Essay On Strengthening Reinforced Concrete

ACI 318-63 requires that the minimum ratio of longitudinal bars shall be at least 1.0%. Also, The vertical center-to-center spacing of the lateral ties shall be one of the smallest of: (1) 16 longitudinal bar diameters to restrain longitudinal bars from buckling, (2) 48 tie diameters to ensure sufficient tie area to restrain the lateral displacement of the reinforcing bars, and (3) the least lateral dimension of the column to develop the maximum strength of the concrete core. As shown in Fig. 1, The dimensions and steel reinforcement details of the columns involved in this experimental program were particularly selected to represent relatively older columns. In this experimental program, the longitudinal reinforcement ratio, ρl, was constant

High compressive strengths are achieved by using a low water-to-cementations materials ratio, requiring the use of water-reducing admixtures to provide adequate workability. High strength concrete offers significant economic advantages over conventional normal strength concrete (NSC) because more slender members can be designed, resulting in reduced material and transportation costs. As structural components become more slender, deflection becomes a more crucial issue, making long-term creep and shrinkage deformations especially important in HSC structures.

Lightweight and normal weight concretes have similar tensile strengths, though lightweight exhibits greater variability. The tensile strength of normal weight concrete of equal compressive strength may vary within a wide range depending, among other parameters, on the shape and surface texture of the aggregate. Experimental tests indicate that the tensile strength of concrete is highly variable and ranges from a bout 8-12% of its compressive strength. The actual value depends on the type of the test and crack propagation pattern at failure. (Ghoneim and El-Mihlmy, 2008)

Concrete is an artificial material in which the aggregates are bonded together by the cement when mixed with water. With the advancement of technology and increased field of application of concrete and mortars, the strength, workability, durability and other characteristics of the ordinary concrete can be made suitable for any situation. For this, definite proportions of cement, water, fine aggregate, coarse aggregate, mineral admixtures and chemical admixtures are

Abstract— Concrete is a composite construction material composed of aggregate, cement and water. There are

To gain perspective on the behavior of lightweight concrete, available literature from the previous research work is reviewed and a review of the codes' and standards' requirements for this kind of concrete. This literature review provides an overview of previous work done on lightweight concrete. This chapter describes the nature of foamed balls concrete, its composition and properties and how it is used in civil engineering works. Because the properties of foamed concrete can vary widely, and it can be used in a wide variety of applications, it is important to define performance requirements for each case.

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Abstract. Considerable network of transportation infrastructures such as highways, rails, and so forth are key providers to economic growth and productivity of countries. Consecutively, Reinforced Concrete (RC) is the predominant construction materials in constructing many of these infrastructures. RC is a unique construction material which allows flexible design layouts and offers safe bending and torsion to satisfy design requirements. However, being exposed to harsh environment and contamination such as salts, acid rain, distilled water, carbonation, sulphur and so on are the reasons for deterioration, thus significantly impacting the performance of these structures. Furthermore, the deterioration of these structures is not only a

Portland cement concrete has been used in the field of construction since the early Roman empire, but until the early twentieth century transporting concrete to great heights or distances was a big challenge. With the invention of the concrete pump handling concrete using wheelbarrows or buckets became obsolete because they require less man-power and can reach those hard-to-get places with ease. There are three types of concrete pumps being used in construction today: truck mounted, trailer mounted or specialized. Each style of concrete pump has it’s advantages and can be tailor made for different construction applications. There is one drawback in using concrete pumps, standard concrete designs can not be used since it is too viscous and would require much larger pumps to reach the required heights. Therefore, admixtures must be added to the concrete design to change the chemical composition of the concrete to make it more flowable. Admixtures are also used to help slow down or speed up setting time, or reduce the amount of water required in the mix depending on the construction site requirements. With such a vast range of applications that concrete pumps can be used for, concrete construction has seen a great increase in production, efficiency, cost-reduction and even safety.

G. Jeenu, U. R. Reji, and V. Syam Prakash, “Flexural Behaviour of Hybrid Fibre Reinforced Self Compacting Concrete”, 32nd Conference on OUR WORLD IN CONCRETE & STRUCTURES: 28 - 29 August 2007

This paper presents the results of an experimental investigation into the seismic performance of a composite moment resisting frame system that consists of reinforced concrete columns (with an embedded steel shape for erection purposes) and composite steel beam-reinforced concrete slab sections. Quasi-static reversed cyclic loading was performed on six two-thirds-scale sub assemblage specimens. Various detailing options were evaluated to provide full moment connection in both orthogonal framing directions at the beam-column joints. With appropriate joint detailing, specimens exhibited a desirable beam plastic hinge mechanism with stable hysteretic response. Composite beam sections maintained near full composite behavior beyond code baseddrift limits with good energy dissipation characteristics and were able to undergo large plastic rotation magnitudes. This framing system may represent a viable alternative for low-to-mid-rise structures in high seismic risk zones.

According to Tam (2002) concrete is a commonly used construction material in most parts of the world.There are many different types, strengths, and compositions of concrete and all of them have different characteristics that make them perform better for different applications. The following report is an outline of the different aspects of concrete itself. It includes the special concretes and their applications that are best suited for the construction of a shopping mall, the types of extenders that may be used together with the different admixtures.

The typical stages in the load-deformation behavior of a reinforced concrete simply supported beam are illustrated in Figure 1.

The tensile force transferred from the steel bar through the bond to the concrete is illustrated and compared for difference reinforcement ratio (ρ = 0. 5%, 0.89% and 1.12% for steel 12 mm, 16 mm and 18 mm) in figure (5.79) and table (5.17). Before first crack accured (Pre-cracking stage), the precentage of tensile force transferred from the steel bar to the concrete accounts is about 8%, 13% and 16%. Aftere first crack accured (cracking stage), the precentage of tensile force transferred from the steel bar to the concrete is about 53%, 60% and 72%. During Post-cracking stage almost all the tensile force is carried by the steel bar 82%, 89% and 90% for P-12- FEM, P-16-FEM and P-18-FEM respectivily.

In order to evaluate the coupled effect of high temperature and heating time on the residual strength of concrete, a series of compressive and indirect tensile tests was performed on normal and high strength concretes. The effect of incorporating polypropylene fibers in high strength concretes was also investigated. Cubical concrete specimens were exposed to different target high temperatures (100, 300, 500 and 700 ºC) for 3, 6 and 9 hours and then cooled in air. Compressive and flexural strengths of these concrete samples were compared with each other and with the unheated samples. Experimental results indicate that concrete strength decreases with