interpretation of hydrophobicity in concrete by …the enhancement of durability of reinforced...

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Int. J. Struct. & Civil Engg. Res. 2013 M N Balakrishna et al., 2013

INTERPRETATION OF HYDROPHOBICITYIN CONCRETE BY IMPREGNATION

M N Balakrishna1*, M M Rahman1, D A Chamberlain1, Fouad Mohammad1 and Robert Evans1

The durability of reinforced concrete structures is greatly affected by corrosion of steelreinforcement through chloride attack. The use of impregnates is the most widely employedmethod to tackle chloride attack for structures in the UK. Impregnate manufacturers and DMRBstandards stresses the use of impregnates on dry surfaces, achieving a dry surface is easyhowever moisture below the surface exists and this can affect the performance of theimpregnates. The Concrete cubes were cast and cured, before being submerged in a waterbath to determine their moisture content at various times. The cubes were surface dried, waterand silane based impregnates were applied and then submerged in salt solution. The cubeswere dry drilled at various depths of 5-20 mm for dust samples, which were used to obtainchloride concentrations by the method of Volhards titration. The performance of impregnates isdependent on the quality of concrete, as it directly influences the pore structure which in turndetermines the rate of chloride ingress. Impregnate application on dry surface showed a chlorideconcentration of 0.029% at 20 mm. However impregnates applied to a dry surface, but with amoisture content of 1.88% showed a chloride concentration of 0.053%. This indicates theperformance of impregnates is effected by moisture. Although solvent based impregnateperformed better than the water based in dry condition, their performance are similar whenapplied in the moist concrete.

a School of Architecture, Design and Built Environment, The Nottingham Trent university, Burton Street, Nottingham, NG1 4BU, UK.

*Corresponding author:M N Balakrishna,[email protected]

ISSN 2319 – 6009 www.ijscer.comVol. 2, No. 4, November 2013

© 2013 IJSCER. All Rights Reserved

Int. J. Struct. & Civil Engg. Res. 2013

Research Paper

INTRODUCTIONIt has been estimated that the value of theinfrastructure built environment representsapproximately 50% of the national wealth ofmost countries within Europe. Because of thisthe degree and rate of degradation of the built

Keywords: Deterioration, Durability, Impregnate, Sorption test, Initial Surface AbsorptionTest (ISAT)

environment in Europe is of enormouseconomic and technical importance. When itis borne in mind that approximately 50% of theexpenditure in the construction industry inEurope is spent on repair, maintenance andremediation then it is evident that even

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marginal savings could result in the release ofsubstantial funds for new developments. Onespecific area which is assuming an increasingproportion of the costs in most countries is thepremature deterioration of concrete structures.It has now been recognized that this lack ofdurability, relative to that anticipated, needs tobe addressed as a matter of urgency. A similarsituation exists in countries where much of theirdevelopment has taken place in this century.However, the proportion of concrete structuresis relatively higher than in Europe. For examplein the United States, conservative estimatesof the current cost to rehabilitate deterioratingconcrete structures are in the 100 billion dollarrange. It is evident, therefore, that thedeterioration of concrete structures is a majorproblem in almost all parts of the world.

The mechanisms of deterioration and theirrate are controlled by the environment, thepaste microstructure and the fracture strengthof the concrete. Environmental factors such asseasonal temperature variations, cyclicalfreezing and thawing, rainfall and relativehumidity changes, and concentration ofdeleterious chemicals in the atmosphere waterin contact with the concrete are the maincauses of degradation. However, the singlemost important parameter that leads topremature deterioration is the ingress ofmoisture into the concrete (Basheer, 1996 andMehta, 1994). Permeability of concrete to themacro-environment during its service lifetherefore can be used as a measure of itsdurability. Moisture is continuously transportedin the form of liquid and vapor from either thesurrounding environment or the internal bodyof the concrete if the surface is relatively dry.The rate of water and ion ingress through the

