Laboratory evaluation of permeability and strength of polymer-modified pervious concrete

  • Published on
    26-Jun-2016

  • View
    216

  • Download
    3

Transcript

<ul><li><p>dde379</p><p>Pervious</p><p>n inntsty, ppertheprope in</p><p> 2009 Elsevier Ltd. All rights reserved.</p><p>te (PCte, is ah eithepproployedarticle</p><p>together to create a system of high porosity and interconnectedvoids that can drain off water quickly. Generally, the void contentof PCPC is between 15% and 25%, and the water permeability is typ-ically about 26 mm/s [5,7]. However, relatively low strength isusually associated with the high porosity in PCPC. The low strengthof conventional pervious concrete not only limits its application inheavy trafc highways but also inuences the stability and</p><p>vious concrete. Wang [10] used river sand to replace approximate7% (by weight) coarse aggregate to improve the concrete strength.Their results indicated that the 7-day compressive strength in-creases from 9.614.5 MPa to 22.222.7 MPa. Although the voidcontent is reduced due to the ne sand in the mixtures, all voidcontent values are still within an acceptable range (&gt;15%) for PCPCapplications, and the permeability value is still higher than theminimum requirement to drain [10]. Yang and Jiang [11] showedthat use of silica fume (SF) and superplasticizer (SP) in perviousconcrete can enhance its strength signicantly. The results also</p><p>* Corresponding author. Tel.: +1 865 974 7713.</p><p>Construction and Building Materials 24 (2010) 818823</p><p>Contents lists availab</p><p>B</p><p>evE-mail address: bhuang@utk.edu (B. Huang).between them. Thus, pores are formed in the pervious materials[1,2]. PCPC has been used for over 30 years in many countries,especially in the United States and Japan. It is increasingly usedin the United States because of its various environmental benetssuch as controlling storm water runoff, restoring groundwater sup-plies, and reducing water and soil pollution [35]. In the meantime,it has the potential to reduce urban heat island effects and can beused to reduce acoustic noise in roads [5,6].</p><p>PCPC contains little or no ne aggregate, using an adequateamount of cement paste to coat and bind the aggregate particles</p><p>aggregates mixtures, and organic intensiers and by adjustingthe concrete mix proportion, strength and abrasion resistance ofPCPC can be improved greatly [11]. Previous studies show that gra-dation, particle size of aggregate, and mass ratio of aggregate to ce-ment are the primary factors affecting porosity, permeability andcompressive strength of PCPC. Water cement ratio has a minor ef-fect on properties of PCPC [12]. Using smaller size aggregate can in-crease the number of aggregate particles per unit volume ofconcrete, the specic surface of aggregate, and the binding area,which eventually results in an improvement in the strength of per-ConcreteFiber reinforcementDurability</p><p>1. Introduction</p><p>Portland cement pervious concreporous concrete or permeable concrement, uniform coarse aggregate, witwithout ne aggregate, and water. Aand cementitious material are empforms a thin coat around aggregate p0950-0618/$ - see front matter 2009 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2009.10.025PC), also referred to asmixture of portland ce-r a small amount of orriate amounts of waterto create a paste thats but leaves free spaces</p><p>durability of the structures, because of, for example, susceptibilityto frost damage and low resistance to chemicals. Therefore, PCPCwith low strength can only be utilized in some applications, suchas sidewalks, parking lots, recreation squares and subbases for con-ventional pavement [810]. And with some effective improvementin strength and using smaller size aggregate, PMPC could be ap-plied in pavement shoulder and local roads.