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[Audio] Dear students My names is Dr A. Ravi Theja Working as Assistant Professor in SVR ENGINEERING COLLEGE, Nandyal, Andhra Pradesh, India today my class is CONCRETE TECHNOLOGY UNIT -I Ingredients of concrete.

Introduction Concrete is considered to be the most widely used construction material in the world. It is a composite material that is made from cement, water, and other aggregates. It is popular due to its durability and strength. Concrete can be used to construct buildings, bridges, roads, and other structures that are essential in modern society. Second only to water as the most consumed substance on earth..

Constituents of Concrete Coarse Aggregates: 30 to Fine Aggregates: 25 - Matrix (paste): • Water: 15-20% • Cementitious materials (cement, pozzolans & slag): 7-15% . Air: I • Chemical Admixtures: < 2%.

[Audio] Cement is a powdery substance made by calcining lime and clay, mixed with water to form mortar or mixed with sand, gravel, and water to make concrete. It is used in construction to bind different materials together. The most common type of cement is Portland cement, which is a generic term for the type of cement used in virtually all concrete. This type of cement is composed of calcium silicates that harden after being mixed with water. Other types of cement include hydraulic cement, non-hydraulic cement, slag cement, and pozzolan cement, among others..

[Audio] chemical composition of cement shown in table.

[Audio] Compounds refer to the four primary compounds found in Portland cement, named after the American chemist Robert Herman Bogue who first identified them. These compounds include Tricalcium Silicate (C3S), Dicalcium Silicate (C2S), Tricalcium Aluminate (C3A), and Tetracalcium Aluminoferrite (C4AF). Each of these compounds contributes differently to the properties of cement. Tricalcium Silicate (C3S) is the most abundant compound, making up around 45-60% of Portland cement. C3S hydrates and hardens rapidly and is largely responsible for the initial set and early strength of cement. Within a few days of the hydration process, C3S forms about 50% of the calcium silicate hydrate (the substance that gives cement its strength). Dicalcium Silicate (C2S) is the next most abundant compound, constituting about 10-30% of the cement composition. C2S hydrates and hardens slowly, and it is responsible for strength increase from one week onwards. It contributes significantly to long-term strength. The proportion of C2S to C3S determines the rate of hydration, and hence the rate of strength gain. Tricalcium Aluminate (C3A) comprises about 5-10% of the cement. C3A hydrates quickly and liberates a large amount of heat, leading to a rapid initial set, and it can also contribute to sulfate attack, a common form of concrete degradation in the presence of water and sulfate ions. The content of C3A in cement is usually limited to a lower percentage to control sulfate resistance and to control the heat of hydration in mass concrete pours. Tetracalcium Aluminoferrite (C4AF) makes up between 5-15% of the cement composition. It hydrates rapidly but contributes very little to strength. It serves to lower the clinkering temperature during the manufacturing process. C4AF, along with C3A, contributes to the grey color of ordinary Portland cement..

CA+C,AF cs Schematic presentation of various compounds in clinkor.

[Audio] The hydration process of cement is a chemical reaction that happens when water is added to the cement. The water interacts with the cement compounds, particularly with Tricalcium Silicate and Dicalcium Silicate, to form chemical bonds leading to the formation of hydrates or hydration products. The primary product of this hydration is calcium silicate hydrate (C-S-H), which imparts strength to the hardened cement paste. The hydration process is not instantaneous but continues over a long time period, often weeks or even years. The rate of this reaction can be influenced by environmental factors such as temperature and humidity, as well as by the specific mix design, including the water-to-cement ratio and the use of chemical admixtures..

[Audio] Which cement to use? The choice of the cement depends upon method the of nature of work,local environment,construction etc. The different type of cement has been achieved by ifferent methods like: (a) Changing oxide composition (b) Changing fineness (c) Using dditives or ineralmixturesl,slag, fly-ash or silica fumes etc..

[Audio] As per the Indian Standard (IS), there are several types of cement defined based on their composition and specific applications. The commonly used types of cement as per IS are: 1. Ordinary Portland Cement (OPC): OPC is the most commonly used type of cement for general construction purposes. It is available in three grades: - OPC 33 Grade: Suitable for plastering works, general RCC constructions where high early strength is not required. - OPC 43 Grade: Used for general construction, especially in the case of RCC (Reinforced Cement Concrete) works where high initial strength is necessary. - OPC 53 Grade: Suitable for the construction of precast structures, high-strength concrete, and structures subjected to severe environmental conditions. 2. Portland Pozzolana Cement (PPC): PPC is a blended cement that consists of OPC clinker, gypsum, and pozzolanic materials like fly ash, volcanic ash, or silica fumes. It offers better workability, durability, and resistance to sulfate and chloride attacks. PPC is suitable for general construction, especially in areas where the availability of good-quality aggregates is limited. 3. Rapid Hardening Cement: This type of cement achieves high strength in a short period, typically within a few days. It is useful in cold weather concreting, precast elements production, and road repair works. 4. Sulfate Resistant Cement: This type of cement is resistant to sulfate attacks, which can occur in areas with high sulfate content in the soil or water. It is commonly used in coastal regions, sewage treatment plants, and foundations where the soil has high sulfate levels. 6. Blast Furnace Slag Cement (BFSC): BFSC is a blended cement that contains a combination of OPC clinker and granulated blast furnace slag. It offers good workability, reduced permeability, and increased resistance to chemical attacks. BFSC is suitable for marine structures, mass concrete works, and aggressive environments..

