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R. A. Khushnood et alii, Frattura ed Integrità Strutturale, 34 (2015) 534-542; DOI: 10.3221/IGF-ESIS.34.59 535 I NTRODUCTION ementitious materials are commonly and extensively used worldwide by construction industry for various types of infrastructures. Despite of their exceptional strength in compression they still possess limited tensile strength and tensile strain capacity. Different types of fibers have been investigated since last fifty decades to reinforce the cementitious matrix against tensile failures and to impart ductility [1–4]. The size of the reinforcing fillers has diminished from macro to micro and now even to the nano scale with recent advancements in nanotechnology. Due to exceptional intrinsic properties and large aspect ratio, carbon nanotubes have been successfully investigated as a reinforcing filler to improve the mechanical strength, fracture toughness, electrical and electromagnetic wave absorbing properties of cementitious composites [5–12]. However the problems associated with its effective dispersion, bondage with the host material as well as related expenses are the main factors that limit its widespread applications on large scale. Recently it has been found that there is the possibility of enhancement in the fracture toughness of cement composites by inducing cost effective nano/micro carbonized bio-waste particles [13–15]. Sajjad et al. reported that the addition of micro carbonized bamboo particles contributes positively in the modification of cracking patterns and thereby enhance the overall fracture properties of cementitious composites [13]. Similar trend of increment in fracture plane and fracture toughness was observed by Ferro et al. on addition of nano/micro carbonized hemp herd and coconut shell particles [14,15]. The optimum content of addition was found similar to the one believed for the case of carbon nanotubes (CNTs) addition i-e 0.08wt% [5]. The current paper is the research continuation concerning exploration of cost effective and sustainable source to synthesize nano/micro carbonized particles that can be effectively used to modify crack path and the final fracture characteristics of cementitious matrices. Sugarcane bagasse is a waste produced form sugar industries which is commonly used as a fuel in sugar mill boilers. Among sugarcane-producing countries, Brazil is the top producer, with 653 million tons of sugarcane in 2014, followed by India and China [16]. Generally, 280 kg of humid bagasse is generated from 1 ton of sugarcane [17]. Due to the advantages offered in term of reduced specific gravity, lower cost and acceptable mechanical properties, these fibers were investigated as a reinforcing material in cementitious composites [17–19]. Also they were successfully explored as pozzolanic material for cementitious matrices after getting burnt into fine ash powder [18]. In the recent work, these fibers have been investigated to produce nano/micro carbonized inerts that can effectively act as a sort of heterogeneity to hinder the tips of propagating cracks and thereby enhance the overall fracture properties of resultant cement composites. M ATERIALS AND METHODS Materials and Mix Proportions he cement used for the research work was ordinary Portland cement (Type-1, grade 52.5) confirming to the requirements of ASTM C150 [20]. The physical and chemical characteristics of cement as per the product data sheet are displayed in Table 1 & 2 respectively [21]. A high range water reducing admixture (HRWRA), based on modified acrylic polymers and confirming to the requirements of UNI EN 934-2:2012 (admixture for concrete, mortar and grout) was used to attain sufficient workability. Distilled water was used in all mix formulations. The inert nano/micro carbonized particles used for enhancing the fracture properties of cement composites were produced from bagasse fibers using the following procedure. Physical characteristics Standard Average values Color - Light grey Density - 2,800 kg/m 3 Blain specific surface area UNI EN 196-6 480 m 2 /kg Initial setting time UNI EN 196-3 98 min Final setting time UNI EN 196-3 125 min Table 1 : Physical properties of cement [22] C T