In this study, the CONCRETE-steel bond strength of CONCRETE filled cylindrical steel tubes has been experimentally investigated. 22 short, high strength and normal CONCRETE filled circular steel tubes were tested. Push-out test was carried out as the common method to evaluate the bond carrying capacity. Four different CONCRETE mixes were used in preparing the specimens. The steel tubes were welded type with the nominal inside diameters of 3, 4, 6 and 8 inches. According to the test results bond strength increases with reduction of the w/c ratio of CONCRETE mixes. The high strength to normal CONCRETE bond strength ratio increases with the diameter of steel tubes. The bond strength decreases for higher diameters in both normal and high strength CONCRETE specimens.

A new method for seismic retrofitting CONCRETE structures is proposed using an X-shaped precast prestressed CONCRETE brace. This PPC brace is made of four precast CONCRETE parts and middle section that are assembled and added to the existing frame. This method has the following benefits: there is no need to work with wet CONCRETE in site or anchor and bolt to the existing frame, which may lead to a fast and economic retrofitting method. The X-shaped CONCRETE brace was made in half size and its efficiency is confirmed. That X-shaped precast prestressed CONCRETE brace was simulated and evaluated by computerized analysis using ABAQUS FEA modeling by authors of this paper earlier, and the proposed brace showed proper results in reducing lateral drifts and that method is considered as a proper method for seismic retrofitting. Here we are suggesting a different setup for the brace, which may lead to faster and more economic strengthening of RC structures. The new setup is omitting the middle section and suggests the brace to be used as a single diagonal. A model of this proposed method is simulated in ABAQUS FEA and the results show it is proper in reducing lateral displacements.

One of the efforts to produce more environmentally friendly CONCRETE is to reduce the use of OPC by replacing the cement in CONCRETE with geopolymers. In geopolymer CONCRETE no cement is used, instead fly ash and alkaline solutions such as sodium hydroxide (Na OH) and sodium silicate (Na2O, SiO2) and potassium hydroxide (KOH) are used to make the binder necessary to manufacture the CONCRETE. One tone of fly ash can be utilized for manufacturing about 2.5 cubic meter of high quality Geopolymer CONCRETE. Test experiments proved as fly ash based Geopolymer CONCRETE has excellent Compressive strength, suffers very low drying shrinkage, low creep, excellent resistant to sulphate attack and good acid resistance. Trial mixes were done and noted the properties of the CONCRETE both in fresh state and in hardened conditions. The workability of the CONCRETE in terms of slump and compacting factor are observed to be excellent. The geopolymer CONCRETE in fresh state observed to be highly viscous and good in workable. Collapsed slump was observed with compaction factor of 0.95. Cube compressive strength of the geopolymer CONCRETE cubes verified at the age the CONCRETE 28 days from the date of their casting. Based on the test results of the trial mixes, this experimental study is carried out for 5 different mix proportions of fly ash to alkaline chemical ratios of CONCRETE specimen. Test specimen of standard sizes of cubes (30 nos), cylinders (30 nos), and prisms (15 nos) were cast and tested for workability in terms of slump and compacting factors in fresh state and for mechanical properties such as Compressive Strength, Splitting Tensile Strength, Flexural Strength, and Modulus of Elasticity of CONCRETE in hardened state. The test experiment proved that a CONCRETE of compressive strength of 30 MPa could be achieved in geopolymer CONCRETE by adopting alkaline solution to fly ash ratio of 0.50 at 16 molarity of Na OH.

In this paper a new method for nonlinear analysis of three dimensional reinforced CONCRETE frames (3D-RCF) under cyclic and monotonic loading is proposed. Each reinforced CONCRETE frame is divided into two types of joint and beam-column elements. The effect of bond-slip has been considered in the formulation of beam-column element. The effect of biaxial flexure and axial load on the cross section is assumed for nonlinear behavior while the effect of tensional behavior of beam-column element is assumed linear. The pull-out effect of reinforcing bar is considered in the formulation of joint elements. Formulation and relevant equations are displacement based upon which a computer program is developed. The reliability of the method has been assessed through the comparison of numerical and an experimental result by achieving of excellent agreement. Also the effect of bond-slip and bar pull-out occurring at joint on the response of RC frames is evaluated by utilizing various analyses.

In this study, four CONCRETE types, including ordinary Portland cement CONCRETE, fly ash CONCRETE, slag CONCRETE, and slag-fly ash CONCRETE, are taken into account in order to estimate their compressive strength by two novel machine learning methods (genetic algorithm and soccer league competition algorithm), and four types of regressions (linear, 2nd order polynomial, exponential, and logarithmic). Subsequently, the precision of prediction models are compared based on performance indicators, and the most accurate models are applied in the optimization problem modeling. Drawing on results, the most precise model to estimate the compressive strength of ordinary Portland cement CONCRETE is the genetic algorithm, and the soccer league competition is the most accurate model to estimate the strength of other CONCRETE types. Afterward, a model is developed so as to design mixture proportions of 40MPa CONCRETEs. Fly ash CONCRETE, slag-fly ash CONCRETE, and slag CONCRETE reduce the unit cost by 35. 2%, 29. 9%, and 23. 1%, respectively, compared with ordinary Portland cement CONCRETE. Fly ash CONCRETE, slag-fly ash CONCRETE, slag CONCRETE, and ordinary Portland cement CONCRETE require 217. 25 kg, 150. 47 kg, 102 kg, and 414. 64 kg cement to be manufactured. Furthermore, the slag CONCRETE can reduce the amount of cement in the mixture proportion by 75. 4%, and it is the most eco-friendly CONCRETE.

In the process of engineering design and construction, the CONCRETE cover thickness is very critical. If the CONCRETE cover thickness does not reach to design specifications and drawing requirements, it will be easy to cause some defects, such as surface cracks on building components and even reduce the structure strength and durability etc. In this paper, strength criteria is consider with three specimens with gradual removal of clear cover thickness (50-25-0 mm) of different grade of CONCRETE to investigate the flexure behavior of over reinforced CONCRETE beam. The results of laboratory investigation on removal clear CONCRETE are present. Data presented includes load v/s deflection characteristics, crack width and stiffness when tested on 28 days.

This research aimed to investigate the mechanical and physical properties of Roller Compacted CONCRETE (RCC) used with Recycled CONCRETE Aggregate (RCA) as a replacement for natural coarse aggregate. The maximum dry density method was adopted to prepare RCC mixtures with 200 kg/m³,of cement content and coarse natural aggregates in the CONCRETE mixture. Four RCC mixtures were produced from different RCA incorporation ratios (0%, 5%, 15%, and 30%). The compaction test, compressive strength, splitting tensile strength, flexural tensile strength, and modulus of elasticity, porosity, density, and water absorption tests were performed to analyze the mechanical and physical properties of the mixtures. One-way Analysis of Variance (ANOVA) was used to identify the influences of RCA on RCC’, s mechanical properties. As RCA increased in mixtures, some mechanical properties were observed to decrease, such as modulus of elasticity, but the same was not observed in the splitting tensile strength. All RCCs displayed compressive strength greater than 15. 0 MPa at 28 days, splitting tensile strength above 1. 9 MPa, flexural tensile strength above 2. 9 MPa, and modulus of elasticity above 19. 0 GPa. According to Brazilian standards, the RCA added to RCC could be used for base layers.