Thermogravimetric analysis and phase characterizations of Portland fly ash limestone cements
- PDF / 2,247,660 Bytes
- 8 Pages / 595.276 x 790.866 pts Page_size
- 28 Downloads / 184 Views
Thermogravimetric analysis and phase characterizations of Portland fly ash limestone cements Arnon Chaipanich1 · Supitchaya Thongsomboon1 · Phakin Chomyen1 Received: 25 August 2019 / Accepted: 29 June 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract In this work, 50% of the Portland cement was replaced with fly ash and limestone powder by mass. Fly ash to limestone powder ratios of 50:0, 45:5, 40:10, and 30:20 were used. Thermogravimetric analysis (TGA), X-ray diffraction and scanning electron microscopy of the paste mixes were carried out after water curing for 7 and 28 days to determine the hydration and pozzolanic reaction that occurred during the early age and after the standard 28-day curing. In addition, the compressive strength and physical properties of the corresponding mortar mixes were also investigated. At 7 days, the use of limestone with fly ash led to an increase in compressive strength when compared to that for a fly ash mix without limestone (50% FA). This was attributed to the filler effect of the limestone rather than the reaction of the limestone powder with C 3A as there was no hemicarboaluminate detected; this was possibly due to a decreased amount of C 3A being available since 50% of the Portland cement was used. At 28 days, the 45% FA and 5% LS mixture showed an increased compressive strength, a decreased water absorption and a decreased number of voids. Again, this can be attributed to the filler effect of the limestone. Interestingly, at 28 days, monocarboaluminate was detected by TGA and XRD when the limestone powder was added. Keywords Thermogravimetric analysis · Phase characterization · Fly ash · Limestone · Cements
Introduction Ground limestone particles, also known as limestone powder, consist mainly of calcium carbonate (CaCO3) in its fine form. It can be incorporated with Portland cement, such as in the EN197-1 standard [1], at up to 35% by mass. It has been reported that when 5% limestone powder is used with 30% fly ash, the compressive strength is improved when compared to that for 35% fly ash [2–4] at early ages. Durability properties (chloride and sulfate resistance) were also found to improve with the use of limestone mixed with Portland cement [2–4]. The improvement with limestone powder can be attributed to the physical mechanism known as the filler effect and the chemical mechanism from the calcium carbonate reactions. Calcium carbonate can react with C3A to form carboaluminate hydrate phases, such as * 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
monocarboaluminate (Ca4Al2O6·CO3·11H2O) and hemicarboaluminate (Ca4Al2O6 (CO3)0.5(OH)·11.5H2O)), that influence the hydration process [5–8]. Fly ash is a by-product from coal power plants. Its use as a supplementary cementitious material to replace part of Portland cement or as an admixture to improve concrete performance is well known due t
Data Loading...
