Shear Behavior of Reinforced Concrete T-Beams Incorporating Glass Powder as Partial Replacement of Cement

Abstract

Waste glass is one of the most waste material that is thrown away and poses threat to human beings and animals, but the recycling of waste glass in various shapes and sizes in concrete has more benefit in enhancing the concrete properties and saving the atmosphere, in addition to minimize the cost of raw materials. Glass powder can be used as pozzolanic material when the size of particles is less than 150μ𝑚, because it has high effect of silica. Ca(𝑂𝐻)2 in cement paste enables chemical reaction with silicates in glass powder to form (C-S-H) that enhances the strength and durability of concrete. This thesis shows the importance of using waste glass powder as a partial replacement of cement in concrete through investigating some properties of hardened concrete, which contains milled glass and comparing them with the control mix without replacement. Three milled glass percentages were used: 0%, 10%, 15%, which are considered the best percentages of adding with particles sized around 75μm. These investigations include compressive strength, flexural strength, splitting strength, and ultrasonic pulse velocity test that increased by 15.4%, 6%, 9.2%, and 2.66% for 10% WGP mix, respectively. While the increment of 15% WGP was 9.1%, 13.1%, 2.8%, and 4.7%, respectively. The results of these tests showed the development of all strength because glass powder has a high pozzolanic effect (high content of silica) which improves the properties of concrete and also reduces the emissions that come from the production of cement. The structural program of this study consisted of casting of 18 specimens of T-beams with three main variables including waste glass ratios (0%, 10%, and 15%), the effect of flange width (300, 375, and 450) mm and amount of transverse reinforcement ratio (Savg and Smax). Nine T-beams were tested by depending on minimum shear reinforcement and the other nine T-beams were tested by depending on average shear reinforcement and every ratio of WGP and the normal mix had three variables flange width. All T-beams designed to fail in shear strength, therefore the flexural was designed according to maximum amount of longitudinal reinforcement of all T-beams. The shear capacity increased by (1.6%-4.2%) compared to WGP with control specimens and the replacement ratio of WGP has slightly increased because of the relatively close results of the compressive strength that has direct relation with shear strength. The flange width has caused a (3.5-8.2) % increase in shear strength and the results showed whenever extensive the width of flange increases in shear capacity because increased compression zone of top flange, and increases the stiffness of T-beams. On the other hand, the high increment of shear capacity appeared in average shear reinforcement about (12.5-16.6) % when compared with minimum shear reinforcement. The strain of concrete in the bending zone and principal strain has increased with increased load capacity, due to the effect of shear reinforcement, the effect of flange width, and the content of WGP with constant amount of longitudinal reinforcement in tension and compression zone. The ductility from deflection showed an increase in finding WGP and the variable flange width at minimum shear reinforcement, whereas on average shear reinforcement gave a decrease in ductility (fragile behavior). However, the results of ductility from curvature showed decreased in values with an increase in flange width but the ductility at minimum in shear reinforcement remained higher than average shear reinforcement.