Reactive powder concrete (RPC) is a type of cement-based composite, a special type of high-performance concrete (HPC) that was discovered in 1995 by Richard and Cheyrezy [1]. It consists of several main materials to improve the microstructure of concrete, such as cement, silica fume, fine aggregate, super plasticizer, and a small amount of water and elimination the coarse aggregate. It has superior mechanical properties and high durability. RPC was exposed to brittle failure more than conventional concrete due to its very dense microstructure, so fibers are added to improve its ductility. The commonly used type of fiber was steel fiber (SF), which was a volumetric proportion of concrete [2–5]. The researchers found that increasing the fiber size ratio 0, 1, 2, 3, and 4 increases the compressive strength of concrete [6]. Joe et al. [7] found that adding 1.5% SF gives better compressive strength than a lower percentage of SF.
The use of RPC with SF in many structural members, for example, Alwash 2018 [8] presented a practical study of a simply supported beam to investigate the effect of using RPC on flexural behavior. Study the effect of changing the volume ratios of SF on the ultimate load of the beam and compare it with conventional concrete. The results showed that changing the percentage of SF from (0–2) % leads to an increase in the ultimate load from (8–85) % compared to conventional concrete. Kareem 2020 [9] studied a continuous beam with two spans using RPC with different SF ratios (0, 0.6, 1.3, 1.8, and 2.5%) and compared it with a conventional concrete beam. The results showed an increase in the ultimate load when using RPC, as well as an increase in the ultimate load when increasing the SF ratio, as the increase ranged from (23%-90%).
After the success of using SF in RPC mixtures, many researchers resorted to the discovery of new fibers that could add improvements to the properties of RPC, including glass fibers (GF). There is very little research on using GF in RPC mixtures, and GF is very useful in improving the properties of flexural strength and splitting tensile of concrete [10–14]. GF has been used in some structural applications with strength (40–60) Mpa [15]. GF is not as effective as SF in mechanical properties, but it has other benefits such as corrosion resistance, which gives long life to RPC, and is lightweight (equivalent to 1/3 the weight of SF) [16].
Resif [17] 2020 used the GF-RPC as a repair material for a simply supported beam with conventional concrete. Prisms of GF-RPC were used in specific zones (lower mid-beam, upper mid-beam, lower edge-beam). The results showed that the repaired beam gives better behavior than the original beam in the ultimate load, first cracking, and deflections.
Reinforced concrete buildings contribute to environmental impacts, as the gases emitted as a result of the greenhouse at the present time represent a global challenge, where 77% of the emissions emitted are carbon dioxide [18]. Therefore, the researchers resorted to the optimal use of concrete and steel reinforcement by redistributing the concrete variable sections according to the presence of high stresses [19–21]. Changing the sections of the members in the width of members causes complications in the construction, so it is preferable to be in the depth. The use of variable depth of the sections provides additional benefits as it facilitates the passage of many utilities and equipment such as (electricity, refrigeration, sewage, etc.) [22, 23].
In 2017 Dawood [24] studied continuous beams with prismatic and non-prismatic sections for the purpose of knowing the effect of changing the sections in depth using conventional concrete and RPC. The results confirmed an increase in the ultimate load of the beams when using non-prismatic sections, where the increase was 51% for the RPC and (4–19) % for the conventional concrete. Kaveh 2020 [18] theoretically studied the effect of using non-prismatic sections on the final cost of the project as well as greenhouse gas emissions (CO2). It was concluded that the use of non-prismatic sections will reduce the final cost by 7%, while the emitted gases will decrease by (3–14) %.
In view of the many advantages of GF-RPC covered in previous studies and the scarcity of its study within the structural sections, therefore, the behavior of a GF-RPC concrete frame was experimentally investigated under static and repeated load. Concrete frames with SF-RPC and conventional concrete were also tested, and comparisons were made between frames with different types of concrete and different type of loads. Comparisons focused on the ultimate frame load, type of failure, first crack, load-deflection curves in the middle of the beam, and frame-deflected shape. All specimens used are non-prismatic sections (variable in depth). The ratio of the small depth to the large depth used in the specimens is (1/3) [25].