Fracture properties of GGBFS-blended fly ash geopolymer concrete cured in ambient temperature

Fracture characteristics are important part of concrete design against brittle failure. Recently, fly ash geopolymer binder is gaining significant interest as a greener alternative to traditional ordinary Portland cement (OPC). Hence it is important to understand the failure behaviour of fly ash based geopolymers for safe design of structures built with such materials. This paper presents the fracture properties of ambient-cured geopolymer concrete (GPC). Notched beam specimens of GPC mixtures based mainly on fly ash and a small percentage of ground granulated blast furnace slag were subjected to three-point bending test to evaluate fracture behaviour. The effect of mixture proportions on the fracture properties were compared with control as well as OPC concrete. The results show that fracture properties are influenced by the mixture compositions. Presence of additional water affected fracture properties adversely. Fracture energy is generally governed by tensile strength which correlates with compressive strength. Critical stress intensity factor varies with the variation of flexural strength. Geopolymer concrete specimens showed similar load–deflection behaviour as OPC concrete specimens. The ambient cured GPC showed relatively more ductility than the previously reported heat cured GPC, which is comparable to the OPC specimens. Fly ash based GPC achieved relatively higher fracture energy and similar values of KIC as compared to those of OPC concrete of similar compressive strength. Thus, fly ash based GPC designed for curing in ambient condition can achieve fracture properties comparable to those of normal OPC concrete

Development of fiber-reinforced slag-based geopolymer concrete containing lightweight aggregates produced by granulation of Petrit-T

Abstract Using by-products as alternatives to ordinary Portland cement (OPC) is attracting growing attention in the sustainable construction material sectors. Alkali-activated binders have been proposed and emerged as an alternative to OPC binders, which seem to have acceptable mechanical and durability performances in addition to positive environmental impacts. These alternative binders, also named “geopolymer,” use a wide range of aluminosilicate precursors, with differing availabilities, reactivates, costs, and CO₂ emissions. The usage of various materials results in obtaining the locally adaptable mix compositions, which establishes a broader toolkit. In this study, Petrit-T as a by-product from manufacturing sponge iron with fine particle-size distribution and rich in calcium was used to prepare the structural lightweight aggregates. Moreover, ground-granulated blast-furnace slag (GGBFS) as the binder was activated by a combination of sodium hydroxide and sodium silicate as the alkali activator. The effects of using different fiber types, including PVA, PP, and basalt, on mechanical properties were investigated. Mechanical properties were addressed in terms of the compressive and flexural strengths. The results showed that reinforcing the composition significantly affected the flexural performance. Moreover, it was revealed that using the granulated Petrit-T presented a lightweight concrete, with density ρ ≤ 1600 kg/m³