Abstract
This present study evaluates the effect of silica modulus (Ms) and curing temperature on strengths and the microstructures of binary blended alkali-activated volcanic ash and limestone powder mortar. Mortar samples were prepared using mass ratio of combined Na2SiO3(aq)/10 M NaOH(aq) of 0.5 to 1.5 at an interval of 0.25, corresponding to Ms of 0.52, 0.72, 0.89, 1.05 and 1.18, respectively, and sole 10 M NaOH(aq). Samples were then subjected to ambient room temperature, and the oven-cured temperature was maintained from 45 to 90 °C at an interval of 15 °C for 24 h. The maximum achievable 28-day strength was 27 MPa at Ms value of 0.89 cured at 75 °C. Samples synthesised with the sole 10 M NaOH(aq) activator resulted in a binder with a low 28-day compressive strength (15 MPa) compared to combined usage of Na2SiO3(aq)/10 M NaOH(aq) activators. Results further revealed that curing at low temperatures (25 °C to 45 °C) does not favour strength development, whereas higher curing temperature positively enhanced strength development. More than 70% of the 28-day compressive strength could be achieved within 12 h of curing with the usage of combined Na2SiO3(aq)/10 M NaOH(aq). XRD, FTIR and SEM + EDX characterisations revealed that activation with combined Na2SiO3(aq)/10 M NaOH(aq) leads to the formation of anorthite (CaAl2Si2O8), gehlenite (CaO.Al2O3.SiO2) and albite (NaAlSi3O8) that improve the amorphosity, homogeneity and microstructural density of the binder compared to that of samples synthesised with sole 10 M NaOH(aq).
Highlights
Concrete is the bedrock of our built environment
The impact of silica modulus (Ms ) and curing temperature on workability, compressive strength, bond properties, reaction products and the microstructures of alkali-activated binder synthesised from the binary blending of volcanic ash powder (VA) and limestone powder (LSP) were investigated
This study has contributed to understanding the impact of silica modulus and curing temperature on the strength and microstructural characteristics of the alkali-activated volcanic ash/limestone powder mortar
Summary
Concrete is the bedrock of our built environment. The construction of critical infrastructures for social and economic development consumed approximately 35 billion tons of concrete inclusive of steel, wood and aluminium [1]. The effect of silica modulus on a binary mix of natural pozzolan (NP) and slag alkali-activated binder (AAB) was Materials 2021, 14, 5204 studied [28]. Ibrahim et al investigated the effect of silica modulus on alkali-activated natural pozzolan concrete [29] Curing temperature is another very important parameter that affects the strength development of alkali-activated binders. Despite numerous works on the effects of alkali activators on the alkaliactivated binder, there is a limited study concerning the role of silica modulus and curing temperature on mechanical, and microstructure properties of alkaline binary blended volcanic ash powder and limestone powder mortar. This paper reports the findings of the influence of silica modulus and curing temperature on the strength and microstructure of alkali-activated LSP/VA mortar. The utilisation of VA/LSP will be an addition to sustainable alternative binders and waste reduction
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
