This research presents the flexural behavior on reinforced concrete beam with transverse web opening constructed from layered concrete. The layered concrete combining normal concrete and lightweight aggregate concrete (LWC) are depended in present study. In the experimental program, 13 models of normal and layered reinforced concrete beams are tested under the effect of four-point loads. All beams had the same overall geometrical dimensions and main longitudinal top and bottom with internal diagonal reinforcement provided around the openings.  One of the beam specimen is tested as control beam and the other specimens are divided into three groups [G1, G2, and G3] to study the effects of the following variables: effect of presence of web openings, layered system, lightweight aggregate (partially volumetric replacement of normal aggregate by thermostone) on the ultimate load, cracking load, cracking pattern and energy absorption capacity. The existing of an opening in beam specimens reduced the flexural capacity of beams with a percentage depending on the size of opening and opening number. The test data obtained from the adopted layered technique of (NEW) and (LWC) have shown that for beams constructed from two layered concrete (LWC with thermostone in the web and bottom flange of I-beam section) ultimate load is decreased about (9.3%-48.8%). It has also, the beams constructed from three-layered of concrete (LWC with thermostone in the web of I-beam section), their ultimate load is decreased about (25.6%-58.1%). On the other hand, magnitude increased of energy absorption capacity are achieved by the decreased opening size, introducing the full size opening of dimension (100×1000) mm reduces the energy absorption capacity of the RC I-section beams at least 80% compared to solid beam while the beam with opening size (100×100) mm decrease up to 16%. In the case of the layered concrete beams specimen, the real influence of lightweight concrete (LWC) type in the layered reinforced concrete is observed significantly after increasing the length of opening more than 100 mm.

The light of the world’s technological development in the construction field and the continuous need to apply of a high-efficiency building materials because old methods is no longer is used after the advent of the solutions that characterized by fast applications and maximum protection in addition to reducing costs and increase the sustainability of the establishment and its design age. The lightweights of various installations are an urgent need to decrease the dead loads. Therefore, this study is specie locally focus on replacing the normal coarse aggregate with lightweight coarse aggregate (claystone (bonza), rubber, thermostone and polystyrene) in various volumetric ratios of (25, 50 and 75) % in addition to a preparation reference mix. For the purpose identifying and studying the important specifications the new concrete which contributes to the self-load reduction of the concrete by reducing the total density of the mixture, were prepared models of cylinders and standard prisms, to evaluate the compressive strength and the splitting tensile strength respectively, Also the modulus of rupture and the unit weight, where carried out. The results tests indicated that a drop in the mechanical properties of the concrete with increasing the lightweight coarse aggregate , mechanical properties values : compressive strength , rupture modulus, splitting tensile strength and flexural strength were between (10.66-28.99) MPa (1.122-3.372) MPa, (3.606-6.83) MPa and (20.101-25.874)MPa compared with a reference mixes (38.44MPa), (3.969MPa), (10.476MPa) and (26.940)MPa respectively for mixes of (25, 50 and75)% with different light coarse aggregate , also the values of an oven dry density were between (1665.5-2287.58)kg/m3 compared with reference mixes (2426.41kg/m³). The best concrete mix was (M7, M10) of low density (1598.4 kg/m3) and (1580.4) kg /m3 and the compression strength within the permissible limits (15.47) MPa.

