The use ofWaste Materials in Utility Poles , Crossarms , Paver , and Reef Balls Concrete Structures : Advantages and Care

Industrial residues such as sludge from water treatment plants (Swtp) from centrifuged method; electrical porcelain residues (Pw); silica fume (Sf1 and Sf2); tire-rubber waste were evaluated in order to be used in concrete structures of electrical energy and environmental sectors, such as utility poles, crossarms, and reef balls technology. e results showed the necessity for evaluating different recycling concentrations in concrete, concomitantly to physicochemical tests allowing to diagnose natural and accelerated aging.


Introduction
One of the most recent challenges of modern society is the research of new alternatives of environmentally responsible technologies for the �nal disposal of residues generated by industrial, domestic, and commercial sectors.
Governmental entities and international communities have been acting together to promote environment protection and pollution reduction through environmental laws concerning well-stablished residue limits and intensive �scalization.
ese actions result in viable application to diverse residues, which can be converted in useful raw materials.An example is the silica fume byproducts, which were initially considered industrial residues, but nowadays are largely used in civil construction due to its greater pozzolanic reaction capacity compared to most of hydraulic cements.Many other different byproducts can be used, like furnace slag, metakaolin, tire-rubber residues, and others [1][2][3][4][5][6][7][8][9][10].
is paper emphasizes the importance of the study of recycling conditions and/or residues disposal in civil construction, by using engineering analyses and science materials evaluation.us, four different residues (silica fume, sludge from water treatment plant, electrical insulator porcelain and tire-rubber wastes) were tested in concrete core samples; in reef balls and concrete blocks technology for �shing habitat and for creating biomass (animal or plant life); in typical concrete structures of the electrical energy sector, such as crossarms, utility poles, and dams.

Materials and Methods
All used materials were submitted to physicochemical analyses and were pretreated prior to concrete samples casting.

Cement Materials.
Filler-modi�ed and sulfate-resistant (type CPII-F 32), high-early strength (type CPV-ARI RS), pozzolan-modi�ed concrete (type CPII-� 32), and sulfateresistant pozzolanic (type CPIV-32 RS) Portland cements were used.Each of these was used in order to meet local standards and extend the durability of the structure in aggressive environments such as seawater and coastal regions.

�rti�cial and �atural Fine and Coarse �ggregates.
Fine and coarse aggregates consisted of washed natural medium sand and crushed basalt stone with maximum nominal size of 4.8 and 19 mm, respectively.ey were tested according to the recommendations of Brazilian standards.Synthetic aggregates from waste samples were crushed to both �ne and coarse nominal size and also tested.

Sludge from Water
Treatment Plant Swtp.e search for economically and environmentally advantageous solutions for the treatment and sludge disposal of WTP remains a challenge, especially for developing countries, living in severe economic constraints and where health problems require emergency solutions.Monthly, approximately 4,000 tons of WTP sludge dry matters are produced throughout the state of Paraná, southern Brazil.In the city of Curitiba (population of 1.9 million people, approximately), capital of Paraná, the potable water supply is provided by Iguaçu, Tarumã, Irai, and Passaúna WTPs, which account for over 50% of all the production of sludge in the state.Passaúna WTP produces, by centrifugation method, about 360 tons/month of sludge.It is the WTP object of study in this work.For this research, collections of hebdomadaires centrifuged sludge were conducted during two months of the year.Aerwards, the �nal content was homogenized, oven-dried at 110 ∘ C, and disaggregated [3].

Electrical Porcelain Waste (Pw).
Arti�cial aggregates of medium and high voltage electrical porcelain waste were obtained by grinding the product in a hammer mill type.e crushed material was classi�ed into different particle sizes aer grinding.e �ne particulate portion was used to study its potential alkali reactivity by mortar-bar method [11] and the coarse one was separated in four quotas, thus considered: glazed porcelain (as obtained and grounded) with sulfur cement phases (cement waste from the junction of the porcelain to the metallic part of the insulator); glazed porcelain without sulfur; porcelain with sulfur and without its surface glaze and plain porcelain material [12].e separation of these parts from the raw material is related to the investigation of their potential contributions to the alkali reactivity in concrete.

Silica Fume (Sf).
Condensed silica fume (Sf) is a byproduct usually originated from induction arc furnaces in the silicon metal or ferrosilicon alloy industrial processes, where the reduction of quartz to silicon at temperatures up to 2000 ∘ C produces SiO vapors, which oxidize and condense in the low-temperature zone to tiny spherical particles consisting of amorphous or noncrystalline silica.e amount of SiO 2 present in this pozzolan is, invariably, close to 80% and is directly related to the existent production process [1].
Currently, Sf was widely used as a supplementary cement material to enhance the strength and durability of concrete.In this research, Sf was also used in order to lower the pH of the resulting concrete to facilitate settlement of marine organisms.(Tw).e use of rubber waste in concrete is important from the ecological point of view.Population growth and increased use of disposable materials such as packaging, tires, and PET bottles, among others, have caused the accumulation of large quantities of solid waste, which are limiting the capacity of land�lls.In 2005, the city of Rio de Janeiro, southwest of Brazil, tires and rubber products accounted for about 0.5% of urban waste and in São Paulo, this quantity is near 3% [13].

