BUILDING ACOUSTICS · Volume 19 · Number 2 · 2012 Pages 75–88 75

Impact Sound Insulation of LightweightConcrete Floor with EVA Waste

B. F. Tutikiana, M. F. O. Nunesb, L. C. Leala, L. Marquettoa

aCivil Construction Engineering Department, Universidade do Rio dos Sinos,RS, Brazil

bArchitecture Department, Universidade de Caxias do Sul, RS, Brazil

(Received 28 November 2011 and accepted 15 June 2012)

ABSTRACTThis study presents an evaluation of acoustic performance of lightweight concrete with EVAwaste to reduce impact noise on floors. Three types of concrete with three different mixproportions were evaluated and were made relationships between impact noise levels and resultsof water absorption, voids and density of the samples. The experimental study of noise impactfollowed the procedures of ISO 140. The results indicate that the lightweight concrete with EVArecycled aggregate can reduce impact noise levels by up to 15 dB and the highest percentage ofcoarse aggregate EVA does not entail a higher acoustic performance.

Keywords: Lightweight concrete, EVA residues, Impact noise insulation

1 INTRODUCTIONLightweight concrete is characterized by the use of low-density clusters with highamount of voids between the particles or by the replacement of solid material by air,which can be achieved through the incorporation of air or foam, or can be achieved alow specific mass producing concrete without fine structure.

The low density of the mixture is achieved due to the use of lightweight aggregateswhich incorporate specific characteristics such as low density, ranging from 300 kg/m3

to 1800 kg/m3, compressive strength ranging from 0.3 MPa and 70 MPa. The coarseand fine aggregates are considered lightweight when their density is less than 1120kg/m3 and less than 880 kg/m3, respectively. [1]

Lightweight aggregates can be classified according to their origin into two groups:natural and industrially produced, which could came from natural materials or industrialby-products [2].

Clay, vermiculite, perlite and expanded slate are examples of main naturallightweight aggregate produced from natural materials. These lightweight aggregatesare obtained by means of adequate heating in rotary kilns until the material is deep,reaching temperatures of 1,000 °C and 1200 °C. At these temperatures the expansion of

the material occurs due to the expulsion of the gases trapped in the plastic mass. Duringcooling, the structure remains porous and therefore the bulk density of the materialbecomes much smaller than it was early in the process [2].

All these features indicate that the lightweight aggregate can be used for acousticperformance qualification in buildings, especially for the impact noise isolation offloors.

The noise in buildings can spread through the air, when they receive the name ofairborne noise, or through the structures themselves, when they are called impact noise.The impact noise is produced by percussion of solid bodies and transmitted through theair (e.g. falling objects, footsteps, hammering, percussion instruments, etc. [3]

The transmission through the structure is the shortest and most direct pathtransmission of impact noise. A hard floor that deforms slightly before the impact, loadsand transmits in a very short time. While a deformable floor over the transmission timeis greater and therefore, the amplitude transmission of impact force is smaller. In bothcases the sound response is very distinct, and is produced higher frequencies in the firstsounds, and lowest in the second. [4]

Bistafa [5] explains that even in thick and dense concrete slabs, impact noise level isvery high. Even if the sound transmission level is reduced by increasing thickness, suchsolution is not adopted due to lack of efficiency and to increasing costs of material andstructure weight.

Brazilian standard NRB 15575-3 [6] characterizes residential building floors as theelement responsible for providing sound insulation, depending on use of distincthousing units or between rooms of the same unit, when for the night’s rest, domesticleisure and the intellectual work. Table 1 shows the performance rating criteriarecommended for the standardized weighted sound impact levels (L’nT, w) provided bythe structural slab.

Table 1. Brazilian recommended classification criteria for the acousticperformance [6]

76 Impact Sound Insulation of Lightweight Concrete Floor with EVA Waste

Layers with deformable elastic materials are very important as the first energyabsorption. Moreover, combined or not with these layers, the floating floors presentsthe most satisfactory results. [4]

Floating floors is the commonly used solution to reduce impact noise. It involvesplacing resilient material between the structural slab and the floor, which can improveby up to 20 dB isolation from the sounds of impact. Insulators (resilient materials) maybe rubber pads, cork and other materials evenly distributed, or plates of glass wool, rockwool, expanded polystyrene among others. [5]

Experimental studies have contributed to the development of products whoseperformance can be compared to traditional materials available in the market. Suchstudies evaluate and compare materials with different waste types used in mitigatingimpact noise floors. In these researches materials using waste carpet [7], recycledrubber [8] [9], coconut fiber [10] and waste industries footwear with PU and EVA [11][12] [13] provide performance similar to glass wool. The materials were used infloating floor system, as a layer between the sub floor and structural concrete slab.

