Jiang Feifei, Deng Min, Mo Liwu, Wu Wenqing
College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211800, China.
College of Naval Architecture Civil Engineering, Jiangsu University of Science and Technology, Zhangjiagang Campus, Suzhou 215600, China.
Materials (Basel). 2020 Jul 9;13(14):3074. doi: 10.3390/ma13143074.
To prevent cracks caused by shrinkage of the deck of the Xiaoqing River Bridge, MgO concrete (MC) and steel fiber reinforced MgO concrete (SMC) were used. The deformation and strength of the deck were measured in the field, the resistance to chloride penetration of the concrete was measured in the laboratory, and the pore structure of the concrete was analyzed by a mercury intrusion porosimeter (MIP). The results showed that the expansion caused by the hydration of MgO could suppress the shrinkage of the bridge deck, and the deformation of the deck changed from -88.3 × 10 to 24.9 × 10, effectively preventing shrinkage cracks. At the same time, due to the restriction of the expansion of MgO by the steel bars, the expansion of the bridge deck in the later stage gradually stabilized, and no harmful expansion was produced. When steel fiber and MgO were used at the same time, the three-dimensional distribution of steel fiber further limited the expansion of MgO. The hydration expansion of MgO in confined space reduced the porosity of concrete, optimized the pore structure, and improved the strength and durability of concrete. The research on the performance of concrete in the in-situ test section showed that MgO and steel fiber were safe for the bridge deck, which not only solved the problem of shrinkage cracking of the bridge deck but also further improved the mechanical properties of the bridge deck.
为防止小青河大桥桥面因收缩产生裂缝，采用了氧化镁混凝土（MC）和钢纤维增强氧化镁混凝土（SMC）。在现场对桥面的变形和强度进行了测量，在实验室测定了混凝土的抗氯离子渗透性能，并通过压汞仪（MIP）分析了混凝土的孔结构。结果表明，氧化镁水化产生的膨胀可抑制桥面收缩，桥面变形从-88.3×10变为24.9×10，有效防止了收缩裂缝。同时，由于钢筋对氧化镁膨胀的限制，桥面后期膨胀逐渐稳定，未产生有害膨胀。当同时使用钢纤维和氧化镁时，钢纤维的三维分布进一步限制了氧化镁的膨胀。氧化镁在受限空间内的水化膨胀降低了混凝土的孔隙率，优化了孔结构，提高了混凝土的强度和耐久性。对现场试验段混凝土性能的研究表明，氧化镁和钢纤维对桥面是安全的，既解决了桥面收缩开裂问题，又进一步提高了桥面的力学性能。
