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S. Ahmad et alii, Frattura ed Integrità Strutturale, 34 (2015) 524-533; DOI: 10.3221/IGF-ESIS.34.58 527 Preparation of cement composite samples In total, three different wt% additions (i.e. 0.05, 0.08 and 0.20%) were studied for each type of carbonized particles and compared with the control mix. The details of the samples composition are reported in Table 3. Notation Pyrolyzed coconut shell particles Weight (%) Weight (mg) CEM Control mix CEM +0.05% PC 0.05 107 CEM +0.08% PC 0.08 171.2 CEM +0.20% PC 0.20 428 Notation Pyrolyzed and annealed coconut shell particles Weight (%) Weight (mg) CEM Control mix CEM +0.05% PCA 0.05 107 CEM +0.08% PCA 0.08 171.2 CEM +0.20% PCA 0.20 428 *For each mix 214 g cement, 75 g water and 3.21 g HRWRA were used Table 3 : Composition of cement composite samples In the preparation of cement composite samples initially, the pyrolyzed coconut shells particles were dispersed in the measured quantity of water and HRWRA solution by using sonication for 15 minutes. The water solution with thoroughly dispersed pyrolyzed coconut shells particles was then mixed with cement and mixing was carried out at 440 rpm for 2 minutes and then at 630 rpm for 2 more minutes [31]. The self-compacting fresh paste was then transferred into the acrylic molds of 20 x 20 x 75 mm 3 . The samples were allowed to dry in an atmosphere with 90% humidity. The prism shaped samples were cured at room temperature for 28 day in water. After the completion of the curing period samples provided with 2 mm thick and 6 mm deep notches for carrying out flexural and subsequently compression tests. Characterization of materials and composites The characterization of the materials was carried out in two steps. Initially, the micro carbonized particles were analyzed to check their microstructure and morphology with the help of field emission scanning electron microscope (FESEM), for chemical composition by means of energy dispersive x-ray (EDX) analysis, for particles size analysis by using laser granulometer and for Raman spectroscopy by means of “Renishaw Raman-scope” equipped with laser beam of 514.5 nm wavelength. In the second phase, the cement composite samples were analyzed for their mechanical strength in flexure and compression. For flexural strength of the cement composites, the samples were tested according to the ASTM C348 standard in three point flexural by using “Zwick-Line Z010” testing machine in crack mouth opening displacement (CMOD) controlled mode. In the present study the CMOD rate was fixed at 0.003 mm/min [32]. The compression tests were carried out by using the broken pieces of the prism from the flexural tests according to ASTM C349 standard [33]. The compression test was carried out in displacement-controlled mode with a displacement rate of 0.5 mm/min. The broken pieces of the cement composites were analyzed by the means of FESEM to study the dispersion of the micro carbonized particles in the cement composite matrix and the fracture/crack growth properties of the cement composites incorporating micro carbonized particles. R ESULTS AND DISCUSSIONS he FESEM analysis results of micro carbonized coconut shells particles at different magnifications are reported in Fig. 2. The FESEM observations revealed that the micro sized coconut shells particles possess smooth and glossy surfaces. The particles showed highly angular edges, which indicates their strength and toughness. T