ملخص البحث :

In this study, a finite element analysis is conducted to study the behaviour of RC beams with different configurations of transverse reinforcement under torsion. These configurations of stirrups are traditional closed stirrups, circular spiral stirrups, and inclined rectangular spiral stirrups. The numerical torsional load values are compared with the experimental torsional load values from previous research. The numerical analysis determined by the ANSYS software shows a reasonable agreement with the experimental torsional load values. The numerical results demonstrate that the use of continuous rectangular spiral stirrups improved the torsional response compared to using another type of beam stirrup. Thus, numerical results show that continuous spiral stirrups are effective at increasing torsional capacity. It is also noted that the behaviour of these beams with continuous spiral stirrups is better than the behaviour of the beams with traditional stirrups. The beams with helical reinforcement, which are TB2, TB3, and TB4 spiral reinforcements, greatly enhanced the toughness. The equivalent stresses are 13.709, 13.728, 14.72, and 15.894 MPa, while the equivalent elastic strains are 0.00421, 0.00377, 0.00347, and 0.00539 mm/mm for the beams TB2, TB3, and TB4, respectively. The beam TB4 had the highest stress and strain value, so its strength improved its ductility properties. As a result, the stirrups' configurations enabled the detection of beam failure mechanisms by improving torsional behaviour when compared to the beam's traditional stirrups. As a result, this research adds more knowledge to the literature on the most effective spiral stirrups for transverse reinforcement to improve the torsional behaviour of beams.

ملخص البحث :

It has become necessary to use damaged tires from various vehicles to produce rubberized concrete structures as a good solution to treat environmental pollution and reduce the total cost of construction. In general, concrete structures, for many reasons, may need to be strengthened. Recently, fiberreinforced polymer (FRP) sheets have been used to reinforce existing concrete structural elements that were deficient. FRP is an effective solution and is moderately common for strengthening and improving the properties of the structural element. Firstly, concrete mixes were poured with replaced sand, with the percentages varying from 0, 10, 20, and 30%. Thus, some mechanical properties in terms of the workability of concrete, compressive strength, tensile strength, and density of recycled concrete were studied using rubber from tires as an alternative to fine aggregate. Secondly, concrete prisms were poured with different proportions of rubber instead of sand. Twelve rubberized concrete prisms measure 100 mm x 100 mm x 600 mm. Then, the effect of fiber reinforced polymer with different forms on concrete prisms was investigated. The results revealed a decrease in the workability, density, and compressive strength of the rubber concrete samples with an increase in the proportions of replaced sand with rubber content. It is also observed that FRP improves the strength, stiffness, and ductility of all concrete prism beams with a different ratio of recycled rubber. In addition, the test results clearly show that the strengthening by width sheets of FPR behaved more favorably than the thin sheets having the same crosssection.

ملخص البحث :

Iraq beside other countries generates tonnes of waste plastic boxes delivered from fruits and vegetable plastic boxes. In the construction sector, an alternative disposal is required for sustainable development of this material. The reducing of this plastic waste can be achieved by adding it in concrete as replacement of coarse aggregate. The investigations of this study carried out at the age of 7, 28, 56 days by testing concrete with and without of plastic coarse aggregate. Five sets of concrete mixtures were cast with percentages of 0%, 20%, 40%, 60%, and 80% of waste plastic boxes as replacement of gravel. Fresh and hardened Properties were tested at a specific age and compared with reference concrete (RC). Concrete with plastic considerably enhanced concrete properties. Results of the study indicated that depending on the quantity of plastic replaced gravel, plastic may effect on strengths. However, the test results demonstrated that this replacement in concrete is promising by comparing results with reference mixtures concrete.

ملخص البحث :

Concrete is considered as an essential material required in construction. If the decreasing cement quantity used in concrete by replacing it with pozzolanic materials leads to required concrete properties, therefore, decreasing cost and the environment protection is the main goal. The current study investigated the fresh and early strength properties of normal concrete (NC) containing fly ash (FA) and silica fume (SF). FA and SF were together used in this work. The percentages of replacement were at a high level to modify the properties of concrete as well as the control NC mix (without FA and SF only OPC) at water/powder (w / p) ratio of 0.35. Slump test investigated the fresh properties and the compressive strength examined the early strength properties at 3 and 7 days. Results showed that the presence of FA and SF in NC has a negative impact by reducing the workability. For all mixtures, workability was lost with increasing amount of both FA and SF, although the rate of reduction was higher for mixtures with a higher amount of SF. However, the use of superplasticizer can be mitigated this reduction. Also, the results of the strengths of the specimens having these two pozzolanic materials are lower than control NZ specimens, especially at 3 days. Conversely, after 7 days the early strengths of the pozzolanic cubes are approaching values to the strength of control mixture. It is clear that a bit improvement in early strength of mixtures containing FA and SF. However, there is on-going of mixtures to develop its performance. NC with (30% FA + l0% SF) partial replacement of cement can be improved the compressive strength compared with control strength and other concrete mixes

ملخص البحث :