The purpose of this study is to evaluate the acoustic performance of a new materialwith ethylene vinyl acetate copolymer (EVA) recycled aggregate as total replacementof conventional coarse aggregate in the production of lightweight concrete sub floor foruse in residential buildings.

3 MATERIALS AND METHODS3.1 MaterialsIn this study two types of coarse aggregate were used: natural and artificial. The naturalcoarse aggregate used was originated by granite rock, with maximum characteristicdimension of 9.5 mm. The choice for this type of natural aggregate for makingspecimens of reference is rooted in similar grain size of EVA coarse aggregate. Thenatural aggregate was previously washed, dried in an oven until constancy of weightand kept packed in sealed plastic container until used.

Characterization of aggregates of EVA was performed according to methodsspecified by ISO 6782 [14]. However, adjustments were necessary to enable the testingof EVA with lightweight aggregates.

In the granulometric analysis test conducted according to ISO 6274 [15], the sampleshowed mass difference during weighing of the fractions retained in the sieves in theweight of the total sample. The solution was to weigh both the total sample and thefractions only after constancy of mass, being held at a temperature of 60 °C [14] [16].

In the EVA aggregate specific mass test, which followed ISO 6783 [17], the samplesfloated when immersed, so it was necessary to make an adjustment to keep the EVAaggregate underwater. It was necessary to install a barrier screen at the test apparatus,in order to prevent the material floated to the surface.

The coarse EVA aggregate used in this study come from two types of recyclingprocesses. The coarse aggregate EVA, named EVA1, is an artificial aggregate obtainedfrom an industrial process that removes the dust generated in the grinding step of thewaste generated by EVA footwear industry in the metropolitan area of Porto Alegre city.

The coarse aggregate EVA, named EVA2, is an aggregate obtained through an

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artisanal recycling process of waste craft footwear companies in the Vale dos Sinoswhich is ground and wrapped for sale. In the production of this aggregate is not giventhe treatment EVA powder generated during the production. The choice for this type ofcoarse EVA aggregate is grounded in the possibility of comparing two different samplesof lightweight aggregates.

The concrete was cast with three different types of mortar. The mix proportion of1:1:4 features 80% of coarse aggregate to 20% fine aggregate; the content of mixproportion 1:1.5:3.5 is 70% of coarse aggregate to 30% of fine aggregate; and the 1:2:3mixture contains 60% of coarse aggregate and 40% of fine aggregate. The samples mixproportions and designations here adopted for each sample are presented in Table 2,resulting in nine samples of concrete tested.

Table 2. Concrete proportions prepared in laboratory

3.2 Water absorption, voids and specific massThe methodology adopted in this work uses procedures in accordance with ISO 6783[17]. The test was made after 28 days of curing with two cylindrical specimens with 100mm in diameter and 200 mm high for each concrete.

The specimens were dried in an oven at 60 ºC until they reached mass constace. Suchtemperature was adopted to preserve the EVA aggregates characteristics. After drying,the specimens piece were kept submerged in water during 72 hours in a climatized roomto a temperature of 23 °C ± 2 °C. Afterwards, they were boiled for five hours.

3.3 Acoustic performance To determine the weighted normalized impact sound pressure levels the specimens weretested using the method described by ISO 140-7 [18] and ISO 717-2 [19].

During the test execution sounds were generated with a normalised tapping machineBruel & Kjaer model 3207. The noises were generated in the source room, on the floorimmediately above the receiving room, where three measurements were carried out

78 Impact Sound Insulation of Lightweight Concrete Floor with EVA Waste

with the sound level analyzer Quest, in third octave bands in the frequency range 100Hz to 3,150 Hz in three different positions.

The rooms are separated by a structural concrete slab with a thickness ofapproximately 10 cm and have masonry walls coated with plaster and paint. The roomdimensions are 4.64 m x 3.5 m x 2.76, with a total area of 16.24 m2 and a volume of44.82 cubic meters. The sample tested was 1 m2 which consisted of four specimensplates of 50 cm x 50 cm x 3 cm.

