Comparative Study Involving Effect of Curing Regime on Elastic Modulus of Geopolymer Concrete

Abstract

Geopolymer Concrete (GPC) as a cement-less construction material has attracted worldwide attention due to its lower carbon footprint. There are numerous studies reported on GPC made using different by-products including fly-ash. However, since the use of bottom-ash is comparatively limited, making potassium-based GPC using this waste can be an alternative to Portland Cement Concrete (PCC). In this study, two methods of accelerated curing were used to determine the influence of elevated temperature on the compressive strength of GPC, composed of 50% bottom-ash and 50% fly-ash. GPC specimens were cured using various temperatures including ambient, 30 °C, 45 °C, 60 °C, and 80 °C for 24 h, all followed by 28 days of ambient curing. The highest compressive strength was obtained with steam curing at a temperature of 80 °C for a duration of 24 h. It is of great significance to evaluate elastic modulus of the concrete mixture so that the short-term rigidity of structures subjected to elongation, bending, or compression can be predicted. In this study, a longitudinal Resonant Frequency Test (RFT) as a non-destructive test (NDT) was used to calculate the elastic modulus of both GPC and a comparative PCC mix. Based on the results, PCC had higher resonant frequency (by about 1000 Hz) compared to GPC. A review of empirical models for predicting GPC’s elastic modulus showed that all of the predicted elastic modulus values were lower than experimental values.

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“…where E is the modulus of elasticity (MPa), σ c is the compressive strength (MPa), and ρ is the unit weight (kg/m 3 ). Hence, as previously noted for mechanical strength, the stiffness properties of geocement-based compounds also depend on the composition (nature of raw materials and mixture), synthesis process, curing regime, and aggregate-GC ITZ [53]. Aboulayt et al [57] reported from their studies that adding FA in MK geopolymer grout reduces the reactivity of the mixtures, increases the packing density of the precursor powders, and promotes the retention of air bubbles in the matrix.…”

“…In terms of technological applicability, the knowledge of this parameter is crucial to evaluate the stress and deformation distributions of a concrete element under a spatial stress state. High compressive strength and stiffness are the fundamental conditions for a civil structure to support high loads and avoid failure of serviceability [53,54]. On the other hand, high mechanical deformability results in a better impact on vibro-acoustic damping and sound insulation performance against impact noise [55].…”

“…In analogy with the mechanical behavior observed in ordinary PC concrete, the elastic modulus varies with the compressive strength. Specifically, as the compressive strength increases, the modulus of elasticity increases [53,54]. Hardjito and Diaz-Loya predictive models, shown in Equations (1) and ( 2) respectively, are the main correlation relationships between elastic modulus and mechanical strength developed in the context of geopolymer concrete made of FA [56]:…”

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“…The unique manufacturing process of these GC pavers includes using fly-ash and bottom ash, collected from waste produced in thermal power plants, then mixing it with sodium, Na-based polymers and curing at a higher temperature to attain strength and desired durability. The detailed process of producing GC pavers as well as their utility in real-applications can be found in [20][21][22]. Based on these findings [20][21][22], trial batches of Na-based Geopolymer concrete paver blocks (with mold of 150 × 150 × 100 mm) were manufactured and cured at 80 • C, at Lovely Professional University, India.…”

“…The detailed process of producing GC pavers as well as their utility in real-applications can be found in [20][21][22]. Based on these findings [20][21][22], trial batches of Na-based Geopolymer concrete paver blocks (with mold of 150 × 150 × 100 mm) were manufactured and cured at 80 • C, at Lovely Professional University, India. The strong and durable pavers obtained from the lab allowed the researchers to purchase 400 fly-ash based paver blocks casted in a commercial facility.…”