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1、精选优质文档-倾情为你奉上Preparation of low-cost waterproofing materialsAlHadidyAI， Yiqiu，DONG Ze-jiao，WANG Jiani(School of Transportation Science and Engineering,Harbin Institute of Technology,H-arbin ,China,E-mail;abdet76yahoo.con)Abstract：To address the need for producing a cheap,singlecomponent,hot-applied

2、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 mixed at a tem

3、perature 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 is a kind of r

4、eliable 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 asphaltCLC number：U214 Document code：A Article ID：100

5、5-9l13(2008)04-0547-061 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 the field of civil engineer

6、ing 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 governmental agencies.Crack sea

7、ling 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. Sealing cracks in asphalt

8、 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 required.Polymer modified asphal

9、t 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 need exists for alternative,l

10、ower-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 better than others;howe-ver,the

11、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 amylopection.It characterized with low weigh

12、t is generally much cheaper(08$/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 fine white powder with an average p

13、artical 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 ppm oxalate.These characteristics m

14、akes 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 exposureThis type of failure is often ch

15、aracterised 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 oint movement before the seal is ful

16、ly 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 bo

17、nd 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 . Spalling This has similar consequences to adhesion failure.It occurs when the cohesive strength of the seal

18、ant is greater than that of the surface layers of the material to which it is applied. Excessive extrusion This is ejection from the joint part of which becomes vulnerable to mechanical the sealant,damage impairs the future ability of the sealant remaining joint to perform its function. Intrusion Th

19、is is common in horizontal ioints in traffic areas.It occurs when the sealant surface is penetrated by grit and debris.On subsequent closing，the grit is not ejected,causing abrasion and eventual failure of the sealant and in extreme case impairing the functioning of the joint. Hardening/weathering/c

20、razing Hardening of the sealant leads to the formation of cracks crazing.It can be brought about by the loss of solvent or plasticisers and by the action of ultraviolet radiation and ozone. Softening Sealant failure caused by softening may be due to improper curing or by thermal/photochemical degrad

21、ation of the polymer. Slumping Sealant flows downwards as a result of gravity.Softened sealants sometimes slump on vertica1 joint.The failure may also result in staining on the facade. Waisting A change in sealant shape resulting from viscous flow,which finally leads to thinning of the sealant in a

22、part of the joint.2 Detailed Description of the Study The following description is included to demonstrate preferred embodiments of the study.It should be appreciated by those of skill in the art that the method disclosed in the description which follows represent method discovered by the author to

23、function well in the practice of the study,and thus can be considered to constitute preferred mode for its practice.However,those of skill in the art should,in light of the present disclosure,appreciate that one may make many changes in the specific embodiments which are disclosed and still obtain a

24、 like or similar result without departing from the scope of the study. Starch represents an ideal material for inclusion as an asphalt modifier for a number of reasons.First,it exists as microscopic white grains that are insoluble in alcohol,ether,and cold water.Second,it is a highly organized mixtu

25、re of two carbohydrate polymers,amylose and amylopection .Third,substantial quantities,of starch are potentially available widely in the world at low cost.Finally,unlike many other materials such as used tires.starch comes from its source as a fine,freeflowing powder,which obviates any need for prep

26、rocessing the starch before mixing it into the asphalt.On the other hand,citric acid is a potential materials for waterproofing and being readily available are much cheaper than polymers such as styrene-butidiene-styrene(SBS),etc. As a result of binder modification with starch and citric acid,the ph

27、ysical and chemical properties of the binder are improved.This improvement takes place because of the change in the chemical properties of the binder.This modification results in higher resistance againstchemicals and fue1. There is one approach for producing a statch modified asphalt is to blend st

28、arch into the asphalt by using hot water (60 l ).Starch granules when heated in water gradually ab sorb water and swell in size,causing the mixture to thicken.With contin-ued heating however,the swollen granule fragments become less thick, and amylose and amylopectin become soluble in the hot mixtur

29、e.This process of granule swelling and fragmenring is calledgelatinization”.Because of the larger size of the swollen granules compared to the size of amylose and amylopection,the viscosity of the swollen granules mixture is much hi gher than the viscosity of the amylose/amylope-ction mixtures. In e

30、mploying this blending method it is extremely important to allow sufficient time to ensure that the starch is uniformly distributed through the asphalt.As a little as 5 minutes or as long as 10 minutes of mixing may be required，depending on the shear rate,which in turn depends 0n the blade configura

31、tion of the mixer impeller and the speed of the motor.In addition,it is necessary to continue stirring the blend until it is about to be used. Citric acid is mixed with asphalt at diferent weight percentages(10,20,&30)for 7 min at temperature of 160 5 to produce an economically mastic,water proofing

32、 and damp proofing asphalt cement.Three modified binders are thus performed from the virgin asphalt. The Starch jpint sealant samples are prepared in the following procedure;A 20citric acid modified asphalt that comply with the physical requirements of asphalt mastic(ASTM D-491)is heated to the desi

