Concrete is an extremely versatile and durable building material. Concrete can be used to build long lasting structures even in very harsh environments when it is made with adequate constituents and mix design and properly handled .performance problems that may arise occasionally are often due to the use of materials that do not full fill minimum quality requirements, unsatisfactory specifications or due to inappropriate construction methods. A concrete consists of sand, coarse aggregate (gravel, stone and etc…), cement and water are mixed and hardened to form a stone like material. This reference assignment is a guide to help you to get a good knowledge about concrete.
TYPESOF CONCRETE:
Light weight concrete
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Due to this expansion, some lightweight aggregate shall be
Absorptive. Such aggregate may require pre-wetting prior to concrete batching.
Lightweight concrete has a range in unit weight from about 1280 to 1920 kg/m3 (80 to 120 lb/ft3)
Depend1760 kg/m3 (110 lb/ft3) and have compressive strengths comparable to conventional concreting on the lightweight material used. Some lightweight aggregate will produce concrete o1760 kg/m3 (110 lb/ft3) and have compressive strengths comparable to conventional concrete.
Figure 1 Figure 2
Reinforced concrete
Reinforced concrete (RC) is a composite material in which concrete's ductility and relatively low tensile strength are counteract by the inclusion of reinforcement having higher tensile strength and/or ductility. Advantages of reinforced concrete
1. Reinforced concrete also has greater compressive strength as compared to other materials used for construction good in tension.
2. It has better resistance to fire than steel and capable of resisting fire for a longer time.
3. It has long service life with low maintenance
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The cost of the forms used to cast concrete is relatively high
3. It has low compressive strength as compared to steel (about 1:10 depending on material) which guide to large sections in columns/beams of multistory buildings. Cracks are developed in concrete due to shrinkage and the application of live loads. Concrete cast in situ
Production
Production is a factor for the resulting concrete and consist basically of dosing and mixing the raw materials. concrete properties are affected by flowing parameters during mixing:
• type of mixture – addition of raw materials
• size of mixture _plant quality control
• mixing intensity_ concrete mixer operator
• mixing time_ cleaning/maintenance of mixture Limited and defined time period is considered to place the concrete. The following factors contribute to the success, which is critical for the concrete quality.
• Delivery note check
• Use of the right equipment
• Avoid overhanding the concrete
• Continuous placing and compacting
• Re compaction on large pours
• Take the appropriate holding measures during interruptions
To achieve constant and consistence concrete quality,
Appropriate and correct curing is essential. The curing measures contribute to
Most people may not realise but concrete plays a vital part in our lives daily. It shapes and creates the built environment in which we are surrounded by, such as schools, bridges, roads, housing, hospitals, dams and so much mores. Concrete is the most used man made material in the world, averaging around 3 tonnes annually for each person. In comparison with other building materials such as wood, steel, plastic and aluminium, over twice as much concrete is used globally than any of these materials. It is the material choice of most purposes due to its strength, durability, thermal mass and its cost.
In this paper we have studied compressive strength of concrete by replacing natural aggregate with recycled aggregate by 25%, 50% and 75%.This mixture formed in the sample of cubes of dimension 150x150x150mm3.
2) While many High Performance Concretes exhibits rapid stiffening and early strength gain, other’s may have long set times and low early strengths.
[20] BS Part 116: 1983. Testing Concrete and determination of compressive strength. British Standards Institution ;
Concrete is one of the world’s most popular construction materials. Some six billion tonnes of concrete is produced each year in the world, making it approximately one ton of concrete for every human being per year (Fardis, 2012, p.116). However, the lifecycle of concrete does not make it the most sustainable building material at the moment. Because of limited natural resources, concerns over green house gases, and landfill problems, concrete production is being cut-back, or at least cannot be increased to keep up with population increase. In this essay, I will look at what makes concrete an unsustainable material and possible solutions to make concrete a more sustainable material.
Coarse aggregate : this material is important to use because it helps to increase the crushing strength of concrete .
Concrete is one of the most widely used construction material in the world. The reason for this is because concrete is strong, easy to make and can be molded into various shapes and sizes. Besides that, concrete is cheap, affordable and is readily mix.
In these cases, such as building a reservoir, a huge number of concrete trucks are generally brought in in a caravan, and they pour their concrete into the forms that have been constructed onsite. In some cases, this order will put a concrete plant out of commission for a period of time due to the demand, and as such it must obviously be coordinated ahead of time.
Generally the strength of concrete is represented by the crushing stress of concrete cube of size ………………………………..
In figure (2.26), eight equations proposed by different researchers have been plotted for lightweight concrete, as shown in table (2.12). The experimental splitting tensile strength values are calculated as follows: Eq. (2.23), (2.24), (2.25) (2.26) for cube specimens and (2.27), (2.28), (2.29), (2.30) for cylinder specimens. The splitting tensile strength of lightweight concrete for Eq. (2.23) ranged from 2.8 – 3.5 MPa, as shown in figure (2.23).
In use from the 1940s onwards, dense aggregate blocks are very much the work-horse of the construction industry. Their distinctive properties of durability and strength make them an ideal and cost-effect solution for all types of load-bearing walls. Dense aggregate concrete blocks are manufactured from cement, sand and aggregates.
The flexural strength usually reported by the time the first crack appears which is corresponding to the point where the load-deformation curve moves out of linearity (Point A on Figure 4). The second value is the failure value or in other words it is called the ultimate flexural strength or the modulus of rupture (Point C on Figure 4). Johnston reported that the prismatic fibers and hooked ones have effects on the strength of the unreinforced matrices by about 100 percent. High strengths can be achieved in mortars with w/c ratio of 0.45 to 0.55. Using 1.5% of volume as fibers may increase the strength value to the range of (6.5 to 10 MPa) and Johnston experiments in 1980 showed that using 2.5% of volume as fibers may increase the strength to 13 MPa.
In figure (2.26), eight equations proposed by different researchers have been plotted for lightweight concrete, as shown in table (2.12). The experimental splitting tensile strength values are calculated as follows: Eq. (2.23), (2.24), (2.25) (2.26) for cube specimens and (2.27), (2.28), (2.29), (2.30) for cylinder specimens. The splitting tensile strength of lightweight concrete for Eq. (2.23) ranged from 2.8 – 3.5 MPa, as shown in figure (2.23).
This study will focus on the chloride penetration to the concrete in various type of the strength and days of the concrete. This study is examined the effect of chloride to the concrete strength and durability of concrete on various type of concrete mixture proportion. Different type of concrete proportions mixture will give the dissimilar result of the experiment.
One of the most important properties of concrete is the measurement of its ability to withstand compressive loads.. The compression tests performed in this project were completed in accordance with IS standard 516 “Methods of Tests for Strength of Concrete”. The apparatus used to determine the compressive strength of concrete in this project was a testing