Macroscopic and microscopic analyses on mechanical performance of metakaolin/fly ash based geopolymer mortar

Zhang, Peng; Wang, Kexun; Wang, Juan; Guo, Jinjun; Ling, Yifeng

doi:10.1016/j.jclepro.2021.126193

Cited by 100 publications

(30 citation statements)

References 47 publications

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“…Generally, several strategies are utilized to control temperature and prevent cracks in practical engineering, including the adoption of pre-cooling aggregate and ice water, a pipe cooling method by circulating cold water through internal pipes during the concrete hardening stage [11], and the usage of a certain dosage of fly ash [12][13][14][15], fibers [16][17][18][19][20][21][22][23], and a magnesia expansion agent (abbreviated as MgO thereafter) [24][25][26][27][28][29][30]. However, the pre-cooling method and pipe cooling method need some additional labor as well as more construction time and cost [11].…”

Section: Introductionmentioning

confidence: 99%

Influence of MgO on the Hydration and Shrinkage Behavior of Low Heat Portland Cement-Based Materials via Pore Structural and Fractal Analysis

Wang

Liu

et al. 2022

Fractal Fract

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Currently, low heat Portland (LHP) cement is widely used in mass concrete structures. The magnesia expansion agent (MgO) can be adopted to reduce the shrinkage of conventional Portland cement-based materials, but very few studies can be found that investigate the influence of MgO on the properties of LHP cement-based materials. In this study, the influences of two types of MgO on the hydration, as well as the shrinkage behavior of LHP cement-based materials, were studied via pore structural and fractal analysis. The results indicate: (1) The addition of reactive MgO (with a reactivity of 50 s and shortened as M50 thereafter) not only extends the induction stage of LHP cement by about 1–2 h, but also slightly increases the hydration heat. In contrast, the addition of weak reactive MgO (with a reactivity of 300 s and shortened as M300 thereafter) could not prolong the induction stage of LHP cement. (2) The addition of 4 wt.%–8 wt.% MgO (by weight of binder) lowers the mechanical property of LHP concrete. Higher dosages of MgO and stronger reactivity lead to a larger reduction in mechanical properties at all of the hydration times studied. M300 favors the strength improvement of LHP concrete at later ages. (3) M50 effectively compensates the shrinkage of LHP concrete at a much earlier time than M300, whereas M300 compensates the long-term shrinkage more effectively than M50. Thus, M300 with an optimal dosage of 8 wt.% is suggested to be applied in mass LHP concrete structures. (4) The addition of M50 obviously refines the pore structures of LHP concrete at 7 days, whereas M300 starts to refine the pore structure at around 60 days. At 360 days, the concretes containing M300 exhibits much finer pore structures than those containing M50. (5) Fractal dimension is closely correlated with the pore structure of LHP concrete. Both pore structure and fractal dimension exhibit weak (or no) correlations with shrinkage of LHP concrete.

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Section: Introductionmentioning

confidence: 99%

Influence of MgO on the Hydration and Shrinkage Behavior of Low Heat Portland Cement-Based Materials via Pore Structural and Fractal Analysis

Wang

Liu

et al. 2022

Fractal Fract

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“…Previous research used polyvinyl alcohol (PVA) fibers and nano-SiO 2 to manufacture geopolymer concrete. The findings showed that PVA fibers enhanced the proprieties' strength, improved toughness, and achieved the optimal value at 0.6% to 1% [13][14][15][16]. Significant values were achieved with high temperatures in BF, and PVA contained geopolymer mortars.…”

