Ultra-high-performance concrete with local high unburned carbon fly ash

Abstract

Ultra-high-performance concrete (UHPC) is a kind of high-tech cementitious material with superb mechanical and durability properties compared to other types of concrete. However, due to the high content of cement and silica fume used, the cost and environmental impact of UHPC is considerably higher than conventional concrete. For this reason, several efforts around the world have been made to develop UHPC with greener and less expensive local pozzolans. This study aimed to design and produce UHPC using local fly ash available in Colombia. A numerical optimization, based on Design of Experiments (DoE) and multi-objective criteria, was performed to obtain a mixture with the proper flow and highest compressive strength, while simultaneously having the minimum content of cement. The results showed that, despite the low quality of local fly ashes in Colombia, compressive strength values of 150 MPa without any heat treatment can be achieved.

A Comprehensive Overview of Recycled Glass as Mineral Admixture for Circular UHPC Solutions

“…For its part, several investigations have focused on the utilization of rejected fly ash along with recycled glass powder in UHPC formulations [28,48]. On the one hand, the research presented in [28] explored the utilization of local high unburned carbon fly ash as a mineral admixture in waste glass-UHPC.…”

“…This way, one must meticulously choose micro-and nano-sized components that can effectively fill the gaps between larger particles, resulting in an improved packing arrangement [22]. It is worth mentioning that certain materials, like SF, quartz powder, slags, fly ash and others, are frequently utilized in this application owing to their fine particle size and pozzolanic features [2,3,6,[23][24][25][26][27][28][29]. Understanding the achievement of optimal density in concrete relies on the use of particle-packing models, like the modified Andreasen and Andersen (A&Amod) or the Compressive Packing Model (CPM) [19].…”

“…However, the removal of coarse aggregates results in a higher amount of powders, such as cement and SF, being needed. This can have negative effects on cost and sustainability, as will be explored in later sections [25,28].…”

Predicción basada en redes neuronales de la resistencia a compresión a los 7 días de los UHPC incorporando SCM

“…El superplastificante, producido a base de éter a base de policarboxilato, ralentiza la hidratación de los silicatos (especialmente la fase alita) y afecta la formación de ettringita, retardando o perjudicando el desarrollo de resistencias a edades tempranas [3, 21,92]. El efecto nocivo del contenido de FA en la resistencia temprana del hormigón ha sido reportado por varias investigaciones [77,81,94,95]. Además, el análisis de CWA sugirió que GP parece tener un efecto negativo reducido en la resistencia a la compresión de UHPC.…”

Modelo predictivo de redes neuronales para estimar la resistencia a compresión de hormigones con materiales cementantes suplementarios y agregados reciclados

“…Por otro lado están las puzolanas, que son materiales inorgánicos o artificiales, silíceos o silico-aluminosos con porcentajes bajos de calcio, magnesio, hierro, potasio y sodio, que por sí solo no tienen valor cementante, pero que son capaces de reaccionar con el agua y el CH liberado del cemento Portland hidratado para formar productos de hidratación secundarios tipo CSH o CASH [13,14]. Algunos ejemplos de materiales puzolánicos serían la ceniza volate tipo F, el polvo de vidrio reciclado, el residuo de craqueo catalítico usado (FC3R), la ceniza de cascarilla de arroz y el humo de sílice [15][16][17][18][19] También importante destacar que algunos de los materiales cementantes suplementarios, como las cenizas volantes, el residuo de catalizador de craqueo catalítico usado, las escorias siderúrgicas o el polvo de vidrio reciclado son a su vez subproductos industriales [10,[20][21][22], por lo que su empleo tiene una aportación adicional a la sostenibilidad final del hormigón.…”