Abstract
Dolomite rock powder (the waste stone residue in the production of machine-made sand and stone processing) and iron tailings powder formed by mineral processing industry are solid wastes, which occupy land resources, pollute the environment and release toxic substances without reasonable processing. The dolomite rock powder and iron tailings powder composing a large number of active substances could be advantageous to the cement-based materials. In this study, the electrical resistivity of cement paste and concrete was measured. Meanwhile, the influence of dolomite rock powder and iron tailings powder on the compressive strength of concrete was investigated. The electric flux of concrete was determined to estimate the chloride ion permeability. The scanning electron microscope (SEM) and X-ray diffraction were obtained to investigate the hydration of cement paste. Results showed the electrical resistivity of all specimens presented in this order: specimens with iron tailings < specimens with dolomite rock powder < blank specimens < specimens with ground granulated blast-furnace slag (GGBS) < specimens with fly ash. The correlation between electrical resistivity and curing age of cement paste or concrete has been deduced as a quadratic function. The addition of GGBS could improve the compressive strength of concrete. Meanwhile, when the other three types of mineral admixtures were added, 5% by mass ratio of the total binder materials was the optimum for the compressive strength. The curing ages, the fly ash, the GGBS and 5% dolomite rock powder or 5% iron tailings powder demonstrated a positive effect on the chloride ion impermeability. However, when higher dosages of dolomite rock powder or iron tailings powder were added, the effect was the opposite. Finally, the compactness of the microstructure and the Ca(OH)2 of cement paste could be improved by a small dosage of dolomites or iron tailings (less than 5%).
Highlights
Concrete is an important human-made civil engineering material, which has been widely used for many years [1,2,3]
When the dolomites or iron tailings were added to the cement paste or concrete, the results were the opposite
This was attributed to the fact that the additions of mineral admixtures could accelerate the hydration process of cement decreasing the free water inner cement-based materials leading eventually to increasing the electrical resistivity of cement paste or concrete [35]
Summary
Concrete is an important human-made civil engineering material, which has been widely used for many years [1,2,3]. The accumulation of solid waste without reasonable treatment will pollute the environment, and affect the appearance of the city [4]. Researchers found that the solid wastes like waste fly ash and rice husk ash possessing active substances could promote the hydration process of cement. The addition of waste fly ash and rice husk ash were proven to increase the mechanical strengths and durability of concrete [7,8,9]. The waste fly ash and rice husk ash could improve the corrosion resistance of steel bars in the reactive powder concrete. The main problem with fly ash is that, as we increase the quantity, the hydration reaction is slowed down and the rate of strength gain is reduced. Other reasonable solid wastes or resources need to be excavated and applied to concrete
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
