Management and valorisation of wastes through use in producing alkali‐activated cement materials

Abstract

ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Abstract 15There is a growing global interest in maximising the re-use and recycling of waste, to 16 minimise the environmental impacts associated with waste treatment and disposal. Use 17 of high-volume wastes in the production of blended or novel cements (including alkali-18 activated cements) is well known as a key pathway by which these wastes can be re-19 used. This paper presents a critical overview of the urban, agricultural, mining and 20 industrial wastes that have been identified as potential precursors for the production of 21 alkali-activated cement materials, or that can be effectively stabilised/solidified via 22 alkali activation, to assure their safe disposal. The central aim of this review is to 23 elucidate the potential advantages and pitfalls associated with the application of alkali-24 activation technology to a wide variety of wastes that have been claimed to be suitable 25 for the production of construction materials. A brief overview of the generation and 26 characteristics of each waste is reported, accompanied by identification of opportunities 27 for the use of alkali-activation technology for their valorisation and/or management. 28

Alkali-activated materials

“…Blast furnace slags intended for use in alkali-activation require quenching (granulation or pelletization) and grinding to yield a reactive material. Other materials which are less commonly used in general Portland cement blends, but which have pozzolanic or hydraulic character such as Ferich clays [24], various slags from ferrous and non-ferrous metallurgy if air-or water-cooled to a reactive state and then finely ground [29,30], clay-rich sludges resulting from water treatment [31] or kaolin purification [32], red mud [33][34][35], ground coal bottom ash [36], agricultural waste ashes [37], and fly ashes which do not meet the criteria specified in standards for use in Portland cement [38] are also of value in alkali-activation, although in the case of non-ferrous and steelmaking slags the leachability of toxic components must be considered with care. This may in fact prove to be a key avenue for the development of alkali-activated systems for niche applications, where there is not competition from Portland blended cements for the desired raw materials [2].…”

Advances in near-neutral salts activation of blast furnace slags

“…Some of the technical challenges associated with the use of near-neutral salt activators have been overcome by incorporating into the activated slag cements minor fractions of clinker or Ca(OH) 2 [26], limestone [27], or utilising blended activating solutions of sodium carbonate or sulfates with sodium hydroxide or silicate solutions [28], or adopting high temperature curing [1]. All these different approaches make the material harden; however, in order to move towards a more standardised way of developing alkali-activated slag binders, it is required to consider the role of the chemical and mineralogical characteristics of slags from different sources, to select the most suitable activator for a given slag.…”

“…These materials have been studied for more than a century, and in the past decades one of the main drivers for their development has been the potential environmental benefits associated with their production [1]. Alkali activated cements are usually produced from industrial wastes or byproducts such as blast furnace slag derived from the ironmaking industry, fly ashes from the coal combustion process, among others [2], and are now commercialised in several places around the world [3]. These materials can develop desirable properties including high mechanical strength [4], good retention of integrity when exposed to high temperatures [5] and acidic media [6], if properly formulated and cured.…”

Reactivity of industrial wastes as measured through ICP‐OES: A case study on siliceous Indian biomass ash

“…While most academic studies investigate the utility of industrial byproducts through chemical characterization and subsequent synthesis of an alkali activated binder, Bernal et al points out that they often neglect supply‐side analysis. As mentioned, silica‐containing agricultural residues such as rice husk and sugarcane bagasse are produced globally at a very large scale (>150 million tons of rice husk and >540 million tons of bagasse annually), with cumulative ash content of at least 40 million tons given complete incineration of organic material .…”

“…Direct emissions and fuel consumption associated with ordinary Portland cement (OPC) production is responsible for most of the estimated 5%‐8% of global annual CO 2 emissions attributed to concrete . Alkali‐activated materials and geopolymers offer cement‐free alternatives with comparable physical properties, and regular use of industrial byproducts as precursors suggests substantially lower environmental footprints . Still, as researchers expand their search for useful precursors, it is becoming increasingly apparent that any byproduct stream must be of adequate scale to offset demand for binder‐based building materials .…”