Ding Xinxin, Geng Haibin, Shi Kang, Song Li, Li Shangyu, Liu Guirong
International Joint Research Lab for Eco-Building Materials and Engineering of Henan, School of Civil Engineering and Communication, North China University of Water Resources and Electric Power, Zhengzhou 450045, China.
Collaborative Innovation Center for Efficient Utilization of Water Resources, North China University of Water Resources and Electric Power, Zhengzhou 450045, China.
Materials (Basel). 2021 Sep 15;14(18):5312. doi: 10.3390/ma14185312.
To ensure the quality of concrete construction, the workability of fresh mix measured by rational test methods is critical to be controlled. With the presence of steel fibers, whether the test methods and evaluation indices of fresh self-compacting concrete (SCC) are adaptable for self-compacting steel fiber reinforced concrete (SFRC) needs to be systematically verified. In this paper, seven groups of self-compacting SFRC, referenced with one group SCC, were prepared by using the mix proportion design method based on the steel fiber-aggregates skeleton packing test. The main factors included the volume fraction and the length of hooked-end steel fiber. Tests for filling ability, passing ability, and stability of fresh self-compacting SFRC and SCC were carried out. Results indicate that the adaptability was well for the slump-flow test with indices of slump flow and flow time to evaluate the filling ability, the J-ring flow test with an index of level to evaluate the passing ability, and the static segregation test with an index of static segregation resistance to evaluate the stability of fresh self-compacting SFRC. By the repeated tests and measurements, the slump cone should be vertically lifted off to a height of 300 mm within 3 s at a constant speed, the spacing of the rebar in the J-ring test should be adjusted to be two times the fiber length. If the table jumping test is used, the dynamic segregation percent should be increased to 35% to fit the result of the static segregation test. Good workability of the self-compacting SFRC prepared in this study is presented with the general evaluation of test results.
为确保混凝土施工质量，采用合理的试验方法控制新拌混凝土的工作性至关重要。在钢纤维存在的情况下，新拌自密实混凝土（SCC）的试验方法和评价指标是否适用于自密实钢纤维增强混凝土（SFRC）需要进行系统验证。本文采用基于钢纤维 - 骨料骨架堆积试验的配合比设计方法，制备了七组自密实SFRC，并参考一组SCC。主要因素包括端钩型钢纤维的体积分数和长度。对新拌自密实SFRC和SCC的填充能力、通过能力和稳定性进行了试验。结果表明，坍落度流动试验（以坍落度流动值和流动时间为指标评价填充能力）、J环流动试验（以J环高度为指标评价通过能力）以及静态离析试验（以抗静态离析性为指标评价稳定性）对新拌自密实SFRC具有良好的适用性。通过反复试验和测量，坍落度筒应在3 s内以恒定速度垂直提升至300 mm高度，J环试验中的钢筋间距应调整为纤维长度的两倍。若采用跳桌试验，动态离析率应提高至35%以符合静态离析试验结果。通过试验结果的综合评价，展示了本研究制备的自密实SFRC具有良好的工作性。
