Journal of Materials and Engineering Structures

3-10

Authors: Mohamed Hassan, Ahmed Abdel Rahman, Alaa Sherif, Mostafa Osman, Asmaa Ahmed

Flat plates are favor structure systems usually used in parking garages and high-rise buildings due to its simplicity for construction. However, flat plates have some inherent structural problems, due to high shear stress surrounding the supporting columns which cause a catastrophic brittle type of failure called "Punching Shear Failure". Several solutions are used to avoid punching shear failure, including the use of drop panels or punching shear reinforcement. The latter is being a more sophisticated solution from the structural ductility, the architectural and the economical point of view. This study aims at investigating the effect of stirrups as shear reinforcement in enhancing the punching strength of interior slab-column connections. A total of four full-scale interior slab-column connections were tested up to failure. All slabs had a side length of 1700 mm and 160 mm thickness with 200 mm x 200 mm square column. The test parameters were the presence of shear reinforcement and stirrups concentration around the supporting column. The test results showed that the distribution of stirrups over the critical punching shear zone was an efficient solution to enhance not only the punching shear capacity but also the ductility of the connection. Furthermore, the concentrating of stirrups shear reinforcement in the vicinity of the column for the tested slabs increases the punching shear capacity by 13 % compared to the uniform distribution at same amount of shear reinforcement.

25-36

Authors: Rahul Sharma, Rizwan A Khan

An investigation is carried out on the development of Self Compacting Concrete (SCC) using copper slag (CS) as fine aggregates with partial and full replacement of sand. Six different SCC mixes (60% OPC and 40% Fly Ash) with 0% as control mix, 20%, 40%, 60%, 80% and 100% of copper slag substituting sand with constant w/b ratio of 0.45 were cast and tested for fresh properties of SCC. Compressive strength and splitting tensile strength were evaluated at different ages and microstructural analysis was observed at 120 days. It has been observed that the fluidity of SCC mixes was significantly enhanced with the increment of copper slag. The test results showed that the compressive strength increases up to 60% copper slag as replacement of sand, beyond which decrease in strength was observed. The highest compressive strength was obtained at 20% copper slag substitution at different curing ages among all the mixes, except for 7 days curing. The splitting tensile strength of the CS substituted mixes in comparison to control concrete was found to increase at all the curing ages but the remarkable achievement of strength was detected at 60% copper slag replacement. The microscopic view from Scanning electron microscopy (SEM) demonstrated more voids, capillary channels, and micro cracks with the increment of copper slag as substitution of sand as compared to the control mix.

51-61

Authors: Samuel Olufemi FOLAGBADE

In order to support the use of cement combination concrete in construction, this paper investigated the resistance of Portland cement and some binary and ternary cement concretes containing fly ash, silica fume and metakaolin to air permeability at equal water/cement ratios and strengths. At equal water/cement ratios, while fly ash binary cement concretes have higher coefficients of air permeability than Portland cement concrete due to delayed pozzolanic reactivity, silica fume and metakaolin binary cement concretes have comparable coefficients with Portland cement concrete due to their higher fineness, improved particle packing and higher pozzolanic reactivity. Consequently, the ternary cement concretes have coefficients comparable with that of Portland cement concrete. At equal strengths, while silica fume and metakaolin binary cement concretes have higher coefficients than Portland cement concrete, fly ash binary cement concretes have lower coefficients which reduced with increasing content of fly ash. Consequently, all the ternary cement concretes have lower coefficients which reduced with increasing total replacement level due to the beneficial effect of fly ash. Hence, high volume fly ash would be required to increase the resistance of concrete to air permeability at equal strength.