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UTILIZATION OF USED FOUNDRY SAND IN CONCRETE
By
Tarun R. Naik
Director, Center for By-Products Utilization
Viral M. Patel
Formerly Research Associate, Center for By-Products Utilization
and
Dhaval M. Parikh and Mathew P. Tharaniyil
Formerly Research Assistants, Center for By-Products Utilization
Department of Civil Engineering & Mechanics
College of Engineering and Applied Science
University of Wisconsin - Milwaukee
P.O. Box 784, Milwaukee, WI 53201
Telephone: (414) 229 - 6696
Fax: (414) 229 - 6958
UTILIZATION OF USED FOUNDRY SAND IN CONCRETE
Tarun R. Naik1, Viral M. Patel2,
Dhaval M. Parikh3, and Mathew P. Tharaniyil3
Abstract: This research was conducted to investigate the performance
of fresh and hardened concrete containing discarded foundry sands
as a replacement of fine aggregate. A control concrete mix was
proportioned to achieve a 28-day compressive strength of 38 MPa (5500
psi). Other concrete mixes were proportioned to replace 25% and 35%
of regular concrete sand with clean/new foundry sand and used foundry
sand by weight. Concrete performance was evaluated with respect to
compressive strength, tensile strength and modulus of elasticity.
At 28-day age, concrete containing used foundry sand showed about
20 to 30% lower values than concrete without used foundry sand. But
concrete containing 25% and 35% clean/new foundry sand gave almost
the same compressive strength as that of the control mix.
_______________________
1 Director, Center for By-Products Utilization, Department of Civil
Engineering and Mechanics, UWM, P.O. Box 784, Milwaukee, WI 53201.
2 Research Associate, Center for By-Products Utilization, Department of Civil
Engineering and Mechanics, UWM, P.O. Box 784, Milwaukee, WI 53201.
3 Research Assistants, Center for By-Products Utilization, Department of Civil
Engineering and Mechanics, UWM, P.O. Box 784, Milwaukee, WI 53201.
INTRODUCTION
During the 1970's and 1980's, federal and state environmental agencies began
to pay increasing attention to industrial pollution, safety and waste management
control. As a result, the foundry industry had to revaluate standard practices
with regard to the disposal of their used sands. One of the main concerns for
the foundry industry has been the need to reduce the disposal cost and minimize
the maintenance costs of landfill sites. Typical current disposal costs in
Wisconsin is about $10 to $20 per ton. During the next decade, the cost is expected
to increase by 5 to 10 fold due to new laws. Also, old landfills are reaching
capacity while new landfills will not be coming to market in sufficient numbers
as desired by industries. Nationwide, this was mainly because of the passage
of Public Law 94-580, the Federal Resource Conservation and Recovery Act of 1976,
which is the nationwide program that regulates and manages by-product disposal
(Naik, 1987). Shrinking landfill space throughout the United States has caused
landfill operators to refuse used foundry sand on the basis of high volume and
"special waste" status.
The typical amounts of total by-product materials from foundries range
between 227 to 2270 kg (500 to 5000 pounds) per ton of produced metal casting
(Murarka, 1987). The eastern and midwestern states are leaders in the number
of foundries per state.
After extensive testing, American Foundrymens Society recommended (AFS
report, 1991) that fine aggregate be replaced by 33% of the used foundry sand
in a batch of normal weight concrete. Based on this report it was decided to
replace 25 and 35% fine aggregates by used foundry sand to determine the effect
of different levels of replacements.
This research was performed to achieve technical, ecological and economical
benefits by utilizing the huge amounts of foundry by-products, produced every
year, in Wisconsin and elsewhere.
SCOPE
The concentration on the work of the initial phase was on the feasibility
of beneficial utilization of used foundry sand in concrete as a partial replacement
of regular sand by studying properties of both fresh and hardened concrete.
An extensive literature search was undertaken and tests were conducted on
by-product samples to determine their physical properties to evaluate the possible
uses (Naik et al. 1991, 1992).
A total of five concrete mixes, two containing 25% and 35% partial replacement
of regular sand with used foundry sand, the other two containing 25% and 35% partial
replacement of regular sand with clean/new foundry sand, and one control mix were
investigated in the laboratory. These mixes were tested to determine axial
compressive strength, splitting tensile strength, modulus of elasticity and bulk
density.
