Properties of Polymer Concrete Polymer concrete may be poured as slabs for large projects.Polymer concrete uses binders, such as epoxies (glues),polyester, or resins, to bind the concrete together. The addition ofbinders gives polymer concrete greater resistance to corrosionthan conventional Portland cement. Polymer concrete, composedof water, finely crushed stone or gravel, sand and a binder,
makes an excellent mortar for filling gaps between bricks, tiles and cement blocks.1. Basics Polymer cement comes in a variety of colors; tan and gray are the most common. For large projects, this material is usually sold as a liquid, which is then poured into a frame. The material cures (dries and hardens) fully after seven days. Polymer cement may be used around the home to patch masonry work. For smaller projects, it is usually sold at home improvement stores in a premixed bucket or as a 50-lb. bag of powder that must be mixed by hand. Polymer concrete has a liquid working temperature between 60 F and 85 F. The maximum workable temperature of this type of concrete is 150 F.2. Strength Strength is an important characteristic of concrete, as it is often used as a structural foundation material. Polymer concrete has an average compressive strength between 10,000 and 12,000 pounds of pressure per square inch (PSI). Exact compression strength varies depending upon the brand of polymer concrete and what type of material is used as a binder. Compressive strength increases over time. Polymer Methyl Methacrylate Concrete has compressive strength of 8,000 PSI
after one hour of setting and 12,000 PSI after seven days of setting.3. Corrosion Polymer concretes main advantageous property is its resistance to a wide range of solvents and oils; it is also resistant to acids with a pH level ranging from 0 to 14. Polymer concrete is resistant to a variety of acids that can eat away concrete over time, including soda and potash lye, ammonia, hydrochloric acid, formic acid, acetic acid, chlorides and ammonium sulfate. Polymer concrete does not corrode in the presence of hydrocarbons, such as acetone, gasoline, ethane, methanol, petroleum, diesel and vegetable oils. This type of concrete offers excellent resistance against water. Flexibility Traditional concrete is vulnerable to shearing forces that can cause cracks and a decline in structural integrity. Resistance to these forces is known as flexural and tensile splitting strengths. To give concrete the ability to expand and contract without cracking, it is poured on a rebar frame. Polymer concrete offers greater resistance to cracking. Polymer concrete has a flexural strength between 3,470 and 3,729 PSI after eight hours. Tensile strength is between 1,800 and 2,014 PSI after the material has been allowed to set for seven days.
Properties and Applications of Fiber ReinforcedConcreteFiber TypesFibers are produced from different materials in various shapesand sizes. Typicalfiber materials are[2,31;Steel FibersStraight, crimped, twisted, hooked, ringed, and paddled ends.Diameter rangefrom 0.25 to 0.76mm.Glass FibersStraight. Diameter ranges from 0.005 to 0.015mm (may bebonded together toform elements with diameters of 0.13 to1.3mm).Natural Organic and Mineral FibersWood, asbestos, cotton, bamboo, and rockwool. They come inwide range ofsizes.Polypropylene FibersPlain, twisted, fibrillated, and with buttoned ends.Other Synthetic FibersKevlar, nylon, and polyester. Diameter ranges from 0.02 to0.38mm.A convenient parameter describing a fiber is its aspectratio (LID), defined as thefiber length divided by an equivalent
fiber diameter. Typical aspect ratio ranges fromabout 30 to 150for length of 6 to 75mm.Mixture Compositions and PlacingMixing of FRC can be accomplished by many methods The mix should have auniform dispersion of the fibers inorder to prevent segregation or balling of the fibers duringmixing. Most balling occurs during the fiber addition process.Increase ofaspect ratio, volume percentage of fiber, and size andquantity of coarse aggregatewill intensify the balling tendenciesand decrease the workability. To coat the largesurface area of thefibers with paste, experience indicated that a water cement ratiobetween 0.4 and 0.6, and minimum cement content of400kg/m are required. Compared to conventional concrete,fiber reinforced concrete mixes are generallycharacterized byhigher cement factor, higher fine aggregate content, and smallersize coarse aggregate.A fiber mix generally requires morevibration to consolidate the mix. External vibration is preferableto prevent fiber segregation. Metal trowels, tube floats, androtating power floats can be used to finish the surface.Compressive Strength The presence of fibers may alter the failure mode ofcylinders, but the fiber effectwill be minor on the improvement ofcompressive strength values (0 to 15 percent).