[Audio] Low Heat Cement: Low heat cement is designed to generate less heat during hydration, making it suitable for massive concrete structures like dams, bridges, and retaining walls. It helps to prevent thermal cracking caused by the heat of hydration..

[Audio] Tests on Cement Field Test and Laboratory test Field Test by consider the Date of Manufacture For 3 months we can get 100% Strength with respect to28 days strength For 6 months we can get 80% Strength with respect to28 days strength For 12 months we can get 60% Strength with respect to28 days strength For 24 months we can get 50% Strength with respect to28 days strength One feels cool by thrusting one's hand in the cement bag. and It is smooth when rubbed in between fingers. A handful of cement thrown in a bucket of water should float..

[Audio] The Indian Standard (IS) codes provide specifications for the testing of cement. The Bureau of Indian Standards (BIS) has set these standards to ensure the quality of construction materials. Here are some of the key tests for cement as per IS codes: 1. Fineness Test (IS 4031-Part 1): This test determines the fineness of cement by dry sieving. The cement sample is passed through a standard sieve, and the residue is measured. 2. Standard Consistency Test (IS 4031-Part 4): This test determines the quantity of water required to produce a cement paste of standard consistency, defined as that consistency which will permit a Vicat plunger to penetrate to a depth of 5-7mm from the bottom of the mould. 3. Setting Time Test (IS 4031-Part 5): This test measures the time taken for cement to start setting (initial setting time) and the time taken for cement to completely set (final setting time). 4. Soundness Test (IS 4031-Part 3): This test checks the ability of cement to retain its volume after setting. It helps to detect any unsoundness in cement due to the excess of lime, magnesia, or sulphates. 5. Compressive Strength Test (IS 4031-Part 6): This test measures the compressive strength of cement. The cement is mixed with sand and water to form mortar, which is then placed in a mould and allowed to harden. After a specified period, the hardened mortar is tested for its compressive strength..

Aggregates. Gene r a ll y div i ded in two groups :.

[Audio] Size: Aggregates can be classified as fine aggregates or coarse aggregates. Fine aggregates are those that pass through a 4.75mm sieve, while coarse aggregates are those that do not pass through a 4.75mm sieve. Shape: Aggregates can be classified as rounded, irregular, angular, flaky, or elongated. Rounded aggregates are those that have been worn down by water or wind. Irregular aggregates are those that have a variety of shapes. Angular aggregates are those that have sharp edges. Flaky aggregates are those that are thin and flat. Elongated aggregates are those that are long and narrow. Origin: Aggregates can be classified as natural or manufactured. Natural aggregates are those that are found in nature, such as sand, gravel, and crushed stone. Manufactured aggregates are those that are created by humans, such as expanded clay aggregate and lightweight aggregate..

[Audio] The Indian Standard (IS) codes provide guidelines for testing the properties of aggregates, which are crucial components of concrete and asphalt mixtures. Here are some of the key tests for aggregates as per IS codes: 1. Aggregate Crushing Value (IS 2386 Part 4): This test helps in determining the aggregate crushing value of coarse aggregates as per IS: 2386 (Part IV). 2. Aggregate Impact Value (IS 2386 Part 4): This test gives a relative measure of the resistance of an aggregate to sudden shock or impact. 3. Specific Gravity and Water Absorption (IS 2386 Part 3): This test helps in determining the specific gravity and water absorption of aggregates. 4. Flakiness and Elongation Index (IS 2386 Part 1): This test is used to determine the particle shape of the aggregate and its suitability for different types of construction works. 5. Sieve Analysis (IS 2386 Part 1): This test is used to determine the particle size distribution of aggregates by sieving them. 6. Soundness Test (IS 2386 Part 5): This test is used to ascertain the weathering resistance of aggregates. 7. Alkali Aggregate Reactivity (IS 2386 Part 7): This test is used to identify the aggregates that may participate in alkali-aggregate reactions, which can lead to serious damage in concrete structures. 8. Stripping Value of Road Aggregates (IS 6241): This test is used to determine the stripping value of bituminous mixes containing aggregate. 9. Abrasion Test (IS 2386 Part 4): This test is used to determine the resistance of aggregates to wear by abrasion..

[Audio] Larger size of aggregate is preferred in concrete because of the following reasons : It reduces the cement requirement It reduces the water requirement It reduces shrinkage of concrete.