Waste Rubber from Retreading Tires
Rubber band scroll waste from retreading tires was used without any pretreatment.e composition of the predominant residue was characterized as styrene butadiene rubber by infrared Fourier transform.e average particle size distribution was 4.8 mm.

Dosage.
Ideal concrete mix proportions (by mass for a concrete mixture (w/w)) are listed in Table 1.For each concrete mix, a reference concrete (RC), without addition, was also produced to serve as comparison.To the concrete mixture Tw, two other ratios were studied as a 5 to 15% (w/w) of rubber addition.However, only the 10% (w/w) Tw was considered due to its performance.
Also, six concrete utility poles and crossarms were casted with Pw 1 , RC, and Sf 1 and tested for �exural strength aer 28 days of concrete curing and also for electrical properties and visual surface inspection during natural ambient exposition.e poles were double-tee cross-section shaped, B type, 11 m long, and with 300 daN of nominal strength, complying with a Brazilian standard [17].

Physicochemical Characterization of Samples.
Cement and natural and arti�cial aggregates were characterized by physicochemical analyses, previously to their use in the mixtures.Elemental chemical composition and chemical phases were obtained from energy dispersive spectroscopy (EDS), X-ray �uorescence (XRF), and X-ray diffractometry (XRD) methods.PW 2400 Philips �uorescence equipment was used to determine the elemental chemical composition.XRD of specimens were measured using a Philips (X'Pert MPD) diffractometer with Cu-K radiation operating at 40 kV and 40 mA.e diffraction patterns were used to identify the structural phases of the specimens.e micrography analyses of fractured concrete surfaces were done using an XL30 model Philips Scanning Electron Microscope (SEM).Gold was applied to the surfaces by sputtering.Potential alkali reactivity of cement and aggregate was evaluated according to ASTM speci�cation [11].
Nondestructive method, such as electrical half-cell potential with copper-copper sulfate reference electrode, CSE, was used to verify the service life performance of reinforcing steel in concrete in a 3.4% w/w chloride solution and of concrete utility poles submitted to natural aging condition, according to the literature [18][19][20].e metallic rebar of the poles was connected as the working electrode.An average potential from thirty measurements was obtained from the testing at both sides of the bottom region of poles, just above the embedment line.

Environmental Corrosion Stations (ECSs).
A marine ECS was built at Caueira beach, in Itaporanga D' Ajuda district, near Aracaju, SE, in northeastern Brazil.It was located at about 2 m above the high tide line of the Atlantic Ocean [19].Utility poles, crossarms, and concrete material core samples casted with Sf 1 were submitted to natural aging for approximately 500 days.Also, an urban ECS was built at Curitiba, PR, southern Brazil, to test Pw 1 concrete casted in utility poles and crossarms.
Sf 2 concrete admixtures were cast as thick plates (20 × 270 × 300) mm to be previously tested in a marine ECS located at 17 m depth, following a perpendicular line of Praia de Leste beach coast until 30 m deep (25 ∘ 30 ′ S).Sample plates were periodically tested by �exural strength and by microstructure concrete surface investigated by Scanning Electron Microscope (SEM) and energy dispersive system analyses (EDS).Aerwards, this composition was cast as reef balls and 1 m 3 concrete blocks technology forms.Both of them were tested in a marine shallow shelf at approximately 30 m of depth for approximately �ve years [21].e pH of this resultant concrete mix lowered from 12.3 to 11.4.Concrete with this pH generally needs to age in the ocean for 3-6 months before the pH in the surface region approaches the 8.3 pH of seawater and favour marine organism's settlement [22].

Results and Discussion
e physicochemical analyses of cements were in accordance to manufacturer speci�cations and Brazilian standards.

Concrete Admixtures
3.1.1.Swtp.e major chemical components obtained by XRF tests from the sludge sample were: 16.55% of silica, 13.07% of alumina, 4.15% of ferrite, 49.79% of volatile materials, and 16.44% of humidity.In natura water treatment sludge was identi�ed as kaolinitic group by XRD as shown in Figure 1.
e result of average compressive strength of 8% (w/w) Swtp concretes at 28 days of curing was 27.6 MPa, being superior to setup limit used for concrete structures as poles for electric energy distribution network.e average �exural strength at 28 days was 3.0 MPa, which is in accordance to the literature data for similar admixtures [1,20].Increasing the concentration of sludge from water treatment plant to 10% w/w in concrete, the microstructures presented large porosity, poor compressive strength lower than 15 MPa and the slump test results was 0 mm.is turned the concrete workability to be nonsatisfactory.
e average permeability resulted from 8% (w/w) Swtp was 0.9 × 10 −10 cm/s.As the permeability of concrete depends on mix proportions, compaction, curing, and microcracks in the core, and also there is a close relationship between the strength and its durability, the results indicated a good  performance mixture resultant from kaolinitic group and cement phases.

