砖骨料地聚物再生混凝土力学性能试验研究

Experimental Research on Basic Mechanical Properties of Brick Aggregate Geopolymer Recycled Concrete

为推动废弃黏土砖的资源化利用,设计了45个含不同砖骨料取代率(0%,30%,50%,70%,100%)的地聚物再生混凝土试块(15个立方体试块和30个棱柱体试块),并对其力学性能进行试验研究。通过单调受压试验,研究砖骨料地聚物再生混凝土试块抗压强度与砖骨料取代率的关系,得到了棱柱体试块的应力-应变曲线,并对其峰值应力、弹性模量、峰值应变和极限应变等进行分析。结果表明:砖骨料地聚物再生混凝土呈现碎块慢慢剥落,最终在纵截面出现一条斜向贯穿裂缝而引起斜向剪切裂缝破坏;随着砖骨料取代率的升高,试件的抗压强度呈下降趋势,但延性有所提高;当σ≤0.35 fck时,表面并无细微裂纹,试块处于弹性受压状态;当0.35fck≤σ≤0.85 fck,试件表面微裂缝开展,试块在由弹性向弹塑性过渡的阶段;当0.85 fck≤σ≤1.0 fck,试件表面破坏加剧,内部有声响及裂缝扩展;峰值荷载过后,试件破坏并丧失承载力。随着砖骨料取代率的增大,试块弹性模量明显降低,棱柱体混凝土试块的峰值应力呈梯度化下降,而峰值应变与极限应变均随着取代率的增加而增大。基于混凝土单轴受压本构模型得到了不同砖骨料取代率下的应力-应变本构模型,且通过模型得到的拟合结果与试验结果吻合良好。

To promote the reuse of wasted clay bricks produced by the buliding demolition,45 geopolymer recycled brick aggregate concrete(GRBAC)specimens(15 cubic specimens and 30 prism specimens)with different replacement ratios of brick aggregates(BA)(0%,30%,50%,70%,100%)were designed and tested to investigate the mechanical properties.Through monotonic compression tests,the relations between compressive strength and replacement ratio of BA was studied,and the stress-strain curves of prism specimens were obtained to analyze the peak stress,modulus,peak strain and ultimate strain.The results showed the GRBAC fell off gradually and finally that the damage of GRBAC exhibited oblique shear cracking damage due to the penetrative crack.With the increase of replacement ratio of BA,the compressive strength tended to decrease while the ductility was enhanced.Whenσ≤0.35 fck,the specimen was in elastic state without cracking;when 0.35fck≤σ≤0.85 fck,some visible cracks developed and the specimens transformed from elastic state to elasto-plastic stage;when 0.85 fck≤σ≤1.0 fck,the damage was aggravated with serious cracks development and audible noise.After reaching the peak load,the specimen was damaged and lost bearing capacity.With the increase of replacement ratio of BA,the strength of concrete decreased in a gradient,the elastic modulus decreased significantly,while the peak strain and ultimate strain increased.Based on the uniaxial compression constitutive model,the stress-strain constitutive model with different BA replacement ratios was obtained,and the fitting results obtained by the proposed model were in good agreement with the experimental results.