</p><p>However, by using appropriately-selected aggregates, neKeywords:Polymers results indicate that it was possible to produce pervious concrete mixture with acceptable permeability</p><p>and strength through the combination of latex and sand.Laboratory evaluation of permeability anpervious concrete</p><p>Baoshan Huang *, Hao Wu, Xiang Shu, Edwin G. BurDept. of Civil and Environmental Engineering, The University of Tennessee, Knoxville, TN</p><p>a r t i c l e i n f o</p><p>Article history:Received 3 February 2009Received in revised form 22 September2009Accepted 15 October 2009Available online 17 November 2009</p><p>a b s t r a c t</p><p>Pervious concrete has beewater quality near pavemeciated with the high porosistructures. A laboratory expervious concrete throughpermeability and strengthnatural sand and ber wer</p><p>Construction and</p><p>journal homepage: www.elsll rights reserved.strength of polymer-modied</p><p>tte96, USA</p><p>creasingly used to reduce the amount of runoff water and improve theand parking lots. However, due to the signicantly reduced strength asso-ervious concrete mixtures currently cannot be used in highway pavementiment was conducted in this study to improve the strength properties ofincorporation of latex polymer. This study focused on the balance betweenerties of polymer-modied pervious concrete (PMPC). In addition to latex,cluded to enhance the strength properties of pervious concrete. The test</p><p>le at ScienceDirect</p><p>uilding Materials</p><p>ier .com/locate /conbui ldmat</p></li><li><p>indicated that SF had a better effect for improving the properties ofpervious concrete than polymer when used with SP. Their resultsindicated that the compressive strength of PCPC can reach50 MPa and the exural strength 6 MPa. At the same time, therequirements of water penetration, abrasion resistance can also</p><p>was used to obtain the effective air voids for the pervious concrete specimens inthis study. The test was conducted by following the ASTM D 7063 procedures.</p><p>3.4.2. Permeability testPermeability is an important parameter of pervious concrete since the material</p><p>is designed to perform as drainage layer in pavement structures. Due to the highporosity and the interconnected air voids path, Darcys law for laminar ow is nolonger applicable for pervious concrete. In this study, a permeability measurementdevice and method developed by Huang et al. [14] for drainable asphalt mixture(similar to pervious concrete in function) were used. Fig. 2 shows the specimenand device for permeability test.</p><p>Two pressure transducers installed at the top and bottom of the specimen giveaccurate readings of the hydraulic head difference during the test. Automatic dataacquisition makes continuous reading possible during a falling head test so that the</p><p>Apparent specic gravity Absorption (%) Void content (%)</p><p>2.797 0.48 40</p><p>60%</p><p>70%80%</p><p>90%</p><p>100%</p><p>ing,</p><p> % </p><p>River sand</p><p>B. Huang et al. / Construction and Building Materials 24 (2010) 818823 819be satised. Some bers are helpful in improving the tensilestrength and permeability of pervious concrete. Generally, the -bers in PCPC slightly increase the void content, signicantly in-crease the permeability, and more signicantly improve thesplitting tensile strength of PCPC [10,13]. The addition of polypro-pylene ber at 0.56% by volume of the concrete causes a 90% in-crease in the indirect tensile strength and a 20% increase in theexural strength. Polypropylene ber does not signicantly affectthe other mechanical properties [12]. Another effective methodto improve strength is to use some chemical additives, such aspolymer. Kevern [13] also presented that the addition of polymer(styrene butadiene rubber, SBR) signicantly improves workability,strength, permeability, and freezethaw resistance, which makespervious concrete obtain higher strength at relatively lower ce-ment contents and results in relative higher porosity.