Modulus ofElasticity Modulus of elasticity of FRC increases slIghtly with anincrease in the fibers content. It was found that for each 1percent increase in fiber content by volume there isan increase of 3 percent in the modulus of elasticity.FlexureThe flexural strength was reported to be increased by 2.5 timesusing 4 percentfibers.ToughnessFor FRC, toughness is about 10 to 40 times that of plain concrete.Splitting Tensile StrengthThe presence of 3 percent fiber by volume was reported toincrease the splittingtensile strength of mortar about 2.5 timesthat of the unreinforced one.Fatigue StrengthThe addition of fibers increases fatigue strength of about 90percent and 70 percentof the static strength at 2 x 106cycles for non-reverse and full reversal of loading, respectively.Impact Resistance
The impact strength for fibrous concrete is generally 5 to 10times that of plain concrete depending on the volume of fiberusedCorrosion ofSteel FibersA lO-year exposureof steel fibrous mortar to outdoor weatheringin an industrialatmosphere showed no adverse effect on thestrength properties. Corrosion wasfound to be confined only to fibers actually exposed on thesurface. Steel fibrousmortar continuously immerse in seawater for 10 years exhibited a15 percent losscompared to 40 percent strength decrease of plain mortar.Structural Behavior of FRCFibers combined with reinforcing bars in structural members willbe widely used inthe future. The following are some of the structural behaviourI6 8l:.FlexureThe use of fibers in reinforced concrete flexure membersincreases ductility, tensile strength, moment capacity, andstiffness. The fibers improve crack control and
preserve post cracking structural integrity of members.TorsionThe use of fibers eliminate the sudden failure characteristic ofplain concretebeams. It increases stiffness, torsional strength, ductility,rotational capacity, andthe number of cracks with less crack width.ShearAddition of fibers increases shear capacity of reinforced concretebeams up to 100percent. Addition of randomly distributed fibers increases shear-friction strength,the first crack strength, and ultimate strength.ColumnThe increase of fiber content slightly increases the ductility ofaxially loaded specimen. The use of fibers helps in reducing theexplosive type failure for columns.High Strength ConcreteFibers increases the ductility of high strength concrete. The use ofhigh strength
concrete and steel produces slender members. Fiber addition willhelp in controllingcracks and deflections.Cracking and DeflectionTests have shown that fiber reinforcement effectively controlscracking and deflection, in addition to strength improvement. Inconventionally reinforced concretebeams, fiber addition increases stiffness, and reduces deflection.ApplicationsThe uniform dispersion of fibers throughout the concrete mixprovides isotropicproperties not common to conventionally reinforced concrete. Theapplications offibers in concrete industries depend on the designer and builderin taking advantageof the static and dynamic characteristics of this new material. Themain area of FRCapplications are1101 :Runway, Aircraft Parking, and PavementsFor the same wheel load FRC slabs could be about one half thethickness of plain
concrete slab. Compared to a 375mm thickness of conventionallyreinforced concrete slab, a 150mm thick crimped-end FRC slabwas used to overlay an existing as-Properties and ApplicationsofFiber Reinforced Concrete 53phaltic-paved aircraft parking area. FRC pavements are now inservice in severe andmild environments.Tunnel Lining and Slope StabilizationSteel fiber reinforced shortcrete (SFRS) are being used to lineunderground openings and rock slope stabilization. It eliminatesthe need for mesh reinforcement andscaffolding.Blast Resistant StructuresWhen plain concrete slabs are reinforced conventionally, testsshowed(llj thatthere is no reduction of fragment velocities or number offragments under blast andshock waves. Similarly, reinforced slabs of fibrous concrete,however, showed 20percent reduction in velocities, and over 80 percent infragmentations.Thin Shell, Walls, Pipes, and Manholes
Fibrous concrete permits the use of thinner flat and curvedstructural elements.Steel fibrous shortcrete is used in the construction ofhemispherical domes using theinflated membrane process. Glass fiber reinforced cement orconcrete (GFRC) ,made by the spray-up process, have been used to construct wallpanels. Steel andglass fibers addition in concrete pipes and manholes improvesstrength, reducesthickness, and diminishes handling damages.Dams and Hydraulic StructureFRC is being used for the construction and repair of dams andother hydraulicstructures to provide resistance to cavitation and severe errosioncaused by the impact of large waterboro debris.Other ApplicationsThese include machine tool frames, lighting poles, water and oiltanks and concrete repairs.Comparative Study of the Mechanical Behavior of FRCUsing Local Materials
