李根峰, 申向东, 邹欲晓, 高波. 基于微观特性分析风积沙粉体掺入提高混凝土的抗冻性[J]. 农业工程学报, 2018, 34(8): 109-116. DOI: 10.11975/j.issn.1002-6819.2018.08.014
    引用本文: 李根峰, 申向东, 邹欲晓, 高波. 基于微观特性分析风积沙粉体掺入提高混凝土的抗冻性[J]. 农业工程学报, 2018, 34(8): 109-116. DOI: 10.11975/j.issn.1002-6819.2018.08.014
    Li Genfeng, Shen Xiangdong, Zou Yuxiao, Gao Bo. Improving frost resistance of concrete mixed with aeolian sand powder based on microscopic characteristics[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(8): 109-116. DOI: 10.11975/j.issn.1002-6819.2018.08.014
    Citation: Li Genfeng, Shen Xiangdong, Zou Yuxiao, Gao Bo. Improving frost resistance of concrete mixed with aeolian sand powder based on microscopic characteristics[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(8): 109-116. DOI: 10.11975/j.issn.1002-6819.2018.08.014

    基于微观特性分析风积沙粉体掺入提高混凝土的抗冻性

    Improving frost resistance of concrete mixed with aeolian sand powder based on microscopic characteristics

    • 摘要: 为研究冻融-盐浸环境下风积沙粉体混凝土的微观特性,设计了强度等级为C35、C25的风积沙粉体混凝土,在浓度为0%、3%、6%硫酸镁溶液中采用快冻法进行抗冻性试验,同时借助核磁共振技术、场发射扫描电镜及能谱分析研究其孔隙特征、微观形貌及水化产物。结果表明,风积沙粉体的掺入显著提高混凝土的抗冻性,且适当提高强度等级,有利于提高风积沙粉体混凝土抗冻性,其中强度等级为C35的风积沙粉体混凝土在6% MgSO4溶液中可承受高达425次冻融循环;相对于基准组,风积沙粉体混凝土中有发育状况良好的针柱状产物钙矾石、纤维状产物石膏生成,填充因冻胀应力作用产生的裂隙,使其内部有害及多害孔数量低于普通混凝土29.78%,抗冻性增强。

       

      Abstract: Abstract: In this study, the utilization of aeolian sand cementitious properties, the development of new cementitious materials, and the durability of concrete under sulfate environment are combined together. Based on the test of compressive strength and splitting tensile strength of aeolian sand powder concrete, the effect of freezing thawing and salt leaching coupling on the microscopic characteristics of aeolian sand powder concrete was studied. The aeolian sand powder concrete specimens (100 mm × 100 mm × 400 mm) with strength grade of C35 and C25 were used to perform the freezing resistance test after immersed in 0%, 3% and 6% magnesium sulfate solution (20±2℃) for 4 d, and the initial dynamic elastic modulus and mass were measured. Then the minimum and maximum temperature of the specimens center were set at -17 and 5 ℃, respectively, each freeze-thaw cycle was ensured to be completed within 3 h, and the transition time between freezing and thawing was 8 min; and the relative dynamic elastic modulus and mass loss rate were measured after 25 freeze-thaw cycles. When the specimen relative dynamic elastic modulus decreased to 60% or the mass loss rate by 5%, the trial was stopped. At the same time, to observe the morphology and hydration products, the solidified slurry was selected at the central part of the test block before and after the freeze-thaw cycle test, then the hydration of samples was terminated by ethanol, and then the samples were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). NMR (nuclear magnetic resonance) analysis was performed for aeolian sand powder concrete (diameter × height: 50 mm × 50 mm), and then its microscopic pore characteristics were analyzed. The results show that the incorporation of aeolian sand powder can significantly improve the frost resistance of concrete, and to increase the strength grade appropriately is beneficial to improve the frost resistance of aeolian sand powder concrete. The aeolian sand powder concrete with strength grade C35 in 6% magnesium sulfate solution was subject to 425 freeze-thaw cycles, the appearance was intact, and the relative dynamic elastic modulus decreased to 43.9%. The relative elastic modulus of aeolian sand powder concrete decreased with the number of freeze-thaw cycles at the beginning and then turned to stable, and finally declined to the destruction. Compared with the reference group, the ettringite (AFt) and the calcined hydrated product gypsum (CaSO4) were produced. With the swelling properties of ettringite and gypsum, cracks in aeolian sand powder concrete due to frost heaving stress were filled, and the number of harmful and more hazardous holes in concrete was 29.78% lower than that in ordinary concrete. In 6% magnesium sulfate solution, the porosity of C35-15 aeolian sand powder concrete was 40.9% lower than that of the reference group, the irreducible fluid saturation was 32.7% higher, the permeability was lowered by 98.7%, the total pore volume was reduced, the proportion of small holes was increased, the impermeability was improved, the density of the structure was significantly improved, and the frost resistance was enhanced. This has very important social and practical significance for the development of aeolian sand industries, environmental governance and improvement, and the application of aeolian sand powder concrete in water conservancy and hydropower projects. It has significant economic benefits in the contemporary era.

       

    /

    返回文章
    返回