Pw.
Porcelain waste concrete admixture resulted potentially in alkali reactive with CPII-F 32 cement type, as shown in Figure 2. e expansion tests resultant from different pickedup porcelain material parts and CPII-F 32 cement type showed that porcelain with glazed and sulphur cement phases (as obtained and grounded) is the most damaging to the concrete materials, followed by porcelain parts, porcelain material with glazed but without sulphur cement phase parts, followed by porcelain materials without glazed and with sulphur cement phases.is latest phase presented the lower expansion results, as demonstrated in Figure 3. Sulphur cement phase did not demonstrate larger expansion in its �rst 16 days agied according to ASTM tests [11].From 16 to 28 ageing time days, the mortar samples demonstrated positive alkali reaction with an exponential slope expansion results passing to noninnocuous limit, as viewed in Figure 3. Besides, this Pw reinforcing steel samples with sulphur cement phase presented too bulk defects that are capable to enlarge cracking probability risk, as shown in Figure 4, by SEM micrography images.
Pw compressive strength resulted in 30.4 MPa at 28 days of curing, being classi�ed as restrained resistance [14].
Because of the reduced lifespan resulted from the potential reactivity essay with porcelain materials and CPII-F 32  cement type, the Pw mortar sample was in a second time cast with special sulfate-resistant cement.Portland highearly strength cement (CPV-ARI RS) reduced its expansion limit in 16-and 28-day ageing test to the recommended values (innocuous consideration) as shown in Figure 5.Nevertheless, additional care should be taken because of a positive slope tendence to high delay expansion values.
In Figure 6 is showed an image of utility poles and crossarms under natural ageing in an ECS urban environment located in Curitiba, PR, Brazil.In the right position is a 25% w/w concrete Pw admixture tested with RC utility poles located at the le.In detail is viewed the electrical half-cell potential electrode system for nondestructive test.Even so the utility poles and crossarms were casted using specially cement type (CPV-ARI RS) with 25% w/w porcelain waste in concrete to reduce the probability risk of alkali expansion presented by the 50% w/w Pw one.e rupture of the RC and Pw utility poles by �exural strength was 360 and 440 daN, respectively, being in accordance with the Brazilian speci�cation �15].Electrical half-cell potential measured during these �rst �ve months on urban ambient ECS condition indicated no corrosion activity for RC and Pw structures.As previously reported, both structures are exposed at low aggressive atmosphere.
e electrical results made in RC and Pw reinforcing steel in concrete partially immersed in 3.4% w/w NaCl aqueous solution as function of ageing time are showed in Figure 7.As viewed, Pw reinforcing steel material has been presenting lower corrosion activity performance than RC reinforcing steel.

Sf 1 and Sf 2 Concrete
Admixtures.Silica fume admixtures in concrete have been presenting better lifespan performance of concrete structure submitted to salt aggressive environment, as viewed in Figure 8, by electrical half-cell potential rebar measurement results.
Tests made in the reinforcing steel in concrete submitted partially immersed in a 3.4% NaCl aqueous solution have been indicating that Sf 1 samples are having a double lifespan in comparison with RC reinforcing steel, both of them tested at the same laboratory salt aggressive condition.
Visual inspection on Sf 1 and RC utility poles submitted to northeast Brazilian Caueira beach ECS demonstrated that RC structures have been presenting, too, rebar corrosion surfaces with consequently concrete microcracks.Any corrosion surface defects have been viewed on Sf 1 concrete structures exposed at same environmental condition.
Besides the increase of lifespan concrete structures, the silica fume material causes economical positive effects when compared to a reference concrete.e economical differences lowered from 34% in 28 curing days to 24% in 90 curing days, at the same compressive strength results.is phenomenon had been attributed to pozzolan-modi�ed Portland �CPII-� 32) cement used to cast both samples [5].
Sf 2 mixes casted in thick plates and tested previously in a 17 m depth marine ECS demonstrated good lifespan performance by �exural strength results in the function of ageing time, as well as in terms of biological marine material habitat, as shown in Figures 9 and 10, respectively.Sf 2 cast as reef balls technology and 1 m 3 blocks, as presented in Figure 11, has showed also lifespan good performance in the last 10 years old in a Parana marine shallow shelf at southern Brazil.In Figure 11 is also shown in detail a nowaday �ew�sh habitat [21].
3.1.4.Tw.Tw concretes cast with up to 20% w/w were tested to be used as paver and curb pieces and as repair materials for hydraulic concrete structures of hydroelectric power plants [4].Until 15% w/w Tw concrete admixtures, the results showed no serious decreasing in fresh and cured concrete properties relative to RC samples, such as the slump test and compressive strength results.Regarding the 10% w/w Tw concrete admixture, its behaviour was even better than the 15% one.
In Figure 12 are presented paver block manufactured with 10% w/w Tw admixture and, in detail, the surface of paver casted with 20% w/w Tw concrete admixture.As shown, the 20% w/w Tw composition presents larger quantities of rubber-tired concrete surface efflorescence and porous defect, causing poor visual market aspect and lower resistance.
Abrasion-erosion test results of Tw samples showed that the wearing was 75% lower than RC samples, meaning that they have better performance.In Figure 13 is showed a sample photograph and the wearing surface plot results aer testing with three different repair materials concentration, such as: 5% w/w Tw; 10% w/w Tw; 15% w/w Tw.In all cases Tw materials wearing results are lower than the RC substrate.

