Shear Failure Control of RC Box Beams Using Internal Transverse Diaphragms

The rapid development in construction and material technology arising the needs for simple techniques to increase the shear strength of RC box beams. This paper is devoted to investigating experimentally the structural behavior of RC box beams which have internal in-plane solid diaphragms under the effect of shear stresses. For this purpose, four beam specimens with (200x300x1200mm) dimensions are poured using normal strength concrete of class (f'c=22MPa) and longitudinal flexural steel of class (fy=410MPa) without transverse reinforcement (stirrups). Three of these specimens were a box with or without different locations of internal diaphragms and one of them was a solid. The number of the internal diaphragms is the major variable adopted in this study, while, the other variables are kept constant for all tested specimens. The experimental results indicated that the shear strength is increased for about (35%) to (47%) for beams containing internal in-plane diaphragms in comparison with the reference beam. Also, the change of beam section from box section to solid section led to increasing the capacity for about (100%). Keywords: Shear Failure, Box Beam, Reinforced Concrete, Diaphragms, ACI-318 Code DOI: 10.7176/CER/12-8-06 Publication date:August 31st 202

Performance of Powdered Polymerized Concrete at Elevated Temperatures

In the domain of concrete modification by using polymers, the present study, focused on the use of Carboxy-Methyl Cellulose (CMC) as a water-soluble polymer and investigate its effects on the behavior of concrete. The study include two issues, the first one is the effect of polymer adding method on mechanical properties of concrete such as compressive strength, tensile strength and modulus of elasticity in additional to impact resistance and the second is the effect of graded temperature on these properties. The polymer/cement ratio used herein is 3%, this ratio never used before in the previous researches on many types of water soluble powder polymers. Three concrete batches were prepared, the first is the reference one as a normal concrete (NOR), the second is a polymerized concrete (POL1) where the polymer added as a latex, and the last also as a polymerized concrete (POL2) but the polymer added as a powder.Each batch contains twelve cubic specimens (100x100x100)mm for compressive strength test, three cubes for each level of temperature, eight cylindrical specimens (150x300)mm for splitting tensile strength test, two cylinders for each level of temperature, and four paneled specimens (450x450x50)mm for impact resistance test, one panel for each level of temperature. It can be considered from the results that when the polymer CMC used herein added as a latex will give better strength behavior in polymerized concrete than the one which added as a powder by about 28.86% in compressive strength, 19% in splitting tensile strength, very high percent in modulus of elasticity and 16.66% in impact resistance. On the other hand, it is found that the temperature level of 200°C will affect the behavior of polymerized concrete and that contrast with the behavior of normal concrete while in temperature levels 400°C and 600°C the effects on polymerized concrete will be more slightly and more clearly on normal concrete