A study examined the ductility and toughness properties of beams made of reinforced concrete, including foamed, normal, and hybrid beams. Nine reinforced concrete beams were produced: three foamed concrete beams, three normal concrete beams, and three hybrid concrete beams. Each beam possessed identical rectangular cross-sectional dimensions of 1500 mm × 250 mm × 150 mm. The flexural parameters (ultimate load, ductility, deflection, and durability) were assessed for each type of concrete utilized. The study's results showed that the load-bearing capacity of hybrid concrete beams was comparable to that of normal concrete beams, whereas foamed concrete beams exhibited slight improvement in their ability to carry loads. The ductility of reinforced foamed concrete beams was lesser than that of normal concrete. For over-reinforced beams, the ductility of hybrid concrete beams showed a significant improvement of 61% compared to foamed beams and an even more significant increase of 91.7% compared to normal beams. Furthermore, the hybrid concrete beam with over-reinforcement had a flexural toughness of 18.7% greater than the normal concrete beam. Suggested that a hybrid section comprising conventional and foamed concrete be utilized to decrease ductility and improve stiffness.
A study was undertaken to produce lightweight aggregate concrete using artificial lightweight aggregate (Lytag) made from sintered fly ash. Cement or fly ash-based geopolymer was utilized as binder material, and its effect on the properties (compressive strength, water absorption, and thermal conductivity) of lightweight aggregate concrete was investigated. Two mixes were designed (using the absolute volumes method) and produced at a density of around 1350 kg/m3 as cement lightweight aggregate concrete and geopolymer lightweight aggregate concrete. Fly ash and an alkaline solution (sodium hydroxide and sodium silicate) were used to produce the geopolymer paste. The results indicated that the compressive strength, water absorption, and thermal conductivity of lightweight aggregate concrete made with geopolymer paste were better than those made with cement paste. An increase in compressive strength by about 49% and a decrease in water absorption and thermal conductivity by about 36% and 25%, respectively, were noticed in fly ash-based geopolymer lightweight mix compared to cement lightweight concrete mix.
Geopolymer concrete is a material manufactured by polymerizing sources of aluminates and silicates like fly ash, metakaolin, slag, zeolite, etc. with an alkaline solution. A study has been undertaken to produce lightweight geopolymer concrete by using waste zeolite particles (zeolite molecular sieve) as aluminates and silicates source and at the same time as lightweight medium. In addition, others three geopolymer lightweight concrete mixes were produced by partially replacing the waste zeolite particles (25% of volume) with sources materials (fly ash type F, fly ash type C and waste zeolite powder. Moreover, the impact of this partially replacement on dry density, compressive strength and permeation characteristics of produced geopolymer lightweight mixes was studied. An alkaline solution of sodium silicate and sodium hydroxide was used in all the investigated mixes as an activator. From the findings, a geopolymer lightweight mix suitable for insulation purposes (density of 1610 kg/m3 and 28 days compressive strength of 5.1 MPa) was successfully produced using waste zeolite molecular sieve. It was found also that the lightweight zeolite particles were uniformly distributed through the produced mixes. Finally, it was found that replacement of 25% of volume of zeolite particles by fly ash (type C) helped in not only enhancing the compressive strength by about 13% but also reducing the water absorption by about 33%.
Foamed concrete (FC) is a type of lightweight concrete characterized by a high void space ratio and cementitious binders. In this research, the fresh and mechanical properties of fiber-reinforced modified foamed concrete (made with fly ash, silica fume, and superplasticizer) with a density of 1300 kg/m³ were studied. Carbon fibers of different lengths (12 mm, 20 mm, and 28 mm) were introduced in two ways: as single fibers (12 mm) and as hybrid fibers combining lengths of 20 mm and 28 mm.
The results showed that the compressive and split tensile strengths increased by approximately 43% compared to the control mix (modified with additives) when using a single fiber of 12 mm at a volume proportion of 0.4%. In contrast, using hybrid fibers resulted in increases of about 65% and 66% in compressive and split tensile strengths, respectively. When compared to the single fiber method, the hybrid approach improved compressive and split tensile strengths by about 15% and 16%, respectively.
Composite beams, made up of a concrete slab and steel in the IPE steel section, are commonly used in bridges and buildings. Their main function is to enhance structural efficiency by merging the compressive strength of concrete with the tensile resistance of steel, thereby improving overall stiffness, ductility, and load-bearing capacity. This study offers an extensive review of the flexural behavior of steel-concrete composite beams, focusing on the interplay of concrete strength, shear connector types, and interaction levels in determining structural performance. It integrates experimental and numerical research to analyze critical parameters, including load-deflection behavior, shear transfer efficiency, and crack propagation at the steel-concrete interface. The study emphasizes the effect of concrete compressive strength, particularly in ultra-high-performance concrete (UHPC) and lightweight concrete, on stiffness, ductility, and load-bearing capacity while reducing self-weight and enhancing sustainability. The study revealed that fully bonded shear connectors, using CFRP sheets and welded plates, enhance flexural capacity and stiffness. In contrast, partial bonding or pre-debonding reduces performance due to crack propagation. Indented and hot-rolled U-section connectors enhance interaction and minimize slip, while uniform distribution of shear connectors optimizes load capacity and stiffness. Lightweight concrete decreases slab weight without compromising performance, and high-performance materials such as ECC, SFRC, and UHPFRC improve strength and ductility. Numerical modeling, particularly finite element methods, and higher-order beam theories validate experimental results, providing accurate tools for predicting structural behavior under various loading and environmental conditions.