concrete depends on the physical structure ofthe paste. Precise characterization of thisphysical structure is, however, extremelydifficult, if not impossible. Therefore averagevalues of permeability, porosity, diffusivity andsorptivity have to be used to model thetransport mechanisms through the complexpore structure. The durability of concretesubjected to aggressive environmentsdepends largely on the penetrability of the poresystem (Sabir et al., 1998). The main transportprocesses which describe the movement ofaggressive substances through concrete canbe categorized as follows such as Absorption,where concrete takes in liquid by capillarysuction to fill the pore space available(McCurrich, 1985 and Nevile, 1995).Permeability, where a fluid passes intoconcrete under the action of a pressuregradient (Perraton, 1992). Diffusion, where aliquid, gas or ion migrates through concrete,due to a concentration gradient (Perraton,1992).

The concrete is a well-known constructionmaterial in civil engineering practice used inmany forms and applications. Howeverconcrete suffers from being a porous material,allowing moisture to penetrate the surface andenter through its surface pores. This is anundesired characteristic which could lead todeteriorating outcomes, affecting its physicalfunctionality, aesthetics and durability in servicelife. In fact application of impregnate materialstreatment have been developed to protectbuilding materials such as masonry andconcrete from water ingression which in turnwill prolong service life and durability. Thehydrophobic impregnate materials is the onewhich lines the surface pores providing

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protection from water ingress, but allows thesubstrate to breathe, moisture to diffuse outand not become trapped internally. Thus in thepresent research work an attempt was madeto investigation, the effect of Hydrophobicityby considering two different Grades ofconcrete and hydrophobic impregnates incase of Sorption test and ISAT to procure rateof flow of water with differential time durationwithout hydrophobic impregnate material.

LITERATURE REVIEWThe enhancement of durability of reinforcedconcrete is typically associated with a denseconcrete matrix, i.e., a very compactmicrostructure expected to lower permeabilityand reduce transport of corrosive agents tothe steel (Beeldens, 2001). This can beachieved with a well graded particle sizedistribution (Hwang et al., 1996),supplementary cementitious materials such asfly ash and silica fume (Chang et al., 2001), orlow W/C ratios (Mehtam, 1996). Theseconcepts, however, rely upon the concrete toremain uncracked within a structure throughoutits expected service life and resist the transportof water, chloride ions, oxygen, etc. In thispresumed uncracked state, numerousconcrete materials have shown promisingdurability in laboratory tests (Weiss, 2002). Inreality, however, reinforced concrete memberscrack due to both applied structural loading,shrinkage, chemical attack and thermaldeformations, which are practically inevitableand often anticipated in restrained conditions(Mihashi, 2004). The durability of concretestructures is intimately related to the rate atwhich water is able to penetrate the concrete.This is because concrete is susceptible to

degradation through leaching, sulfate attack,freezing-and-thawing damage, and othermechanisms such as steel corrosion inreinforced concrete structures that depend onthe ingress of water. Because crackssignificantly modify the transport properties ofconcrete, their presence greatly acceleratesthe deterioration process.

Similarly in Initial surface absorption test,the rate of penetration of water into a definedarea of concrete (5000 mm2) after intervals of10, 30 and 60 min at a constant water head(200 mm height) and temperature (200C) ismeasured. There are specifications forpreparing the test area, initial moisturecondition, surface area to be in contact withwater and the time at which measurementshave to be taken. The guidelines on the testmethod, calibration and sample preparationare available in BS 1881: Part 208 (1996). Themain advantage of this test is, that it is a quickand simple non-destructive in situ test formeasuring the water penetration into aconcrete surface. This test method providesreasonably consistent results on oven driedsamples. The limitations of this test include thedifficulty of ensuring a water tight seal in siteconditions, the influence of the moisturecondition of concrete on measured propertyand insufficient water head. The initial surfaceabsorption is defined as the rate of flow of waterat a constant applied head and temperatureinto the concrete surface per unit area at astated interval from the start of the test (Bungey,1989). The first version of this test [16] wasfurther developed into a commercial test andincorporated into the British Standards. Bymonitoring the movement of the water in thecapillary tube the initial surface absorption

