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

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. When σ≤0.35 f_ck, the specimen was in elastic state without cracking; when 0.35f_ck≤σ≤0.85 f_ck, some visible cracks developed and the specimens transformed from elastic state to elasto-plastic stage; when 0.85 f_ck≤σ≤1.0 f_ck, 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.