MATERIAL SELECTION AND MIX PROPORTIONING
General
Concrete was produced at the Center for By-Products Utilization (CBU)
laboratory using conventional mixing techniques. For economic reasons, locally
available materials were used in the mixture. An optimum design was developed
for the available materials on the basis of strength, cost, and performance.
Materials
Cement
ASTM type I cement from one source was used in this research program.
Physical properties of the cement were determined in accordance with the
appropriate ASTM tests, (ASTM, Vol. 04.01, 1990). The temperature and relative
humidity in the laboratory were maintained at 21 ± 1.7 C (70 ± 3 F) and 45
± 5%, respectively. These results are reported in Table 1. The chemical
compositioning of Type 1 Portland Cement was also determined. The results are
reported in Table 2.
Aggregates
The coarse and the fine aggregates used in this research program were obtained
from a local ready mixed concrete company (Central Ready Mix, Inc.). The coarse
aggregates were a mixture of crushed and rounded natural gravel with a 19 mm (3/4")
maximum size. The fine aggregate was natural sand with a 6.4 mm (1/4") maximum
size. ASTM Standard tests were conducted to determine the physical properties
of the aggregates (ASTM, Vol. 04.02, 1990). Fineness modulus for sand was also
determined by the ASTM C 136 method. These test results are presented in Table
3.
Types of Foundry Waste
The raw materials used for making sand molds for metal castings are usually
recycled. After a repeated use they lose their characteristics, thereby becoming
unsuitable for further use in the manufacturing process. All these materials
are then discarded as a waste. They are mainly molding sand and core sand.
Molding sand is the sand which is compacted and shaped according to a pattern
that is going to be produced. The by-product materials that result from the molding
sand are dust particles and cleaned sand from the casting, and excess system sand
which is in the form of large lumps of fine sand.
Core sand is used to provide the desired cavities, which are produced during
casting. By-product that results from core sand is called core butts and is removed
during the shake out process (Heine et al. 1975).
The other by-products from foundry industry are slag, furnace or Cupola
dust, molten metal, etc. Coremaking and molding sands usually produce 75% of
the various by-products generated in foundries (Greer et al. 1987).
Both of these used sands contain a variety of binders depending on the
specific application for which they were used. A binder is defined as a material
that gives binding action to the sand mixture. The most common binder in molding
sand is clay. A typical molding sand contains approximately 4% to 10% clay.
The binders used in core sand may be organic or inorganic. Organic binders
generally used are oil, cereal proteins, and wood protein. These may be present
any where from 0.5% to 4% in a core sand mixture, depending on the application.
Inorganic binders generally used in core sand are portland cement and sodium
silicate. All these binders loose their binding property after repeated use.
A clean/new foundry sand supplied by the Badger Mining Corp. was used in
this project. The discarded foundry sand used in this project was obtained from
one source, Falk Corporation. All sands used were tested in accordance with ASTM
C33. The test results are presented in Table 3. Sieve analysis was performed
on regular concrete sand (Sand 1), Falk - crushed core sand (Sand 2), and clean
foundry sand from Badger Mining Co. (Sand 3). Figure 1 shows the sieve analysis
results for Sand 1, 2, and 3, together with the ASTM C-33 upper and lower limits
for each sieve size. Gradation for Sand 4, 5, 6, and 7 is shown in Figure 2.
Sand 4 is a blend of 75% regular concrete sand with 25% used foundry sand from
Falk Corporation. Sand 5 is a blend of 65% regular concrete sand with 35% used
foundry sand from Falk Corporation. Sand 6 is a blend of 75% regular sand with
25% clean sand from Badger. Sand 7 is a blend of 65% regular concrete sand with
35% clean sand from Badger.
Mixture Proportioning
Five trial mixes were produced in the CBU laboratory. One of these five
mixes was a control mix. Two mixes contained used foundry sand, and the other
two contained clean/new foundry sand. These by-products were used as one on one
replacement of regular sand by weight. A portland cement concrete was proportioned
to have 28-day compressive strength of 38 MPa (5500 psi). In addition to the
reference concrete (Control Mix), other concrete mixtures using discarded foundry
sand with replacement of 25% to 35% of regular sand by weight were prepared.