The main objective of the research is to study the preparation of one way slabs of ordinary concrete, and then to prepare concrete slabs by replacing the main reinforcing steel with two kinds of steel fibers (ordinary steel fibers and recycled steel fibers) by fraction volumes of 0.125, 0.250, and 0.375%. Also, study the mechanical properties of the mixtures as a ompressive strength, indirect tensile strength, and flexural strength. Concrete slabs of these mixtures have been prepared with specific geometrical dimensions700 * 300 * 70 mm, exposed to line load, to study the bending moment and maximum failure load of these slabs. A concrete mixture was produced after proportionment based on the ACI and casting six cubes tested at the ages of 7 and 28 days where the strength requirements for design were achieved. The main mixtures of research were produced, three cubes for compressive strength testing, twenty one cylinders for indirect tensile strength testing, and twenty one prisms for modulus of rupture testing. Also sixteen concrete slabs were prepared, two of them were reference slabs without reinforcing steel, the other two with main reinforcing steel only, six of them replaced by the main reinforcing steel with ordinary steel fibers, and the last six replacing the main reinforcing steel with recycled steel fibers. The results showed that both the failure load and the resultant deflection in concrete slabs decreased by (20.09%, 51.91%) for maximum load and by (35.18%, 81.48%) compared to the reference slabs when replacing the main reinforcing steel with steel fiber, also by (25.72%, 38.29%) to failure load and (38.88%, 79.63%) for the deflection compared to the reference slabs when replacing the main reinforcing steel with recycled steel fibers. The best value for maximum load and deflection could be obtained from this study was at 0.125% replacement ratio of the main reinforcing steel with recycled steel fibers, the highest value of ductility was 3.77 at the replacement ratio of 0.250% of the main reinforcing steel with the ordinary steel fibers, also the highest hardness value was 11.67 kN / mm with the replacement ratio of 0.125% of the main reinforcing steel with recycled steel fibers and increased by 61.85% than the hardness of the reference slabs.

This research presents an experimental investigation of the rehabilitation efficiency of the damaged hybrid reinforced concrete beams with openings in the shear region. The study investigates the difference in retrofitting ability of hybrid beams compared to traditional beams and the effect of two openings compared with one opening equalized to two holes in the area. Five RC beams classified into two groups, A and B, were primarily tested to full-failure under two-point loads. The first group (A) contained beams with normal weight concrete. The second group (hybrid) included beams with lightweight concrete for web and bottom flange, whereas the top flange was made from normal concrete. Two types of openings were considered in this study, rectangular, with dimensions of 100×200 mm, and two square openings with a side dimension of 100 mm. A full wrapping configuration system for the shear region (failure zone) was adopted in this research. Based on the test results, the repaired beams managed to recover their load carrying capacity, stiffness, and structural performance in different degrees. The normal concrete beam regains its total capacity for all types of openings, while the hybrid beams gain 84% of their strength. The strength of hybrid concrete members compared with normal concrete is 81 and 88% for beams of one opening and two openings, respectively. Doi: 10.28991/CEJ-2022-08-01-012 Full Text: PDF

This paper presents an experimental algorithm with the results of using steel fibers in ferrocement panels, which were recovered from tires scrap. Waste steel fibers were cut with the same geometrical characteristics of normal steel fibers and were used in the panels at different layers. To have a reference ferrocement specimen, a plain mixture without fibers and mixtures containing a ratio of recycled steel fiber were also prepared. Some mechanical tests, such as compressive strength, splitting tensile strength and flexural strength were determined. Furthermore, load deflection behaviors for 24 panels specimens were carried out under patch load. Test results show that the recycled steel fibers layers recovered from scrap tires affected the mechanical behavior of ferrrocement panels that are similar to the number of wire mesh layers. Depending on the distribution of R.S.F layers and wire mesh layers, the load-deflection curves were found. A comparison between these curves indicates that the R.S.F can reduce the deflection of panels, and increasing the number of wire mesh layers can increase the ability to bear stresses for panels. Rehabilitation with carbon fiber strips CFRP carried out with three forms (box network, inclined with diagonal, parallel to the diagonal and mix of diagonal and box network). The curves show that the rehabilitation with a parallel form to the diameter of the sample is a better treatment, which is characterized by resistance to stresses rather than other forms. We estimate that the recycled steel fibers increase the flexural strength and tensile strength, and 10% is the optimal ratio for increasing the flexural strength and tensile, increasing the number of wire mesh layers increases the ability to bear stresses of the panels. Recycled steel fibers can cause reduction in the deflection of ferrocement panels and can give the same bearing strength proximity (or less) to the panel containing the same number of wire mesh layers.