Abstract
Development of geopolymers from wastes or by-products introduces a sustainable approach to replace ordinary Portland cement (OPC)-based concrete with an eco-material of lower green-house gases emissions. However, safety concerns related to the conventional two-part geopolymer has limited large-scale applications of the product. In this context, a novel one-part geopolymer from coal fly ash and water treatment sludge has been presented. The transformation of raw materials to geopolymer was observed by FTIR, SEM and XRD analyses. Acid resistance test has proved that the new binder had great durability against sulphuric acid attack. After 28 days immersion in 5% H2SO4 solution, weight of all samples was hardly changed. Compressive strength, on the other hand, has not decreased but significantly increased as curing time increased. The properties were also compared to those of control samples cured in water. It was demonstrated that strong acid immersion did not create any noticeable effect on the weight and strength of one-part geopolymer system developed from coal fly ash and water treatment sludge.
Highlights
Since the first attempt of Davidovits to create geopolymer in 1972, numerous efforts have been dedicated to develop an advanced material for wide range of applications [1]
Both sludge and fly ash compose of high proportions of Si and Al., The percentages of SiO2 and Al2O3 in raw materials are similar with the range of these materials from various sources of water treatment sludge (WTS) (Waijarean et al, 2014; Suksiripattanapong et al, 2015; Huang and Wang 2013) and FA (Blissett and Rowson, 2012)
The microscale images of raw materials in Figue 1 show that FA consists of typical microspheres from 1 to 20 μm [11], sludge does not contain any sphere but flaky phases
Summary
Since the first attempt of Davidovits to create geopolymer in 1972, numerous efforts have been dedicated to develop an advanced material for wide range of applications [1]. Aqueous alkali solution is used to dissolve aluminate and silicate species from starting materials so as to form a three-dimensional network [1]. To avoid the usage of corrosive and viscous alkali solution, recent researches has explored the feasibility of one-part geopolymer using solid activators [4]. Coal fly ash (FA) and water treatment sludge (WTS) were used as raw materials for the production of one-part geopolymer. WTS is the residue from water treatment process that consist significant fraction of precipitated alum. The FA and WTS mixtures were activated by sodium hydroxide and sodium aluminate. The durability of the formed- geopolymer against acid attack is investigated in this study
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