33、red temperature in a three,neck flask provided with stirrer and contact thermometer.The temperature is held constant by an automatic control system while stirring intensively.The starch iS dispersed into the citric acid modified asphalt by using hot water(601).The resultant asphalt is then combined

34、with filler.The citric acid modified asphalt is treated with different percentages of starch(10,30,and 50 wtof virgin asphah)and one percentage of calcium carbonate filler (125 wtof virgin asphalt).The best results are achieved when the blending temperature is maintained above about 160 (as shown in

35、 Fig.4).2、1Expermintal2、1、1Asphalt cement The test is conducted on asphalt cement according to ASTM1.The result of these tests are listed in Tab.1.2、1、2 Stone aggregates are crushed and mineral filler obtained by passing the crushed stone through a 200 mesh sieve.The chemical and physical properties

36、 of filler are reported in Tab.2.213 Starch Starch has a chemical unitC6H10O5n=100-1000 and purity of 99.2.The composition of starch is reported in Tab.3.214 Citric acidCitric acid,with an average partical size of 100 mesh,is a white powder material having purity of 99.98.22 Tests of Samples A serie

37、s of conventional tests which are still in use throughout the world are carried out in the asphalt industry to characterize the mixtures designed for different percentages of cetric acid according to ASTM1. These tests include： 1Penetration test;ASTM D-5. 2Ductility test;ASTM D-1 l3. 3Softening poin

38、t test;ASTM D-36. 4Solubility test;ASTM D-2042;and 5Compatibility test;ASTM D-4124. Weather,the following tests are carried out on starch ioint sealant samples according to ASTM 1methods. 1Penetration test before and after aging;ASTM D-5. 2Softening point test;ASTM D-36. 3Flow test;ASTM D-1191. 4Rec

39、overy test before and after aging;ASTM D-5329. 5Flexibility test;ASTM D-5329. 6Compatibility test;ASTM D-5329. 7Density test;ASTM D-70. 8Tensile adhesion;ASTM D-4l2 Die C. 9Chemical resistance;ASTM D-147. 10Fuel resistance;ASTM D-3569. A descfi btion of some of ioint sealant tests are in the followi

40、ng paragraphs:221Tensile adhesion to concrete Nine specimens of each mixture are prepared to determine the tensile properties using Materials Testing System (MTS一810).Specimens are divided into three groups.The first group placed in water bath at 25 ,and then loaded at a ratio of 127 mm/min.The seco

41、nd group is cured in a cooling room maintaining a temperature of-19 for more than 3 h，and then loaded at a ratio of 0.05 mm/min.The third group is immersed in benzene solvent for 4 h,and then loaded at a ratio of 12.7 mm/min,and the stress and elongation values are recorded.Tensile adhesion test res

42、ults are summarized in Tab.4.222 Chemical(Alkali and acid) resistance test Two groups of starch joint sealant samples are subjected to alkali and acid resistance test in accordance with ASTM D147.The first group is placed in 40 percent NaOH at 21 solution for 1000 hours.The second group is immersed

43、in 95 percent Hcl at 21 solution for 1000 hours.The samples are then brought toweight loss determination as designated as alkali and acid-resisting.Chemical resistance test results are summarized in Tab.4.223 Z resistance test Three groups of starch ioint sealan t samples are tested for fuel resista

44、nce in accordance with ASTM D5329.The first group is immersed in JP-4 fuel bath at 401 for 24 h.The second group is placed in hydraulic bath at 251 for 7d.The third group is immersed in glycol/water(50/50) bath at 251 for 7d.The samples are then brought to weight loss determination as designated as

45、fue1-resisting.Fuel resistance test results are summarized in Tab.4.3、Results and Discussion The physical and chemical properties of citric acid-asphalt binders are evaluated and the results are presented in Tab.5.The results indicate that citric acid is effective in improving the rheological proper

46、ties of asphalt cement. Examining Tab.5,it can be seen that the modified asphalt with citric acid is complies with the ASTM-specifications(D-312 and D-449)5 for asphalt used in roofing，dampproofing and waterproofing except for the penetration property at 46 . Fig.5 ilustrates the relationship betwee

47、n the asphahenes percent and citric acid contents.It can be seen that citric acid is well dissolved in asphalt matrix. The effect of starch contents on the physica1,me-chemical and chemical properties of the starch joint sealant are shown in Tab.4.To investigate the novel improvement of the properti

48、es of the starch ioint sea1ant,the results are compared with the ASTM specifications and MaiBe department of transportation6. Examining Tab.4 indicates that sample SJS of joint sealant comply with ASTM D-1191,D-6690-06a and D-7116-05 requirements for ioint sealant,hot type,fuel resistance types for Portland cement concrete and asphal