Que1.21. What’s fineness modulus? How is sieve analysis conducted for fine summations and coarse summations?
Answer Fineness Modulus( FM)
1. The FM is an indicator of the fineness of the total. The advanced the FM the coarser the total. FM of fine total is useful in estimating proportions of fine and coarse total in concrete fusions.
2. The fineness modulus( FM) for both fine and coarse summations is attained by adding the accretive probabilities by mass retained on each of a specified series of sieves and dividing the sum by 100. FM = ( Accretive retained on specified seive) Beach Fineness Modulus Fine2.2 –2.6 Medium2.6 –2.9 Coarse2.9 –3.2 Sieve Analysis
1. This is the name given to the operation of dividing a sample of aggregate into colorful fragments each conforming of patches of the same size.
2. The sieve analysis is conducted to determine the flyspeck size distribution in a sample of total, which we call gradation.
3. The summations used for making concrete are typically of the maximum size 80 mm, 40 mm, 20 mm, 10 mm,4.75 mm,2.36 mm, 600 micron, micron and 150 micron.
The aggregate bit from 80 mm to mm is nominated as coarse total and the bit from mm to 150 micron is nominated as fine total. 4. As Per IS 2386( Part- 1) Fine total 6 standard sieves with openings from 150 m to4.75 mm.( 150 m, 300 m, 600 m,1.18 mm, mm,4.75 mm).
5. Coarse total 5 sieves with openings from4.75 mm to 80 mm. 4.75 mm, 10 mm,12.5 mm, 20 mm, 40 mm). 6. The size4.75 mm is a common bit appearing both in coarse aggregate and fine total( CA and FA).
7. Grading pattern of a sample of CA or FA is assessed by raising a sample consecutively through all the sieves mounted one over the other in order of size, with larger sieve on the top.
8. The material retained on each sieve after shaking, represents the bit of aggregate coarser than the sieve in question and finer than the sieve over.
9. Sieving can be done either manually or mechanically.
Que1.22. Explain different system of dimension of humidity content of summations.
Answer Following are the system of dimension of humidity cement of summations 1. Drying Method
i. The operation of drying system is fairly simple. Drying is carried out in an roaster and the loss in weight ahead and after drying will give the humidity content of the total. , If the drying is done fully at a high temperature for a longtime.the loss in weight will include not only the face water but also some absorbed water.
iii. A fairly quick result can be attained by hotting the aggregate snappily in an open visage. iv. The process can also be speeded up by pouring ignitable liquid similar as methylated spirit or acetone over the total and kindling it.
2. relegation system
i. In the laboratory the humidity content of total can be determined by means of pycnometer or by using Siphon- Can Method.
ii. The principle made use of is that the specific graveness of normal total is advanced than that of water and that a given weight of wet total will enthrall a lesser volume than the same weight of the aggregate when dry.
iii. By knowing the specific graveness of the dry total, the specific graveness of the wet total can be calculated.
iv. From the difference between the specific earnestness of the dry and wet summations, the humidity content of the total can be calculated.
3. Electrical Meter Method lately electrical measures have been developed to measure immediate or nonstop reading of the humidity content of the total.
ii. The principle that the resistance gets changed with the change in humidity content of the total has been made use of.
4. Automatic dimension
1. In modem batching shops face humidity in summations is automatically recorded by means of some kind of detector arrangement.
2. The arrangement is made in such a way that the volume of free water going with total is automatically recorded and contemporaneously that much volume of water is reduced.
Que1.23. What are the goods of contaminations in the mixing water on concrete?
OR
Write a short note on the feasibility of use of ocean water for mixing concrete.
Answer goods of Mixing Water from Different Sources
1. Ground Water Presence of sulphates in ground waters largely pernicious to concrete foundations.
2. Sea Water
i. The ocean water generally contains3.5 of mariners with about 75 of sodium chloride, about 15 of chloride and sulphate of magnesium.
ii. It has been set up to reduce the strength of concrete by 10- 20 and slightly accelerate the setting time. iii. Sea water may lead to erosion of underpinning.
iv. The chlorides in ocean water may beget efflorescence in concrete.
v. The use of ocean water isn’t recommended for prestressed concrete because of stress erosion and the small periphery cables. , particular If ocean water can not be avoided for making corroboratedconcrete.precautions should be taken to make the concrete thick by using low water/ cement rate coupled with vibration and to give an acceptable cover of at least7.5 cm.
3. Industrial Waste Water When artificial waste water is used as mixing water in concrete, the reduction in compressive strength is generally lower than about 10.
4. Water For Washing summations
i. When summations are washed with water containing contaminations, they get carpeted with layers of ground, mariners and organic matters. ii. These reduce the bond between the summations and cement and markedly affect the strength.
5. Water for Curing Waters containing contaminations and leading to stains is reprehensible.
ii. When concrete is subordinated to prolonged wetting, indeed a veritably low attention of iron and organic matter may beget staining.
iii. Water containing further than0.08 ppm of iron isn’t recommended for curing.
Que1.24. Enumerate the colorful contaminations in water having injurious goods on concrete.
Answer contaminations in water can be of following types
1. Chlorides Chlorides can beget erosion of the sword underpinning and can accelerate setting.
ii. The water used may be defiled with chlorides because of it being ocean water, the presence of cocktails andde-icing mariners, or deliberate chlorination for disinfection.
2. Sulphates Sulphates can lead to the reformation of ettringite as well as reduction of long- term strength situations.
3. Organic Matter The goods of organic matter on concrete are varied. still, it shouldn’t be used because it’ll affect If algae are present inwater.setting and strength development.
4. Sugar Sugar retards the setting time. Too important sugar may ‘ kill ’ the concrete( i.e., it’ll not set).
5. Wastewater It’s stylish not to use wastewater. Alternately it can be used after proper testing and treatment.