Concrete is a material that is strong in compression but weak in tension. To overcome this issue, reinforcement must be used to improve the tensile strength of the concrete. However, it is acknowledged that steel has its drawbacks, such as the fact that it has a high cost and corrosion potential, and the rebar is heavy, non-renewable, and non-environmentally friendly. Thus, this experimental study investigates the potential product of economical reinforced concrete slabs using eco-friendly materials. Firstly, to enhance the concrete properties, a compressive, tensile, and flexural test, also a concrete with the addition of polypropylene fiber outlasted the control mix design in terms of strength and durability. The results included the control mix (CM), F1 0.25%, F2 0.50%, F3 0.75%, and F4 1%. The specimen with the highest compression and tensile strength was 24.28 MPa and 3.15 MPa, respectively, for the F1 specimen with 0.25% short fibers. Secondly, the bending test was carried out on ten slabs to check the structural behavior of these slabs reinforced with reed rods as the eco-friendly material. The good results of the bearing capacity of a partially reinforced concrete slab with a reed have been obtained at 23.8 kN. Meanwhile, to obtain better results, this research has enhanced the behavior of the concrete slab by improving the concrete's properties by adding polypropylene synthetic microfiber to the mixed concrete. In addition, giant reeds treated with epoxy increase the bonding strength with concrete, improve tensile strength properties, and reduce the absorption of reeds. Therefore, the bearing capacity results of the reed-reinforced concrete slab became the best, which were 35.83 kN. Thus, reinforcement of one-way slabs by reed partially with appropriate diameters could be substituted to obtain good performance in the reconstruction of low-cost buildings. As a result, economical reinforced concrete slabs have been produced using eco-friendly materials.

ملخص البحث :

In general, producing environmentally friendly concrete is necessary to conserve concrete material resources and reduce construction costs. Recycled tire rubber has been used to produce concrete in various construction works. In the beginning, rubber concrete mixes are done with different percentages of 0%, 6%, 12% and 24% of rubber tires. Then the slump test and the density of the concrete have been tested, in addition to the compressive strength and tensile strength. The strengthening of rubberized concrete slabs with fibre-reinforced polymer sheets is experimentally investigated to increase strength and durability. Thus, in this paper, twelve rubber concrete slabs have been strengthened by FPR sheets with different methods as external reinforcement in order to improve the fracture and shear strength. It is found out that the strengthening rubbered concrete slabs with inclined angles are unnoticeable higher than the straight strengthening configuration. In addition, the type of failure of rubberized concrete panels is affected by the configuration of external reinforcement.

ملخص البحث :

Iron filings are considered waste products produced from metalworking processes as small pieces of iron that look like fine powder. In this research, the landfill is the method of dealing with this waste. In the current investigation, iron filings have been employed to determine their appropriateness as afine aggregate in concrete production. Replacing all or a portion of the fine aggregates with iron filings would result in significant environmental benefits. The replacement percentages of fine aggregate by IR are 0 %, 10 %, 20 %, 30 %, and 40 %. The water cement ratio adopted in this work is 0.58. The experimental investigations in the fresh state show that the slump of the mixtures containing 10 %–40 % of iron filings (IR) varied from 71 to 76 mm. The results showed a decrease in the slump of up to 16.47 % for the mixtures containing different percentages of IR compared to the reference mixture. This decrease is evident in mixtures containing IR ratios between 20 % and 40 %. However, the superplasticizer (SP) addition improved each slump and compaction factor. The compressive strength of the mixtures containing 10 %–40 % was within the range of (28.21 to 40.44) MPa at 28 days. The flexural strength was within the range (of 4.51 to 6.51) MPa at 28 days. According to the results of this study, the addition of IR decreased the compressive strength and flexural strength by up to 38.51 % and 44.32 percent at the age of 28 days, respectively. The importance of the study comes from the attempt to reuse waste iron filings as fine aggregate to save sources of our environment and contribute to the sustainable concrete industry.

ملخص البحث :

The research aims to study the behaviour of concrete columns reinforced with fibreglass as bars exposed toseawater. Firstly, hardened concrete properties as the compressive strength and the tensile strength were investigatedat ages 14, 28, and 56 days. Secondly, the experimentaltesting also involved casting 18 short concrete columnsthat have a length of 300 mm with the cross-sectional dimensions of 100 mm × 100 mm. Six samples were plain concrete,six were reinforced with a diameter of 6 mm longitudinalfibreglass bars, and six polypropylene fibre concrete columns were reinforced with a diameter of 6 mm fibreglassbars. The results added useful information using fibreglassbars (anti-corrosion materials) as reinforced longitudinalconcrete columns, so the ultimate load of the reinforcedconcrete column with fibreglass rod exposed to seawaterwas 174.8 kN that it was higher than that of the plain concrete column at 104.9 kN. Thus, the fibreglass reinforcementtechnology enhances the capacity of the columns. So, it couldbe used in non-impacting structural parts. Meanwhile, theultimate load of the fibre-reinforced concrete column withfibreglass rod exposed to seawater was 201.8 kN. It is 15.4%higher than that of the ultimate axial load of the reinforcedconcrete column with fibreglass rods only. Also, the resultsachieved of this research were encouraging, as the maximumfailure load for short columns reinforced with fibreglass rodsreached approximately 84 to 87% of failure load relative topolypropylene fibre concrete columns containing reinforcingfibreglass bars. As a result, the structural behaviour bars havebeen enhanced using fibreglass rod and polypropylene fibre.