Recycling options for used sandblasting grit into road ... - wseas.us

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Recycling options for used sandblasting grit into road construction 1

DANIELA LAURA BURUIANA, 1MARIAN BORDEI, 2 IOANA DIACONESCU, 2AUREL CIUREA 1 Faculty of Metallurgy, Materials Science and Environment 2 Faculty of Engineering “Dunarea de Jos” University of Galati 47, Domneasca Street, 800036, Galati, ROMANIA e-mail: [email protected], http://www.fmsm.ugal.ro Abstract: The grit is an abrasive blasting material used for the preparation of the metal surfaces in the ship building and ship repair processes prior the application of coatings. The waste is a spent grit used for sand blasting in the cleaning operations of tankers in the dock yard. This paper presents the modified properties (chemical composition, the shape and size of the particle) of the steel grit during the blasting process and the possibility of recycling the waste as a fine aggregate in the road construction industry. The management of solid waste from abrasive blasting is an issue which will be more frequently encountered in the future. While existing guidelines and regulations are available, a single resource which spans such a wide array of information does not currently exist. Future work should concentrate on collecting and summarizing best management practices for abrasive blast material (ABM) waste management in a format which could be used by the many industries which perform abrasive blasting, and the engineering and regulatory community. The recycling of spent sandblasting grit, commonly referred to as spent ABM, into asphalt concrete is investigated by the shipyard as an alternative to disposing the spent ABM in a landfill. Key-Words: abrasive blasting material, sandblasting grit, road, shipyard, ship building, repair process.

the development of superior technologies that substantially reduce emissions; the growth in efficiency of the regaining and recycling of the by-products close to 100% values. The ecological concept applied to industrial systems engineering imply the development of these technological production processes with closed loop in which no resource is eliminated all the are continuously reused, no waste material or other product is evacuated in the environment that in the subject literature is found as “waste free industry” or “zero waste industry”.

1 Introduction The naval industry is facing at the beginning of this century major problems. These appear not to be linked either to an eventual raw material resources or energetic crisis, or to the metallic materials competition with other materials, but they are rather linked to the acute demands of the environment protection. The development of the construction and naval repairing industry is conditioned by the major problems solving that come out of the industry nature relationship on the pollution control and natural and energetic resources protection. In the ship repairing area, there should be given up to the waste notion for the grit used for ship body sanding/blasting, more correctly being talked about by products. The preoccupations followed in the development strategies of the shipyards around the world go in two directions:

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In the cleaning of the metallic surfaces of the ships, new or for fixing, there are used mixtures made of metallic pellets, grit (cast iron or steel) and natural sand (derived from natural or artificial rock grinding). After many usage cycles in the sanding operations, the material

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or Norway promoted the environmental management plan which supervises the polluting emissions of the technological processes from the shipyards [1]. The naval industry generates important waste amounts and that is why an environment management plan is needed to assure the valorization on a large scale of these wastes (the used grit quantity is about 130 [grit waste tons/month], the packaging number is about 180 [boxes/month]). In the monitoring system, for the emission impact pollution supervision, quantitative and quality emissions measurements (NO2, NOx), powder in suspension and sedimentable powders in different spots on the shipyard’s platform were made. Spherical grit pellets are produced from steel wire cold worked with medium carbon content, or stainless steel, according to standards DIN 8201 (St D-Z), DIN 50310, DIN 50311, DIN 50315, EN ISO 11241, EM ISO 1125-3. The composition limits, as well as the hardness of the grit are given in Table 1. The study concerning the recycling of used grit appeared because of the necessity of solving the great storage problems, to the fines paid for the uncontrolled storage [5] and the big waste taxes [7]. Under the circumstances the reduction of the pollution level in the naval field by raising the level of valorization of the grit waste and the controlled storage represents an important problem in the environment protection policy.

loses the abrasive properties, entering to the waste category. The grit fractions from the waste material can be recycled and used in constructions field. This is of both economical and environmental importance because by recycling them, the grit wastes dump disappears not polluting the environmental. Before recycling them, the waste materials came from the sanding operations; first they have to undergo some component separation operations, metallic respectively non-metallic and then each of them go through studies for properties determination. These have to be compared to the technical conditions provided for each usage domain. In comparison with practice and the tendencies manifested globally, the naval industry in Galati has collecting shipping and depositing deficiencies for all categories of waste and in the technologies for valorization by recycling and/or their reutilization. The naval industry in Romania reports an average 130 (grit waste tons) at a sanded surface of 8800 [m2 sanded/month] (a ship of 8800 surface [m2]), from which more than 90% from the wastes derived from this process are not presently valorized [1], comparing to the naval shipyards from Germany and Sweden that have a lesser un-valorized quantity. The technological processes have a negative impact upon the environment, being a problem for all the shipyards in the world. The most modern shipyards, such as those from Germany, Japan

