It is Civil engineering test related ppt
- 1. CIVIL ENGINEERING MATERIAL Mrs. Trushna Jena Assistant Professor Department of CIVIL Engineering IGIT Sarang
- 2. ENGINEERING PROPERTIES OF AGGREGATE • Composition • Size & Shape • Surface Texture • Specific Gravity • Bulk Density • Voids • Porosity & Absorption • Fineness Modulus of Aggregate • Deleterious Material • Crushing Value of Aggregate • Impact Value of Aggregate • Abrasion Value of Aggregate
- 3. 7. FINENESS MODULUS OF FINE AND COURSE AGGREGATE The Fineness Modulus (FM) is an empirical figure obtained by adding the total percentage of the sample of an aggregate retained on each of a specified series of sieves, and dividing the sum by 100. ... In general, however, a smaller value indicates a finer aggregate. To find fineness modulus we need to perform sieve analysis and for that above mentioned sieve sizes, mechanical shaker and digital weigh scale are required. To find fineness modulus of coarse aggregate we need sieve sizes of 80mm, 40mm, 20mm, 10mm, 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm and 0.15mm. To find fineness modulus of fine aggregate we need sieve sizes of 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm and 0.15mm. Sample preparation : Take a sample of coarse aggregate in pan and placed it in dry oven at a temperature of 100 – 110oC. After drying take the sample weight to nearest gram.
- 4. Test Procedure: Arrange the sieves in descending order and put the arrangement on mechanical shaker. After proper sieving, record the sample weights retained on each sieve and find out the cumulative weight of retained particles as well as cumulative % retained on each sieve. Finally add all cumulative percentage values and divide the result with 100. Then we get the value of fineness modulus.
- 9. DELETERIOUS MATERIALS • The materials whose presence in aggregates may adversely affect the strength, workability & long-term performance of concrete are termed as deleterious materials. These are considered undesirable constituents. The total amount of deleterious materials in aggregate should not exceed 5% as per IS 383-1970. • Ex- Organic Impurities, Clay, Silt and crusher dust, Salts, Unsound Particles • Alkali- Aggregate Reactions o Reaction between alkali from cement and silica or carbonate from aggregate is called “alkali- aggregate reaction”. o The most common reaction is that between the active silica constituents of the aggregate and that alkalis in cement, called as “alkali-silica reaction” o Another type of the alkali-aggregate reaction is that between dolomitic limestone aggregates, containing carbonate, and alkalis in cement, called as “alkali-carbonate reaction”. o Both types of the reactions cause deterioration of concrete, mainly cracking.
- 10. o The reactive forms of silica opal (amorphous, i.e. shapeless), Chalcedony (cryptocrystalline fibrous), and tridymite (crystalline). o The gel formation on the surface of aggregate particles destroys the bond between the aggregate and cement paste. o The swelling nature of the gel exerts internal pressure and eventually lead to expansion, cracking and disruption of the hydrated cement paste. o In case of alkali-carbonate reaction also, gel is formed, which upon swelling cause expansion of concrete. o Gel is formed around the active aggregate particles, causing cracking within rims and leads to a network of cracks and loss of bond between the aggregate and the cement paste.
- 11. Aggregate crushing value Test(IS-2386-4(1963)) • Aggregate crushing value test on coarse aggregates gives a relative measure of the resistance of an aggregate crushing under gradually applied compressive load. Aggregate crushing value is a numerical index of the strength of the aggregate and it is used in construction of roads and pavements. Its range must be Within 30 and 50%. Procedure: • Put the cylinder in position on the base plate and weigh it (W). • Put the sample in 3 layers, each layer being subjected to 25 strokes using the tamping rod. Care being taken in the case of weak materials not to break the particles and weigh it (W1). • Level the surface of aggregate carefully and insert the plunger so that it rests horizontally on the surface. Care being taken to ensure that the plunger does not jam in the cylinder. • Place the cylinder with plunger on the loading platform of the compression testing machine. • Apply load at a uniform rate so that a total load of 40T is applied in 10 minutes. • Release the load and remove the material from the cylinder. • Sieve the material with 2.36mm IS sieve, care being taken to avoid loss of fines. • Weigh the fraction passing through the IS sieve (W2).
- 12. Calculation: The ratio of weight of fines formed to the weight of total sample in each test shall be expressed as a percentage, the result being recorded to the first decimal place. Aggregate crushing value = (W2 x 100) / (W1-W) W2 =Weight of fraction passing through the appropriate sieve W1-W =Weight of surface dry sample.
- 13. Grading of Aggregates: The particle size distribution of an aggregate as determined by sieve analysis is termed as gradation of aggregates. The particle size distribution of a mass of aggregate should be such that the smaller particles fill the voids between the larger particles. Grading Curve of Aggregates • The grading of aggregates is represented in the form of a curve or an S-CURVE. The curve showing the cumulative percentages of the material passing the sieves represented on the ordinate with the sieve openings to the logarithmic scale represented on the abscissa is termed as Grading Curve. The grading curve for a particular sample indicates whether the grading of a given sample conforms to that specified, or it is too coarse or too fine, or deficient in a particular size.
- 14. DENSE-OR WELL-GRADED AGGREGATE – A dense gradation refers to a sample that is approximately of equal amounts of various sizes of aggregate. By having a dense gradation, most of the air voids between the materials are filled with particles. A dense gradation will result in an even curve on the gradation graph. 1. Wide range of sizes. 2. Grain-to-grain contact. 3. Low void content. 4. Low permeability. 5. High stability. 6. Difficult to compact. GAP-GRADED AGGREGATE – Gap-graded aggregate contains only a small percentage of aggregate particles in the mid-size range. The curve is flat in the mid-size range. 7. Missing middle sizes. 8. No grain-to-grain contact. 9. Moderate void content. 10. Moderate permeability. 11. Low stability. 12. Easy to compact. Types of Grading of Aggregates
- 15. UNIFORMLY GRADED AGGREGATE It refers to a gradation that contains most of the particles in a very narrow size range. In essence, all the particles are the same size. The curve is steep and only occupies the narrow size range specified. • Narrow range of sizes. • Grain-to-grain contact. • High void content. • High permeability. • Low stability. • Difficult to compact. • OPEN-GRADED AGGREGATE – Contains only a small percentage of small-size particles. This results in more air voids because there are not enough small particles to fill in the voids between the larger particles. The curve is near vertical in the mid-size range, and flat and near-zero in the small-size range.