Hasan Mohammed Ahmed Albegmprli

This paper presents the effect of adding recycled crumbly rubber to engineering composite concrete (ECC) on the main mechanical properties. 12 specimens were prepared with variants that included different proportions of PVA fibers, micro steel fibers, and crumb rubber. The results showed that mixtures containing rubber recorded a decrease in the modulus of elasticity, where the value of the mixture M4 (0.5% PVA & 3% CR) reached 19.85 GPa, while the hybrid mixture M12 (0.5% PVA & 0.25% MS + 3% CR) decreased to 11.09 GPa. In contrast, the M9 mix (0.5% PVA & 0.25% MS) achieved the highest compressive strength of 60.64 MPa, highlighting the synergy between fibers in enhancing rigidity. The results also showed that the addition of rubber improved flexural strength and energy absorption, with the M12 mixture recording a flexural strength of 13.48 MPa. These results confirm that rubber enhances flexural and deformability but reduces rigidity, while hybrid mixtures achieve a balance between strength and elasticity. In addition, the use of rubber contributes to environmental sustainability by recycling waste tires and turning them into a construction material with acceptable performance.

The building industry has made extensive use of types of concrete in recent decades. Geopolymer Concrete is one of several common types of concrete and does not require a water spray after casting. The research was limited to the use of industrial waste and waste harmful to disposal in structural technology. This paper investigates the effect of the curing type and hybrid fibers on the properties of reinforced geopolymer concrete. Binder materials for geopolymer mixes consist of 70% fly ash, 20% slag, and 10% cement. Four steel fiber proportions 0%, 0.5 %, 1 % and 1.5%, were studied in addition to mixing reinforced with hybrid steel fiber 0.5% and polyolefin fiber 0.5%. All geopolymer concrete specimens were cured at oven and ambient temperatures for 7, 28, and 56 days. The binder materials were activated with sodium silicate and sodium hydroxide solutions. Trial used the best ratio for an alkaline solution, which is assigned as Alkali Activators/Binder = 0.5, Sodium Silicate/Sodium Hydroxide = 1.5, and 14 Molarity. The mixture containing 1% steel fiber was selected and studied with a hybrid fiber. Hardened properties were tested using compressive strength, flexural strength, splitting tensile strength and modulus of elasticity. The results showed a difference between ambient and oven curing, with oven-cured specimens exhibiting higher compressive strength than ambient-cured specimens at early ages. At the same time, compressive strength was higher at late ages under ambient curing than under oven curing. Also, the other mechanical tests, splitting tensile strength, flexural strength and modulus of elasticity, exhibit the same as compressive strength in both curing conditions. The increase in compressive strength at 0.5%, 1%, and 1.5% steel fiber content at later ages was 20%, 33%, and 49%, respectively. As for the hybrid fiber mixture for Geopolymer Concrete, the increase in compressive strength was 24%. The addition of fibers in Geopolymer Concrete mixes did not affect the modulus of elasticity values. The results concluded that the geopolymer concrete exhibits an efficient performance in both ambient and oven curing. Consequently, it can be the best alternative to Ordinary Portland Cement concrete in site-cast without special curing conditions.

This research investigated and compared the structural behavior of reinforced concrete straight beams and beams made with out-of-plane parts. This study focused on the influence of the location and number of out-of-plane parts, as well as encasing the beams with a steel section, on the ultimate strength, deflection, and rotation in addition to the ductility, energy absorption, and failure mode. A total of nine beams were modelized numerically, divided into three series. The first one included one straight beam, while the remaining two series included four beams each made with out-of-plane parts with and without steel sections. The beams with out-of-plane parts connected the two, three, four, and five concrete segments. The outcomes revealed that the beams made with out-of-plane parts showed less strength than straight beams, which increased the connected segments and reduced the ultimate strength capacity. The regular beam’s linearity was dissimilar to the zigzag beams, which showed a linearity of 32% and was reduced to 22%, 20%, 19.67%, and 16% for beam out-of-plane parts made with two, three, four, and five segments, respectively. Forming a zigzag in the plane of the beams reduced the cracking load, but the decrement depended on the number of parts, which led to more reduction in the yielding load. Concerning the deflection and deformations, the concrete straight beams failed in flexure, with maximum deflection occurring at the midspan of the beam, which was different for beams without plane parts, which showed a combined shear-torsional failure for which the maximum deformation occurred at the midspan with inclination of connected parts on the interior perpendicular axis. Encasing the beams’ out-of-plane parts with steel sections enhanced the structural behavior. The ductility and energy absorption of the out-of-plane parts beams were less than the straight ones, but encasing the beams with a steel section improved the ductility and energy absorption twice.

This study adopted a review of bond strength and discussed the research in geopolymer concrete. Studies and research on the structural properties of geopolymer This study adopted a review of bond strength and discussed the research in geopolymer concrete. Studies and research on the structural properties of geopolymer

The study aimed to explore the possibility of strengthening RC corbels with many strengthening techniques. The research analyzed the RC corbels behavior under a wide range of variables. The theoretical study consisted of twelve models reinforced with GFRP bars with strengthening by steel plate. Finite element analysis with ANSYS APDL was used to verify five specimens. This research deals with a static nonlinear FE simulation to investigate the behavior of RC Corbels reinforced internally and externally. The verification with experimental work demonstrated a satisfactory agreement in the load-displacement relationship, ultimate load and displacement, and failure mode. The parametric study was implemented which included strengthening the four concrete corbels externally and four corbels internally by a steel plate in many configurations while the remaining three were modeled with varied compressive strength (30, 40, and 50) MPa. The external strengthening included the placing of steel plate externally around the corbel in a U-shaped form and partial strengthening by strips and bottom plate. The models with internal strengthening involved placing the steel plate internally instead of stirrups. The results discovered that the strengthening provided enrichments in the stiffness, ductility, and energy absorption by 37 %, 4 %, and 26 %. In addition, in the case of full external strengthening more than internal retrofitting, there is a maximum improvement in the cracking and ultimate load carrying capacity. The external strengthening was better than internal one due to the confinement effect of the concrete. The stress distribution and crack pattern were affected by the strengthening techniques and more cracks appeared in the corbels with external steel plates.

In this investigation, a kenaf/PLA composite specimen was subjected to the fatigue load, and the results were analyzed numerically. Some of the most significant fatigue tool aspects that were looked into were life expectancy, damage, alternative stress, and biaxiality indication. The static structural tool was utilized in order to predict the numerical analysis, and the calculations were performed with the GoodMan theory of fatigue. The loading was completely reversed so that it was equal to 30 kN. When it was discovered that the system could continue to function even after 1e6 cycles had been completed. After applying the alternative load of 30 kN, the biaxiality indication was found to be 0.425, with a minimum value of 0.9. It has been determined how much damage has occurred. The minimum amount of cycles necessary to reach the maximum damage potential is 1000, while the maximum amount of cycles necessary to reach the maximum damage potential is 1.7662·10⁶. It has been established that there is another stress that is comparable to this one. Based on the findings of the investigation, it was determined that the fillet regions of the specimen were subjected to a maximum alternative stress of 716.4 MPa. The alternative stress cannot drop below 31.276 MPa under any circumstances. It has been determined that 10⁶cycles have been spent living in total by the calculation. It has been found out that there is not going to be any damage regardless of the number of cycles that pass due to the fact that that number is 1. It was found that the alternative stress could reach a maximum value of 716.4 MPa, so that was the value that was used for the alternative stress