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    A COMPARATIVE STUDY ON THE THERMAL INSULATION PERFORMANCE OF UNLOADED AND PLASTICALLY DEFORMED HTPP-ECC
    (Turkish Soc Thermal Sciences Technology, 2019) Godek, Eren; Tosun Felekoglu, Kamile; Kun, Mete
    Engineered Cementitious Composite (ECC) is a type of micro-mechanically designed, high performance composite compared to conventional concrete. A considerable number of research in the existing literature concentrate on mechanical performance and ductility improvement of ECCs. In this paper, thermal properties of special type of ECC incorporating high tenacity polypropylene fiber by 2% of total matrix volume (HTPP-ECC) have been investigated. For this purpose, prismatic composites were prepared and thermal conductivity tests were performed. Tests results were compared with the data obtained from existing literature. The mechanical performance and multiple cracking ability of HTPP-ECCs were also tested under bending load. In addition to the existing literature, thermal heat insulation performance of HTPP-ECCs have been tested at virgin (before bending test), cracked (up to 10% of load drop after peak load) and failed (up to 5 mm major crack width at the bottom of the specimen) state by using an insulation test setup which simulates actual site conditions. The effect of steady state micro-cracking on the thermal insulation performance of HTPP-ECC was evaluated. Results showed that, HTPP-ECCs produced in this study has better performance in terms of thermal conductivity when compared to other types of cement-based materials even at the plastically deformed state. Also, HTPP-ECCs exhibited an effective thermal insulation performance even in micro-cracked state as a promising alternative thermal insulation material with improved mechanical properties and multiple cracking ability.
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    MECHANICAL AND THERMAL CHARACTERIZATION OF HTP FIBER REINFORCED LIGHTWEIGHT ENGINEERED CEMENTITIOUS COMPOSITES (HTP-LECC)
    (Serban Solacolu Foundation, 2019) Felekoglu, Kamile Tosun; Godek, Eren
    In this study, the matrix rheology, mechanical performances and thermal insulation properties of high tenacity polypropylene fiber (HTP) incorporated lightweight engineered cementitious composites were investigated. Matrices were prepared by using air entraining admixture 2, 4 and 8% of cement weight and HTP fibers added to matrices by 2% of total matrix volume. Before fiber addition, rheological properties of matrices were investigated by using a ball type rheometer. After fiber addition, the air entrainment percentages of composites were determined through theoretical calculations, aerometer test, and image processing methodology for comparison purpose. Specimens were cast into: 25x60x300 mm prismatic molds for flexural strength and thermal tests; dog-bone molds for tension tests; 50x50x50 mm cubes for compression tests. Crack numbers and crack widths of specimens were measured additionally to the mechanical test by using a portable hand microscope at unloaded state in order to investigate crack properties after flexural and tensile test. Thermal properties of composites were also investigated by thermal conductivity and thermal permeability measurements. The thermal conductivity values of composites were achieved by using prismatic specimens before flexural tests. Correlations between air-dry densities and thermal conductivities were calculated. Additionally, thermal permeability of composites were obtained by using a novel thermal camera integrated test setup, which simulates actual site conditions, and related with the thermal conductivity test results. In conclusion, composites were lightweightened by 19-35%. The accuracy of the aerometer test was confirmed by image processing technique. Yield stress and viscosity of matrices were decreased by increasing air entraining admixture dosage and 8% of air entraining admixture dosage was found much preferable in terms of consistency preservation. First crack (in both flexural and tensile tests) flexural, tensile and compressive strengths of composites were decreased by increasing air entrainment percentage. By taking air entrained composites into account, deflection and strain capacity of HTP-LECCs were increased by increased admixture dosage. Also, crack numbers were increased and crack widths were decreased by increasing admixture dosage within air entrained composites. Thermal permeability of composites were investigated by novel thermal camera test setup. Strong correlation (R=0.96) was found between thermal conductivity and thermal permeability tests.