[Audio] Thickness of section maximum size of aggregate (MSA) should not be greater than the thickness of section Spacing of Reinforcement MSA should not be greater than spacing of steel Clear Cover MSA should not be greater than cover provided than 5 mm less than 5 mm less You can absorbed in the figure.

[Audio] There are two type of Surface texture Smooth texture Rough texture.

[Audio] (a) Smooth texture In general, smooth textured aggregates are rigid, dense, and fine grained. Because there is less surface area and less paste covering the irregularities, less lubrication is needed. However, although the bonding area with the matrix is greater, it also decreases as smoothness rises. As a result, while compressive strength may be attained with less water needed, the flexure strength declines as a result of inadequate bonding and interlocking. (b) Rough texture In comparison to smooth aggregates, rough textured aggregates show greater strength in tension, but compressive strength is lower because a larger water-cement ratio is needed for the same workability..

[Audio] The quality of water used in concrete mixtures is crucial as it directly affects the strength, durability, and overall quality of the concrete. The Indian Standard (IS) code that provides guidelines for the quality of water for use in concrete is IS 456:2000. According to this code, the water used for mixing and curing should be clean and free from injurious amounts of oils, acids, alkalis, salts, sugar, organic materials, or other substances that may be deleterious to concrete or steel. Here are some specific requirements as per IS 456:2000: 1. Potable Water: If the water is fit for drinking, then it's generally considered suitable for use in concrete. 2. pH Level: The pH level of the water should ideally be within the range of 6 to 8. 3. Impurities: The water should be free from harmful substances. The permissible limits for solids are: - Organic: 200 mg/liter - Inorganic: 3000 mg/liter - Sulphates (SO4): 400 mg/liter - Chlorides (Cl): 500 mg/liter for reinforced concrete, 2000 mg/liter for concrete not containing embedded steel - Suspended matter: 2000 mg/liter 4. Testing: If there's doubt about the quality of water, or if the water is from a source other than the public supply, it should be tested to ensure it doesn't reduce the strength of the concrete or promote steel corrosion. 5. Sea Water: Sea water should not be used for mixing or curing reinforced concrete as it can lead to corrosion of reinforcement. However, it may be used for plain concrete provided the structures are washed with fresh water after construction. 6. Water Used for Curing: Water used for curing should not produce any objectionable stain or unsightly deposit on the concrete surface. The presence of tannic acid or iron compounds is objectionable. 7. Water from Concrete Mix: Water from the concrete mix itself, or water freshly drained from aggregate storage bins may be used provided it meets the requirements..

[Audio] Requirements of water used in concrete Are given below Organic should be not more than 200 mg/lit In Organic should be not more than 3000 mg/lit Sulphates should be not more than 500 mg/lit Chlorides Organic should be not more than 500 mg/lit Suspended matter Organic should be not more than 2000 mg/lit.

[Audio] Effect of Sea Water The salinity level of ocean water is roughly 3.5%. Using seawater is a major concern due to the risk of corroding steel and the consequent loss in strength..

[Audio] Hydration Concrete achieves its strength through a chemical process called Hydration..

Water/Cement Ratio and Strength ement parttcles stsperded m mix vatgr Fully hydrated Lov Pomi —H h th H hPOØ$i —Lov th.

[Audio] Adding extra water to concrete!!! Adding more water creates a diluted paste that is weaker and more susceptible to cracking and shrinkage Shrinkage leads to micro-cracks that is zones of weakness Once the fresh concrete is placed, excess water is squeezed out of paste by weight of aggregate and cement The excess water bleeds out onto the surface..

[Audio] Here some of the Advantages of low water/cement ratio Increased strength. Lower permeability. Increased resistance to weathering. Better bond between concrete and reinforcement. Reduced drying shrinkage and cracking. Less volume change from wetting and drying..

[Audio] ADMIXTURE Chemical admixtures are substances added to concrete during mixing to modify its properties and enhance performance. They are classified into different categories based on their specific functions and effects on concrete. The common classification of chemical admixtures in concrete includes:.

Admixture types Admixtures to enhance workability o Mineral (Fly ash, Silica fume, GGBFS) o Chemical o Air entraining.

[Audio] Water-reducing admixtures An admixture which either increases workability of freshly mixed mortar or concrete without increasing water content or maintains workability with a reduced amount of water R o le of water r educer s is to deflocculate the cement particles agglomerated together and release the water tied up in these agglomerations.

[Audio] Air-entraining admixtures Which causes air to be incorporated in the form of minute bubbles in the concrete or mortar during mixing, usually to increase workability and resistance to freezing and thawing and disruptive action of de-icing salts Reduces bleeding and segregation of concrete.

[Audio] Super-plasticizing admixtures Which imparts very high workability or allows a large decrease in water content for a given workability Reduce water content by 12 to 30% percent The effect of superplasticizers lasts only 30 to 60 minutes and is followed by a rapid loss in workability. Superplasticizers are usually added to concrete on the job site..

[Audio] if you have any questions related to this chapter kindly contact me to my mail id ravitheja.civil@svrec.ac.in.