Effect of milled fluidised bed cracking catalyst waste on hydration of calcium aluminate cement and formation of binder
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Effect of milled fluidised bed cracking catalyst waste on hydration of calcium aluminate cement and formation of binder structure Valentin Antonovič1 · Renata Boris1 · Jurgita Malaiškienė1 · Viktor Kizinievič1 · Rimvydas Stonys1 Received: 27 July 2019 / Accepted: 30 April 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract This study analyses the effect of fluidised bed cracking catalyst (FBCC) waste, milled to nano-sizes and unmilled, on the hydration of calcium aluminate cement after hardening under normal conditions and after thermal treatment of the samples at 1200 °C. Differential thermal analysis (DTA), X-ray analysis (XRD), and electron scanning microscopy analysis (SEM) were conducted. Results of calorimetry studies showed that milled FBCC added up to 5% slightly slows down the hydration processes of aluminate cement, whereas 10% of FBCC accelerates the hydration. The total amount of heat released in the samples with milled FBCC was lower than that in the samples with unmilled FBCC. The thermogravimetry analysis (TG) revealed higher mass loss in samples with unmilled FBCC. Additionally, XRD results after hardening showed that, compared to the samples with unmilled FBCC, the samples with milled FBCC yielded a higher relative intensity of unreacted minerals of cement. After burning the samples at 1200 °C, anorthite crystals were formed in the samples with FBCC. The effect of unmilled FBCC on the hydration process was explained by the ability of the particles to absorb water at the initial hydration stage and subsequently to transfer it to further hydration steps, thereby promoting the formation of crystallohydrates in larger quantities. Keywords FBCC · Calcium aluminate cement · Calorimetry · DTA · XRD · SEM
Introduction Fluidised bed cracking catalyst (FBCC) waste accounts for more than 800,000 tons per year worldwide [1]. The base of this waste consists of A l2O3 (~ 40%) and S iO2 (~ 50%) [2]. Many studies have shown that the catalyst activity has a positive effect on the hydration of Portland and calcium aluminate cements (CACs). Therefore, research on the secondary use of this waste in various cement materials is being carried out intensively. By adding it up to 10–20%, FBCC, which exhibits a zeolite-type structure, has been shown to possess pozzolanic properties that increase the strength of Portland cement mortar and concrete and the resistance of the material to carbonate corrosion [3, 4], chloride ingress attack [5], and alkaline corrosion [6]. Most of the examined FBCC particles * Renata Boris [email protected] 1
Laboratory of Composite Materials, Institute of Building Materials, Vilnius Gediminas Technical University, Linkmenų Str. 28, 08217 Vilnius, Lithuania
are 10–100 µm in size. A better enhancement of properties is achieved using smaller FBCC particles or higher treatment temperature (850 °C), resulting in improved pozzolanic activity of the waste and enhanced cement strength [7–9]. Previous studies [10, 11] have revealed that FBCC accelerates the hydration of Portland cement
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