Xiao Shijie, Yang Jianyu, Liu Zelin, Yang Weijun, He Jiangang
College of Civil Engineering, Changsha University of Science & Technology, Changsha 410076, China.
School of Civil Engineering and Architecture, Jishou University, Zhangjiajie 427000, China.
Materials (Basel). 2024 Aug 18;17(16):4094. doi: 10.3390/ma17164094.
Shotcrete is widely used in mine and civil engineering as supporting structure. A new type of ultra-high-strength shotcrete (UHSSC) with viscosity-enhancing agent was taken as the research object in this paper. A microstructure model of UHSSC under different curing conditions (standard curing, natural curing and film curing) was reconstructed using X-ray computed tomography (X-CT). The grey theory was used to analyze the correlation between pore characteristics and strength of UHSSC. The results showed that the porosity and the pore size of UHSSC were significantly reduced, the compressive strength was obviously improved by the new spraying process. The effects of curing conditions on the pore characteristics and compressive strength of UHSSC were obvious. Under natural curing, the hydration degree was the highest, the maximum pore size was the smallest, and the compressive strength was the highest, reaching 95.8 MPa, but the porosity was the highest. The curing condition had a certain influence on the sphericity distribution of UHSSC pores. Under film curing, the proportion of special-shaped pores (S < 0.4) was the largest and compressive strength was the smallest. There was a good correlation between pore characteristic parameters and the compressive strength of UHSSC under different curing conditions. In particular, the large pore size (D ≥ 5000 µm) and special-shaped pores (S < 0.4) had obvious effects on the strength of UHSSC, and the grey correlation coefficients were 0.8539 and 0.8080, respectively. Additionally, the pore direction of UHSSC had obvious directionality, and the anisotropy of UHSSC may be more prominent than poured specimen. The results will lay a foundation for the study of its mechanical properties and durability.
喷射混凝土作为支护结构在矿山和土木工程中被广泛应用。本文以一种添加增稠剂的新型超高强喷射混凝土（UHSSC）为研究对象。利用X射线计算机断层扫描（X-CT）技术重建了不同养护条件（标准养护、自然养护和覆膜养护）下UHSSC的微观结构模型。运用灰色理论分析UHSSC孔隙特征与强度之间的相关性。结果表明，通过新的喷射工艺，UHSSC的孔隙率和孔径显著降低，抗压强度明显提高。养护条件对UHSSC的孔隙特征和抗压强度影响显著。自然养护下，水化程度最高，最大孔径最小，抗压强度最高，达到95.8MPa，但孔隙率也最高。养护条件对UHSSC孔隙的球度分布有一定影响。覆膜养护下，异形孔（S<0.4）比例最大，抗压强度最小。不同养护条件下，孔隙特征参数与UHSSC抗压强度之间具有良好的相关性。特别是大孔径（D≥5000µm）和异形孔（S<0.4）对UHSSC强度影响明显，灰色关联度系数分别为0.8539和0.8080。此外，UHSSC的孔隙方向具有明显的方向性，其各向异性可能比浇筑试件更为突出。研究结果将为其力学性能和耐久性研究奠定基础。
