Concrete cylinders

Crete is stressed in tension. Although the tensile strength of concrete-polymer is higher by a factor of 4 than that of concrete, it is still relatively low compared with that of steel. Standard tests on reinforcing bars in which a 1-inch diameter steel rod is pulled out of a 6-inch diameter concrete cylinder indicated that the force needed to pull the bar from a concrete-polymer cylinder was three times the force required for a cylinder of ordinary concrete. This greatly improved bond strength between concrete-polymer and steel is important in concrete structural design. 

A short concrete cylinder 15 cm in diameter and 30 cm long is initially at 25°C. It is allowed to cool in an atmospheric environment in which the temperature is 0°C. Calculate the time required for the center temperature to reach 6°C if the heat-transfer coefficient is 17 W/m2 °C. 

Figure 6. A comparison of leaching rates of sulfur-infiltrated and -uninfiltrated concrete cylinders by acids of different concentrations...

Figure 9. Photograph of sulfur-infiltrated concrete cylinders immersed 10 months in distilled water. Note the abundance of flowery sulfur extrusions and the trace of a sulfur-fitted fracture ( ) formed during aemolding. Dark rings are iron sulfide.

The installation is characterized by an ozonation chamber hydraulically closed by the pressure of the water to be treated, which flows through it. For these demonstrations, the ozonation chamber was contained in a reinforced concrete cylinder 126 cm. in inside diameter and 230 cm. in inside height. It was compartmented as indicated in Figure 4. 

Table 1 shows the three mix designs the six different tests performed to the plastic modified concrete. Axial compression on concrete cylinders was tested in two different mix designs, No. 1 and No. 2. The other properties were examined only for one of the mix designs. 

For this test 3-in. by 6 in. (75-mm by 150-mm) concrete cylinders were cast following the method described in ASTM C 39-86. Mix designs No. 1 and No. 2 were evaluated under axial compressive load. 

Concrete subjected to freeze-thaw cycling may suffer from micro cracks and surface scaling. Dynamic modulus of elasticity was measured to evaluate the degree of deterioration in the concrete cylinders. A decrease in dynamic modulus indicates that the concrete is internally deteriorating by micro cracks and/or surface scaling. 

Measurements are taken on the three principal joint directions and in 6-cm diameter boreholes. Each measurement point corresponds to two boreholes, both perpendicular to the joints and 20 cm apart (see Fig. 3). A pressure gauge for measuring hydrostatic pressure is placed in the first borehole and a vibrating wire extensometer is installed in the second in order to monitor deformation normal to the joint. This extensometer is positioned within a concrete cylinder. The deformation measurement is thus that of the cylinder with a 6-cm diameter and 50-cm length. The recorded deformations are then transformed into normal displacements by referring to the basic measurement length, i.e. the 15-cm extensometer length. 

The composite cylinder is tested in compression. If the composite cylinder has a strength of 90% of that of a standard concrete cylinder, the epoxy compound is adequate for use with concrete. 

Fig. 12.2 Details of concrete cylinder tested (a) schematic of concrete cylinder, (b) concrete cylinder with 1.27 cm diameter rebar in middle in a testing solution, and (c) front view of the cylinder.

A theoretical model to study chloride diffusion in concrete has been developed by Arora and Popov [77]. Two different coordinate systems are considered to model structure geometry. A chloride ion adsorption and diffusion schematic in a one-dimensional concrete cylinder is shown in Fig. 12.6, comparable to a planar slab with one-dimensional chloride diffusion. Chloride ingress follows Pick s law of diffusion for cured concretes [77]. 

Fig. 12.6 Chloride ion adsorption and diffusion schematic in a one-dimensional concrete cylinder [77].

The resistance of the concrete against chloride penetration was mainly tested by use of the Rapid Chloride Migration (RCM) method [6] and electrical resistivity measurements based on the two-electrode method [7], The testing was carried out on 50 mm cut slices from 0100 x 200 mm concrete cylinders, and the concrete samples were mainly cured in water with a temperature of 20 2 C and tested at regular intervals of up to 90 days. In addition, some samples from two of the concrete mixtures (PO O and Pl. O) were wrapped in plastic sheeting after demoulding and stored in air with a temperature of 20 2°C until time of testing. 

The NACE standard states explicitly in its title that it refers to atmospherically exposed reinforced concrete. NACE also has a standard on cathodic protection of prestressed concrete cylinder pipe RPOlOO-2000, also reaffirmed in 2005 and undergoing revision. 

NACE RPOl 00-2000 Cathodic Protection of Prestressed Concrete Cylinder Pipelines. NACE Standard Recommended Practice. 2000 March. 

Removable Concrete Shield. To fill the void space in the large ateel liner outside the radiation door, a steel-encased concrete cylinder is provided for necessary shielding. Eccentrically located in the concrete billet is a steel-encased cylindrical hole of approximately 10 in. I.D. which forms a portion of the experimental hole. Removal of this shield permits access to the radiation door. 

Figure 11.10. Stress-strain curves for concrete and concrete-polymer (CP-type concrete, cylinders 3 in. in diameter and 6 in. high). The upper (solid) curve is for CP concrete (PMMA, loading 5.4 wt %, = 5.5 X 10 psi) and the lower (solid) curve is for plain concrete (unloaded, E = 1.8 x 10 psi by the U. S. Bureau of Reclamation method, = 1.3 x 10 psi by secant method). The upper ends of the curves correspond to fracture. (Auskern and Horn, 1971.)...

Li, G. (2006) Experimental tudy of FRP confined concrete cylinders. Engineering Structures, 28, 1001-1008. 

Li, G. and Maricherla, D. (2007) Advanced grid stiffened FRP tube encased concrete cylinders. Journal of Composite Materials, 41, 1803-1824. 

Various tests have been developed to ensure that concrete used in particular applications satisfy specifications. One of these is a compression test for testing concrete cylinders. The concrete cylinder is t ically formed using a test cylinder mold. The mold is a hollow cylindrical container including a bottom waU used to test specimens of concrete at a construction site. Such molds are generally disposable (17). 

In the absence of a concrete maturity test, a concrete maturity curve can be estimated using the results of concrete compressive strengths at various ages by performing a heat transfer analysis for a concrete cylinder cured under laboratory condition. The methodology for the heat transfer analysis of the lab samples is the same as previously discussed. Provided that the parameters used in the heat transfer analysis are representative of the concrete mix. 

The rupture strains of FRP measured in recent tests on FRP-confined concrete cylinders are substantially below those from flat coupon tensile tests [71-73]. This discrepancy is attributed mainly to the curvature of the FRP jacket and the non-uniform deformation of concrete. 

Figure 11.2 Force-time response for the compression of two concrete cylinders. The cylinder without rubber has a higher compressive strength but lower failure strain and energy absorption. The cylinder with rubber shows an opposite trend. Such a trend has been extensively observed in other similar tests [11].

Standard Test Method for Compressive Strength of Concrete Cylinders Cast In-Place in Cylindrical Molds (ASTM C873-85). 

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