Figure 5-3.-Sieve sizes.Limestone.Limestone is widely usedfor road surfacing, in concrete, and forl i m e .Gneiss. Most varieties of gneisshave good strength and durability and makegood road aggregates.Quartzite.Quartzite is both hardand durable. Because of these qualities,it is an excellent rock for construction,although it is often difficult to quarry.Marble. The texture and color ofmarble make it very desirable fordimension stone, and it can be used forbase course or aggregate material.Sieve AnalysisSoil is composed of particles ofvarious sizes and composition. Figure 5-2shows the major types of soils. Soil canbe analyzed by size by sifting a dried andweighed sample through a set of testingsieves (fig. 5-3) and weighing thematerial retained on each screen. Furthertesting may be required by thespecifications for the product you need toproduce. These tests are normallyperformed by the soil laboratory in theengineering department of the battalion.Soil is classified according to theparticle size, such as coarse aggregate,fine aggregate, and mineral filler. Themaximum size of the aggregate varies,depending upon the constructionspecifications. Particle size is definedby passing a soil mass through severalsieves with different sized openings (fig.5-3).Particles that pass through a givensieve are said to be passing that sievesize. Particles that fail to passthrougha given sieve are said to be retained onthat sieve. The sieve permitsparticlessmaller than the opening to fall throughand retains the larger particles on thesieve. When you use sieves with screenopenings of different sizes, the soil canbe separated into particle groups based onsize.A weighted sample of aggregate isplaced in the top sieve, and the entireset of sieves (largest on the top,smallest on the bottom) is vibrated eitherby hand or mechanically. The individualweights are calculated as a percentage ofthe total weight, as shown in thefollowing example: Assume we take 3,000grams of soil mass and determine how muchaggregate passes each sieve.Aggregate passing 1/2-inchsieve and retained on3/8-inch sieve = 720 grams = 24%Aggregate passing 3/8-inchsieve and retained on No. 4sieve = 600 grams = 20%Aggregate passing No. 4sieve and retained onNo. 10 sieve = 450 grams = 15%Aggregate passing No. 10sieve and retained onNo. 40 sieve = 570 grams = 19%Aggregate passing No. 40sieve and retained onNo. 200 sieve = 420 grams = 14%Aggregate passingNo. 200 sieve = 240 grams = 8%3,000 grams = 100%The above percentages are one way ofexpressing the gradation of a sample ofaggregate.5-5
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business