A Day Concrete Test : Introduction And Objective

Hard concrete test were conducted at the age of 3, 7, 14, 21 and 28 days after curing(but we tested it for 7 days only). The concrete strength increases according to the age,the mixture of its concrete design and the strength increment will continue for sometimes. Nevertheless, for most of the work, the concrete strength on the 28 days is set as standard even though it might be determined at a much earlier or longer period. The increment rate of the concrete strength will depend on the temperature and moisture during hardening process.

Most people think concrete is an impenetrable solid. But in actually, concrete is a porous material with many capillaries and voids throughout the surface. Although concrete is strong in compressive strength, it is weak in tensile stength and elasticity. Concrete can tolerate heavy loads, but it is susceptible to damage which causes it to break apart over time.

Aggregate is one of the basic constituents of concrete. Its quality is of considerable importance because about three-quarter of the volume of concrete is occupied by aggregates. One of the physical properties of aggregate that influence the property of concrete is the grading of aggregate. The grading of aggregate defines the proportions of particles of different size in the aggregate. The grading of fine (size < 5 mm) and coarse (size > 5 mm) aggregates are generally required to be within the limits specified in BS 882: 1992.

The testing is done in a laboratory off-site. The only work done on-site is to make a concrete cylinder for the compression test. The strength is measured in Megapascals (MPa) and is commonly specified as a characteristic strength of concrete measured at 28 days after mixing. The compressive strength is a measure of the concrete’s ability to resist loads which tend to crush it.

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

Concrete is one of the essential component of public infrastructure and most buildings. It can only be more effective if we used reinforcement with it, because tensile strength without reinforcement is very low. It usually get cracked with time as it is brittle in property. There are some more causes of these cracks are shrinkage, inadequate water for hydration… etc. these cracks causes reinforcement exposes to atmosphere now reinforcement come into contact of O2 & H2O. That can cause corrosion which results in weaken of structure. That being said concrete is a high maintenance material. Concrete cracks and suffer wear and tear. Concrete is not as much flexible that it can handle significant amount of strain.

Reinforced concrete is a common building material for the construction of facilities and structures.  While concrete has a high compressive strength, it has a very limited tensile

Concrete samples are considered over different time period for example the fresh concrete,7 days as well as 28 days and tested after keeping those specimens under different weather conditions. In lab, samples were kept under different conditions as follows:-

ABSTRACT Self compacting concrete with suitable chemical admixtures like Super Plasticizer and viscosity modifying agent can be cured, alternatively by addition of an internal curing agent instead of using large quantities of water. Steel fibers on the other hand have been used in cement and concrete composites for more than four decades, most of the steel fibers were introduced in the market prior to 1980. This is in sharp contrast to the continuous progress and development in the cement matrix itself. The proposed aim of the experiment is to examine the behavior of self compacting self-cured concrete by changing the steel fiber content. The mix incorporated 40 % replacement of cement with fly ash. The compressive strength and flexural strength of concrete were compared with conventional concrete by adding 0.5%, 1% and 1.5% of steel fibers and a notable accession of 79% in flexural strength was observed without compromising with the compressive strength.

The report will mainly focus on the differences between reinforced, prestressed and partially stressed concrete. These concrete reinforcing methods differ in the period they have been used. Reinforced concrete was developed by a nursery owner in Paris in 1867, Joseph Monier, applying it to practical use for the first time (Salmon & Wang, 2007). Prestressed concrete’s discovery dates back to the late 1800’s. Freyssinet was one of the first engineers who used this method and realised that, for this method, high quality concrete with very high tensile steel wires, stressed as high as possible was needed (Chris Burgoyne, 2005).

There is a strong correlation between the compressive strength and other mechanical properties of concrete (Neville, 1996, Mehta and Monterio, 2005). Compressive strength is used as an index of flexural strength, tensile strength and shear strength of concrete. The flexure strength or modulus of rupture of normal concrete is approximately 7.5 to 10 times the square root of the compressive strength. Similarly, the tensile strength is about 8 to 12% of the compressive strength and is often estimated as 5 to 7.5 times the square root of the compressive strength. The shear strength of concrete is about 20% of the compressive strength (PCA, 1988). These correlations between compressive strength and flexure, tensile and shear strength varies with concrete ingredients and environment.

The test specimens were divided into three series (R1.5, R2.0 and R2.5) on the basis of cross-sectional aspect ratio, and complete details of the test columns are summarized in the table 1 and Fig. 1. The specimen identification convention, which are utilized in Table 1, is in accordance with the first letter R defining the rectangular column. In addition, the following numbers 1.5, 2.0, and 2.5 refer to different sets of cross-sectional aspect ratios. The following letter and number refer to the volumetric ratio of hoop (H) reinforcement with 0 denoting plain concrete, 1, and 2 denoting transverse reinforcement of 0.3 and 0.6% volumetric ratio, respectively. The third last symbol L and number following it refer to the number of layers of CFRP wrap. The final symbol in the specimen identification of M or C refers to monotonic uniaxial loading and complete unloading/reloading of cyclic axial loading patterns. In this paper, complete unloading/reloading refers to unloading from the envelope curve to zero stress followed by reloading to the envelope curve. For further clarification, R2.5H2CL4, for example, had aspect ratio 2.5 and hoop steel reinforcement ratio 0.6% .As well, before it was tested under cyclic axial compression loading, this specimen was externally confined with four layers of CFRP material.

A preliminary investigation of strength and durability properties of a low-cost concrete-like system made of pH-adjusted fluorogypsum (FG), class C fly ash (FA), and type II Portland cement (PC). A series of compressive strength tests and volumetric expansion measurements were conducted on specimens after 28 days of curing. The experimental results were used to develop response surface models (RSMs). These RSMs can be used to predict accurately compressive strength and volumetric expansion as functions of the relative content, in dry weight, of different components. The RSMs

The macroscopic material behavior of concrete is influenced by the geometry, spatial distribution and material properties of individual material constituents and their mutual interactions. Therefore, it is essential to study the influence of each material constituent in order to estimate the residual strength of the structural components. Thus, failure of concrete is a complex phenomenon due to its multiscale and multiphase nature. When the normal stress in a material reaches its tensile strength, the inhomogeneities in concrete promote the formation of an inelastic zone ahead of an existing crack termed as the fracture process zone (FPZ). The FPZ is dominated by various complicated mechanisms such as crack shielding, crack deflection, aggregate bridging and microcracking around the crack tip and exhibits a post-peak softening behavior under tensile loading. It therefore becomes necessary to include these effects for predicting reasonably well the residual strength of existing cracked and damaged structures.

Concrete as is well known is a heterogeneous mix of cement, water and aggregates. The admixtures may be added in concrete in order to enhance some of the properties desired specially. In its simplest form, concrete is a mixture of paste and aggregates. Various materials are added such as fly ash, rice husk, and admixture to obtain concrete of desired property. The character of the concrete is determined by quality of the paste. The key to achieving a strong, durable concrete rests in the careful proportioning, mixing and compacting of the ingredients.