Yun Kyong-Ku, Choi Seunghak, Ha Taeho, Kim Seong Kwon, Hossain Mohammad Shakhawat, Han Seungyeon
Department of Civil Engineering, Kangwon National University, 1 Gangwondaegil, Chuncheon 24341, Korea.
Institute for Advanced Construction Materials, Kangwon National University, 1 Gangwondaegil, Chuncheon 24341, Korea.
Materials (Basel). 2021 Jan 26;14(3):580. doi: 10.3390/ma14030580.
In this study, cement minerals, aluminates, and alkali-free accelerators incorporated with steel fiber were used to scrutinize the influence of accelerating agents on the long-term performance of tunneling shotcrete. Performance tests were identified based on the core compressive strength of mix shotcrete specimens with different types of accelerating agents throughout timeframes of 1, 3, 6, and 12 months. Here, 37 kg of steel fiber was incorporated into the cement mineral and aluminate mixes, and 40 kg of steel fiber was incorporated in an alkali-free mix for the shotcrete mix design. The KSF 2784 and ASTM 214 standards were followed for specimen fabrication and core cutting. For all specimens, shotcrete test panels of 250 × 600 × 500 mm were manufactured for core compressive strength tests conducted using 100, 75 and 55 mm diameter cylindrical molds and a length-to-diameter ratio of 2. The 1-month compressive strength of all test variables satisfied the Korea Expressway Co. standard of 21 MPa. The core compressive strength of the shotcrete specimens showed a tendency to increase with age, but a strength reduction occurred in 6 months and increased again at 12 months. Moreover, the impact of the diameter changes in the shotcrete core specimens was analyzed based on the mixing. For 12 months, a large increase in the core compressive strength occurred, particularly in the alkali-free specimens. The comparison also focused on the relative strength compared with a cast concrete mold and shotcrete core specimens. It is necessary to use alkali-free accelerators considering the long-term performance of tunnels and worker safety.
在本研究中，将水泥矿物、铝酸盐和不含碱的速凝剂与钢纤维结合使用，以研究速凝剂对隧道喷射混凝土长期性能的影响。根据不同类型速凝剂的喷射混凝土混合料试件在1、3、6和12个月时间范围内的芯部抗压强度来确定性能测试。在此，在水泥矿物和铝酸盐混合料中掺入37千克钢纤维，在喷射混凝土混合料设计的无碱混合料中掺入40千克钢纤维。试件制作和芯部切割遵循KSF 2784和ASTM 214标准。对于所有试件，制作尺寸为250×600×500毫米的喷射混凝土试验板，用于使用直径为100、75和55毫米的圆柱形模具以及长径比为2进行芯部抗压强度试验。所有试验变量的1个月抗压强度均满足韩国高速公路公司21兆帕的标准。喷射混凝土试件的芯部抗压强度呈现出随龄期增长的趋势，但在6个月时强度降低，在12个月时再次升高。此外，基于混合料分析了喷射混凝土芯部试件直径变化的影响。对于12个月的情况，芯部抗压强度大幅增加，特别是在无碱试件中。比较还集中在与现浇混凝土模具和喷射混凝土芯部试件相比的相对强度上。考虑到隧道的长期性能和工人安全，有必要使用无碱速凝剂。