Researches are being carried out in the Civil EngineeringDepartment of King Abdulaziz University about the mechanicalproperties of fibrous concrete and the structural behaviour offibrous concrete beams with and without prestressing subjectedtodifferent combinations of bending, shear, and torsion. A study ofthe mechanical behavior of fibrous concrete using local materialsis presented in this section.MaterialsTable 1shows the different properties of the straight and thehooked fibers used inthis study. The hooked fibers are glued together into bundles witha watcr-stlluhkadhesive. The collating of the 30 fibers create" an artificial aspectratio ot approxi-54 Faisal Fouad Wafamately 15. The plain fibers were obtained by cutting galvanizedsteel wires manually.Type I portland cement, lOmm graded crushed stone aggregate,desert sand offineness modulus 3 .1, and a 3 percent superplasticizer were used for all the mixes. Themix proportion was 1.0:2.0:1.6 and the water-cement ratio was0.44.TABLE 1. Properties of straight and deformed steel fibers.
Straight fiber Hooked fiberMaterial Galvanized Steel Carbon SteelLength (mm) 53.00 60.00Diameter (mm) 0.71 0.80Aspect ratio (LID) 75.00 75.00f/MPa) 260.00 660.00WorkabilityThe conventional slump test is not a good measure ofworkabilityof FRC. The inverted slump cone test (2.4) devised especially forthe fibrous concrete is recommended. The time it takes aninverted lamp cone full of FRC to be emptied after avibrator is inserted into the concrete is called the inverted-conetime. It should varybetween 10 and 30 seconds.The conventional slump test (ASTM CI43-78) and the invertedslump cone test(ASTM C995-83) were conducted to compare the performance ofthe plastic concrete reinforced with the two different types offibers. The hooked fibers performedwell during mixing because no balling occurred even though thefibers were added to
the mixer along with the aggregate all at one time. The straightfibers had to besprinkled into the mixer by hand to avoid balling. It tookapproximately 2 minutes toadd the straight fibers to the mix, resulting in a 2 minutes extramixing time. Figure 1shows the effect of fiber content on both slump and inverted conetime. It is clearlyseen that as the fiber content increased from 0.0 to 2.0 percent,the slumps value decreased from 230 to 20mm, and the timerequired to empty the inverted cone time increased from 20 to 70seconds. For the highest fiber volume percentage used (Vf=2.0 percent) it was noticed that the FRC in the test specimenswas difficult to consolidate using the internal vibrator.Compressive StrengthSixty concrete cylinders (1500 x 300mm) were cast and tested incompression(ASTM C39) at the end of7, 28 and 90 days. Figure 2 shows theeffect of the hooked
fiber content on the compressive strength values and shows thestress-strain relationship. The fiber addition had no effect on thecompressive strength values. However,the brittle mode of failure associated with plain concrete wastransformed into amore ductile one with the increased addition of fibers. Figure 3presents the effect ofProperties and Applications ofFiberReinforced Concrete2.10 j-----------------------,55200160E 120a.:E:3 80Vl40/:::, SLUMP (mm) o TIME (SECOND)60 U(l)
0.5 1.0 1.5 20 25FIBER CONTENT (VI 0/0)FIG. t. Effect of fiber content on workability.40ca.;;,30w20""IVlW<v;VlW""a.;;,0u
0COMPRESSIVE STRAINFIG. 2. Effect of hooked fiber content on compressive stress-strain curves (28 days).56 Faisa/ Fouad Wafa=7 DAYS 28 DAYS 090 DAYSJ!.500.5 1.0 1.5 2.030 -.I.II........L.-_....L:=----_--""=---_.-IIU-l. L.U....J0.0wC);: 35:I:...ClZw45"w
<v;"w40ouFIBER CONTENT (VI %)FIG. 3. Effect of hooked fiber content on compressive strength atdifferent ages.hooked fiber content on the compressive strength after 7, 28 and90 days. It is observed that although slight scatter exists, thepercentage of fiber volume content haspractically no influence on the compressive strength of concreteeither at early orlater stage of its life. Table 2 and Fig. 4 present a comparison ofthe strength forhooked and straight fibers which indicates that the fiber typesand content have littleeffect on the compressive strength. The results are similar tothose of other investigators[2,31.
