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Introduction about Self Compacting Concrete

Civil Concrete Engineering

Introduction about Self Compacting Concrete

introduction of  is Self – compacting concrete (SCC) is a fluid mixture, which is suitable for placing difficult conditions and also in congested reinforcement, without vibration. In principle, a self – compacting or self – consolidating concrete must have a fluidity that allows self – compaction without external energy remain homogeneous in a form during and after the placing process and flow easily through reinforcement.

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Self-consolidating concrete consists of cement, aggregates, water, and chemical admixture and/or VMA. Most common chemical admixtures used for SCC are HRWR, VMA and AEA. Aggregates, cement, water, and HRWR are the principal materials whereas SP, VMA, AEA, and other chemicals can be used as the optional materials.

The three properties that characterize a concrete as self-compacting Concrete are Flowing ability—the ability to completely fill all areas and corners of the form work into which it is placed Passing ability—the ability to pass through congested reinforcement without separation of the constituents or blocking Resistance to segregation— the ability to retain the coarse components of the mix in suspension in order to maintain a homogeneous
material.

Self compacting concrete making material

Cement

Portland cement is most widely used to produce various types of concrete. It is hydraulic cement, which is produced by pulverizing clinker consisting of calcium silicates, and usually containing calcium sulphate as an inter-ground addition. Portland cement is also a key component of SCC. It is used alone or in combination with SP to produce SCC. Portland cement improves the flowing ability of SCC when used with water to lubricate the aggregates. Portland cement can also affect the segregation resistance of SCC by affecting the density of cement paste matrix of concrete. After reacting with water, Portland cement also reduces the porosity and results in a packed concrete mass leading to low transport properties and good durability.

The Indian cement industry is directly related to the country’s infrastructure sector and thus its growth is paramount in determining the development of the country. With a current production capacity of around 366 million tonnes (MT), India is the second largest producer of cement in the world and fueled by growth in the infrastructure sector, the capacity is expected to increase to around 581 million tons by Year 2025 Cement production can be causes to serious environmental influences. These include emissions gases in the form of dust, gases, noise and vibration when operating machinery and during blasting in quarries, and damage to countryside from quarrying.

Introduction

Production of Cement (2007 to 2015)

Estimation of Cement production (2016 to 2025)

The amount of CO2 produced by the cement manufacturing is nearly 1100 kg of carbon dioxide for every 1 ton of cement manufacture. In the European Union the specific energy ingesting for the manufacture of cement clinker has been reduced by about 30% since the 1970s. This decrease in primary energy requirements is equivalent to approximately 11 million tons of coal per year with matching benefits in decrease of CO2 emissions. Use of rice husk ash in concrete reduce amount of cement and save environment.

introduction of production of cement

introduction of Aggregate

Two types of aggregate were used, coarse aggregate of size 10mm and 20mm, fine aggregate of particle size no not more than 4.75 mm.

 introduction of Coarse aggregate
The aggregates retained on the 4.75-mm sieve are defined as coarse aggregates. They are granular materials, such as gravel or crushed stone, and are usually used with fine aggregate and cementing material or binder to produce concrete. As in any concrete, coarse aggregates are also a key component of SCC. Coarse aggregates significantly influence the performance of SCC by affecting the flowing ability, segregation resistance, and strength of concrete.

The physical characteristics such as the size, shape, surface texture, and porosity of coarse aggregates affect the properties and durability of concrete. The nominal maximum size for SCC can be 20 mm. However, the smaller size is preferable to produce higher strength and to reduce segregation in fresh SCC. The shape and texture of coarse aggregates influence the packing of combined aggregates in. the shape of the coarse aggregates also considerably affects the properties of SCC.

The porosity and reactivity of coarse aggregate are also of great concerns for the durability of SCC. Porous aggregates produce less strength and less resistance to freezing and thawing. Some aggregates may cause alkali-aggregate reactions. Therefore, the selection of coarse aggregates should be conducted carefully. In general, good quality coarse aggregates should be used to enhance strength, aggregate-matrix bond, flow properties, and durability of SCC. In this study two types of aggregate were used as 10mm and 20mm having angler shape.

introduction of Fine aggregate
Fine aggregates are the second ingredient of aggregate phase in SCC. Sand is the most commonly used fine aggregate for concrete. Fine aggregates pass the 4.75 mm sieve but are retained on the75 μm. They occupy a greater volume in SCC, as compared to ordinary concrete. Similar to coarse aggregates, fine aggregates also influence the performance of SCC. They increase the flowing ability and segregation resistance when used at a suitable amount.

The physical properties of fine aggregate influence the performance of concrete in fresh and hardened states. For instance, the particle shape, surface texture, surface area, and void content affect the mixing water requirement and compressive strength of concrete. Also, the physical characteristics of fine aggregate considerably influence the mortar flow and thus it may affect the flowing ability of SCC. The published guidelines show that fine aggregates may produce more significant effect than coarse aggregates on the fresh properties of SCC. Therefore, the physical properties of fine aggregate should be important to the performance of SCC.

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