Bulking Of Fine Aggregate 366i1

BULKING OF FINE AGGREGATE AIM To study the behaviour of sand grains under varying percentage of moisture content . APPARATUES. 250 ml measuring cylinder ,weighing balance etc . PROCEDURE (i) Take 500gm (W1) of the aggregate. (ii) Keep the sample in an oven in a tray at a temperature of 100°C-110° C for 24 ± 0.5 hours . (iii) Cool the sand in an air tight container and weight it (W2) Water content of the sample = (W1-W2)x 100/W1 (iv) Take out about 250gm of sand and pour it into a pan. (v) Add 2% (by weight) of water and mix well. (vi) Pour the sand sample into a 250 ml measuring cylinder and consolidate by shaking. (vii) Level the surface and read the volume in ml (Yi). (viii) Take out the whole quantity of sand and continue the experiment by adding 2% water more each time and note the corresponding volume of sand (Y2,Y3…..) until the dump sand volume starts decreasing. (ix) Beyond this point, add 4% more water each time until the sample become fully saturated. (x) To the standard sample in the measuring cylinder, add about 50 ml water ore and stir the sample well. (xi) Note down the surface level of inundated sand (Y ml).

CALCULATIONS Bulking =(Y1-Y)x100/Y GRAPH A graph drawn with % water content along X-mas and % bulking along Y- axis. From the graph, pick out maximum % of bulking occurred, % of water content at maximum bulking , % of water content When bulking is zero & % of bulking for the initial water content (W) of the sample. RESULTS % of bulking occurred = % of water content at maximum bulking= % of water content when bulking is zero= % of bulking for the initial water content (W) of the sample = FIELD TEST FOR BULKING OF FINE AGGREGATES

AIM To determine necessary adjustment for the bulking of fine aggregate, in the field. APPARATUES 250 ml measuring cylinder PROCEDURE (I) Pour the dump sand in to a 250 ml measuring cylinder up to the 200 ml mark. (II) Fill the cylinder with water and stir well (sufficient water should be poured to submerge the sand compleately and it can be see that the sand surface is now below its original level) (III) Take the reading at the sand surface (Y ml) CALCULATIONS % of bulking { (200/Y)- 1] x100 Report the percentage bulking of the sand to the nearest whole number. RESULT Percentage bulking of field sample=

Bulking of sand – its significance and calculation| IS 2386 April 27, 2015 0 Comment

Bulking of sand – Its effects and calculation as per IS 2386 Moist sand occupies larger volume if loosely filled in, than dry sand. Due to moisture, thin-film of water forms around sand grain which results in increase of volume. This effect of increase in volume (if loosely filled in) due to moisture content is called “Bulking of sand”. The bulking of sand is largely depends on 1.

grain size – Small the grain size, larger will be bulking effect and vise versa.

2.

moisture content – 5 – 8 % moisture can result in 20-35 % increase in volume Bulking increases with increase in moisture content up to a certain limit and beyond that the further increase in moisture content results in decrease in volume.

Effect of bulking of sand in concrete production : While batching of aggregates, if weight batching is adopted which is precise and prefered method of batching of aggregate,no effect is taken place due to bulking of sand. How ever, if batching is done by volume, then less sand than required as per mix design, will be measured. This results in disproportionate and non uniform concrete mixes and may affects the compressive strength of concrete. Therefore it will be necessary to increase the volume of sand by the ‘percentage’ bulking.

How to calculate % bulking IS 2386 part 3 provides detail test approach to find out % of bulking. Two methods are suggested in this code. Both depend on the fact that the volume of inundated sand is the same as if the sand were dry.

Method 1: 1. Loosely fill the container about 1/3 of its capacity with moist sand. 2.Level the top surface and measure the height (h) of sand by pushing rod at the middle till bottom of container. 3.Empty the sand out of the container into another container where none of it will be lost. 4.Half fill the first container with water.Put back about half the sand and rod it with a steel rod, about 6 mm in diameter, so that its volume is reduced to a minimum. 5.After this add the remainder of the sand and rod it same as describe above. 6.Level the top surface of the inundated sand and measure its depth (h’) at the middle. calculate % bulking using following formula: Percentage bulking = ((h/h1) -1) X 100

Method 2 :

1. Loosely fill moist sand up to mark of 200 ml. Use container of capacity 250 ml. 2. Fill the container with water above top of sand surface and stir the sand thoroughly. 3. Note down the level of top of sand (y) calculate % bulking using following formula: Percentage bulking = ((200/y) -1) x 100

BULKING OF FINE AGGREGATE – WHAT, WHY & HOW? Suryakanta | February 11, 2014 | Aggregate, Concrete, Concrete Technology, How To, Materials, Tests On Aggregate | 3 Comments

The volume increase of fine aggregate due to presence of moisture content is known as bulking. Fine sand bulks more as compared to coarse sand. Extremely fine sand particularly the manufactured fine aggregate bulks as much as about 40%. Note: Fine aggregate do not show any bulking when it is absolutely dry or completely saturated.

WHAT CAUSES BULKING OF AGGREGATE? The moisture present in aggregate forms a film around each particle. These films of moisture exert a force, known as surface tension, on each particle. Due to this surface tension each particles gets away from each other. Because of this no direct is possible among individual particles and this causes bulking of the volume. Bulking of aggregate is dependent upon two factors, 1.

Percentage of moisture content

2.

Particle size of fine aggregate

Bulking increases with increase in moisture content upto a certain limit and beyond that the further increase in moisture content results in decrease in volume. When the fine aggregate is completely saturated it does not show any bulking. Fine sand bulks more as compared to coarse sand, i.e. percentage of bulking in indirectly proportional to the size of particle.

percentage of bulking of sand with moisture content

WHY TO DETERMINE PERCENTAGE OF BULKING? Due to bulking, fine aggregate shows completely unrealistic volume. Therefore, it is absolutely necessary that consideration must be given to the effect of bulking in proportioning the concrete by volume. If care is not given to the effect of bulking, in the case of volume batching, the resulting concrete is likely to be undersanded and harsh. It will also affect the yield of concrete for a given cement content.

HOW TO DETERMINE PERCENTAGE OF BULKING? The extent of bulking can be estimated by a simple field test. 

Fill a sample of moist fine aggregate (sand) into a measuring cylinder in the normal manner. Note down the level, say h1.

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Pour water into a measuring cylinder and completely cover the sand with water and shake it. Since the volume of the saturated sand is the same as that of the dry sand, the saturated sand completely offsets the bulking effect. Note down the level of sand, say h2.

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Subtract the final level h2 from initial level h1 (i.e. h1-h2), which shows the bulking of sand under test.

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Calculate percentage of bulking using formula given below.

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Percentage of bulking = [(h1-h2)/h2]*100