Figure 2 shows that the initial slope of the stress-strain curve ispractically the samefor all mixes and equal to 31,900 MPa compared to 30,400 MPaobtained using theACI formula. This indicates that the modulus of elasticity does notchange much bythe addition of fibers.Flexural Test· Modulus ofRuptureSixty concrete beams (100 x 100 x 350mm) were tested inflexure (ASTM C78-75) after 7, 28 and 90 days. Figures 5 and 6 show the load-deflection curves forhooked and straight fibers with different volume content. Theload-deflection curvefor plain as well for fibrous concrete is linear up to point A (Fig. 5)and the strengthat A is called the first cracking strength. For plain concretebeams, cracking immediately leads to failure. Beyond point A, thecurve is non-linear due to the presence of fibers and reaches theultimate strength at B. After reaching the peak value,the flexural strength drops and attains a steady value of 60 to 70percent of the peak58
_ 20z"Cl"910o01.0I1.BmmII30 40 5.0 6.0 705%8.0DELECTION (mm)FIG. 6. Load-deflection curves for straight fibers.Properties andApplicatiollS ofFiber Reinforced COllcrele 59value in the case of hooked fibers. For straight fibers, the flexuralstrength goes on
dropping until failure, showing continous slippage of the straightfiber. This behaviour can be explained as follows. For the fibrousconcrete, once cracks are initiated, the fibers start working ascrack arresters. Use of fiber produces more closelyspaced cracks and reduces crack width. Additional energy isrequired to extend thecracks and debond the fibers from the matrix. The deformed endsof the hooked fibers contributed significantly to the increase inthe bond between fiber and matrix andextra energy is required for straightening the deformed endsbefore a complete debonding can take place.Figure 7 shows the effect of hooked fiber content on flexuralstrength after 7, 28and 90 days. The addition of 1.5 p rcent of hooked fibers givesthe optimum increaseof the flexural strength. It increased the flexural strength by 67percent, whereas theaddition of 2.0 percent straight fiber gives the optimum increaseof the flexuralstrength by 40 percent more than that of the plain concrete(compared to the 250 percent increase given in literatureI21 uing 4 percent fibers). At a high dosage of hooked
fiber (2 percent), the test specimens were difficult to consolidateand fibers wereprobably not randomly distributed. This caused a slight reductionin strength. Table2 and Fig. 4 show the comparison between the two fibers.....<S:IXX........u.....Cl<S:IX....<<S:=7 DAYS
12111098765 1--1_"-1-1- __28 DAYS o 90 DAYS0.0 0.5 1.0 1.5 2.0FIBER CONTENT (VI % IFIG. 7. Effect of hooked fiber contenl on flexural .-trength atL1ilkr<:nl a!!<:,.60 Faisal Fouad WafaSplitting TeosHe StrengthSixty concrete cylinders (150 x 300mm) were tested for splittingstrength (ASTMC496) after, 7,28 and 90 days. Fig. 8 shows the effect of hookedfiber addition on thesplitting tensile strength. It is clear that the highest improvementis reached with 1.5
percent fiber content (57 content more than plain concrete).Table 2 and Fig. 4 showthe comparison between hooked and straight fibers.8.--------------------------,o 7 DAYS • 28 DAYS 90 DAYS765......"z...I-430.0 0.5 1.0 1.5 2.01C)I- 2::!
