Multiscale Characterization at Early Ages of Ultra-High Performance Geopolymer Concrete

The main obstacle of using geopolymer as a construction repair material is its slow strength development rate, which is the most significant attribute of an early-age opening for traffic and striking-off formwork. Geopolymer technology has recently attracted huge interest as an alternative to traditional cementitious materials with low environmental impact. Thus, this study investigates the feasibility of developing an ultra-high performance geopolymer concrete (UHPGC) with the aim of achieving high early-age strength. For this purpose, UHPGC mixtures activated with different potassium hydroxide molarities and aluminosilicate material types were developed and examined being cured with different curing temperatures. The early strength and durability of the UHPGC after 8 and 24 h were investigated. Experimental results revealed that the optimal mix design of UHPGC corresponds to a KOH molarity of 16 M and a 30% silica fume content. Furthermore, former mixture cured at 100 °C gave superior 8 and 24 h early strength values of 79 and 134 MPa, respectively. Moreover, a superior interaction of slag, silica fume, and activator solution at early age for UHPGC is revealed by the microstructural characteristics examined by a field emission scanning electron microscope (FESEM) with energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy analysis, and thermogravimetric (TGA) techniques. It was also found that the compressive strength results and the results of the microstructure analysis are well coincided. The experimental results obtained in this study emphasize the feasibility of using developed UHPGC as an eco-friendly quick repair materials The development of one-part UHPGC as a quick, cost-effective, and high-strength product for all construction repair maintenance will lead to huge improvements in the structural capacity and durability of structural components.