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value can be calculated in units of ml/m2/s. Themain advantage of the ISAT is that it is a quickand simple non-destructive in situ test methodwhich can be used to measure the waterpenetration of a normal cast concrete surface.It can also be used on exposed aggregate andprofiled surfaces provided a water-tight sealis achieved. The practical difficulty of ensuringa water-tight seal is probably one of the test’sgreatest limitations but another limitation is thatthe measured property is greatly affected bythe moisture condition of the concrete. This,however, applies to nearly all near-surfaceabsorption and air permeability tests and isbest summarized by a quote from Neville(1995). The lower value of initial surfaceabsorption may be due either to the inherentlow absorption characteristics of the concretetested or else to the fact that the pores in poor-quality concrete are already full of water. Thusthe main application of the ISAT is as a qualitycontrol test for precast concrete units whichcan be tested whenever they are dry. A newmethod for testing concrete using the initialSurface Absorption Test (ISAT) has beendeveloped for site use which was conductedby Dhir (1993). It is based on applying avacuum to an ISAT cap placed on the concretesurface until drying is achieved. The progressof the drying is monitored by placing indicatingsilica gel desiccant in the ISAT cap andobserving the color change. The method isquick, simple and practical for in situapplications. Results of comparisons with theexisting in situ method in BS 1881 show thatthe new method is potentially more capable ofproducing reliable and reproduciblemeasurements and therefore will allow bettercomparison of in situ and laboratory-obtained

data.

Another research work carried out by [19]discusses the current approach for specifyingconcrete durability in structures. Theshortcomings of the use of bulk parameterssuch as strength, water-binder ratio, andbinder content to specify durability arediscussed. Studies carried out over the last10 years at Dundee University, using simplepermeation tests, which are sensitive to curing,cement type, and concrete grade, have shownclose association between permeationproperties and concrete durability. Paper dealswith the measurement of concrete durabilityby the Dundee-modified Initial SurfaceAbsorption Test (ISAT). A wide range ofconcrete mixes made with ordinary Portlandcement and blends with Pulverized Fuel Ash(PFA) and ground granulated blast furnaceslag were designed. The duration of moist-curing was varied from 0 to 28 days, and themaximum aggregate size ranged from 5 to 40mm. All mixes were tested for absorptivity anddurability, including freeze-thaw resistance,carbonation, chloride ingress, and mechanicalwear. Results show that the absorptivity ofconcrete, measured with the ISAT, can be usedas an accurate specification for concretedurability, irrespective of curing, grade, or mixconstituents. A tentative surface absorptivityclassification for durability has been proposed.The investigation carried out by [20] inferredthat water absorption of mortar modified withcombinations of polymer and pozzolan byusing initial surface water absorption test.Since surface of mortar or concrete serves asmedium that will be most easily penetrated bymoisture that can cause corrosion ofreinforcement that leads to durability problem,

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it’s imperative to make it durable. Polymeradditive and pozzolanic cement replacementused in this study was Styrene ButadieneRubber (SBR) and Fly Ash (FA) respectively.Mixes were prepared with two w/c ratio of 0.3and 0.4 with different combinations of 5%, 7%,and 10% SBR additive and 10%, 20%, and30% FA cement replacement. Results showedthat modified mortar with combinations ofhigher percentages of polymer additive andlow percentages of pozzolanic cementreplacement have the lowest initial surfaceabsorption rate compared to unmodifiedmortar. It can concluded based on this studythat high percentage of polymer addition andlow percentages of pozzolanic cementreplacement in mortar can increase itsresistance to water absorption. The effect ofcuring conditions and silica fume replacementon the compressive strength and the initialsurface absorption of high performanceconcrete is reported by Al-Oraimi (2007). Thesilica fume contents were 5, 10, 15 and 20%,by weight of cement. Four different curingconditions were used: air curing, control curingand two other curing conditions recommendedby BS8110 and ACI308-81. The cementitiousmaterial (binder) content was constant (400kg/m3); the water/cement (w/c) ratio was alsomaintained at a constant value of 0.35; whilethe water/binder (w/b) ratio ranged from 0.35to 0.28. The addition of silica fume enhancedthe compressive strength significantly up to30%.