....A."FIBER CONTENT (Vf 0/0FIG. 8. Effect of hooked fiber content on splitting tensile strengthat different ages.Toughness (Energy Absorption)Toughness as defined by the total energy ab orbed prior tocomplete separation ofthe specimen is given by the area under load-deflection curve.Toughness or energyabsorption of concrete is increased considerably by the additionof fibers. The toughness index is calculated as the area under theload deflection curve (Fig. 5) up to the1.8mm deflection divided by the area up to the first crackstrength (proportionallimit). The calculated toughness index for each mix is~iven inTable 3. All specimensmade of plain concrete failed immediately after the first crackand, hence, th~ toughness index for these specimens is equal to1. The addition of fiber increases the toughness index of hookedand straight fibers up to 19.9 and 16.9, respectively. The average
toughness index for pecimens reinforced with hooked fibers wa25 to 65 percent greater than that for specimens reinforced withstraight fibers.Properties and Applications ofFiber ReinforcedConcreteTABLE 3. Effect of fiber content on the toughness index.Fiber content(%)Toughness IndexHooked fibers Straight fibers0.0 1.0 1.00.5 11.4 9.21.0 18.0 11.11.5 19.9 13.62.0 16.7 16.961Impact StrengthFifteen short cylinders (150mm diameter and 63mm thick) werecast and tested forimpactl4] after 28 days. The results of impact test are given in Fig. 9.The rest results
show that the impact strength increases with the increase of thefiber content. Use of2 percent hooked fiber increased the impact strength by about 25times compared to10 times given in literature[21.4000~----------------------3600310026009ID2100 ...oaI:w1600(;:Z1100First Crack
o Failure174762337950.0 0.5 1.0 1.5 2.0FIBER CONTANT (Vf .,.)FIG. 9. Effect of hooked fiber content on the impact strength.h2Faisal FOllad WafaConclusionBased on the test of one hundred and ninety five specimensmade with the available local materials, the following conclusionscan be derived:1. No workability problem was encountered for the use of hookedfibers up to 1.5percent in the concrete mix. The straight fibers produce balling athigh fiber contentand require special handling procedure.2. Use of fiber produces more closely spaced cracks and reducescrack width. Fibers bridge cracks to resist deformation.3. Fiber addition improves ductility of concrete and its post-cracking load-carrying capacity.
4. The mechanical properties of FRC are much improved by theuse of hookedfibers than straight fibers, the optimum volume content being 1.5percent. While fibers addition does not increase the compressivestrength, the use of 1.5 percent fiberincrease the flexure strength by 67 percent, the splitting tensilestrength by 57 percent, and the impact strength 25 times.5. The toughness index of FRC is increased up to 20 folds (for 1.5percent hookedfiber content) indicating excellent energy absorbing capacity.6. FRC controls cracking and deformation under impact load muchbetter thanplain concrete and increased the impact strength 25 times.The material covered by this investigation mainly is concernedwith the mechanical properties of FRC using local materials.Researches are being conducted in theCivil Engineering laboratory of King Abdulaziz University on thestructural behavior of FRC members.References[I] Ramualdi, J.P. and Batson, G.B., The Mechanics of CrackArrest in Concrete, Journal of the Engineering Mechanics Division,ASCE, 89:147-168 (June, 1983).
[2J ACE Committee 544, State-of-the-Art Report on FiberReinforced Concrete, ACI Concrete International, 4(5): 9-30(May, 1982). Naaman, A.E., Fiber Reinforcement for Concrete, ACIConcrete International, 7(3): 21-25 (March,1985). ACI Committee 544, Measurement of Properties of FiberReinforced Concrete, (ACI 544.2R-78),American Concrete Institute, Detroit, 7 p. (1978). Halrorsen, T., Concrete Reinforced with Plain and DeformedSteel Fibers, Report No. DOT-TST76T-20. Federal Railroad Administration, Washington, D.C., 71 p.(Aug., 1976). Craig, R.J., Structural Applications of Reinforced FibrousConcrete, ACI Concrete International,6(12): 28-323 (1984). Abdul-Wahab, H.M.S., AI-Ausi, M.A. and Tawtiq, S.H., SteelFiber Reinforced ConcreteMembersunder Combined Bending, Shear and Torsion, RILEM Committee49-TFR Symposium, Sheffield,England (1986).
 Craig, R.J., McConnell, J., Germann, H., Dib, N. and Kashani,F., Behavior of Reinforced FibrousConcrete Columns, ACI Publication SP-81: 69-105 (1984). Swamy, R.N., AI-Taan, S. and Ali, S.A.R., Steel Fibers forControlling Cracking and Deflection,ACI Concrete International, 1.(8): 41-49 (1979). Henger, C.H., Worldwide Fibrous Concrete Projects, ACIConcrete International, 7(9): 13-19(1981).(II] Williamson, G.R., Response of Fibrous-Reinforced Concrete toExplosive Lading, U.S. Army Engineer. Division, Technical ReportNo.