The results treatment consists in obtaining single-number for the standard impactsound levels pressure (L’nT). This number results from the comparison of measurementsspectra curve and reference curve by ISO 717-2 [19], which expresses the acousticperformance of the floor system tested in dB. Were tested the nine samples prepared inthe laboratory and uncoated concrete slab.

4 RESULTS4.1 Materials characterizationThe cement used in the preparation of the specimens was the CPV-ARI, due to its highinitial resistance and the need to deform the material molded into plates with smallthickness compared to width and length. The results of the characterization of cementare shown in Table 3.

Table 3. Results of physical and mechanical cement CPV-ARI properties

It is observed that the analyzed properties of the cement CPV-ARI met the regulatoryrequirements, approving the material for testing.

Table 4 presents the physical characteristics of the used aggregates, includingnatural, fine and coarse, and the two types of EVA.

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Table 4. Physical characterization of aggregates

According to Table 4, it can be observed that the EVA1 aggregate has bulk densitycorresponding to 6% of the bulk density of the natural coarse aggregate; in contrast, forthe EVA2 aggregate this difference is 7%. Similar relationships are observed for the drysurface bulk saturated masses aggregate, showing that EVA aggregate has the densitywell below the natural aggregates, as was expected.

The bulk density was also lower for EVA aggregates. The EVA1aggregate presentedunit mass corresponding to 8.5% of unit mass of natural coarse aggregate, while theEVA2 aggregate had unit mass corresponding to 5% of unit mass of natural coarseaggregate. That is, the low mass of the EVA aggregates also occurs in the voidspresence.

The EVA1 aggregate had fineness modulus 4% lower than the natural coarseaggregate while the EVA2 aggregate of fineness modulus was 12% lower than thenatural coarse aggregate. As they have the same characteristic dimension and themaximum distribution of the particles, it is concluded that the aggregates are similar insize and distribution.

However, it can be seen that the EVA aggregates required more water to wet theirgrain than the natural aggregates and the aggregate of EVA2 will need more water towet their grain than the aggregate of EVA1 because EVA1 and EVA2 aggregates had awater absorption 42.5 and 44.5 times higher, respectively, than the natural coarseaggregate. However, the EVA2 absorption of water was 5% higher than the EVA1.

4.2 Water absorption, voids and specific mass Table 5 presents the results of water absorption, voids and specific mass of concretes.

80 Impact Sound Insulation of Lightweight Concrete Floor with EVA Waste

Table 5. Water absorption, voids and specific mass of concretes

It is observed that, in general, the concrete with EVA aggregates showed higherwater absorption, higher amounts of voids and lower specific gravity dry, saturated andreal.

It can be notice that most absorption occurs in trace 1:1:4, molded with EVA2aggregate, which had the highest water absorption. This sample had water absorptiongreater than 8.9 times the absorption of the reference trace and 2.2 times greater thanthe trace with EVA1 added. In parallel, the sample showed the highest percentage ofvoids was the dash 1:1:4 with aggregate EVA2 shaped, with a percentage of 38.56%.

It was also noted that the average specific mass EVA1 actual sample corresponds to46% of the specific mass of the sample trace reference, whereas the sample EVA2corresponds to 63% of the specific mass of the mark.

Among the concrete with EVA, EVA1 showed more satisfactory results than EVA2,with lower water absorption and voids. In terms of specific gravity, the behavior of themixtures was similar, although the samples with EVA1 had lower masses than the oneswith EVA2.

In addition, the lower the content of mortar, that is, the greater amount of coarseaggregate in relation to the fine aggregate, the lower values of bulk density. Forexample, the trace with EVA1 1:1:4 (E1a) had a dry bulk density 15% lower than thetrace with the same materials 1:1.5:3.5 and 18% that the characteristic 1:2:3.

4.3 Acoustic performance Figure 1 combines the results of all samples tested with their respective L’nT, pointingout that the sample called slab presents sound pressure levels without the use of materialbetween the slab and the tapping machine.

Sample Water absorption

(%) Voids (%)

Dry specific

gravity g/dm

Saturated specific

gravity g/dm

Specific gravity

g/dm

Na 4.87 11.53 2,370 2,480 2,670

Nb 3.11 7.53 2,420 2,500 2,620

Nc 2.40 5.75 2,400 2,460 2,550

E1a 19.65 17.58 890 1,070 1,080

E1b 17.08 17.76 1,040 1,220 1,260

E1c 12.28 13.33 1,090 1,220 1,260

E2a 43.54 38.56 890 1,270 1,440

E2b 29.53 32.95 1,120 1,450 1,660

E2c 20.77 27.11 1,310 1,580 1,800

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Fig. 1. L’nT sound pressure levels by frequency

It is verified that the results can be divided into three distinct groups in relation tocoarse aggregate mix proportions.

