Sieve Analysis of Sand - Assignment Example

Abstract This begins by giving a brief introduction where the importance of the test is highlighted. The aim of this test was to determine the particle distribution in the sample. The particles were found to be well distributed with Effective size d10 = 190, Uniformity coefficient Cu = 10.5, Coefficient of gradation Ck = 0.66. The test was found to have been done accurately as the error in the sample mass and the total retained mass low with a value of 0.4% compared to the allowable value of 0.7%. Introduction and Objectives In construction aggregate is recognized as a very important material. It is the major component of concrete as in takes about 60 -75% by volume and this fact makes the quality aggregate to be very important with regards to the long term performance of the material (ASTM C 136-04,2004). The typical composition of aggregates are crushed and uncrushed minerals such as granite, sandstone and limestone. There are other minerals from lightweight stone such as mica, pumice, man-made pulverised fuel ash. Aggregate properties have been identified to have significant effect on the workability of concrete in addition to its influence on strength, thermal properties, durability and the density of hardened concrete. Other minerals can be used from lightweight stones such as pumice, mica, granulated ground blast furnace slag (ggbs), man-made pulverised fuel ash (pfa), or expanded clay to dense iron ore such as hematite (ACI 213R-03, ,2003). Aggregate has other applications like utilisation as hardcore or fill material that can be used in the creation of bases to concrete foundations, floors, slabs and pavements. Aggregate can be classified as being natural or artificial depending on where it has been sourced from and the preparation method involved. Through weathering and wind and water action natural sands and gravels are obtained and by crushing natural stones coarse and fined manufactured aggregate is obtained. Aggregated sourced from stone quarries or sand and gravel deposits may need to be crushed, screened and washed as mandatory processing procedures. Igneous, metamorphic or sedimentary rocks may be used as the raw materials in the production of concrete but the geology of the rock used does not make an aggregate superior. When it comes to choosing the suitable aggregate for specific job information from tests that gives the aggregates quality or its service record need to be used. In this test the aim will be to establish particle size distribution or sieve analysis. The test will find out the percentage distribution of particle size of the aggregate sample. The of aggregate will have effect on the strength, voiding and the ease of placement of the mix (workability). The ideal case is where there is a good range of particle size from large to fine aggregates. PERCENTAGE BY MASS PASSING Coarse Percentage Medium Percentage Fine Percentage 5 to 45 30 to 70 55 to 100 Table 1: Coarseness or fineness based on the percentage passing the 5mm sieve. (BS EN 12620:2002 Table B.1) Procedure In this test there was use of British Standard test sieves in grading of aggregate for concrete where the mesh size used were: 10mm, 5mm, 2.36mm, 1.18mm, 600mm, 300 mm, and 150 mm. the first step involved in the experiment was weighing of 600g dry sand. The sieves were placed on a mechanical shaker in order of their size with the 10mm sieve being at the top. The sand was then passed successfully through the sieves starting with the largest size where the process involved shaking the nest of sieves for 15 minutes. The material which was retained on each of the sieves and the final tray was weighed. The sieves were cleaned out using an appropriate wire brush, where the aggregate was brushed back out of the sieve. Brushing the aggregate through the sieve was avoided as this could distort the sieve or result to the blockage of the sieve. Results After the test the result were as shown in Table 2. From the table it can be seen the sieve on which the highest value of mass was the 2.36mm sieve with 187.4g being retained on this sive. From the table it is observed that 219.6 g could not pass through the 2.36mm sieve this being the sum of the mass of the particles retained on 5mm sieve (32.2g) and the mass of particles retained on 2.36mm itself. There was no particle which was more than 10mm as there was no particle which was held in the 10mm sieve. It is clear from the table that 94.6% could pass through the 5mm sieve. Table 2 From figure 1 it can be seen that 10% of the particles had a diameter of 190 mm or smaller and the size of the particles at this mark is designated as d10. The d10 is also defined as the maximum size of the smallest 10% of the sample. From the graph the value of d30 which is defines as the maximum size of the smallest 30% of the sample is 500mm . Also on the figure d60 which is maximum size of the smallest 60% of the sample is 2000mm which simply means that 60% 0f the particles had a size of 2000mm or less. From d10, d30 and d60 grading characteristics can be obtained. There are three grading characteristics that can be obtained namely: the effective size, uniformity coefficient and the coefficient of gradation. Effective size d10 = 190 Uniformity coefficient Cu= d60/d10 = 2000/190 = 10.5 Coefficient of gradation Ck = d302/d60d10 = 5002/ (2000x190) = 0.66 Another characteristic of the particles that can be calculated from the results in the fineness modulus(FM). The FM is obtained by dividing the sum of total percentages coarser than a specified sieve series by 100. The specified sieves are 75.0, 37.5, 19.0, and 9.5 mm 4.75 mm, 2.36 mm, 1.18 mm, 600μm, 300 μm, and 150 μm . From table 2 the sum of total percentage = 5.36+36.5+55.3+68.5+81.7+93 = 340.4 FM = 340.36/100 = 3.4 Discussion When dealing with particles that are single sized the Cu and Ck will be 1. A Cu value greater than 5 is an indication a well graded aggregate and for a value less than 3 it is an indication of uniformity of the particles. On the other Ck that ranges from 0.5 to 2.0 shows the aggregate is well graded while for Ck value less than 0.1 will mean gap graded particles (ACI 213R-03, 2003). In this test the Cu value has been found to be 10.5 and this is an indication that the aggregate is well graded. The Ck value of 0.66 obtained for this is between 0.5 and 2.0 which also indicates that the particles are well graded. The FM value of 3.4 obtained for this test indicates that the aggregate slightly is above the mark of being classified as fine aggregate. Aggregate with FM range of 2.3 to 3.1 is classified as fine aggregate. In the process of performing sieve analysis there is a possibility that the total masses which are retained on the sieves and the pan may not add up to the original sample mass. This may arise due 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 determinations. In this test it is expected that we have an error of 0.7% of the original mass. In this test the original mass was 601g and the total mass of particles retained was 603.4g. this is a difference of 2.4g which is only 0.4% much lower that the maximum acceptable value of 0.7% in this case. Conclusions From this test it can be concluded that the particles were well graded 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.” Read More