Tikrit Journal of Engineering Sciences

The use of conventional flocculants such as Aluminum sulphate (Alum) alone to treat the wastewater may be insufficient to get the required turbidity, suspended solids removal. It also requires relatively a long residence time. Magnetic flocculation is one of the techniques used for increasing the efficiency of the turbidity removal. In the present study, three sets of experiments are carried out in order to investigate the possibility of increasing the suspended solid removal efficiency from Al Doura oil refinery wastewater using iron oxide (Fe3O4), Nickel (Ni), and Cobalt (Co) ferromagnetic powders with alum. The following operating conditions namely, pH, alum dose, ferromagnetic powder dose, and initial turbidity are studied. The results revealed that an improvement in turbidity removal efficiency is satisfied, as well as, a reasonable reduction in the sedimentation period is achieved. The highest turbidity removal is 99.88% that obtained for 122NTU sample for alum dose 120 mg/L+ Nickel dose of 80mg/L and pH of 6.5.

In modern buildings, transverse openings are often used beams for the purpose of supplying and service pipes. Due to the presence of the openings in the concrete beams lead to the formation of cracks around the openings due to the stresses concentration in a small area above and below of the opening. The repairing, maintenance, and upgrading of structural members, are maybe one of the most pivotal problems in civil engineering applications. In this research, an experimental work is conducted to study the behavior of the reinforced RPC T-beams that containing openings and repair this beams using CFRP strips. The Experimental program of the present study includes two parts, the first part includes testing of seven reinforced reactive powder concrete RPC T-beams, which casted and tested, one beam is without opening as a reference beam and the rest, were provided with an opening. and these beams are divided into two groups. The first group was used to study the effect of the openings shape (circular and square) and the second group was used to study the effect of the openings locations, which consists three locations (Lc/2, Lc/3 and Lc/4). These are measured from the support center to the openings center. While the second part including a repaired all beams in the first part the using carbon fiber polymer. The test results indicated that the presence of openings in the beams web caused a reduction in the reinforced RPC T-beams ultimate load carrying capacity with about (10-55)%, Also lead to increasing in deflection compared to control beam before repairing at same loading. Studying the shape effect showed that the beams with square openings have average ultimate load carrying capacity lower by 36% compared with the control beams. While beams with containing circular openings have average ultimate load carrying capacity lower 29%. From the test results, it could be concluded that the presence of the openings in the shear region led to a decrease in ultimate load carrying capacity a about 38% to 49% for opening of opening at (Lc/3 and Lc/4) respectively. While the presence of openings in the flexural region led to a decrease in the ultimate load carrying capacity rate of 11%. Related to the repairing study part it was found that the average ultimate load carrying capacity for repairing beams was 103% compared with the not repaired beams.

The Gypseous soil which is used is taken from Tikrit city in Salah Aldeen governorate and specially from Tikrit University from a depth (1.5-2) m. It's type is sandy gravely with a small percentage of silt and clay while the percentage of gypsum is (34-36) %. The tests on soil are standard proctor compaction, direct shear, collapsibility and California bearing ratio. The number of samples is (70). The effect of adding concrete waste (2, 4, 6 and 8%) and waste of Asphalt mixture (2, 4, 6 and 8) % on dry soil, as well as the effect of mixture of the optimum percentages of both additions on the properties of gypseous soil, is the aim of the study. Adding concrete waste at optimum percentage (6) % causes an increase in maximum dry density at (16)% and a decrease in optimum moisture content at (5) %. Whereas adding concrete mixture waste in its optimum percentage (2) % caused a decrease in maximum dry density values with an increase of optimum moisture content, and when adding a mixture of optimum percentage of waste, an increase happened in the M.D.D.(14)% with a decrease in O.M.C. at (4) %. Adding the optimum percentage (8) % for both, the value of cohesion increases (100) % when adding concrete waste with an increase in the angle of internal friction (14)% and a decrease in collapsibility in a percentage of (90)% , while adding waste of asphalt mixture shows an increase in cohesion value (112) % with a decrease in the angle of internal friction (2) % and a decrease in collapsibility in a percentage of (90) %, when adding mixture of optimum percentages the value of cohesion increase (108) % with an increase in angle of internal friction (14)% and a decrease in collapsibility in a percentage of (91) %. Values of California Bearing Ratio in dry and soaked condition increases (49) % when adding (8) % of concrete wastes which is the optimum percentage, while adding waste of asphalt mixture causes a decrease in the value of C.B.R. and the optimum percentage is (2) % , but adding optimum percentages mixture of them causes an increase in values of (52) % in dry condition and (53)% in soaked condition.