The 28-day compressive strength wasfound to be 69.9 MPa without silica fume andit was determined to be 89.9 MPa with silicafume under the standard curing condition. The28-day compressive strength results under the

control curing condition were found to be higherthan the compressive strength for specimenscured under other curing conditions. Thesurface absorption (ml/m2/s) was found todecrease as the percentage replacement ofsilica fume was increased. Control curing alsodecreases the surface absorption of watercompared with air curing. Concrete with silicafume was less sensitive to drying than thatwithout silica fume. The deterioration ofconcrete structures is a major problem in manycountries throughout the world. This hasprompted the search for methods of predictingthe service life of both existing and newstructures. Current prediction methods are stillin their infancy and, before they can be usedwith confidence, more reliable information onthe properties of the concrete in thesestructures will be required. The different rangeof test methods for determining the strengthand transport properties and the extent ofcorrosion are critically reviewed by Long(2001). Whilst all provide useful information theability to measure the transport properties hasbeen shown by many researchers to give themost reliable indication of the likely durability.In spite of this it is recommended that anholistic overview is adopted as no single testis sufficiently reliable at present. Using suchan approach, durability-based design criteriacan be developed for concrete and theremaining life of existing structures estimated.Furthermore research conducted byinvestigator presents the results of anexperimental data on the water absorption andsorptivity properties of mechanically loadedEngineered Cementitious Composites (ECC).It is a newly developed high performance fibrereinforced cementitious composite with

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substantial benefit in both high ductility andimproved durability due to tight crack width.By employing micromechanics-basedmaterial design, ductility in excess of 3% underuniaxial tensile loading can be attained withonly 2% fibre content by volume, and the typicalsingle crack brittle fracture behavior commonlyobserved in normal concrete or mortar isconverted to multiple micro cracking ductileresponse in ECC as noted by Mustafa (2009).

Thus in the present research work anattempt was made to investigation the effectof Hydrophobicity by considering two differentGrades of concrete and hydrophobicimpregnates in case of Sorption test and ISATto procure rate of flow of water with differentialtime duration without hydrophobic impregnatematerial. The permeability, which is a measureof the flow of water or various gases underpressure gradient, is generally used toexamine durability characteristics of concrete.It is of significance where concrete is exposedto water pressure such as water retainingstructures. However, in structures locatedabove ground level, measurement of capillarywater absorption (sorptivity) characteristics ofconcrete would be more appropriate. Capillarywater absorption of concrete is measured byallowing all face of a concrete specimen to bein contact with water and to determine the rateof absorption of water through substrates by

inspection of changes in mass

EXPERIMENTAL WORKIn order to achieve the objectives, a series oftests such as Sorption could be carried out toevaluate the effectiveness of impregnation incase of case of impregnated as well as controlconcrete cube and also ISAT could beconducted on concrete cube withoutimpregnation. In fact both tests were to beconducted within laboratory conditions onconcrete cubes of size 100 mm3. In whichconsidered two Grades of concrete (C30 andC40) and produced total number of 24concrete cubes, where in which split up intotwo groups of 12 for each Grade of concrete.Also selected two types of impregnate materialsuch as Solvent Based (SB) as well as WaterBased (WB) impregnant material for thisinvestigations. To determine the effectivenessof these two impregnants, these concretecubes will be divided into three groups suchas solvent based impregnation, water basedimpregnation and a control variable. Thesecubes will undergo a series of experiments toproduce comparative data to determine whichform of impregnant performs the mosteffective. The concrete cubes will be testedvia Sorptivity tests, before and afterimpregnation is applied, and an Initial SurfaceAbsorption Test (ISAT) without impregnation.The concrete used for investigation saw theproduction of 24 concrete cubes, sized at 100

