全铁尾矿混凝土梁受弯性能试验研究

Experimental study on flexural performance of full iron tailingsconcrete beam

为了充分利用铁尾矿,对铁尾矿混凝土结构的力学性能进行探究,以铁尾矿粉为掺合料,铁尾矿碎石和铁尾矿砂分别作为粗、细骨料,制备成全铁尾矿混凝土(FITC)梁,并与以粉煤灰作掺合料,普通碎石及河砂作粗、细骨料的常规混凝土(CC)梁进行弯曲试验对比。首先,测试铁尾矿的各项参数,验证其作为混凝土原材料的可行性;其次,基于现行规范公式计算梁各阶段的承载力和挠度;最后,将FITC梁和CC梁的实测数值和计算数值对比分析。结果表明:FITC的强度比CC略低,弹性模量显著降低;FITC梁的开裂弯矩和极限弯矩与CC梁相当,梁的抗裂能力与承载力并未因FITC的强度和弹性模量比CC低而明显降低;在裂缝出现之前,FITC梁的混凝土应变与平截面假定基本一致;在荷载作用下,FITC梁受拉区混凝土应变比CC梁的大;FITC梁的延性、裂缝开裂间距均与CC梁接近,FITC梁弯剪区斜裂缝比CC梁更接近梁的顶部;在同等弯矩下,FITC梁的挠度大于CC梁的挠度,FITC梁的受拉纵筋应变也大于CC梁;中国现行设计规范对FITC梁的承载力计算是安全的,但挠度计算公式需要修正。

In order to make full use of iron tailings,and study the mechanical properties of concrete structures with iron tailings,using iron tailing powder as admixture,iron tailing gravel and iron tailing sand as coarse and fine aggregate respectively,the full iron tailings concrete(FITC)beams were prepared.FITC was compared with conventional concrete(CC)beam using fly ash as admixture,common crushed stone and river sand as coarse and fine aggregate in the bending test.First of all,the parameters of iron tailings were tested to verify their feasibility as concrete raw materials.Secondly,the bearing capacity and deflection of each stage of the beam were calculated based on the current code formula.Finally,the measured and calculated values of FITC beams and CC beam were compared and analyzed.The results show that the strength of FITC is slightly lower than that of CC,and the elastic modulus is significantly reduced.The cracking moment and ultimate moment of FITC beam are equivalent to those of CC beam.The crack resistance and bearing capacity of the beam do not significantly decrease due to the lower strength and elastic modulus of FITC compared to CC.The concrete strain of FITC beams is in good agreement with the plane section assumption before cracks appear.Under load,the strain of concrete in the tension area of FITC beams is larger than that of the CC beam.The ductility and crack spacing of FITC beams are close to those of CC beam,and the oblique crack in bending shear zone of FITC beam is closer to the top of beam than that of CC beam.The deflection of FITC beams is larger than that of CC beam under the same bending moment,and the strain of longitudinal reinforcement in FITC beams is also larger than that in CC beam.The current design code of China is appropriate for calculating the bearing capacity of FITC beams,but the deflection calculation formula should be modified.