Table 1. Standard characterization of abrasive material, grit Chemical composition [%] (density 7.4 g/cm3)

Material class

GP GL GH

C

Mn

Si

P

S

0.75-1.20

0.60-1.10

0.60-1.10

Max. 0.04

Max. 0.04

Grit GN Grit GH

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Hardness [HV]

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450-560 600-700 800-950


2.1 The determination of physical and chemical properties of the sandblasting grit Although no specific regulations are in place for used sandblast grit waste, it is a solid waste, and as with any non-excluded solid waste the generator of the waste is responsible for determining if the waste possesses hazardous characteristics, and is thus a hazardous waste. This is therefore a necessary step in determining the disposal and reuse options available. Environmental regulations require that a Toxicity Characteristic Leaching Procedure (TCLP) test be performed to determine if the material is hazardous. If it is hazardous, the material must be managed accordingly. If not determined hazardous, the grit is a solid waste which must be disposed of properly. There are many types of abrasive blasting media available. Sand is one of the most common blasting materials. Sand is the least expensive non-reusable media. Alternatives to sand abrasives include other mineral sands with no free silica, metal slag, and coal slag. Coal slag has been used frequently as a blasting material. The research concerning the capitalization possibilities of grit waste derived from sanding, proposed in this paper is an outcome of thermogravimetric analysis (TGA), X-ray diffraction, granulometric composition and statistics methods of PCA (Main Components Analysis) and BET surface area and porosity using Micrometrics ASAP (Accelerated Surface Area and Porosimetry Analysis). The structural characteristics were analyzed using electronic microscopy. In this study we compared the grit waste composition with the materials of similar compositions used in cement factories and construction materials, from the point of view of specific properties, by controlling different compositional factors. Granulometric fractions were separated both at the unused material, in its initial state and at the used grit that goes though a capitalization analysis after granulometry.

2 Experimental researches For the grit waste usage for the road construction there must be taken into consideration first the hydraulic power of the addition pendant material, which depends on stability rate α. In chart 3 it can be found the recipes for the mixtures determined, considering the rate. The evaluation of α rate gives the material quantity necessary for the preparation of the mixture. For other materials it is recommended an α rate between 40-60. The material with α < 20 or α >80 cannot be used. The binding agent can be quick lime although the experience shows us that the slaked lime gives complete necessary reactions. The lime amount/proportion/dose fluctuates to 1-2% from the total weight of the base mixture. The quick lime must have small dimensions, between 0-2 mm and CaO content >70%. The comparing results of the experimentations are presented in Chart 3. In road construction, grit can replace some natural insertions with the same granulation. Generally speaking, the road structure consists of four sub layers made out of different granulation material mixtures. The thickness of the layers differs according to the used mixtures, this first reassuring the necessary resistance. The research demonstrated that the grit usage in materials for road construction has a series of advantages and also technical disadvantages of the material: - it is easily feasible; - presents homogeneity at a high level of binding agent; - the possibility of repairing when there are damages caused by the heavy traffic; - the possibility of some damage that in the future, can reduce the bituminous thickness, that is expensive; - on bad weather the traffic is stopped; - there is a possibility of scattering during traffic.

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Table 2. The separation of granulometric fractions ABM/waste ABM Abrasive blasting material Abrasive blasting material (sandblasting grit) (used sandblasting grit) Initial weighed quantity = 100 g magnet passing 1 = 9.2 g magnet passing 2 = 5.0 g magnet passing 3 = 5.5 g remains = 80.3 g Screening through magnet 1 = 9.2 g screen 0.16 = 5.2 g screen 0.07 = 2.3 g screen 0.05 = 1.2 g dust = 0.5 g Screening through magnet 3 = 5.5 g screen 0.16 = 3.3 g screen 0.07 = 1.2 g screen 0.05 = 0.5g dust = 0.5g Screening through screens of the remained grit = 80.3g screen 0.16 = 54 g screen 0.07 = 13.3 g screen 0.05 = 3 g dust = 10 g

Initial weighed quantity 100 g magnet passing 1 = 2.7 g magnet passing 2 = 2.2 g magnet passing 3 = 2.1 g remains = 91.8 g screening 0.16 = 90.6 g screening 0.07 = 1.2 g

Absorption), because they are preferred by the cement industry. Shipyard being directly interested in the final results collaborated with the author offering her the analysis bulletin for the research concerning the capitalization of grit waste. For the determination of the elements from used grit composition it was used the atomic absorption spectroscopy technique AAS (table 3). AAS measures the concentration of an element from a given sample, by the determination of the absorption made by the atoms brought to a very high temperature. A big advantage of AAS method is the possibility of organic solvents usage for sample concentration. The basis of the analytic chemistry consists in the chemical analysis methods, methods that allow the identification of the composition for the raw material used in technological processes, for the example the raw materials used in road asphalting process. The chemical used composition of the analyzed grit waste was made with the support of the Shipyard of Galati, waste producer in the analyzed area.

