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

Internal Curing Using Superabsorbent Polymers for Alkali Activated Slag-Fly Ash Mixtures

Increased shrinkage is often noted as a concern for alkali activated materials. In this study, two slag-fly ash paste and mortar mixtures with slag:fly ash ratios of 30:70 and 50:50 activated using 4M sodium hydroxide are formulated. The effects of two dosages of a commercial superabsorbent polymer (SAP) on the reaction heat, strength gain, autogenous shrinkage, drying shrinkage, and mass loss behavior are presented here. The SAP increases the heat of reaction of the alkali activated pastes, however, this increase is less than 5% at 7 days. The SAP slightly decreases the compressive strength of the alkali activated mortars, and this decrease is generally less than 10% at 1, 7, and 28 days. The SAP significantly reduces the ultimate autogenous shrinkage (by more than 50%) and reduces the drying shrinkage (by 15–30%) of the mortars. Mixtures with SAP have autogenous shrinkage between 50–300 με and drying shrinkage between 600–700 με. When SAP is used, the mass loss in the mortars increases, however, the slope of the mass loss-drying shrinkage curve decreases. Shrinkage mitigation in the studied mixtures increases as the SAP dosage increases. Further studies on this system, and on other binders, activator combinations, and SAP types are currently ongoing