</p><p>2. Research objective and scope</p><p>The objective of the present study is to evaluate the effect ofpolymer modication on the mechanical and physical propertiesof PCPC. The research efforts were made to balance the permeabil-ity and strength of the polymer-modied pervious concrete(PMPC) so that the mixtures are permeable and also strong enoughto support trafc loading.</p><p>In this study, three types of single-sized limestone aggregates(12.5 mm, 9.5 mm, and 4.75 mm) were used, and one type of poly-mer (SBS latex) was considered to make the pervious concrete mix-ture. The properties of pervious concrete were evaluated throughair void test, permeability test, compressive strength test, and splittensile strength test.</p><p>3. Laboratory experiment</p><p>3.1. Materials</p><p>Ordinary Type I portland cement was selected in the experiments. Three grada-tions of single-sized sieved limestone were considered as coarse aggregate:12.5 mm, 9.5 mm, and 4.75 mm. The properties of coarse aggregate were measuredaccording to ASTM specications and listed in Table 1. The grain-size distribution ofthe river sand from the Tennessee River used in this study is shown in Fig. 1.</p><p>Latex polymer, styrene butadiene rubber (SBR), was selected and incorporatedinto the mixtures in order to improve the strength of pervious concrete. Styrenebutadiene rubber (SBR) latex is a type of high-polymer dispersion emulsion com-posed of butadiene, styrene and water, etc., which is similar to natural rubber inits resistance to mild solvents and chemicals and, like natural rubber, can be suc-cessfully bonded to many materials. It is one of the popular raw materials in the tiredip fabric industry, because of its good intermiscibility with vinylpyridine latex forfabric dipping. For the application in engineering construction, it can be used tosupply or replace cement as binder to improve tensile, exural and compressivestrength of concrete. The SBR used in this study is manufactured by anionic solutionpolymerization using an organo-lithium initiator. It is a product with medium sty-rene and high vinyl content. A white thick liquid in appearance, it has good viscositywith 52.7% water content.</p><p>In addition to latex, polypropylene ber was also added into the mixture to fur-ther enhance the mechanical properties of PMPC. Polypropylene ber has featuresand benets as follows: inhibits and controls the formation of intrinsic cracking inconcrete; reinforces against impact forces, reinforces against the effect of shattering</p><p>Table 1Properties of coarse aggregate.</p><p>Aggregate size (mm) Unit weight (kg/m3) Bulk specic gravity</p><p>12.5 1426 2.759</p><p>9.5 1393 2.7584.75 1374 2.760forces, and provides improved durability. The polypropylene ber was 100% virginpolypropylene brillated bers containing no reprocessed olen materials with anaverage length of 20 mm.</p><p>3.2. Mix design</p><p>The control pervious concrete mixture was comprised of portland cement,water, and coarse aggregates of three gradations. To improve the overall behaviorof PMPC, latex, ber, and ne aggregate (natural sand) were selectively added intothe mixture. The mix proportions are presented in Table 2. The basic mix proportionfor the control mix is cement: coarse aggregate: water = 1:4.5:0.35 by weight.When latex and/or ne aggregate were included in the mixture, the solid portionof latex was used to replace 10% cement and natural sand to replace 7% coarseaggregate by weight. The performance and properties of PMPC were compared tothose of the conventional pervious concrete.</p><p>3.3. Sample preparation</p><p>Pervious concrete mixtures were mixed using a mechanical mixer, and cylindri-cal specimens 152 mm in diameter and 305 mm high were made by applying stan-dard rodding for compaction. The specimens were cured in a standard moisturecuring chamber until the days of testing. Except for the compression test, the sam-ples were cut into about 76 mm thick small specimens for other tests before testing.The specimens were prepared in triplicates.