The separation of granulometric fractions wad made by waste screening, for fractions separations according to granule dimensions, using screens of different dimensions (Granulometric analysis table2)[1]. Separate granulometric fractions have the following dimensions: 0.16; 0.07; 0.05; 0.01 [mm]. The screen is laid on a white surface, on the screen remaining only rough fraction. The sample on the screen is removed and the quantity gone through the screen is weighed. The basic technical characteristics for the solid materials that mostly determine the properties and their quality are: composition, granulometry, density, the specific surface and pore structure. The cognition of these characteristics make possible the parameters determination of the sand blasting with the optimum efficiency/output. To establish the recycling channel, the used grit properties were determined using granulometric analysis. The authors collaborated with managing Shipyards of Galati. We chose the PCA method using AAS technique (Spectroscopy of Atomic

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Table 3. The chemical composition of the used sandblasting grit Analysis Bulletin Beneficiary Shipyard of Galati Name of the material Used sandblasting grit

Elements [%] Mn 0.39

SiO2 39.28

CaO 6.7

MgO 6.57

EDX analysis indicates the particles composition as well as the elements distribution in the examined area. Samples 1 - 4 have

Cr2O3 1.20

Al2O3 7.56

Fe2O3 38.28

P.C. absent

similar structures. The samples have similar microstructures, highlighting the thinnest diffusion area.

Sandblasting grit samples coated with carbon 90%

Fig. 1-4. EDAX analysis of the elements marked using a high energy surface that allows in-depth view The study highlights a very important issue for the used grit recycling and that is the grit composition doesn’t go through major deviations from its initial state. The analyzed waste has as main components Si and iron oxides. The composition is similar to that which is formed at hydraulic materials hardening. A more rugged texture, characteristic to aggregates, assures bigger adhesion forces between aggregate granules and the binding agent, an extremely important thing for road concretes. The fully automated ASAP Accelerated Surface Area and Porosimetry System is designed for high-performance/high sample throughput to help today's busy laboratories expand their workflow while providing highly accurate and precise surface area and porosimetry measurements. With six independently operated analysis ports, a new analysis can begin as soon as another is finished. This provides an important advantage over many multi-port instruments that require all samples to be prepared or analyzed at the same time. In addition, a key, standard feature of the

ISBN: 978-1-61804-052-7

ASAP is a programmable and fully automated sample preparation module with twelve independently operated ports. Samples may be added or removed from degas ports without disturbing the treatment of other samples undergoing preparation or analysis. The term BET was derived from the first initials of Burnauer, Emmett and Teller, and refers to the method of measuring the surface area and porosity of solid materials using the principals of physical adsorption and de-sorption of gas. The Micrometric's ASAP 2000 system has the versatility to characterize samples using a number of different adsorptive gases as Nitrogen. In physical gas adsorption, an inert gas, mostly nitrogen, is adsorbed on the surface of a solid material. This occurs on the outer surface and, in case of porous materials, also on the surface of pores. Most widely known is the determination of the BET surface area by gas adsorption. Adsorption of nitrogen at a temperature of 77 K leads to a so-called adsorption isotherm, sometimes referred to as BET isotherm, which is mostly measured over porous materials

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Fig. 5. Analysis grit BET pore size influenced by factors which can be impurities content, dimensional characteristics of the granules and the physic-chemical characteristics. The results interpretation of the grit samples show that the analyzed grit has physical and chemical properties similar to standard analysis of the sand used in asphalt composition: - an angular granulation, unrounded (considerably influences the concrete resistance); - a silicon-aluminous composition (the compounds are similar to those which are formed at the construction materials hardening, formed puzzolanic asphalt, mainly from reactive silicon dioxide and aluminum oxide which can contain other oxides too – iron oxide). The aimed general objective in used grit capitalization process for asphaltic material includes the production of a composite with adequate physic-mechanic properties, competitive and comparable with traditional materials used in road asphalting domain: - reduced connection capacity of the heavy metals in watery environment; - less quantities that doesn’t negatively affect the connection and hardening properties of heavy metals. Out of the materials used for road construction, the grit waste can be classified at hydraulic/puzzolanic binding agents, together with sand and furnace slag.

