《【郭】第二章》由会员分享，可在线阅读，更多相关《【郭】第二章（20页珍藏版）》请在金锄头文库上搜索。
1、CIVIL ENGINEERING MATERIALSLESSON TWO Outline l INTRODUCTION TO CIVIL ENGINEERING MATERIALSlCementlConcrete lTimberlMetals lBituminous materials l l THE CHOICE OF BUILDING MATERIALS INTRODUCTION TO CIVIL ENGINEERING MATERIALSAs an engineer, one must know about the materials used in the construction
2、site. It is necessary for an engineer to be conversant with the properties of such materials. Civil engineering materials can be natural and manmade. They contain cementcement, metals, timber, concrete, bituminousbituminous etc. INTRODUCTION TO CIVIL ENGINEERING MATERIALSNow green civil engineering
3、materials and even eco-materials (n.生态材料)for civil engineering are recommended based on the consideration of sustainable development. This has the benefits of reducing energy, saving resources and protecting the environment, having minimum harm to human health.CementCement is obtained by burning at
4、a very high temperature a mixture of calcareouscalcareous and argillaceousargillaceous materials. CalcinedCalcined product is known as clinker clinker . A small quantity of gypsum is added to the clinker and is pulverized into very fine powder known as cement. On setting, cement resembles a variety
5、of sandstone found in Portland in England and is, therefore, called Portland cement. CementBy changing the chemical composition and by using different raw materials and additives, many types of cements can be manufactured to cater to the need of the construction industry for specific purposes. Cemen
6、tRapid hardening cement (快硬性水泥)is used where high strength is required instantly in initial stages. Portland pozzolana cement (火山灰质硅酸盐水泥)produces less heat of hydration and offers greater resistance to the attack of aggressive water. Air-entraining cement (引气水泥)is produced by mixing a small amount o
7、f an air-entraining agent with ordinary Portland cement. By adding this, the properties of concrete can be changed and it also increases the frost resistance of hardened concrete.ConcreteCement is mixed at or near the construction site with sand, aggregate (small stones, crushed rock, or gravel), an
8、d water to make concrete. Concrete has a high and its strength depends on the proportion in which cement, and, stones and water are mixed. It hardens with age and the process of hardening continues for a long time after the concrete has attained sufficient strength.ConcreteNormal concrete has a comp
9、aratively low tensile strength and for structural applications it is normal practice either to incorporate steel bars to resist any tensile forces (steel reinforced concrete) or to apply compressive forces to the concrete to counteract these tensile forces (pre-stressed concrete or post-stressed con
10、crete). pre-stressed concrete & post-stressed concreteConcreteConcrete is used structurally in buildings, shell structures, bridges, sewage-treatment works, railway sleepers, roads, dams, chimneys, harbors, off-shore structures and so on. It is used also for a wide range of precast concrete products
11、 which include concrete blocks, cladding panels, and pipes. The impact strength, as well as the tensile strength, of normal concrete is low and this can be improved by the introduction of randomly orientated fibers into the concrete.TimberTimber is one of the oldest known civil engineering materials
12、. In addition to its usefulness as a structural material, timber has also fulfilled a role in temporary structures.Although timber is a kind of sustainable resource, the consumption speed of forests must be slowed down because of the relative slowness of tree growth. TimberTimber has a wide use in f
13、looring, facing, skirting, windows, doors, stairs, paneling and furniture. The requirements for this purpose include ease of working and finishing, good grain pattern and appearance when clear-finished, dimensional stability in conditions of variability of temperature and humidity, both internal and
14、 external, and resistance to infestation and fungal attack etc. Timber木材在楼地板、饰面、踢脚板、窗户、门、楼梯、镶板和家具上都有着很广泛的用途。为了满足这个目的，就需要所选用的木材易于加工，表面易于整修，具有美观的纹理和外观，在内部和外部的温度、湿度变化的条件下尺寸稳定，并且具有抗虫害和抵抗真菌侵蚀等特点。TimberNowadays timber is also playing an important role in falsework carpentry, such as shuttering for in-situ
15、 or precast concrete work, supporting formwork for brick or stone arch or shell forms, or jigs for glued-laminated timber beam or shell forms. Timberfalsework carpentry（脚手架木工作业）、shuttering for in-situ（原位立模板）、supporting formwork（支模）、glued-laminated timber beam（胶合叠层木梁），jig（夹具），Timber如今，木材在脚手架木工作业中起的作用
16、越来越重要了，如原位立模板，预制混凝土工作，为砖、石拱桥或壳的支模，或是胶合叠层木梁或壳形的夹具等。MetalsThe applications of metals in civil engineering are wide and varied, ranging from their use as main structural materials to their use for fastenings and bearing materials. The properties of metals which make them unique among constructional mat
17、erials are high tensile strength, the ability to be formed into plate, sections and wire, and the weld ability. MetalsOther properties of metals are electrical conductivity, high thermal conductivity and metallic luster (金属光泽), which are of importance in some circumstances.Perhaps the greatest disad
18、vantage of the common metals, and steels in particular, is the need to protect them from corrosion by moist conditions and atmosphere.MetalsThe importance of metals as constructional materials is almost invariably related to their load bearing capacity (承载能力)in either tension or compression and their ability to withstand limited deformation without fracture. It is usual to assess these properties by tensile tests in which the modulus of elasticity (弹性模量), the yield stress (屈服应力), the tensile strength and the percentage elongation can be determined.