Table 1: Mix Proportions of Concrete (kg/m3)

Concrete Grade Water (Kg) OPC (kg) Sand (kg) Aggregate(10mm) (kg) Total Mass (kg)

C30 2.3 4.3 8.9 14.3 29.8

C40 2.0 3.4 9.4 14.2 29.0

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mm3, with twelve cubes forming C30 and theother twelve at C40. These concrete cubesamples have been made following BritishStandards. The mixture ingredients used forthe production of concrete cubes are as shownin the Table 1.

SORPTIVITY TESTAfter 28 days of curing the concrete needs tobe fully dried and preconditioned before anytests and experiments can continue. Thisrequires the concrete specimens to be placedin an oven to dry off and eliminate any internalmoisture that may have been left in. The ovenis set at 100°C and dried overnight as well aswiping down the sample surface ensures thatany loose aggregate is removed and thereforenot considered within the results. The Sorptivitytest is an experiment, which is employed todetermine the rate of absorption of waterthrough substrates by inspection of changesin mass. The Sorptivity measures the rate ofwater ingress through the concrete byrecording an initial dry mass of the concrete,saturating the sample cubes in water andrecording the values of the concrete mass atdifferent time intervals. The change in masscompared to the original mass values willindicate how much water has entered theconcrete and will determine the rate of waterpenetrates the concrete interior by the time itwas recorded. This test was conducted byrecording the masses of the concrete samplesat different time intervals such as 5 min, 10min, 30 min, 1 h and 24 h. The initial massesof the dry concrete cubes are recordedindividually, using the digital scale andrecording values to the nearest 2 decimalpoints. The concrete cubes are then saturatedin the water bath filled with water at room

temperature. After 5 min of saturation, thecubes are then taken out, and instantly wipedby using the cloths. This removes any excesswater from the substrate samples and that theexterior is wiped dry. The cubes are thenweighed again and recorded. The change inmass will indicate that there has been watertransport through the concrete and that thevalues of mass recorded represent the originalmass of the concrete with additional massmade from water build up within the concreteinterior. This method is repeated for the timeintervals at 10 min, 30 min, 1 h and 24 h. Theconcrete cubes are sorted into two groupsdifferentiated by their concrete grades (C30and C40), these concrete samples need to bedivided further, into groups of three. Thesegroups separate the concrete cubes by theirimpregnant materials, a control, solvent basedand water based impregnants. C40 Concretecubes (100 mm3) x 12; Control (noimpregnation) x 4; Water based impregnationx 4; Solvent based impregnation x 4 and C30Concrete Cubes (100 mm3) x 12; Control (noimpregnation) x 4; Water based impregnationx 4; Solvent Based Impregnation x 4. As thesecubes have been already labelled 1-12 foreach concrete grade to help identify themindividually. The first four cubes were notexperience any impregnant treatment and willact as the control variable. Cubes 5-8 will haveSB impregnants applied and cubes 9-12 withWB impregnants. On usage of impregnationapplication, it is essential that the concretecubes have been preconditioned and fullydried initially and that the surfaces have alsobeen cleaned, dried and dust free. This is sothat the impregnant materials have beenproperly applied and so that more accurate

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and reliable data can be obtained. In order toproceed with this method, using acompressed air gun, fire compressed air overthe concrete surfaces to remove dust and anyloose aggregate from the surface. This is sothat the impregnant layer can be suitablyapplied. The impregnant is applied using abrush and takes up to 4 h-1 day to completelyset and ready to be worked on. In order to havethese concrete samples readily available fortesting it is important that they are left to dryand are protected from rain or water for at least24 h to prevent any washout of the waterrepellent agents and that a fair test can beconducted and reliable results and recordingscan be acquired.

