The basic materials used in civil engineering application or in construction projects are aggregate, Portland cement, concrete, timber or wood, reinforced metal or steel, structural clay (brick), bitumen and polymer. The common properties of engineering or construction materials are physical, mechanical and chemical properties.
Purpose of Testing Materials
Every materials shall be tested before using it in any construction works. Reasoning of testing construction materials as follows:
- Required for any construction project at preliminary stage, on-going progress works, at completion stage, and during maintenance period.
- To make sure the cost-effective in utilizing materials and factor of safety guaranteed upon test achievement.
- Testing specification and guidelines are met as accordance to technical standards requirements; example technical manuals like British Standard or ASTM.
- Testing of construction materials becomes one of project benchmark in terms of quality control assurance.
- To make sure the durability and longevity of the constructed structures could be achieved and maintain.
- To prevent any possible damage or defect to the structure at early stage before completion.
- And so forth…
Materials Physical Properties
Physical Test of Materials
Density – Defined as an objects mass (property) per unit volume or physical property of matter; solid, liquid and gas. Compaction would be soil and bitumen usual testing method whereby optimum moisture content and maximum dry density as an outcome of test. Density also becomes timber or wood an important property.
Porosity – A measure or percentage of the void spaces (pore volumes) in a material such as soil, aggregate, concrete, and etc. There are several methods can be employed to measure porosity; namely as water evaporation, direct methods, gas expansion, mercury intrusion porosimetry, and optical methods.
Moisture Content – Materials contained certain percentage or quantity of water inside; materials such as soil, aggregate, timber and bitumen. The commonly used method to determine it is based on removing soil moisture by oven-drying a soil sample until the weight remains constant.
Specific Gravity – Defined as a substance comparison (ratio) of its density to that of water or relative density with respect to water. It can be measure within three general forms – in liquids, solids and gases form. It can theoretically be used to describe any type of matter, but in practice it’s typically used only for liquids (measurement using a hydrometer) and dimensionless unit.
Permeability – A capacity or ability measurement of a porous material for transmitting a fluid. Materials like aggregate and soil which having a certain cross-section and thickness under given pressure, measured using Darcy’s Law or by empirical derived formulas. It can be measure by using constant head method for soil (with water) or determination of the coefficient of specific permeability for the flow of air through rocks.
Texture and Color – Texture, the distinctive physical composition or structure of substances, especially with respect to the size, shape, and arrangement of its structures. This can be done by simply using our hands via touching whereby soft or hard as a result. Color on the other hand, means the visual perceptual property corresponding in our natural judgment to the categories called green, blue, red, yellow, and so forth.
Shape and Size – Shape defines as the characteristic surface configuration of an object (an outline or contour) and size defines as the physical dimensions, proportions, magnitude, or extent of an object. Grading of aggregate by sieve analysis method refers to the process of dividing a sample of aggregate into fractions of same particle size. Shapes of aggregate could be rough textured, angular, or elongated.
Soundness – It refers to the ability of the cement paste to retain its volume after setting, and is related to the presence of excessive amounts of free lime or magnesia in the cement or supplementary cementitious material. Soundness of cement is determined by Le-Chatelier method.
Materials Mechanical Properties
Mechanical Test of Materials
Compressive Strength – Defines as the capacity of a material to withstand axially directed pushing forces whereby the material will crushed when the limit of compressive strength is reached. The mechanical test measuring the maximum amount of compressive load a material can bear before fracturing. The test piece, usually in the form of a cube, prism, or cylinder, is compressed between the platen of a compression-testing machine by a gradually applied load. Materials used for testing are normally aggregate, cement, concrete, timber, brick, and etc.
Brittle – A material is brittle if it is liable to fracture when subjected to stress and has little tendency to deform (or strain) before fracture. This fracture would absorb relatively little energy, even in materials of high strength, and usually makes a snapping ‘pop’ sound especially tested against metal or steel.
Ductility – The ductility of a metal is the property that allows it to be stretched or otherwise changed in shape without breaking and to retain the changed shape after the load has been removed. The ductility of a metal can be determined from the tensile test and it is done by determining the percent of elongation.
Materials Chemical Properties
Chemical Test of Materials
Chemical Reaction – Process which respect to the reaction of two or more elements together results in the formation of a chemical bond between atoms and the formation of a chemical compound. Water is the key ingredient, which when mixed with cement, forms a paste that binds the aggregate together whereas causes the hardening of concrete through a process called hydration. Hydration is a chemical reaction in which the major compounds in cement form chemical bonds with water molecules and become hydrates or hydration products.
Chemical Composition – Defines as the unit cell of any substance will contain one or integral multiple of chemical formula units and the formulas of minerals are based on the relationship to unit cell volume and the positions of atoms within the unit cell.s an example, the composition of cement is varied depending on the application which typically contains C3S (Tricalcium silicate), C2S (Dicalcium silicate), C3A (Tricalcium aluminate), and C4AF (Tetracalcium aluminoferrite).
Natural Attributes – The natural attributes of materials also important in chemical properties – acid, alkali, or neutral.
In conclusion, testing construction materials is a must for every civil engineering projects and the results we obtained from the experiments shall becomes the construction index guidelines.
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Author: Civil-Guy | Blog: Civil Craft Structures | Subscribe: RSS or Email