The samples with natural coarse aggregate had the highest measured values, and,among them, the lowest value was the sample with stroke 1:1:4 (Na). One can alsoobserve that the frequencies up to 160 Hz with natural aggregate samples showedhigher values than those of simple slab, featuring those frequencies near resonancefrequency, with the simultaneous vibration of the set, which leads to the amplificationof sound.

The second group, formed by the specimens EVA1 aggregate presented intermediatesound pressure levels at similar frequencies from 315 Hz, except for trace 1:2:3 (E1C),which showed higher values. The best results were obtained for specimens prepared onthe basis of EVA with a higher proportion of coarse aggregate, ie, with traces of 1:1:4and 1:1.5:3.5, which had submitted the lowest densities. Still, the specimens with EVA1residues on the 1:2:3 mix proportion presented sound pressure levels above the simple

82 Impact Sound Insulation of Lightweight Concrete Floor with EVA Waste

slab at frequencies of 125 and 160 Hz, with the influence of the resonance frequency ofthe system.

In the third group, one can check the different behavior of the sample with 1:1.5:3.5(E2B) mix proportion, which, as of 2,000 Hz, the specimens showed similar results ofthe second group. In general behavior, the third group, using the EVA2 aggregate, gaveresults intermediate between the concrete and the reference EVA1.

The L’nT,w values can be comparatively analyzed in Figure 6, with the grouping bytype of material composition of the specimens.

Fig. 2. Weighted standardized impact sound pressure level of samples

The samples with natural coarse aggregate obtained results between 71 and 72 dB,with a minimum performance rating for structural concrete slabs and outside theminimum performance standards for affordable coverage. It is observed that thevariation of the ratio coarse aggregate and fine aggregate had little influence on the finalresults. Since the samples with EVA1 results showed greater variation, between 54 and62 dB, and only specimens with 1:1.5:3.5 mixture can be classified with superiorperformance. In the specimens prepared on the basis of EVA2 results ranged from 56 to62 dB, with minimum performance rating for roof terrace and intermediate affordable.

Table 6 illustrates the classification of each of the mixtures over the limitsestablished by NBR 15575 [6].

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Table 6. Brazilian classification for each specimen type

4.4 Relationship between Impact noise and voidsThe test results of impact noise and amount of voids showed an inverse relationship, ascan be seen in Figures 3, 4 and 5. It can be said for the specimens studied in this article,the increase in amount of voids leads to better performance acoustic slabs and toppingsavailable.

Fig. 3. Relationship between impact noise and voids: samples of natural courseaggregate

Specimen Slabs performance Roof terrace performance

Na M No classification

Nb M No classification

Nc M No classification

E1a I M

E1b S I

E1c I M

E2a I M

E2b I M

E2c I M

84 Impact Sound Insulation of Lightweight Concrete Floor with EVA Waste

Fig. 4. Relationship between impact noise and voids: samples of EVA1 courseaggregate.

Fig. 5. Relationship between impact noise and voids: samples of EVA2 courseaggregate.

4.4 Relationship between impact noise and dry bulk densityThe relation between the impact noise level and dry bulk density showed variationbetween the results of natural aggregate specimens and specimens with added EVA.Most of the increase results from the dry density caused worse acoustic impact noiseperformance in the specimens studied. In specimens with natural aggregate reduction inthe proportion of coarse aggregate resulted in increases in noise levels measured.However, the dry density did not follow the same trend, with a reduction in valuebetween Nb and Nc specimens, with 70% aggregate and 60% respectively (Fig. 6).

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Fig. 6. Relationship between dry bulk density and impact noise levels: samplesof natural course aggregate.

Specimens with EVA industrialized process residues the reduction in the proportion ofcoarse aggregate rise higher values of dry density. However, changes in these proportionsdid not follow the same trend in noise levels measured, as it observed in Figure 7.

Fig. 7. Relationship between dry bulk density and impact noise levels: samplesof EVA1 course aggregate.

The group of specimens prepared with EVA residues obtained by means of recyclingcraft had more direct relationships between the dry density increases and noise levelsmeasured. In Figure 8 these relations can be observed comparing the two upwardgraphs profiles, indicating that the increase in dry density corresponds to an increase innoise levels measured. In these specimens group the increase in dry density andreduction in the proportion of coarse aggregate contribute to the worst performance ofimpact noise.

