List And Describe The More Common Tests That Can Be Carried Out On Materials.

Why is a compression test used for brittle material not a tensile test?

If you are familiar with stress strain characteristics of materials such as ductile and brittle, you shall be aware of why we use compression test for brittle materials Generally brittle materials are known to be strong in compression. Before moving in to the question, let’s see some basics in material failure.There are mainly two kinds of failure. Brittle failure and ductile failure. The ductile failure occurs in ductile materials where as brittle failure in brittle materials.Brittle materials do not undergo plastic deformation under stress since the failure is sudden at the ultimate limit.you can’t see necking in brittle materials.which means Brittle materials will give on clean and flat break.Necking is the reduction of cross sectional area prior to ductile failure.Why we perform material strength tests?? To know the safe limit of loading. right?!The compression strength of brittle material is much more than its tensile strength. Due to this we design brittle materials for compressive loading . So we have to perform its compression strength test instead of tensile strength test. Why brittle materials have better compression strength than tensile strength is very complicated topic. To understand the core reasons for this kind of nature of brittle material, molecular or atomic level understanding is required.Brittle materials under compression testBrittle materials in compression typically have an initial linear region followed by a region in which the shortening increases at a higher rate than does the load. Thus, the compression stress – strain diagram has a shape that is similar to the shape of the tensile diagram.As you can see the ultimate stress for compression is much higher than for tension.

What are some tests related to road construction?

Oh, where to begin? If you are building a roadway with federal funding, there are many, many tests that need to be done. I will give you just a sampling of what tests need to be done, but I won’t go into the test number.At the beginning of the Contract, we place all kinds of BMPs for stormwater pollution prevention. If we are placing silt fence, the silt fence has to be sampled and tested. Most of these items can be approved based on the testing performed by the manufacturer, where the Contractor simply gives as a Manufacturer’s certification that the product has been tested and meets all of the specifications.Once we are at the final grading for subgrade, we test for compaction of the material. This is usually done with a nuclear density gage.The base, or subbase material needs to be sampled and tested for many things to make sure it is within specifications:Gradation: the combination of sizes of aggregateDegradation: measuring the aggregates resistance to breaking down into finer particlesEthylene Glycol: measuring the presence of deleterious claySodium Sulfate, or Magnesium Sulfate Soundness: measuring the aggregates resistance to disintegration from these compoundsAggregate reactivity to various componentsSand equivalentorganic impuritiesDeleterious substanceMortar-making propertiesLos Angeles AbrasionR-ValueFractured FaceOnce the base is compacted, we test for compaction or document the number of roller passes if it is too granular to test.Assuming that we are placing asphalt, the aggregrate for the asphalt mix must also be tested per above.A few of the things that the asphalt concrete mix also has to be tested for:Oil ContentBinder ContentAir voidsRelative densityDust to binder ratioVoids filled with asphaltBulk specific gravityWhen the asphalt is placed, we test for compaction and document the roller passes.There is a lot more testing that goes into construction of a roadway. I could go on for days. This is just a sampling.