admin June 8, 2020 No Comment
Civil engineers use sieve analysis to determine the material makeup of soil samples. It’s typically used for construction and conservation purposes. In this procedure, also referred to as gradation of the sample, engineers assess the distribution of particle size in the soil.
Granular material passes through a sieve or series of sieves that decrease in mesh size. Weighing the amount retained in each sieve results in a percentage calculation of each particle class. Keep reading to learn more about sieve analysis.
Why is sieve analysis important?
Sieve analysis is important in the construction industry. Geotechnical engineers use it to test materials needed in building projects. For example, sieve analysis testing allows construction companies to ensure they meet the requirements for concrete blending.
Concrete mixes incorporate various course aggregate materials of specific diameters. High-strength concrete requires large-sized aggregates, and pre-stressed concrete also uses maximum-diameter aggregates to push through the reinforcing bars (rebar).
Nest of sieves
A nest of sieves, called a sieve stack, enables engineers to separate the aggregate sizes in a sample. The nest has the largest openings in the top sieve and the smallest openings in the bottom sieve. In between, sieves have gradually declining opening sizes to separate out smaller materials.
During the testing, you place a lid on the top sieve and a pan under the smallest sieve to retrieve material that passes through it. When removing each sieve, use precaution. Because the sieves fit tightly together, it’s easy for them to get stuck. This makes it hard to separate each one. If you spill the contents, you might have to start over. Therefore, take extra care when removing each sieve.
For ideal results, use horizontal shaking motions to separate the materials. If you shake the sieve stack vertically, the granules could break up, skewing your results.
Particle size analysis
Pour dry soil onto the top of the nest of sieves. Then, cover the nest and shake the stack by hand or by using a mechanical sieve shaker. At this point, each particle continues sifting from sieve to sieve until it reaches one with holes too small for it to pass through.
Once all the particles have separated, weigh each sieve. Divide the weights by the total mass of the sample. This gives you the composition of the tested soil. Typically, the analysis is presented graphically. Plot the percentage passing (x-axis) versus the sieve size (y-axis) and connect the plotted points to demonstrate the gradation curve.
Sieve analysis testing helps engineers and scientists determine the makeup of soil and stone samples. These results are used to build safe buildings, bridges, dykes and other structures.