Cement has been well documented to positively affect the early-age strength of the cement asphalt emulsion mixtures (termed as CAEM) without compromising workability. However, the long-term performance of the CAEM incorporating multiple cement combinations is not conclusive. This study explored the effect of the combined usage of ordinary portland cement (OPC) and sulfoaluminate cement (SAC) on the long-term performance and microstructural properties of a CAEM system in detail. Three tasks were conducted, including (1) designing six CAEM formulations by introducing different types (OPC and SAC) and contents (2-6 wt%) of cement; (2) evaluating the long-term performance by moisture susceptibility, frost damage, abrasion resistance, and rutting resistance; and (3) characterizing the microstructural properties by scanning electron microscopes and energy-dispersive spectrometers. The experimental results revealed that the relative dynamic elastic modulus of CAEM was increased to 69.7% when admixing 90 wt% OPC and 10 wt% SAC. The mixture incorporating 90 wt% OPC and 10 wt% SAC demonstrated excellent rutting resistance up to ~31,000 cycles/mm of dynamic stability. The improved long-term performance actually originated from the reduced voids and produced a dense microstructure. The outcomes could facilitate tailoring CEAM products with better long-term performance.
Iron tailing powder (ITP) is considered to have the potential to replace cement to manufacture ultra-high-performance concrete (UHPC). However, the performance of UHPC with the addition of ITP after exposure to high temperatures is more complex. This investigation prepares seven UHPC formulations by introducing different contents of ITP and investigates the mechanical behavior (residual strength), bound water content, and microstructural properties (crystalline and amorphous phases, chemical structure, and morphology) of UHPC subjected to elevated temperatures. The experimental results show that the addition of ITP postpones the spalling of concrete when exposed to high temperatures. The concrete incorporating 15% ITP maintains 53.8% of its original strength at 800°C, unlike the concrete without ITP that maintains 31.6% of its original strength. The addition of ITP increases the number of micropores/cracks in concrete and helps release the vapor pressure caused by water evaporation. The findings of this investigation highlight the potential application of ITP for future UHPC design and manufacture.
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