The ASAP 2000 measures high-resolution adsorption isotherms on a wide range of materials. The interactive display allows users to zoom in on the fine details of the isotherm. The expanded graph shows the precise closure of the adsorption and desorption isotherms. The results of sample analysis device sandblasting grit with ASAP 2000 surface area and porosity using ASAP 2000 apparatus under the guidance using Department of Environmental Engineering and Chemical Technology, Pannon University Hungary. 3. Recycling options for used sandblasting grit into road construction A better knowledge of leaching tests and results, as well as of material properties, is very important in the assessment of waste ABM for use in road construction. The aim of this work has been to investigate leaching of primary and secondary road-making materials and study factors that may have an influence on the release of trace elements such as chromium, zinc and manganese, magnesium that are regarded as pollutants. The main objective of the study is the determination of the optimum between the grit composition and its grinding fineness. The value of the resulted analyses values were compared to those estimated in the quality norms of aggregates, value decisively

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Table 4. Comparative results of the used abrasive blasting material [1, 4, 8, 10] Bonded Bitumen 60/70 [84] reinforcement Composition % weight [1,8,10] Large aggregate 10/20 30 30 30 Aggregate average 5/10 25 25 25 40 Used sandblasting grit [8] 13 sand 0/3 13 13 29 12 Chalk 4 3 Cement 4 - 7 Bitumen 5 5 5 6 Granularity % weight [1] Screening through ¾” 100 100 100 ” Screening through 1/2 95.8 95.8 95.8 100 Screening through 3/8” 72.7 72.7 72.7 7.6 ” Screening through ¼ 57 57 57 78.3 Screening through mm 5 44.8 44.8 44.8 60.8 Characteristics [4] Density of mix real [kg/dm3] Specific gravity bitumen [kg/dm3] Specific gravity conglomerate [kg/dm3]

40 12 12 8 6

40 12 42 6 6

100 7.6 78.3 60.8

100 7.6 78.3 60.8

2.717

2.693

2.711

2.723

2.681

2.701

1.025

1.025

1.025

1.025

1.025

1.025

2.519

2.499

2.514

2.490

2.456

2.477

References: [1] D. NegoiŃă (Buruiana), Contribution to the reduction of waste generated by shipyards” PhD thesis, 2007. [2] Al-Sayed M. H., Madany I. M., Use of copper blasting grit waste in asphalt mixes in Bahrain, Construction and Building Materials, Vol. 6, Issue 2, 1992, pp. 113-116. [3] Amada S., Hirose T., Senda T., Quantitative evaluation of residual grits under angled blasting, Surface and Coatings Technology, Vol. 111,1999 [4] Gheorghe M., Valorificarea deşeurilor si subproduselor industriale în construcŃii, Ed. MatrixRom, Bucuresti, 2004. [5] Henley, N, Spash, C., Cost-Benefit Analysis and the environment, UK, Edward Elgar Publishing Ltd., Gower House Aldershot, 1993.

4 Conclusions The paper presents the research results made for the purpose of recycling options for used sandblasting grit in composite materials realization used into road construction. The purpose of this research was to emphasize the possibility of recycling used grit was an asphalt composition material, presenting the necessary grit granulation as well as the Si and iron oxides concentration necessary for the mixture used in asphalting (asphaltic mixture) process. Looking for a way/method of using grit waste, the propounded solution could be the large scale use of stabilized mixture technology (treated granular aggregate with puzzometric binding agents using used grit), following the example of advanced countries (in our country the roads rehabilitation problem needs big material, aggregate, binding materials consumption, difficult to be provided from traditional resources). Conclusions conclude that theoretical and experimental research presented in the paper was called for by the importance of recycling grit wastes. Proposals for using the material obtained from recycling of grit wastes in stabilized mixtures with binders used in roads asphalt, the shipyard studied being able to benefit from economic advantages by reducing costs allocated to the collection, transport and disposal grit wastes.

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Slow Cure

[6] Mandravel C., Stanescu R., Metode fizico chimice aplicate la măsurarea noxelor in mediul profesional, Ed. Academiei Române, Bucureşti, 2033, pp. 139-158. [7] Mohammad Ismail M., Madany H., Raveendran Al-Sayed, Utilization of copper blasting grit waste as a construction material, Waste Management, Volume 11, Issues 1-2, 1991, pp. 35-40.

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