Conclusion
e Swtp obtained by centrifuged method can be used as concrete admixture up to 10%.e best mechanical behaviour was achieved with 8% w/w Swtp concrete mixture, indicating that it can be used in concrete utility poles and crossarms.
Pw concrete admixture cast with CPII-F 32 cement type had its lifespan reduced due to the large potential reactivity values in all partial chemical phases analysed.ese alkali aggregate reactions were reduced aer the change of the cement type to a high-early strength and sulfate-resistant one (CPV-ARI RS).is composition could be cast in utility poles and crossarms applied in electrical distribution energy until 25% w/w porcelain waste.Even so is strongly recommended laboratory tests previously cast it in civil structures.
Sf 1 and Sf 2 silica fume mixtures cast as utility poles and crossarms, and reef balls technology and cubic concrete blocks showed good resistance performance when used in high salt Brazilian northeast coastal areas and into 17 m depth marine environment, respectively.Poles, crossarms, reef balls structures and cubic concrete blocks with silica fume Tw composition up to 15% w/w concrete mixture had good mechanical performance during tests, showing that it can be used as paver, curb pieces, and as repair materials for hydraulic structures concrete dams.e 20% w/w Tw composition presented large quantities of rubber-tired concrete surface efflorescence and porous defect, causing poor visual market aspect and low mechanical resistance.
As observed, the worry on the use of recycled materials is not limited to structural stability, but also their durability in concrete structures, meanly submitted to salt aggressive environment.

F 2 :
Expansion of Pw admixture mortar sample.

F 3 :
Expansion of mortar admixtures containing porcelain insulator waste.F 4: SEM of sulphur cement phase micrography in porcelain concrete admixtures.

F 5 :
Expansion results of Pw mortar casted with high-early strength sulfate-resistant cement (CPV ARI-RS).

F 6 :
e image shows 3 utility poles and crossarms.Two of them were cast with RC and Pw admixtures (right positions).In detail, is illustrated a CSE system used to measure the seasonal reinforced steel corrosion potential performance.

F 7 :
Electrical half-cell potential results of RC and Pw reinforcing steel in concrete as a function of aging time in 3.4% NaCl solution.

F 9 :
poles in Caueira beach ECS F 8: Electrical half-cell potential results of RC and Sf 1 utility poles submitted to the natural aging for 480 days in northeast Brazilian Caueira beach ECS.time, in a 17 m depth marine ECS (days) Flexural strength (MPa) Flexural strength of Sf 2 concrete admixture in terms of ageing time in a 17 m depth marine ECS.

F 10 :
Sf 2 concrete admixture and other materials thick plates tested in marine ECS located at 17 m depth, at Praia de Leste beach.F 11: Sf 2 reef balls technology and block forms of Sf 1 concrete mixture before installation in a marine shallow shelf at Parana state, southern Brazil.e detail shows nowaday �ew�sh in the block habitat.

F 12 :
Paver block with 10% w/w Tw concrete mixture.e paver surface view of 20% w/w Tw concrete mixture is shown in detail.

F 13 :
Abrasion-erosion Tw samples image tested and the schematic wearing surface plot results.e wearing surface resulted from three different repair materials concentration: 5% w/w Tw; 10% w/w Tw; 15% w/w Tw. admixtures (Sf 1 and Sf 2 ) showed good chemical resistance performance in high salt Brazilian Northeast coastal areas and, into 17 m depth marine environment, during 500 days and approximately 5 years of tests exposition, respectively.
T 1: Mix ideal proportions (by mass for a concrete mixture) and properties of fresh concrete with admixtures.