ARTICLE | doi:10.20944/preprints202209.0462.v2
Subject: Materials Science, Other Keywords: Compressive strength; metakaolin; nanomaterial; refractory; zirconia
Online: 30 September 2022 (03:08:01 CEST)
Geopolymer is an emerging material alternative to Portland cement and has potential as a refractory material. Adding filler in geopolymer material is a strategy to increase the advantages of its physical and mechanical properties. It has been previously reported that adding nanoparticles can increase the compressive strength value, but there is no reported interaction between nanoparticles and geopolymer during the geopolymerization process. This study aims to study the effect of adding nano-zirconia fillers on the physical and mechanical changes of metakaolin-based geopolymers with nano-zirconia fillers. The geopolymer samples were made with 100 g of metakaolin as the base material and nano-zirconia in amounts of 2 gr, 5 gr, 10 gr, and 15 gr. Further characterization was carried out by XRD, FTIR, and SEM-EDX. This study showed that the compressive strength of the MZr05 sample increased significantly by 58.7% compared to the control sample. The test results of the structure and functional groups did not lead to any new compounds formed in the geopolymerization reaction. Therefore, the interaction of metakaolin geopolymer with nano-zirconia only creates an interfacial bonding.
ARTICLE | doi:10.20944/preprints201912.0214.v1
Subject: Materials Science, Other Keywords: geopolymers; metakaolin; biomass bottom ash; mechanical properties
Online: 16 December 2019 (11:15:41 CET)
In this research, the feasibility of using bottom ashes generated by the combustion of biomass (olive pruning and pine pruning) as a source of aluminosilicates (OPBA) has been studied, replacing the metakaolin precursor (MK) in different proportions (0, 25, 50, 75 and 100 wt. % substitution) for the synthesis of geopolymers. As alkaline activator an 8 M NaOH solution and a Na2SiO3 have been used. The geopolymers were cured 24 hours in a climatic chamber at 60 ° C in a water-saturated atmosphere, subsequently demoulded and cured at room temperature for 28 days. The results indicated that the incorporation of OPBA waste, which have 19.7 wt. % of Ca, modifies the characteristics of the products formed after alkaline activation. In general terms, the incorporation of increasing amounts of calcium-rich ashes results in geopolymers with higher bulk density. The compressive strength increases with the addition of up to 50 wt. % of OPBA with respect to the control geopolymers, contributing the composition of the residue to the acquisition of a better behaviour mechanical. The results indicate the potential use of these OPBA waste as raw material to produce unconventional cements with 28-day curing strengths greater than 10 MPa, and thermal conductivities less than 0.35 W/mK.
ARTICLE | doi:10.20944/preprints202012.0747.v1
Subject: Engineering, Automotive Engineering Keywords: alkali activated; fly ash; blast furnace slag; silica fume; metakaolin; ambient curing; strength development; flexural strength; freeze-thaw resistance
Online: 30 December 2020 (09:03:09 CET)
Concrete is the most commonly used construction material due to its various advantages, such as versatility, familiarity, strength and durability and it will continue to be in demand far into the future. However, with today’s sensitivity to the environmental protection, this material is facing unprecedented challenges due to its high greenhouse gas emission mainly during cement production. This paper investigates one of the promising cement replacement materials, alkali activated cement (AAC) concrete. Being produced mainly from byproduct materials and having a comparable structural performance to conventional concrete, AAC concrete has a potential to transform the construction industry. Mechanical properties such as compressive and flexural strength and the relationship between them are studied. Different source materials such as fly ash (FA), ground granulated blast furnace slag (GGBS), silica fume (SF) and Metakaolin (MK) are used. The effect of the source materials and the activator solutions on the concrete performance is studied. Furthermore, the freeze-thaw resistance of the concrete is studied. The results of the study showed that the behavior of AAC depends highly on the source material combinations as well as type used. The effect of the alkaline solution is also dependent on the source material used. Mixes with higher GGBS content in general showed the highest strength while mixes with MK showed the highest flexural strength. The results from the freeze-thaw test showed that proper design of AAC concrete with a lower water content is critical to achieve a good resistance.