Binding organic liquids are strong base of amidine have been used for CO2 capture. Up to now, there is no known datum on the reaction kinetics of CO2 with 1.5-Diazabicyclo [4.3.0] non-5-ene (DBN). In this paper, Kinetics of reaction between CO2 and DBN/MDEA in 1-Pentanol was performed utilizing the stirred cell reactor with DBN concentration (2 – 2.9 M) and at room temperature. The reaction path was qualified using zwitterion and the termolecular mechanism. From the kinetic datum with DBN concentrations (2 - 2.9 M), it was found that the capturing process happened in a fast reaction system with a second-order reaction kinetics of DBN/MDEA and first order with CO2. In addition, CO2 absorption was achieved using gas-liquid contact system. CO2 absorption rate was (2×10−5−2.8 × 10−5kmol⁄m2.sec) at DBN concentration (2 – 2.9 M). Finally, it is known that DBN/MDEA/1-Pentanol/CO2 system is easily switchable and can be used both CO2 capture and for other applications that require rapid change of medium from nonionic to ionic liquid.

In the light of the world's technological development in the construction field and the continuous need to apply high-efficiency building materials because old methods are no longer used after the advent of the solutions characterized by fast applications and maximum protection in addition to reducing costs and increasing 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 a local 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 of reference mix. For the purpose of 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, models of cylinders and standard prisms were prepared, to evaluate the compressive strength and the splitting tensile strength respectively. In addition to that the modulus of rupture and the unit weight, where carried out. The tests results indicated a drop in the mechanical properties of the concrete with increase in 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.

This study investigates the effect of the load eccentricity on the deep beams, in terms of failure load and failure mode, using ANSYS nonlinear finite element program. Three RC deep beams with shear span to depth ratios, varying from 0.91 to 1.67 are modeled. A comparison between the experimental and numerical results, under central load, showed approximately full matching between them. This had been done in order to ensure that the model was represented properly. The used model for investigating the behavior of the RC deep beams under an eccentric load with various heights of beams showed that under eccentric load there was a significant reduction in the failure load. Increasing the beams height cause of an increase (gradually) of the failure load with the incremental increases of the height, also there was a clear reduction in the failure load due to eccentricity. For the load eccentricity value 50 mm all the beams of different heights possess the same failure load and all of them failed due to concrete crushing at the beam compression face.

Hollow sections of steel are widely used in many engineering applications as structural members. This paper aims at studying the flexural behavior of a composite beams with steel tubes sections through a series of bending tests in order to study and examine the influence of the steel tube section shape, (square, rectangular and hexagonal) with the same shear connector type (headed stud or angle or perfobond) on its flexural behavior and the bending properties of these sections. As well as study the effect of different shear connectors types (headed stud, angle and perfobond) in the same steel tube sections (hexagonal, square, or rectangular) on the flexural behavior of the composite beams. The experimental program (in this work) has been divided into two groups, the first consists of nine specimens tests focusing on three types of steel section. Using shear stud first, angle at second, and perfobond at third as shear connector type. The second group consists of testing nine specimens of composite beams too. This group focuses on testing every steel section (hexagonal, square and rectangular) alone when using three types of shear connectors with it. All the specimens are of the same length, width and height (2000, 400 and 130) mm respectively. The tested steel tubes thickness was 2 mm, yield stress of 322 MPa and the ultimate strength was 390 MPa. The results showed that these shapes of hollow steel sections (hexagonal, square and rectangular) sustain the quality of services for the buildings, and these tested specimens are applicable by giving a distinctive strength and stiffness starting from 114 kN as ultimate load reaching to 170 kN. The experimental results proved that the perfobond and angle connector types are clearly effective shear connectors. Shear connector of the perfobond type increased the ultimate load of the composite beams by (6.25-9.74) % compared with the stud shear connector.