Experiment Study And Numerical Simulation On Modification Recycled Aggregate Concrete Compressive Strength

The reuse of abandoned concrete is in line with the strategic thinking of thecountry to save resources, protect the environment and sustainable development.Due to the existence of old mortar, the interfacial transition zone (ITZ) between oldmortar and new mortar has such features as high porosity, high water absorptionand low bond strength, which cause Recycled Aggregate Concrete(RAC) has lowerstrength comparing with natural aggregate concrete. To realize the modification ofthe recycled aggregate through adding fly ash in concrete which filled the pores andcracks of the transition zone, increase interface dense and cohesive effect. Themechanical properties of recycled aggregate is improved by strengthening the ITZ.This paper discusses the influence of the content of fly ash and water-cementratio on the compressive strength of RAC through RAC cube compression testingand prism compression testing with different fly ash content, the elastic modulusformula applicable to the fly ash is obtained. RAC is regarded as four-phasematerials composed by natural aggregate, old mortar, old mortar and ITZ whichtruly reflects the complexity of RAC microstructure. Combined with Monte Carlomethod and Fuller distribution theory, On micro-level, this paper uses APDLparametric programming of Ansys to generate3D spherical and2D circularnumerical simulation specimens of recycled aggregate based on random aggregateparameter model and simulate the compressive test of recycled concrete specimens.Visually demonstrating how the stress-strain changes and the cracks occur until thedestruction is under the load steps at different levels, comparing the stress-straincurve of simulation with the stress-strain curve of true test and analyzing moresystematically the influence of recycled aggregate’s microstructure on RACcompressive strength. Based on the simulation method This paper put forward amethod predicting the best replacement ratio of fly ash to make RAC compressivestrength reaches the maximum which provides a new ideas we can learn from tostudy fly ash RAC further in the future.