176 / 2022-04-30 14:56:43

Development of lightweight engineered geopolymer composite with fly ash cenospheres

Engineered Geopolymer Composite,fly ash cenosphere,tensile-strain capacity,lightweight

Engineered geopolymer composite (EGC) has attracted great attention due to its superior tensile performance and crack control capacity. For its application in structural repair, reducing the weight of EGC can facilitate the installation of EGC and limit additional load. Therefore, lightweight EGC has been recognized as an innovative and effective composite for structural repair. Fly ash cenospheres (FACs), with hollow sphere structure, have been proved as a successful lightweight filler in cementitious materials. The FACs may react with alkaline activator, which alters the properties of EGC containing FACs. This study proposes a lightweight EGC with a high tensile strain capacity. The FACs are incorporated into EGC as the lightweight fillers. Increasing the FACs content gradually decreases the density and compressive strength of EGC due to their hollow structure. All the EGCs incorporating FAC present strain-hardening and multiple cracking behaviour. Using FAC to replace silica sand results in similar tensile strengths of EGCs around 6 MPa. Increasing the FAC/binder ratio from 0.3 to 0.7 slightly decreases the tensile strength of EGCs to around 4.6 MPa, which is mainly due to the reduced the fibre/matrix frictional bond. Besides, increasing the FAC content has a marginal impact on the ultimate tensile strain capacity of EGCs, which is around 9%. In addition, a higher content of FAC introduces more flaws to the matrix, and consequently increases the crack numbers and reduces the average crack width of EGCs. The scanning electron microscopic image demonstrates FACs partially react with the alkaline activator, which is beneficial to the properties of lightweight EGCs. Overall, the FACs can be utilised as effective fillers to produce lightweight EGC with acceptable strength and ultra-high tensile strain capacity.