CHAPTER 15MATERIALS TESTING: SOIL AND CONCRETEIn previous chapters of this TRAMAN, youstudied the importance of many and various con-struction materials. However, one material thatwas not discussed was SOIL which, as you willlearn in this chapter, is perhaps the most impor-tant material of all. Just as a poorly constructedand weak concrete foundation will not supporta building, neither will a poorly “constructed”and weak soil, since the ultimate foundation forany road, airfield, building, or other structure isthe natural earth upon which it is built.During this chapter you will learn what soilis. You will learn the different types of soil youmight encounter. You will also learn the basicproperties and characteristics of soil and theimportance those characteristics play in deter-mining the adequacy of a soil for use as a con-struction material. In addition, you will learn howto collect (sample) soil for testing purposes andhow to perform certain tests that you, as an EA3,will be responsible for performing. Most impor-tantly, you will learn why those tests are per-formed and their importance in properly andcorrectly identifying and classifying the manytypes of soil that exist in nature.Finally, this chapter begins your studies ofconcrete testing. In this chapter you will learnwhat the various tests are and the purpose andimportance of those tests. You will learn how toperform certain tests and how to prepare concretesamples for other tests that will be performed bymore senior EAs.SOIL ORIGINAs defined by Webster’s New World Dic-tionary, soil is the surface layer of the Earth thatsupports plant life. While that is certainly acorrect definition and one that is perfectly satis-factory to many groups of people, it lacks theprecision required by the civil engineer and soiltechnician. A more precise definition is that soilis a mixture of uncemented or loosely cementedmineral grains enclosing various sizes of voids thatcontain air (or other gases), water, organic mat-ter, or different combinations of these materialsin varying amounts. The importance of under-standing this definition will become obvious asyou progress through this chapter; but, first, letus consider where soil comes from.SOIL FORMATIONThe formation of soil is a continuous processthat is still in action today. Basically, the Earth’scrust consists of rock, which geologists classifyinto three groups: igneous, which is formed bycooling from a molten state; sedimentary, formedby the accumulation and cementing of existingparticles and remains of plants and animals; andmetamorphic, formed from existing rocks thathave been subjected to heat and pressure. Whenexposed to the atmosphere, this rock under-goes a physical and chemical process calledWEATHERING, which, over a sufficient lengthof time, disintegrates and decomposes the rockinto a loose, incoherent mixture of gravel, sand,and finer material. It is this process that producessoils of various designations.RESIDUAL SOILAny soil that results from weathering in place,and that is not moved during the weathering pro-cess, is called a RESIDUAL soil. A mantle ofresidual soil reflects the characteristics of theunderlying parent rock from which it was derived.TRANSPORTED SOILWhen the forces of nature cause the mantleof soil to be moved to a place other than that ofits origin, the soil becomes a TRANSPORTEDsoil. One of these soils often bears properties in-duced by its mode of transportation. The chiefagents of transportation are water, wind, ice, andthe force of gravity.15-1
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