Recycling options for used sandblasting grit into road...
Transcript of Recycling options for used sandblasting grit into road...
Recycling options for used sandblasting grit into
road construction
1DANIELA LAURA BURUIANA,
1MARIAN BORDEI,
2IOANA DIACONESCU,
2AUREL CIUREA
1Faculty of Metallurgy, Materials Science and Environment
2Faculty 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.
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:
- 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”.
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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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
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 1124-
1, 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.
Table 1. Standard characterization of abrasive material, grit
Material Chemical composition [%]
(density 7.4 g/cm3)
Hardness
[HV]
GP C Mn Si P S 450-560
GL 600-700
class
GH 0.75-1.20 0.60-1.10 0.60-1.10 Max. 0.04 Max. 0.04
800-950
Grit GH
Grit GN
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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.
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 thermo-
gravimetric 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.
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Table 2. The separation of granulometric fractions ABM/waste ABM
Abrasive blasting material
(sandblasting grit)
Abrasive blasting material
(used sandblasting grit)
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
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
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
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.
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Table 3. The chemical composition of the used sandblasting grit Analysis Bulletin
Beneficiary Shipyard of Galati
Name of the
material Elements [%]
Mn SiO2 CaO MgO Cr2O3 Al2O3 Fe2O3 P.C. Used sandblasting
grit 0.39 39.28 6.7 6.57 1.20 7.56 38.28 absent
EDX analysis indicates the particles
composition as well as the elements distribution
in the examined area. Samples 1 - 4 have
similar structures. The samples have similar
microstructures, highlighting the thinnest
diffusion area.
SSaannddbbllaassttiinngg ggrriitt ssaammpplleess ccooaatteedd wwiitthh ccaarrbboonn 9900%%
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
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
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
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.
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Table 4. Comparative results of the used abrasive blasting material [1, 4, 8, 10]
Bitumen 60/70 [84] Bonded
reinforcement Slow Cure
Composition % weight [1,8,10]
Large aggregate 10/20 30 30 30 - - -
Aggregate average 5/10 25 25 25 40 40 40
Used sandblasting grit [8] - - 13 - 12 12
sand 0/3 13 13 29 12 12 42
Chalk - 4 3 - 8 6
Cement 4 - - 7 - -
Bitumen 5 5 5 6 6 6
Granularity % weight [1]
Screening through ¾” 100 100 100 - - -
Screening through 1/2” 95.8 95.8 95.8 100 100 100
Screening through 3/8” 72.7 72.7 72.7 7.6 7.6 7.6
Screening through ¼” 57 57 57 78.3 78.3 78.3
Screening through mm 5 44.8 44.8 44.8 60.8 60.8 60.8
Characteristics [4]
Density of mix real [kg/dm3] 2.717 2.693 2.711 2.723 2.681 2.701
Specific gravity bitumen [kg/dm3]
1.025 1.025 1.025 1.025 1.025 1.025
Specific gravity conglomerate [kg/dm3]
2.519 2.499 2.514 2.490 2.456 2.477
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.
References:
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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
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[6] Mandravel C., Stanescu R., Metode fizico
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[7] Mohammad Ismail M., Madany H.,
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ISBN: 978-1-61804-052-7 178