毕业论文外文翻译-低成本防水材料的制备

Preparation of low-cost waterproofing materials

Al—HadidyAI， Ⅳ 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—et76@yahoo.con)

Abstract：To address the need for producing a cheap,single—component,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 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 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 Document 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 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 governmental 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.

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％-4％per 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 asphalt crack sealer materials,as defined by American Society for Testing and Materials[1,2],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,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 better 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 amylopection.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 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 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 exposure．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 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.1[3,4].

①Adhesion 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] . ②Cohesion failure

This is a failure within the sealant material.The effect of movement is likely to make the failure progressive(Fig.3)[3,4] .

③Spalling

This has similar consequences to adhesion failure.It occurs when the cohesive strength of the sealant is greater than that of the surface layers of the material to which it is applied.

④Excessive 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.

⑤Intrusion

This 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. ⑥Hardening/weathering/crazing

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. ⑦Softening

Sealant failure caused by softening may be due to improper curing or by thermal/photochemical degradation of the polymer. ⑧Slumping

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. ⑨Waisting

A change in sealant shape resulting from viscous flow,which finally leads to thinning of the sealant in a 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 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 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 mixture 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 preprocessing 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 physical 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 starch 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 mixture.This process of granule swelling and fragmenring is called\gelatinization”.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 employing 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 configuration 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 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 20％citric acid modified asphalt that comply with the physical requirements of asphalt mastic(ASTM D-491)is heated to the desired 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(60±1℃).The resultant asphalt is then combined with filler.The citric acid modified asphalt is treated with different percentages of starch(10,30,and 50 wt％of virgin asphah)and one percentage of calcium carbonate filler (125 wt％of virgin asphalt).The best results are achieved when the blending temperature is maintained above about 160℃ (as shown in Fig.4). 2、1Expermintal

2、1、1Asphalt cement

The test is conducted on asphalt cement according to ASTM[1].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 of filler are reported in Tab.2.

2．1．3 Starch

Starch has a chemical unit[C6H10O5]n=100-1000 and purity of 99.2％.The composition of starch is reported in Tab.3.

2．1．4 Citric acid

Citric acid,with an average partical size of 100 mesh,is a white powder material having purity of 99.98％. 2．2 Tests of Samples

A series 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 ASTM[1]. These tests include：

1．Penetration test;ASTM D-5. 2．Ductility test;ASTM D-1 l3.

3．Softening point test;ASTM D-36. 4．Solubility test;ASTM D-2042;and 5．Compatibility test;ASTM D-4124.

Weather,the following tests are carried out on starch ioint sealant samples according to ASTM [1]methods.

1．Penetration test before and after aging;ASTM D-5. 2．Softening point test;ASTM D-36. 3．Flow test;ASTM D-1191.

4．Recovery test before and after aging;ASTM D-5329. 5．Flexibility test;ASTM D-5329. 6．Compatibility test;ASTM D-5329. 7．Density test;ASTM D-70.

8．Tensile adhesion;ASTM D-4l2 Die C. 9．Chemical resistance;ASTM D-147. 10．Fuel resistance;ASTM D-3569.

A descfi btion of some of ioint sealant tests are in the following paragraphs: 2．2．1Tensile 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 12．7 mm/min.The second 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 results are summarized in Tab.4.

2．2．2 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 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.

2．2．3 Z resistance test

Three groups of starch ioint sealan t samples are tested for fuel resistance in accordance with ASTM D5329.The first group is immersed in JP-4 fuel bath at 40±1℃ for 24 h.The second group is placed in hydraulic bath at 25±1℃ for 7d.The third group is immersed in glycol/water(50/50) bath at 25±1℃ for 7d.The samples are then brought to weight loss determination as designated as 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 properties 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 between 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 properties of the starch ioint sea1ant,the results are compared with the ASTM specifications and MaiBe department of transportation[6].

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 asphalt concrete Pavements.Howev- er,these joint sealant samples are resistant to water,fuel,oil and most other liquids and chemicals in a range of conditions,and provide a high level of sealing properties for extended periods of time.It is therefore,recommended for sealinghorizontal and inclined joints on highways,airport runways,bridges,driveway- s,and for interior uses including sealing joints in industrial floors,garage floors ,airplane hangar floor witho- ut using primer for installation.

In view of the above disclosure,one skill in the art should understand that one

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