مسلم عبد الأمير خضير الكنون

Post-fire curing techniques for thermally damaged concrete are widely discussed, yet no dedicated study has quantified the extent of strength recovery. This research introduces an empirical model built upon a comprehensive experimental database that accounts for key input variables: exposure temperature, re-curing method, re-curing duration, and water-to-binder (W/B) ratio. The model was developed using 464 collected datasets. Statistical evaluation through ANOVA and regression analysis identified temperature as the dominant factor influencing strength recovery (F-value = 109.37), followed by re-curing type, re-curing duration, and W/B ratio. An optimization analysis further determined the conditions that maximize strength recovery: temperatures of 150–250 °C, hybrid re-curing methods, re-curing periods of 94–182 days, and W/B ratios between 0.30 and 0.45. The proposed model predicts the strength recovery percentage with demonstrable accuracy. It was subsequently refined into a more conservative formulation suitable for design codes, incorporating a conservatism parameter of 53.2%. Among the regression-based machine learning algorithms tested, XGBoost achieved the highest predictive performance (R2 = 0.74, MAE = 8.81%).

This research aims to study the effect of adding steel fibers on the mechanical properties of concrete. Steel fiber has a very significant effect on concrete because it delays the propagation of micro cracks that generate due to loading on concrete members such as beams and slabs, therefore ,it increases the strength of concrete. The steel fiber was used in this study as a percentage of the volume of concrete. Mix proportion was 1: 2:4 (cement: sand: gravel) by volume for all mixes and using 0% as (control mix),0.1 %,0.2%,0.5 % and 1.0% of steel fibers, these ratios leads to increase the compressive, tensile ,and flexural strength of concrete, where the improvement in flexural strength was significant. Keywords:Steel fiber, Composite materials, Flexural strength, Tensile Strength, Compressive Strength.

The objective of this study was to develop Three Dimensional Finite Element Model (3D- FEM) that can be used to investigate the structural analysis of apron area plain and reinforced concrete slab under Airbus A380-800 aircraft land gear loading. The computer program ANSYS (2014) was selected to develop 3D-FEM for this study. Suggested rigid pavement for apron area was studied with different thickness (20,30, 40 and 50 mm) and Young modululi (E1 = 30000[MPa], E2 = 40000[MPa], E3 = 50000[MPa] resting on various reaction modululi (k) of subgrade layer: k1=15[MN/m3], k2=30[MN/m3], k3= 50[MN/m3], k4=75[MN/m3], and k5=150[MN/m3]. The structural design of apron concrete pavement including geometrical and loading characteristics of loading gear configurations, material properties of apron concrete layers and apron pavement responses such as; total stresses and deflections by finite element methods. Statistics model have been developed to correlation of maximum tensile stress, elastic modulus and thickness of concrete slab.

Carbon Fiber Reinforced Polymer (CFRB) has been effectively utilized in structural engineering; particularly in strengthening structural members. The current study addresses the utilization of CFRP in one way strips concrete slabs subjected to a two line static loading system. Two different CFRP techniques have been used: externally strengthening and near surface mounted (NSM) techniques. Four samples of one way reinforced concrete strips slabs strengthened by several CFRP systems have been tested. Analysis results indicated that the laminate plate CFRP system is more efficient than other techniques. The maximum load carrying capacity of a 1500mm reinforced concrete slab with 0.314 steel ratio has been increased largely by 671%. This technique of strengthening has resulted in a decrease in the RCS maximum deflection by about 21%. In addition, the stiffness of RCS has increased and failure due to deflection occurred at 1.75% of the span length.