Section: Introductionmentioning

confidence: 94%

The Effect of Basalt Fiber on Mechanical, Microstructural, and High-Temperature Properties of Fly Ash-Based and Basalt Powder Waste-Filled Sustainable Geopolymer Mortar

et al. 2021

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As the human population grows and technology advances, the demand for concrete and cement grows. However, it is critical to propose alternative ecologically suitable options to cement, the primary binder in concrete. Numerous researchers have recently concentrated their efforts on geopolymer mortars to accomplish this objective. The effects of basalt fiber (BF) on a geopolymer based on fly ash (FA) and basalt powder waste (BP) filled were studied in this research. The compressive and flexural strength, Charpy impact, and capillary water absorption tests were performed on produced samples after 28 days. Then, produced samples were exposed to the high-temperature test. Weight change, flexural strength, compressive strength, UPV, and microstructural tests of the specimens were performed after and before the effect of the high temperature. In addition, the results tests conducted on the specimens were compared after and before the high-temperature test. The findings indicated that BF had beneficial benefits, mainly when 1.2 percent BF was used. When the findings of samples containing 1.2 percent BF exposed to various temperatures were analyzed, it was revealed that it could increase compressive strength by up to 18 percent and flexural strength by up to 44 percent. In this study, the addition of BF to fly ash-based geopolymer samples improved the high-temperature resistance and mechanical properties.

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“…In this regard, nano silica acts as a filler to fill the microcracks and also promoting the cement hydration. Another investigation shows that the addition of certain nano silica can help geopolymerization of the mortar; however, further increasing the nano silica content than its critical ratio can negatively impact the mechanical properties [ 75 ].…”

Section: Recyclable Materials In Constructionmentioning

confidence: 99%

Circular Economy of Construction and Demolition Waste: A Literature Review on Lessons, Challenges, and Benefits

et al. 2021

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Conventionally, in a linear economy, C&D (Construction and Demolition) waste was considered as zero value materials, and, as a result of that, most C&D waste materials ended up in landfills. In recent years, with the increase in the awareness around sustainability and resource management, various countries have started to explore new models to minimize the use of limited resources which are currently overused, mismanaged, or quickly depleting. In this regard, the implementation of CE (Circular Economy) has emerged as a potential model to minimize the negative impact of C&D wastes on the environment. However, there are some challenges hindering a full transition to CE in the construction and demolition sectors. Therefore, this review paper aims to critically scrutinize different aspects of C&D waste and how CE can be integrated into construction projects. Reviewing of the literature revealed that the barriers in the implementation of CE in C&D waste sectors fall in five main domains, namely legal, technical, social, behavioral, and economic aspects. In this context, it was found that policy and governance, permits and specifications, technological limitation, quality and performance, knowledge and information, and, finally, the costs associated with the implementation of CE model at the early stage are the main barriers. In addition to these, from the contractors’ perspective, C&D waste dismantling, segregation, and on-site sorting, transportation, and local recovery processes are the main challenges at the start point for small-scale companies. To address the abovementioned challenges, and also to minimize the ambiguity of resulting outcomes by implementing CE in C&D waste sectors, there is an urgent need to introduce a global framework and a practicable pathway to allow companies to implement such models, regardless of their scale and location. Additionally, in this paper, recommendations on the direction for areas of future studies for a reduction in the environmental impacts have been provided. To structure an effective model approach, the future direction should be more focused on dismantling practices, hazardous material handling, quality control on waste acceptance, and material recovery processes, as well as a incentivization mechanism to promote ecological, economic, and social benefits of the CE for C&D sectors.

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Macroscopic and microscopic analyses on mechanical performance of metakaolin/fly ash based geopolymer mortar

Cited by 100 publications

References 47 publications

Influence of MgO on the Hydration and Shrinkage Behavior of Low Heat Portland Cement-Based Materials via Pore Structural and Fractal Analysis

Influence of MgO on the Hydration and Shrinkage Behavior of Low Heat Portland Cement-Based Materials via Pore Structural and Fractal Analysis

The Effect of Basalt Fiber on Mechanical, Microstructural, and High-Temperature Properties of Fly Ash-Based and Basalt Powder Waste-Filled Sustainable Geopolymer Mortar

Circular Economy of Construction and Demolition Waste: A Literature Review on Lessons, Challenges, and Benefits

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