1、中文 3800字 Preparation of low-cost waterproofing materials Al HadidyAI， Yi qiu， DONG Ze-jiao， WANG Jia ni (School of Transportation Science and Engineering,Harbin Institute of Technology,H- arbin 150001,China,E-mail；abd et76yahoo.con) Abstract： To address the need for producing a cheap,single componen
2、t,hot-applied compound joint sealant with high quality for sealing joints and cracks in concrete and flexible pavements without using primer for installation,a hot-applied modifled asphalt sealant was produced by blending up about 30 starch into 20 citric acid. The starch and the asphalt cement were
3、 mixed at a temperature of above 160 .Thus the waterproofing asphalt was manufactured to protect the surface of various shapes and types from water leakage using the citric acid.Results indicate that this sealant complies with the requirements of ASTM D-1191,D-6690-06a and D-71 16-05.The citric acid
4、 is a kind of reliable materials for asphalt cement,which can be widely used in paving and waterproofing construction materials,and this offers profound engineering and economic advantages/ Key words： joint sealant； starch； citric acid； waterproofing material； paving asphalt CLC number： U214 Documen
5、t code： A Article ID： 1005-9l13(2008)04-0547-06 1 Background of the Study The present study relates to waterproofing materials,and in particular to water- proofing asphalt cement and joint sealant. Joint sealant and waterproofing asphalt is regarded as one of the important primary materials used in
6、the field of civil engineering work.Their selection must always be a matter of compromise between price and performance.For example, Crack treatment,including crack sealing,crack filling,and crack repair,is one of the most common maintenance activities performed on bituminous pavements by local gove
7、rnmental agencies.Crack sealing is the method of placing material in a crack to create a watertight barrier.Transverse and longitudinal crack sealing is performed frequently in order to extend pavement life by preventing or substantially reducing the infiltration of water into the pavement structure
8、. Sealing cracks in asphalt pavements has long been regarded as an annual preventive maintenance procedure and is expected to have a growth rate of 3 -4per year.With limited maintenance budgets and increasing labor and material costs,so- me means of reducing the life,cycle cost of crack seals is req
9、uired.Polymer modified asphalt crack sealer materials,as defined by American Society for Testing and Materials1,2,have demonstrated the potential to deliver 5 or more years of service life.Because the polymer modifiers that have been employed beneficially as asphalt modifiers are rather expensive， a
10、 need exists for alternative,lower-cost modifiers that nonetheless impart improved properties comparable to those achived by using the more expensive polymers. Highway agencies use different materials and methods to treat cracks in asphah concrete pavements.Some of these treatments are inherently be
11、tter than others；howe- ver,the use of starch as a modifier has not been investigated by other researchers in the world. Substantial quantities of starch are potentially available widely in the world. Starch is a fine white powder mainly composed of two carbohydrate polymers,amy- lose and amylopectio
12、n.It characterized with low weight is generally much cheaper(0 8$/kg)thanother conventional polymers such as ,styrene-butadiene-styrene,polyethy- lene,and polypropylene. Starch granule size varies from (1-100)microns in dimeter and shape.On the other hand,beta-hydroxytrisarboxy1ic(citric) acid is a
13、fine white powder with an average partical size of 100 mesh.Citric acid is a very useful and effective preservative,obtained from naturally oecurring organic acids.It consists of 10 ppm heavy meatal,150 ppm sulphate,not more than 0.1 percent sulphate ash,0.2 ppm aluminum,less than 3 ppm ash,and 350
14、ppm oxalate.These characteristics makes citric acid and starch especially desirable to develop low cost-effective waterproofing materials. The causes of sealant failure depend on the types of sealant used,installation and service conditions.Sealant as a material can fail due to age and weather expos
15、ure This type of failure is often characterised by discolouration,crazing and stiffening of the sealant surfaces,and is the result of the individual or combined effects of solvent evaporation,ozone attack,migration of plasticisers,ultraviolet radiation,etc.Failure can also occur if there is a large
16、oint movement before the seal is fully cured.In other cases,sealant failures occur because the sealants are required to take cyclic movements beyond their limits. The various modes of failure experienced with sealants in service are illustrated in Fig.13,4. Adhesion Failure This is the most common type of failure due to the loss of bond between the sealant and the substrate(Fig.2)3,4 . Cohesion failure This is a failure within the sealant material.The effect of movement is likely to make the failure progressive(Fig.3)3,4 .
