Microstructure and phase characterizations of fly ash cements by alkali activation
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Microstructure and phase characterizations of fly ash cements by alkali activation Sak Sanchindapong1 · Chalermphan Narattha1 · Manow Piyaworapaiboon2 · Sakprayut Sinthupinyo2 · Prinya Chindaprasirt3 · Arnon Chaipanich1,4 Received: 23 August 2019 / Accepted: 2 July 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Microstructure and phase characterizations of fly ash cement by alkali activation were investigated. High calcium fly ash (FA) at 70%, 80%, 90% and 100% by mass of binders was used in combination with Portland cement (PC), thus producing alkaliactivated fly ash cements with some part of Portland cement and geopolymer (at 100%FA). Alkali solutions ( Na2SiO3 and NaOH) were used as activators at alkali liquid/binder of 0.65, and Na2SiO3/NaOH ratio used was 0.67. Samples were cured at 23 °C (55% RH) and 60 °C (95% RH). The results showed that curing temperature significantly affects the reacted products. By curing at higher temperature ≈ 60 °C, a denser structure due to high-temperature curing plays a crucial role in terms of producing more semi-crystalline (N–A–S–H) structure as characterized by X-ray diffraction. Moreover, higher-temperature curing gave higher compressive strength than curing at 23 °C in all mixes. Optimum compressive strength obtained at 23 °C and 60 °C curing samples was found in 80FA20PC and 100FA samples, respectively. Thermal analysis results showed that N–A–S–H/(N, C)–A–S–H was detected in all mixes. Scanning electron microscope and energy-dispersive X-ray showed elements belong to N–A–S–H and (N, C)–A–S–H phases. Keywords Compressive strength · Thermal analysis · Curing condition · Alkali-activated · Fly ash · Portland cement
Introduction Portland cement is the most used materials in producing concrete because of its unique properties such as compressive strength, long-term durability in normal conditions and capability of casting in many desired shapes. Therefore, Portland cement consumption increases every year
* Arnon Chaipanich [email protected] 1
Advanced Cement‑Based Materials Research Laboratory, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
2
Research and Innovation Center, SCG Cement Co., Ltd, Saraburi 18260, Thailand
3
Department of Civil Engineering, Faculty of Engineering, Sustainable Infrastructure Research and Development Center (SIRDC), Khon Kaen University, Khon Kaen 40002, Thailand
4
Center of Excellent in Materials Science and Technology, Chiang Mai University, Chiang Mai 50200, Thailand
but unsustainable [1] due to Portland cement production released approximately 5–8% of global carbon dioxide (CO2) emission to the total quantity of C O2 in the world [2]. For better sustainability, a lot of by-products from the industries were used to replace Portland cement quantities which have a specific property called pozzolan. Commonly used pozzolans those continued to be of research interests are industrial by-products such as fly ash, metakaolin, silica fume and
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