INITIAL SURFACE ABSORPTIONTEST (ISAT)The ISAT is the test procedure developed bythe British standards in accordance to (BritishStandards BS 1881-5, 1970) and (BritishStandards BS 1881-208, 1996). This testprocedure is one, which is carried out underlaboratory conditions and is designed in thepresent research work to determine the rateof flow of water into concrete at 10 min, 30min and 1 h. It is the investigation of the porosityof concrete and water penetration via capillarysuction through a specified unit area.

RESULTS AND DISCUSSIONSorptivity Test

From the findings made regarding theSorptivity test, the results provided a goodgauge in the rate of absorption throughconcrete. Where the change in mass over timeindicates the increase in percentage ofmoisture content building up within the concrete

interior. Two Sorptivity tests were carried outbefore and after the application ofimpregnants. The first Sorptivity test identifiedthe nature of unprotected concrete and the rateof which water enters it. The second test wascarried out after the impregnant agents wereapplied to their respective cubes andabsorbed the effected performance in wateringression between two Solvent-based, Waterbased and a control. The results from the

Figure 1: Averaged Initial Sorptivity

second Sorptivity provided comparativevalues between these three variables toidentify which impregnant materials performthe best and by how much.

The graph shown in Figure 1 shows theaveraged recordings of the increase in massover time between C30 and C40 concretebased on the Sorptivity readings. It can be seenfrom the graph that a similar trend is occurringin the rate of water ingression throughuntreated concrete. It can be identified that thecharacteristics in water absorption betweenthe two concrete grades are alike and that theyboth allow water to flow through the concreteat a very similar rate. From the Figures 2-3, itis clear based on average Sorption result thatthe cubes impregnated with Solvent-based

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impregnants performed more better than theControl and Water-based impregnatedconcrete cubes. This is identified by the low

moisture content maintained throughout theexperiment, significantly lower than the Water-based impregnated samples and it is alsoproven to be most effective in both Grades ofconcrete.

The results from the second Sorptivity testshows the changes in mass of the concretecubes and the effects after impregnantmaterials have been applied. In which concretecubes 1-4 without impregnation and are usedas a control specimen to comparative values

with concrete cubes 5-8 and 9-12 which haveSolvent-based and Water-based hydrophobicimpregnants applied respectively. Afterrevising these results, it was found that thechange in mass from its initial mass recordingsafter 24 h of saturation, the impregnantmaterials applied to concrete cubes 5-12could achieved significant reductions in waterpenetration. These results indicate that thesecubes do not completely stop the penetrationof water through the substrate material but theapplication of impregnants make significantreductions in water ingression. In comparison,the control samples experience a higher rateof water ingression compared to the rest of

Figure 2: Average Sorption Resultsfor C30 concrete

Figure 3: Average Sorption Resultsfor C40 concrete

Figure 4b: Moisture Content viaSorptivity with Control samples at C30

Figure 4a: Sorptivity Resultsin Control Samples at C30

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Figure 5a: Sorptivity results in SBsamples at C30

Figure 5b: Moisture Content viaSorptivity with SB samples at C30

Figure 6a: Sorptivity results on WBsamples with C30

Figure 6b: Moisture Content viaSorptivity with WB samples at C30

Figure 7a: Sorptivity results on Controlsamples at C40

Figure 7b: Moisture Content viaSorptivity with Control samples at C40

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Figure 8a: Sorptivity results on SBsamples at C40

Figure 9a: Sorptivity results on WBsamples with C40

the cubes, where the masses at each timeintervals are consistently increasing. TheSorptivity results in Control, Solvent and Waterbased concrete cube can be represented inthe Figures 4(a)-9(a) and Moisture contentvariation with Sorptivity which is also shown inFigures 4(b)-9(b).

