SIEVE ANALYSIS Essay Example

SIEVE ANALYSIS

Introduction and Objectives

Sieve analysis is very important when it comes to testing the aggregate quality and soils so as to establish their engineering functions suitability. The composition of aggregates include both crushed and the uncrushed minerals that include sandstone, limestone and granite. Aggregates are classified as natural or artificial depending on the way of preparation and their source. Weathering by wind or water action yielding natural sand and gravel are the processes that are involved in aggregate formation.

The soil analysis test aims at establishing the particle size distribution popularly known as sieve analysis of the soil sample. The test will be used in finding the percentage distribution of various particle sizes of the soil sample. The particle size distribution of aggregate determines strength, voiding and the ease of placement of the mix.

Procedure

The tests involved use of British Standard test sieves in the grading of aggregate for concrete with the mesh sizes used being: 10mm, 5mm, 2.36mm, 1.18mm, 600mm, 300 mm, and 150 mm. The first task of the experiment was weighing the sample. The sieves were put on a mechanical shaker with the 10mm sieve occupying the top most position. The sample was passed through the layer of sieves from the top to bottom where the sieves were shaken for about 15 minutes. There was of materials retained on each of the sieves and the tray. Cleaning of the sieves was done using appropriate wire brush with the aggregate being brushed back out of the sieve but not being forced to pass through the sieves.

After the test the result were as shown in Table 1 where it is observed that the sieve with the highest value of mass was the 300mm sieve where 889.5 g was retained on this sieve. From the table it can also be seen that 467.17g was retained was retained on the 6.3mm sieve while 6.82g passed through all the sieves only to be retained by the pan.

Mass on sieve (g)

(Column a)

% retained

(column c)

% passing

(column d)

Total of all sieves + tray

In figure 1 it can be seen that 10% of the particles were 300 mm in diameter or of smaller size with the designation of d10. The d10 is defined as the maximum size of the smallest 10% of the sample. From the graph also the value of d30 which gives the maximum size of the smallest 30% of the sample was 400mm. On the other hand d60 which is maximum size of the smallest 60% of the sample was 3000mm meaning that 60% 0f the particles were 3000mm or less.

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Using d10, d30 and d60 it is possible to obtain the grading characteristics. The three grading characteristics obtainable are: the effective size, uniformity coefficient and the coefficient of gradation.

Effective size d10 = 300

Uniformity coefficient Cu= d60/d10 = 3000/300 = 10

Coefficient of gradation Ck = d302/d60d10 = 4002/ (3000×300) = 0.18

Discussion

value of 0.18 obtained for this is below 0.5 which is an indication of poor gradation. In the process of performing sieve analysis there is a chance of the total masses which are retained on the sieves and the pan not adding up to the original sample mass. This may be experienced due to losses or gains that may occur during the process of sieving or this may have been cause by round-ff errors. It is not expected to have a situation where the difference of expected mass and the actual mass exceeding 0.1% times the number of mass determinationsk value has been found to be 10 meaning that that the soil is well graded. The Cu. In this test the CACI 213R-03, 2003) value less than 0.1 will is a pointer of gap graded particles (k ranging from 0.5 to 2.0 is an indication that sample particles are well graded while for Ck value greater than 5 gives an indication that sample particles are well graded soil while for a values less than 3 it is an indication that there is uniformity of the particles. On the other hand Cu will be 1. A CkIn dealing with particles of almost the same size then Cu and C

Conclusions

From this sieve analysis test the conclusion is that the particles were not well graded. It can also be concluded that the test was carried out appropriately as the difference in the total mass retained and the original mass was within the range of 0.7%.

Reference

ASTM C 702-98(2003), “Standard Practice for ReducingSamples of Aggregate to Testing Size.”

ACI 213R-03, (2003) “Guide for Structural Lightweight Aggregate Concrete,” American Concrete Institute, Mich.Farmington Hills,

ASTM C 136-04,(2004) “Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates.”

Experiment 2

Liquid Limit (LL) The lowest water content above which soil behaves like liquid and begins to flow.

▪ Plastic Limit (PL) The lowest water content at which soil begins to behave like a plastic material.

▪ Plastic Index (PI) The range between LL and PL

• Shrinkage Limit The water content below which soils do not decrease their volume anymore as they loose water

Container NO.

Wt. wet soil+con

Wt. dry soil+cont.

Wt. cont.

Wt. moist.

Wt. dry soil

Moist. content

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Liquid limit = 19.6

Plastic limit (13.8+11.8+20)/3=15.2

Plastic index= LL-PL=19.6-15,2=4.4

Soil classification : sand with clay