availability of raw materials and energy input concerns. Additionally the construction 34 industries significantly contribute to the global greenhouse gas emission and consequent 35 events. Therefore need for alternative and sustainable way of manufacturing construction 36 materials have been discussed over the decades. Particularly masonry construction is widely 37 used in low and medium rise buildings around the world. The main constitutive material used 38 in the masonry construction is the units, which can be brick or block depends on the 39 perforation percentages. Inordinate amount of masonry units are produced daily by the 40 construction industry around the world. The commonly kiln fired clay bricks and ordinary 41 Portland cement (OPC) concrete blocks are extensively used as masonry units. However 42 production of fired clay bricks and concrete blocks consume intensive energy and raw 43 materials, which has become an environmental concern in the present day world.
44 45 This predicament has led the researchers to shift their forces towards developing more 46 sustainable masonry units from waste materials with less energy inputs. Turgut (2012) and 47 Zhang (2013) have outlined various ways of manufacturing sustainable masonry units 48 attempted by the researchers from waste materials. General observations from the past studies 49 reveal, mostly the supplementary cementitious materials such as fly ash, blast furnace slag 50 and rice husk ash (RHA) were used to partially replace the OPC usage in the concrete/cement 51 masonry unit manufacturing (Kumar 2002; Chou et al., 2001; Xu et al., 2005). Similarly 52 instead of clay and natural aggregates, various industrial and agricultural wastes were used in 53 the past in masonry unit production (Faria et al.
, 2012; Lin 2006; Rahman et al., 2014; Ismail 54 et al., 2010). Also recycled construction demolition wastes were utilised to partly replace the 55 natural aggregate in the masonry unit production (Poon et al., 2002; Alonso-Santurde, 2012; 56 Wattanasiriwech et al., 2009; Lee et al., 2013).
57 58 The present work aims to study the feasibility of using untreated Rice Husk Ash (URHA), 59 Quarry dust (QD) and water treatment sludge (WTS) for manufacturing units for masonry 60 construction. The use of URHA and WTS into masonry unit production not only alleviates 61 disposal problems of these industrial waste materials but also has economic, ecological and 62 energy saving advantages.