【郭】第二章.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,CIVIL ENGINEERING MATERIALS,LESSON TWO,Outline,INTRODUCTION TO CIVIL ENGINEERING MATERIALS,Cement,Concrete,Timber,Metals,Bituminous materials,THE CHOICE OF BUILDING MATERIALS,INTRODUCTION TO CIVIL ENGINEERING MATERIALS,As an engineer,one must know about the materials used in the,construction 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,cement,metals,timber,concrete,bituminous,etc.,INTRODUCTION TO CIVIL ENGINEERING MATERIALS,Now green civil engineering 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.,Cement,Cement is obtained by burning at a very high temperature a mixture of,calcareous,and,argillaceous,materials.,Calcined,product is known as,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 of sandstone found in Portland in England and is,therefore,called,Portland cement,.,Cement,By 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.,Cement,Rapid 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 of an airentraining 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.,Concrete,Cement is mixed at or near the construction site with sand,aggregate(small stones,crushed rock,or gravel),and 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.,Concrete,Normal concrete has a comparatively 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 concrete,).,prestressed concrete&post-stressed concrete,Concrete,Concrete 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,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.,Timber,Timber is one of the oldest known civil engineering materials.,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.,Timber,Timber has a wide use in,flooring,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 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。,Timber,Nowadays timber is also playing an important role in,falsework,carpentry,such as,shuttering for in-situ,or precast concrete work,supporting formwork for brick or stone arch or shell forms,or,jig,s for,glued-laminated,timber beam or shell forms.,Timber,falsework,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。,Metals,The 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 materials are high tensile strength,the ability to be formed into plate,sections and wire,and the,weld ability.,Metals,Other 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 disadvantage of the common metals,and steels in particular,is the need to protect them from corrosion by moist conditions and atmosphere.,Metals,The 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.,