The graphs have been separated betweenthe Grades of concrete and grouped basedon the type of impregnation applied. The firstgraphs, labelled 4(a)-9(a) are presentedacross a logarithmic time scale displaying thechanges in mass over different time intervals.The graphs labelled 4(b)-9(b) demonstrate theincrease in moisture content over the squareroot () of the time intervals. It could beobserved from the graphs above, based onthe Sorptivity experiments carried out, it’s clearthat both forms of impregnant materialssuccessfully work in the protection of concretefrom water penetration. However it can alsobe seen that the impregnated cubes do notcompletely prevent water penetration, and thatthere is still some water entering it. Betweenthe two types of impregnant materials, it canbe seen from the graphs that the Solvent-

Figure 8b: Moisture Content viaSorptivity with SB samples at C40

Figure 9b: Moisture Content viaSorptivity with WB samples at C40

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based product performs more efficiently in theprevention of water intrusion through theconcrete. This is backed from both resultscarried out on the two concrete grades wherein which concrete cubes 5-8 maintain a fairlyconsistent mass over the increase of time andincreases small fractions of percentage ofmoisture content. The water-based productshows a similar trend in mass increase overtime between the two Grades of concrete , andthey do not perform as well as the resultsobtained by the solvent based impregnants.Comparing the all the outcomes from theSorptivity tests, the Grade of concrete C40permits more water through the substrate morethan in C30.

Initial Surface Absorption Test

The results show from (Figures 10 to 18) thatin both Grades of concrete (C30 and C40),the first four concrete cubes shows higher flowrate of water ingression in case of withoutimpregnation. The results also indicatesignificant effective performance in caseimpregnation. In reference to cubes samples1-4, Grade of concrete C40 absorbs a higherflow rate of water than in C30. As it was earlier

Figure 10: Flow rate/timefor Cube 1, C30




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identified that if the graduation of the water leveldecreases 20% or more within 20 min it isconsidered as a failure. Where 20% of the tubeis marked at the 1 ml graduation, the resultssuggest that the C40 concrete control cubeshave experienced failure whereas in C30, itcan be identified that none of the concretesamples can be considered as failed.

From the results shown in the graphs above(Figures 10 to 18), there is a general gradualdecrease trend in flow rate of water with theincrease in time during the ISAT test. It can be





Figure 18: Average Flow rate/time forCubes, C30 &C40

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observed from these graphs that the rate offlow of water by capillary action slowlydecreases as time increases represented ingraphs. Results also indicate where the timemeasured is extended for 2 min, the flow rateat that given time is higher than what would bepredicted from this trend identified. Takingaverages from the readings between the twoconcrete grades it can be absorbed that C30experiences a greater flow rate of water and ahigher fall in flow over time. This is due to thefact that where more than 30 divisions havepassed within 5 s and flow rate is then alreadydetermined as 3.60 (ml/m2/s).

CONCLUSION1. It could be confirmed from the present

research that the Solvent-basedimpregnant, Alkylalkoxysilanes baseperforms most effectively in the process ofwater ingress and its represented by itsconsistency results in both Grades ofconcrete as concerned

2. In the ISAT experiment it was found that, it isnot possible to determine the bestperforming impregnate material by usingBritish Standards method from this test.

3. Based on the results obtained by theexperiments conducted, it can beconcluded that, generally hydrophobicimpregnants provide good protection fromthe ingress of water through the concrete.However, where it was found that the testsconducted do not reflect the long-termeffects of impregnate on water ingress. Thiswould suggest that the requirement of furtherdevelopments in the testing methods to fully

investigate how effective impregnants areduring long-time duration.

4. It could be determined from research thatbetween two Grades of concrete (C30 andC40), the initial Flow rate of water throughuntreated concrete is relatively the samewhich is represented in the similar gradientlines from the results.

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