جنان نعمه ياسر الموسوي

The rising amounts of construction and demolition waste lead to several environmental problems, thus necessitating the need to recycle such materials in concrete production. In this paper, the use of demolition concrete waste aggregate in concrete mixes in replacement ratios of 0-100% is considered. Furthermore, the effects of PC- 200 superplasticizer in combination with decreased water-cement ratio on mechanical and fresh properties of the investigated concrete are evaluated. Two groups of mixes were analyzed such as ordinary concrete mixes containing a water-cement ratio of 0.42 and modified concrete mixes with 1.2% PC-200 superplasticizer and a decreased water- cement ratio of 0.28. The experimental results show that the use of demolition waste aggregate reduces the mechanical properties and workability of ordinary concrete mixes, while modified mixes have better results under the given experimental conditions. It was found that the mechanical properties, such as compressive strength, tensile strength, and flexural strength, and the modulus of elasticity increase with the rise in replacement ratios in modified mixes. Nevertheless, it must be noted that these results are obtained by the effect of a combination of a decreased water-cement ratio and superplasticizer and are only valid in the context of the current experiment. However, the lack of information regarding durability testing, microstructure investigation, and long-term performance makes it difficult to implement the findings into practice, and further investigations are needed for practical implementation.

This study investigates the enhancement of mechanical properties in polymer-modified steel fiber-reinforced concrete (PMSFRC) incorporating demolition waste as a sustainable coarse aggregate replacement. The work addresses the dual objectives of resource recycling and performance optimization within environmentally responsible construction practices. Results show that replacing natural coarse aggregates with demolition waste slightly reduces compressive strength from 44.1 MPa to 41.6 MPa. However, the incorporation of PC-600 Flocrete superplasticizer effectively compensates for this reduction, increasing compressive strength to 49.4 MPa. Significant improvements were also observed in tensile strength, which increased from 5.7 MPa to 6.1 MPa, and in flexural strength, which increased from 12.1 MPa to 15.5 MPa for mixes with 100% waste replacement. Additionally, the modulus of elasticity improved from 26.5 GPa to 30.5 GPa, demonstrating enhanced stiffness and structural viability. These findings confirm that polymer modification enables effective utilization of concrete waste without compromising structural integrity, promoting cleaner production, circular material use, and sustainable innovation in civil infrastructure.

Due to its excellent torsional properties, box beams are frequently used for structural elements that are both curved and straight. One of the most important problems in the steel thin section is warping, so the strengthening technique was used in the current research to reduce warping and increase the torsion capacity. The paper presented an experimental investigation of the torsional behavior of seven steel box beams under pure torsion. One of the beams without strengthening was used as a reference, while the other specimens were strengthened using an internal steel truss with different lengths and sizes. The internal steel truss consists of (38×38×3)mm or (50×50×2)mm smooth steel angles as upper and lower chords and steel plates with a thickness of 3.8mm at 365mm center to center were used as struts in all steel trusses. The results of tests indicated that strengthening influenced the torsional failure loads and angle of twist, and the torsional behavior of the strengthening steel box beams was improved. The maximum torsional moment capacity of strengthening beams by steel truss with steel angle size of (38×38×3)mm or (50×50×2)mm was nearly more significant than reference beam and reached to 49.54% and 42.2% respectively. On the other hand, the torsional strength of strengthening steel box beams was increased as the width/ thickness ratio (b/t) of the steel angle leg decreased. However, the torsional capacity was raised by about (37.1-41.7)% as the length of the strengthening increased from 20% to 100% of the full length of the box beam. Furthermore, the strengthening of box beams could advance their torsional rigidity and stiffness through reducing the angle of twist.

A monopanel is a system building which consists of two thin ferrocement block-like faces and thick layer of low strength, density and cost polystyrene foam insulation between them as a core. The simple structure idealization of monopanel system is that the core provides shear transfer between the faces that provide flexural resistance. Transverse trusses made of steel bars. In flexural bars connected by inclined steel bar forming trusses shape making an angle equal to 45° with the longitudinal bars. The core material can be made of low cost and low density. This core provides the excellent thermal and sound insulation properties. The main object of this research is to present investigation on the behavior and load carrying capacity of monopanel slabs. The experimental results show that effect of number of internal lacing, number of layers of steel wire mesh in each of monopanel unit (one layer or two layer) . The experimental nominal loads of monopanel slab specimens were compared with the results computed of the ACI-318 M- 08 .code and save to use

An essential element of a composite beam is the shear connection between the concrete slab and the steel section. In this paper, an experimental investigation of a new type of shear stud manufactured using the wastes of rebars was conducted by push-out experiments. The slabs were cast using two types of con- crete: normal, and steel fiber concrete. According to the experimental results, specimens cast with SFC had an approximate 7.87% increase in the connector’s shear capacity more than NC specimens, while the slip at the ultimate shear capacity decreased by about 16.23 %. Comparisons were made between the experimental results and some standard design codes, demonstrating that they may be used to deter- mine the shear resistance of shear studs for both NC and SFC.

Open web steel joists (OWSJs) are truss-type members which represent a smart load bearing element because of its ability to transfer both tensile and compressive forces, and less material results not only in smaller costs but also in a lowered self-weight, and in addition, reducing vibration noticeability. And the costs are lower because they can be made from recycled steel and are therefore better for the environment, from this advantage came the idea to conduct this study. The aim of this study is to investigate three prefabricated models of a new product of hybrid open web steel joists (HOWSJs) having three different cross section. The experimental results showed that the shape of cross section of (HOWSJs) had a considerably effect on the behavior of the steel joist, where for the HOWSJ specimens which fabricated by welding angles of the top and bottom chord back to back (Model A), the ultimate capacity was increased almost (7.4%) and (14.5%) when compared it with specimens which fabricated by welding angles of the chords face to face without gap (Model B) and specimens which fabricated by welding angles of the chords face to face with gap (Model C), respectively. While the ductility index of the (Model C) specimens was 1.52 and 1.35 times the ductility index of the (Model A) and (Model B), respectively.