Hydration-strength-durability-workability of biochar-cement binary blends

초록

This study presents the workability, mechanical properties, ultrasonic pulse velocity (UPV), heat of hydration, degree of hydration, hydration products, durability (chloride ion diffusion and electrical resistivity), meso-structure, and microstructure of biochar blended specimens with various biochar contents (2% and 5% of cement). Based on the various test results, we found that (1) the workability decreases with an increase in the biochar replacement ratio. (2) The addition of biochar reduces the compressive strength, and compared with the early age, the reduction in strength at later ages is less obvious. (3) The addition of biochar reduces the UPV. For all specimens at various ages, the compressive strength can be regressed as an exponential function of the UPV. (4) With the increase in biochar content, the cumulative heat decreases. Compared with the dilution effect, the nucleation effect of biochar is marginal. (5) X-ray diffraction (XRD) and thermogravimetric analysis (TGA) showed that as the biochar content increases, the Ca(OH)(2) content decreases. Moreover, the TGA results showed that as the biochar content increases, the degree of cement hydration decreases. (6) As the biochar content increases, the chloride diffusivity increases. Moreover, because biochar is non-conductive, the electrical resistivity increases with increasing biochar content. (7) Optical micrographs showed that as the biochar content increases, the meso air voids also increase. Moreover, scanning electron microscopy (SEM) analysis revealed that the internal pores of biochar particles can provide space for the formation of hydration products.

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