Utilization of cold bonded fly ash lightweight fine aggregates as a partial substitution of natural fine aggregate in self-compacting mortars Erhan Güneyisi a,⇑ , Mehmet Gesog ˘lu a , _ Inan Altan a , Hatice Öznur Öz b a Department of Civil Engineering, Gaziantep University, 27310 Gaziantep, Turkey b Department of Civil Engineering, Nig ˘de University, Nig ˘de, Turkey highlights  Lightweight fine aggregates (LWFAs) were manufactured via pelletization technique.  LWFAs were replaced with natural one at various levels up to 100%.  Self-compacting mortars (SCMs) were produced at fixed slump flow diameter.  The superplasticizer needed decreased with increasing percentage of LWFAs.  Increasing amount of LWFAs improved fresh state but adversely affected hardened state of SCMs. article info Article history: Received 20 May 2014 Received in revised form 26 September 2014 Accepted 14 October 2014 Keywords: Lightweight aggregate Permeability Self compacting mortar Strength Workability Viscosity abstract In this study, lightweight fly ash fine aggregates (LWFAs) were used as a partial replacement of natural fine aggregate to investigate the fresh and hardened states of self-compacting mortars (SCMs). For this, a powder mixture of 90% fly ash (FA) and 10% Portland cement (PC) by weight were pelletized in a tilted pan through a cold-bonded agglomeration process. Thereafter, a total of five mixtures of SCMs were pre- pared in which natural fine aggregate was replaced by LWFA partially started from 0% to 100% by 25% increment. Subsequently, tests carried out on the fresh mortar involved mini-slump flow, mini-V-funnel flow time and viscosity while the hardened properties of SCMs were evaluated using the compressive strength, ultrasonic pulse velocity, gas permeability and sorptivity tests. The hardened characteristics of SCMs were determined at different ages up to 56 days. It was observed that the increased percentage of LWFA improved the workability and the flowability of SCMs. On the other hand, the strength and per- meability properties of SCMs had a negative effect due to the substitution of LWFAs for natural fine aggre- gate, especially at higher replacement level. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The solid waste management control is one of the most chal- lenging matters in our country and worldwide. Considering the environmental pollution, it is crucial to reuse and recycle the demolition waste. Coal-fired thermal power plants fabricate large quantities of fly ash (FA), but only a small amount can be used in concrete industry [1]. Utilization of industrial waste powder mate- rials such as FA in production of artificial aggregate has attracted the attentions of investigators and practitioners as an alternative way for larger consumption [1–11]. Artificial aggregates can be obtained through processing of different materials and utilizing methods like cold bonding pelletization [1,5–11]. The agglomera- tion of fly ash particles by a cold-bonding process, where the water is the wetting agent acting as a coagulant, is a practical way of pro- ducing lightweight aggregate (LWA) with an environmental impact and minimum energy consumption [2,11]. Therefore, the use of natural aggregates can be limited, and the waste products can be evaluated by offering valuable solution to the protection of the environmental effect [12,13]. Diversity of the sources and manu- facturing processes for LWA necessitates better understanding of the influence of LWA characteristics on properties of the concrete [14–16]. Self-compacting concrete (SCC) is an innovative type concrete having the advantageous properties such as settling with high flowability and uniformity into place without vibration, filling the formwork and encapsulate reinforcement without any bleed- ing or segregation as well as less workmanship, earlier removal of formworks and easier aesthetic design of structures and high http://dx.doi.org/10.1016/j.conbuildmat.2014.10.021 0950-0618/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +90 342 3172410; fax: +90 342 3601107. E-mail address: guneyisi@gantep.edu.tr (E. Güneyisi). Construction and Building Materials 74 (2015) 9–16 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat