Abstract
The influence of four factors (water-binder ratio, recycled coarse aggregate replacement rate, fly ash substitution rate, and superplasticizer content) on the workabilities and mechanical properties of recycled coarse aggregate self-compacting concrete (RCASCC) was studied using the orthogonal test method. Based on the orthogonal test design and range analysis method of the fresh and hardened properties of RCASCC, the optimal mix is as follows: water-binder ratio of 0.269, recycled coarse aggregate replacement rate of 30%, fly ash substitution rate of 40%, and superplasticizer content of 0.50%. Then, the porosity and aperture size distribution of nine groups of RCASCC were tested by mercury intrusion porosimetry (MIP) at the microlevel. The macroscopic and microscopic relationship was established by combining the results of mechanical property tests and MIP. Fractal dimension D of the B.B. Mandelbrot model was used to study the fractal characteristics of pore volume of RCASCC. Results showed that porosity and strengths are negatively correlated, and the relative strength can be roughly judged according to the porosity. The pore structure of nine groups of RCASCC materials has evident fractal characteristics of irregular shape. The complex pore structure adversely affects strength.
Highlights
Concrete is one of the most versatile building materials on Earth and makes up a significant proportion of the past, present, and future infrastructure [1]
Only 9 instead of 81 experiments are required to sufficiently consider and optimize these parameters. rough this trial mix design, the orthogonal table is adopted to design the mix of recycled coarse aggregate self-compacting concrete (RCASCC). e specific orthogonal test distribution and material consumption are shown in Tables 7 and 8
According to previous studies [33, 34], the content and shape of recycled aggregates and the change of water in the mixture will have an impact on slump flow
Summary
Concrete is one of the most versatile building materials on Earth and makes up a significant proportion of the past, present, and future infrastructure [1]. E method of mixing and disposing fly ash and steel slag has been adopted to reduce costs Another cost-effective and environmentally friendly method to produce SCC might be the utilization of recycled concrete aggregate (RCA). En, according to the ordinary concrete mix design method for the calculation, the orthogonal test method is adopted to improve the concrete mixture ratio test [19,20,21]. Several authors have demonstrated the applicability of the orthogonal test method for the SCC and recycled aggregate concrete (RAC). E results showed that concrete designed in L9 orthogonal array with 25% replacement of cement with fly ash, 20% replacement of fine aggregate with waste foundry sand, and addition of 1% polypropylene fibers was found to be the optimal mix for maximum compressive strength and split tensile strength. Strength tests are conducted to obtain an accurate optimal mix to prove the accuracy and applicability of mix, which can provide reference for the design and application of RCASCC in green concrete projects
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