用下高性能混凝土回弹测强曲线。这将对控制现代混凝土工程质量、防范工程事故、解决混凝土强度问题、促进混凝土发展、准确评价工程的质量具有重要的现实意义和工程实用价值。本文设计研究了水灰比、粗骨料粒径、矿物掺合料种类和掺量,试件尺寸、养护龄期、养护方法、试块表面湿度以及碳化深度等因素。以回弹值、抗压强度和碳化深度作为测量指标,建立了高性能混凝土测强曲线。研究结果表明：随着水灰比的减小,混凝土表层硬度随龄期的增加呈现先增长迅速后增长缓慢最终趋于稳定的趋势：掺加10%矿渣表层硬度最大,且随着掺量的增加,混凝土表层硬度减小；比较相同掺量的粉煤灰和矿渣,掺加矿渣的混凝土表层硬度和强度均大于掺加粉煤灰的混凝土；标准养护下高性能混凝土表层硬度大于相同龄期的自然养护；随着试块表面湿度的增加,表层硬度在减小但减小幅度在降低：碳化对表层硬度影响很大,碳化后其表层硬度可增大40%以上。采用最小二乘法建立的高性能混凝土测强曲线平均相对误差为8.3%,平均相对标准差为10.6%,均满足地区回弹测强曲线的精度要求。最后采用了XRD, SEM,TG-DSC,MIP和CT等现代测试技术研究了高性能混凝土表层固相组成和孔相结构的演变规律,研究发现：随着水灰比的减小,龄期的增加,水化程度增大,水化产物增多,孔隙率减小；随着表层的碳化,生成的碳酸钙导致大量的孔被细化,从而结构更加密实。
[Abstract]:The concrete is the main body of the capital construction project, the strength of the control concrete can effectively guarantee the overall safety of the building structure. Because the springback method has the advantages of convenient use, low cost, convenient carrying of the instrument, and will not cause damage to the detection structure, etc. Therefore, it has been widely used in the field testing of concrete strength in China. However, in recent years, high performance concrete has developed rapidly because of its characteristics of high fluidity, large amount of mineral admixture, and so on. As a result of the deviation between the concrete strength predicted by the national unified strength curve and the actual strength of the high performance concrete, this paper makes a systematic study on the surface factors affecting the high performance concrete on the basis of detailed investigation. The rebound strength curve of high performance concrete under the action of multiple factors is established, which will control the quality of modern concrete engineering, prevent engineering accidents, solve the problem of concrete strength and promote the development of concrete. It is of great practical significance and practical value to evaluate the engineering quality accurately. In this paper, water cement ratio, coarse aggregate particle size, mineral admixture type and amount, specimen size, curing age, curing method are designed and studied. The surface humidity and carbonization depth of the test block are taken as the measurement indexes. The strength curve of high performance concrete is established with the springback value, compressive strength and carbonation depth as the measuring index. The results show that: with the decrease of water-cement ratio, the strength measurement curve of high performance concrete is established. The hardness of the surface layer of concrete increases rapidly at first and then grows slowly with the increase of age. The hardness of the surface layer with 10% slag admixture is the largest, and the hardness of the surface layer decreases with the increase of the amount of admixture. Compared with the same amount of fly ash and slag, the surface hardness and strength of the concrete mixed with slag are higher than that of the concrete with fly ash, and the hardness of the surface layer of high performance concrete is greater than that of the natural curing of the same age under standard curing. With the increase of surface humidity, the hardness of the surface decreases, but the extent decreases. Carbonation has a great effect on the hardness of the surface. After carbonization, the hardness of the surface layer can be increased by more than 40%. The average relative error and the average relative standard deviation of the strength measurement curve of high performance concrete established by least square method are 8.3 and 10.6 respectively, which meet the precision requirements of the rebound strength curve in the region. The evolution of solid phase composition and pore phase structure in the surface layer of high performance concrete was studied by using modern testing techniques such as XRD, SEMG-DSCN MIP and CT. It is found that with the decrease of water-cement ratio, the increase of age, the increase of hydration degree, the increase of hydration products and the decrease of porosity; with the carbonization of the surface layer, a large number of pores are refined and the structure is more dense.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

【相似文献】