Abstract
The main aim of this investigation is to develop backfill concrete including coal gangue and metakaolin to reduce solid waste. For this purpose, a total of 30 concrete mixtures were designed by the inclusion of 0%, 25%, 50%, 75% and 100% coal gangue as coarse aggregates and 0%, 10% and 20% metakaolin as binder at 0.55 and 0.45 water to cement ratios. The compressive strength was tested after 3, 7 and 28 days for a total of 90 samples. Meanwhile, the influences of coal gangue and metakaolin on the elastic modulus, ultrasonic pulse velocity, rebound number and open porosity were explored. Then, the relationship between physical and mechanical properties was revealed by design code expressions and empirical models. Furthermore, an extreme learning machine was developed to predict compressive strength by concrete mixtures. The results show that the inclusion of coal gangue results in a poor performance in physical and mechanical properties of concrete. However, the drawbacks of concrete containing coal gangue can be compensated by metakaolin. The predicted results of design code expressions and empirical models are closed to the experiment results, with a 10% error. In addition, the findings reveal that the extreme learning machine offers significant potential to predict the compressive strength of concrete with high precision.
Highlights
More recent attention has focused on the provision of coal gangues (CG) as a substitute for coarse aggregate. Surveys such as that conducted by Li (2021) have shown that the fluidity loss of fresh concrete was due to the porous structure of CG with high water absorption capacity [4]
The main purpose of this study is to develop an understanding on the development of physical and mechanical properties of concrete containing both CG and metakaolin
It can be noticed that there is a steady drop in the compressive strength of the sample with the increase in CG addition regardless of curing ages and w/c ratios
Summary
The rapid development of infrastructure has seen a dramatic increase in the consumption of construction materials [1]. More recent attention has focused on the provision of CG as a substitute for coarse aggregate Surveys such as that conducted by Li (2021) have shown that the fluidity loss of fresh concrete was due to the porous structure of CG with high water absorption capacity [4]. The loss of mechanical properties is more than 20% in concrete where CG completely replaces coarse aggregate [2]. The studies presented far provide evidence that CG replacing coarse aggregate leads to the degradation in concrete properties. This is the main reason that CG has not been widely used in the production of concrete.
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