Enhancing the Performance of Recycled Aggregate Mortars Using Alkali-Activated Fly Ash
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pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
DOI 10.1007/s12205-020-0260-6
Structural Engineering
Enhancing the Performance of Recycled Aggregate Mortars Using Alkali-Activated Fly Ash Muhammad Asad Nawaz
a
, Liaqat Ali Qureshib, and Babar Ali
c
a
Civil Engineering Department (CED), University of Engineering and Technology (UET), Taxila 47050, Pakistan Civil Engineering Department (CED), Swedish College of Engineering and Technology (SCET), Wah Cantt 47060, Pakistan c Civil Engineering Department (CED), COMSATS University Islamabad (CUI), Sahiwal Campus, Sahiwal 57000, Pakistan b
ARTICLE HISTORY
ABSTRACT
Received 20 February 2020 Accepted 11 September 2020 Published Online 27 November 2020
The aim of this paper is to advance the research on the use of alkali-activated fly ash in recycled concrete aggregate (RCA) bearing mortar (RAM) to achieve low carbon footprint and sustainability in construction. To this end, the present paper explores the advantages in terms of improved properties of RAM by incorporating fly ash with an alkali-silicate activator. Results of testing reveal that compressive strength of RAM is improved by more than 30% by using 20% fly ash with 3 − 6% silicate-activator. RAM with activated-fly ash showed significant improvement in resistance against water absorption, chloride penetration, and acid attack. The durability parameters are fairly correlated with the compressive strength: improvement in durability performance is noticed with increasing compressive strength, indicating that microstructural developments that yield high mechanical strength also contribute to improvement in durability.
KEYWORDS Alkali activation Chloride ion penetration Water absorption Fly ash Recycled aggregate Compressive strength
1. Introduction According to an estimate of Freedonia group (2016), total demand of world for construction aggregates can reach up to 51 billion tons per year in 2019. On the other hand, in 2012, construction and demolition waste generated at the rate of three billion metric tons per year in 40 important countries and this rate was seen continually increasing (Akhtar and Sarmah, 2018). To minimize sustainability issues, demand for aggregates can be partially satisfied by using the aggregates recycled from demolition waste. Many researchers have addressed the issue of sustainability in the production of concrete by utilizing recycled concrete aggregates (RCA) instead of natural aggregates. In the last few decades, the largest part of the research has been focussed on the use of coarse RCA in concrete (Rahal, 2007; Huda and Alam, 2014; Brand et al., 2015; Bostanci et al., 2016; Ahmadi et al., 2017; Das et al., 2018; Ali et al., 2019b). However, rapidly increasing consumption of natural resources for production of fine aggregates, the complications in discovering potential natural sources of sand, the inevitability to find new application areas where fine RCA can be used that is produced involuntarily with coarse RCA, CORRESPONDENCE Babar Ali Pakistan
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