Circulation Fluidized Bed Combustion Fly Ash as Partial Replacement of Fine Aggregates in Roller Compacted Concrete.

Wei-Ting Lin,Kinga Korniejenko,Kae-Long Lin,Michał Łach,Marek Hebda,Kailun Chen

doi:10.3390/ma12244204

Abstract

Recently, many people around the world have been concerned with environmental protection and sustainability. The goal of various countries’ research has been focused on how to regenerate existing resources. Circulation fluidized bed combustion (CFBC) technology is one of the emerging combustion technologies for electricity generation and produces more than 800,000 tons of CFBC fly ash (CFA) per year for combustion. CFA has been widely applied in cement additive, new building materials and cement-based materials. The goal of this study was to discuss the engineering properties of roller-compacted concrete containing CFA. Test subjects included compressive strength, flexural strength, absorption, setting time, unit weight, sulfate resistance, SEM microscopic observations and XRD ingredient analysis. Test results indicate the following: (1) using CFA as a substitute of fine aggregates up to 10 wt.% would improve the development of later flexural strength; (2) the increases in pre-pressure would increase the compressive strength and unit weight and decrease absorption; (3) using CFA would reduce the initial setting time by 30%–60% and reduce the final setting time by 16%–20%; (4) using CFA would reduce the absorption; (5) using CFA would reduce the unit weight by 0.5%–2.8%, and the increases in pre-pressure would increase the unit weight by about 0.9%–2.1%; (6) CaO in CFA helps to improve sulfate resistance; (7) scanning electron microscopy (SEM) observation shows that the increases in pre-pressure would reduce the pores; and (8) X-ray diffraction (XRD) analysis shows that the inclusion of CFA would increase the content of Ca(OH)2 in concrete.

Highlights

Since the Industrial Revolution in the 19th century, the exhaustion of resources has seemed to be an insoluble problem
The consistency of Roller-compacted concrete (RCC) was examined by VC using the Vebe test, and the test results revealed that the water demand increases with the increase of fine aggregates replaced by CFBC fly ash (CFA)
2, Aft, ettringite crystals and Ca(OH)2 was higher than that of the blending effect produced by C–S–H gel increase of of thethe dosage of of CFA, thethe intensity of of thethe diffraction peaks of SiO

Summary

Introduction

Since the Industrial Revolution in the 19th century, the exhaustion of resources has seemed to be an insoluble problem. With the rapid development of science and technology, the value of non-renewable resources has soared, and industrial waste has become a serious problem. Compared to conventional pulverized coal combustion technology, CFBC presents greater performance and lower pollutant emissions. It is suitable for a variety of fuels, and its application to petroleum coke with a sulfur content of less than 5% firmly follows the principle of waste recycling [3]. Several research works have been conducted on the use of CFA in cement manufacturing, soil improvement, road basements, new building materials and building fillers [1,4]. By-products such as fly ash are usually accompanied as aggregates or cement substitutes due to industrial development [7,8]

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Conclusion