</p><p>3.4. Test methods</p><p>3.4.1. Air voids testIn order to obtain the air voids content, it is necessary to know the bulk volume</p><p>of the compacted concrete. Since the pervious concrete has high interconnected airvoids, it is not suitable to use the submerged weight measurement to obtain thebulk volume. Geometrical measurement of the specimen dimension will not reectthe surface texture (for different sized aggregates). A vacuum package sealing de-vice, CoreLok, commonly used to measure the specic gravity for asphalt mixtures,</p><p>0%</p><p>10%</p><p>20%30%</p><p>40%</p><p>50%</p><p>0.01 0.1 1 10 100Sieve Size, mm.</p><p>Perc</p><p>ent P</p><p>ass</p><p>Fig. 1. Grain-size distribution of river sand.2.801 0.56 432.811 0.66 41</p></li><li><p>uildTable 2Mix proportions for PMPC (unit: kg/m3).</p><p>Agg. Mix type Cement Latex binder</p><p>No sand12.5 mm A 320.2</p><p>B 314.8 31.5C 320.2D 314.8 31.5</p><p>820 B. Huang et al. / Construction and Btest can be conducted even at very high ow rate, such as in pervious concrete. Thespecimen is placed in an aluminum cell. Between the cell and the specimen is ananti-scratch rubber membrane that is clamped tightly at both ends of the cylindri-cal cell. A vacuum is applied between the membrane and the cell to facilitate theinstallation of the specimen. During the test, a conning pressure of up to103.5 kPa is applied on the membrane to prevent short-circuiting from the speci-mens side. The top reservoir tube has a diameter of 57 mm and a length of914 mm. The cylindrical specimen has a diameter of 152 mm and a height of76 mm.</p><p>In this test, the falling head method was used. From the paper of Huang et al.[14] hydraulic head difference vs. time curve obtained from the two pressuretransducers:</p><p>9.5 mm A 330.4B 324.9 32.5C 330.4D 324.9 32.5</p><p>4.75 mm A 352.6B 346.7 34.7C 352.6D 346.7 34.7</p><p>With sand12.5 mm A 300.6</p><p>B 295.8 29.6C 300.6D 295.8 29.6</p><p>9.5 mm A 311.9B 306.9 30.7C 311.9D 306.9 30.7</p><p>4.75 mm A 329.8B 324.5 32.5C 329.8D 324.5 32.5</p><p>Note: A control; B latex modied; C ber added; D latex and ber.</p><p>Fig. 2. Permeability testCoarse aggregate River sand Water Fiber</p><p>1440.8 112.11416.6 93.61440.8 112.1 0.91416.6 93.6 0.9</p><p>ing Materials 24 (2010) 818823h a0 a1t a2t2 1where, a0, a1 and a2 are regression coefcients.</p><p>Then, differentiate equation,</p><p>dhdt</p><p> a1 a2t 2</p><p>where a1 and a2 are regression coefcients for differential equation of head and time.Therefore, the discharge velocity is expressed as:</p><p>v dQdt</p><p> A1A2</p><p>dhdt</p><p> r21</p><p>r22</p><p>dhdt</p><p>3</p><p>1486.9 115.61461.9 96.61486.9 115.6 0.91461.9 96.6 0.9</p><p>1586.9 123.41560.3 103.11586.9 123.4 0.91560.3 103.1 0.9</p><p>1352.6 94.7 105.21331.0 93.2 87.91352.6 94.7 105.2 0.91331.0 93.2 87.9 0.9</p><p>1403.6 98.3 109.21381.2 96.7 91.31403.6 98.3 109.2 0.91381.2 96.7 91.3 0.9</p><p>1483.9 103.9 115.41460.3 102.2 96.51483.9 103.9 115.4 0.91460.3 102.2 96.5 0.9</p><p>setup and sample.</p></li><li><p>ead</p><p>0</p><p>5</p><p>10</p><p>15</p><p>20</p><p>25</p><p>30</p><p>35</p><p>Control mix Mix with latex Mix with latexand sand</p><p>Mix with latex,sand, and fiber</p><p>Poro</p><p>sity</p><p> (%)</p><p>12.5 mm 9.5 mm 4.75 mm</p><p>Building Materials 24 (2010) 818823 821Time (s)</p><p>H</p><p>Fig. 3. Hydraulic head vs. time.</p><p>Hydraulic Gradient vs. Discharge Velocity</p><p>ty: v</p><p> (mm/</p><p>s)</p><p> (m</p><p>m)</p><p>Time vs. Head</p><p>B. Huang et al. / Construction andwhere A1; A2; r1; r2 are the cross section areas and radius of upper cylindrical reser-voir and the specimen.</p><p>According to Fig. 3 and Fig. 4, the pseudo-coefcient of permeability K0 and theshape factor m can be obtained. Based on the results, the relationship betweenhydraulic gradient and discharge velocity is v = 7.6208i0.3538 so the K0 is7.621 mm/s.</p><p>3.4.3. Compressive strengthThe compressive strength was tested at 7-days by following the ASTM C39 test-</p><p>ing procedures. The compressive strength test was conducted on an INSTRON load-ing frame on triplicate cylindrical...</p></li></ul>

Recommended

View more >