86 Impact Sound Insulation of Lightweight Concrete Floor with EVA Waste

Fig. 8. Relationship between dry bulk density and impact noise levels: samplesof EVA2 course aggregate

5 CONCLUSIONSThe concrete molded EVA had lower levels of density of fresh concrete in comparisonwith the reference mix proportion. It can be argued that the higher the percentage oflightweight aggregate added to the mix, the lower values of density.

In testing, the impact noise lightweight concrete achieved the best acousticperformances, with satisfactory performance for structural slabs. In the case ofcoverage available, the classification of acoustic performance decreased. However,other available coatings that can help with soundproofing should be considered in roof.

It was noted that the incorporation of EVA material as resilient in the sub floor tobreak the rigidity of floors in the system has good efficiency. However, it also showsthat the highest percentage of coarse aggregate EVA does not match the performance ofacoustic noise impact. In the samples studied the reduction of 80% to 60% of coarseaggregate resulted in better acoustic performance, with 15 dB in noise levels reductionmeasured, and 77 dB to 62 dB.

The relationships obtained between the measured sound levels, voids and bulkdensity indicate that the major benefit in reducing the weight provided by thelightweight aggregate structures could be a higher acoustic quality in concrete floors.

REFERENCES [1] ISO 22966 Execution of concrete structures, 2009.

[2] R. S. Polari Filho, Contribution to the process of the footwear industry wasterecycling in civil construction, João Pessoa, Paraíba, 2005.

[3] J. Pujolle, La pratique de l´isolation acoustique des batiments, Paris: Moniteur,1978.

[4] V. M. Sancho and A. G. Senchermes, Acustica en arquitectura, Madrid: ColegioOficial de Arquitectos, 1982.

[5] S. R. Bistafa, Noise control applied, São Paulo: Edgard Blücher, 2006.

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[6] ABNT, NBR 15575 Residential buildings up to five floors - Performance, Rio deJaneiro: ABNT, 2008.

[7] I. M. Rushforth, M. Horoshenkov, M. Miraftab and M. J. Swift, “Impact soundinsulationand viscoelastic properties of underlay manufactured from recycledwaste,” Applied Acoustics, vol. 66, pp. 731-749, 2005.

[8] M. A. T. Pedroso, Comparative study of the modern compositions of floatingfloors for performance in impact sound insulation, Santa Maria, 2007, p. 141 p.

[9] R. Maderuelo-Sanz, M. Martín-Castizo and R. Vílchez-Gómez, “Theperformance of resilient layers made from recycled rubber fluff for impact noisereduction,” Applied Acoustics, vol. 72, pp. 823-828, 2011.

[10] L. Morais, A. Pereira and L. Godinho, Experimental characterization of theimpact noise insulation of floating slab systems and floating floor system using asmall footprint, Natal: ANTAC, 2009.

[11] M. F. d. O. Nunes and J. Rauber, EVA waste material to reduce transmission ofimpact noise, São Paulo: EDUSP, 2010.

[12] M. F. d. O. Nunes, M. Z. Andrade, A. M. C. Grisa, A. J. Zattera and A. N.Menegotto, Evaluation of polymeric material with waste in impact noisereduction on floors, Canela: ANTAC, 2010.

[13] S. P. P. Hax, Study the potential of waste EVA impact noise insulation in buildings,Santa Maria: Federal University of Santa Maria, 2002, p. 111 p.

[14] ISO 6782 Aggregates for concrete - Determination of bulk density, 1982.

[15] ISO 6274 Concrete - Sieve analysis of aggregates, 1980.

[16] E. Q. R. Santiago, Use of the EVA aggregates and RCD to obtain lightweightconcrete, Feira de Santana, Bahia: Programa de Pós-Graduação em EngenhariaCivil e Ambiental, 2008.

[17] ISO 6783 Coarse aggregates for concrete - Determination of particle density andwater absorption - Hydrostatic balance method, 1982.

[18] ISO 140 Acoustics: measurement of sound insulation in buildings and of buildingselements, 1998.

[19] ISO 717 Acoustics: rating of sound insulation in buildings and of buildingelements, 1996.

[20] ISO 3310 Test sieves - Technical requirements and testing, 2000.

[21] ISO 9597 Cement - Test methods - Determination of setting time and soundness,2008.

[22] ISO 1920 Testing of concrete, 2004.

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