The corresponding mixtures were designated as 20-F2 and 20-F3. Also concrete
mixtures containing 25% and 35% replacement of regular concrete sand with clean/new
foundry sand were prepared. These mixtures were designated as 20-F4 and 20-F5,
respectively. The water-to-cement ratio was maintained at 0.48 for all mixes.
All mixes were non-air-entrained. Details of the mixture proportions and
rheological properties of the five concrete mixes are given in Table 4.
MANUFACTURE OF CONCRETE AND CASTING OF TEST SPECIMENS
All the five trial mixes were produced in the laboratory of the Center for
By-Products Utilization at the University of Wisconsin-Milwaukee. An electric
tilting drum type mixer having a 0.14 m3 (5 cu. ft.) mixing capacity was used
to mix the concrete. For each mix slump, unit weight, temperature of the fresh
concrete, and the amount of air, were determined. 150 mm x 300 mm (6" x 12")
cylinders were cast in accordance with ASTM C 192 for measuring the compressive
strength of concrete, modulus of elasticity and splitting tensile strength at
3,7 and 28 days. All of the specimens were demolded after 24 hours and immersed
in lime saturated water at 23 ± 1.7 C (73 ± 2 F) until the time of test. The
cylinders were capped using a sulfur capping compound to ensure that the test
surfaces were parallel and smooth.
TESTING PROGRAM
Three cylinders for all mixes were tested at each test age, to determine
their uniaxial compressive strength in accordance with the ASTM C39. Splitting
tensile strength tests were also carried out on three cylinders for each mix,
at each test age in accordance with ASTM C496. Also three cylinders for each
mix were tested at each test age in accordance with the ASTM C469, to determine
the modulus of elasticity.
RESULTS AND DISCUSSIONS
The fresh concrete data (Table 4) showed that mixes with used foundry sand
(Mix No. 20-F2 and 20-F3) had a substantially low values of slumps of less than
35 mm (1½") while the control mix (Mix No. 20-F1) had a slump of 154 mm (6") for
the same water content. Thus the water demand increases for mixes containing
used foundry sands. This is believed to be due to presence of binders. The test
results for clean/new foundry sand mixes (Mix No. 20-F4 and 20-F5) show the increase
in the slump 120 to 135 mm (4¾" to 5¼"). From the Table 3 it is clear that the
saturated surface dry condition absorption of the used foundry sand is considerably
higher than the regular concrete sand. Bond between aggregate particles and the
cement paste may have been weakened due to the presence of the binders in the
sand. Probably this led to reduced strength for the concrete with used foundry
sand.
Compressive Strength
The compressive strength data for all the five mixes is presented in Table
5. The test data shows that all the five mixes averaged compressive strengths
greater than 30 MPa (4400 psi) at the 28-day age. The compressive strength was
found to increase with age for all of the mixtures as shown from the test data.
The compressive strength results show that the mixtures containing used
foundry sands showed lower strengths at all test ages. The compressive strength
of concrete containing 25% used foundry sand is 23% lower than control mix at
28-day age. Similarly concrete containing 35% used foundry sand has 30% lower
value than that of control mix. However, the decrease in the compressive strength
of 20-F2 and 20-F3 as compared to the design strength of 38 MPa (5500 psi) is
11% and 19%, respectively at 28 days. But concrete containing 25% and 35%
replacements of regular concrete sand with clean/new foundry sand showed almost
the same compressive strength as control mix at all ages. At 28 days testing
20-F4 and 20-F5 showed a compressive strength within 1% of the control mix. Hence
the decrease in strength when used foundry sand is used in concrete is due to
the presence of the binder in the used sand.
Splitting Tensile Strength
The splitting tensile strength for all mixes are shown in Table 6. The
test data showed an increase in the tensile strength with age.
Concrete mixtures containing 25% and 35% used foundry sand showed 20% to
40% reduction in tensile strength than that of control mix at the 28-day age.
However, the ratio of tensile to compressive strength was relatively constant
at 10 to 11% of compressive strength, except Mix 20-F5 for which the ratio was
seven percent.
Modulus of Elasticity
The static modulus of elasticity data is presented in the Table 7. It is
observed from the test results that modulus of elasticity increases with age.
From the table, the modulus of elasticity of the concrete containing 25%
and 35% used foundry sand is lower than that of control mix at early ages. However
at 28-day age the control mix and mix with 25% foundry sand shows approximately
the same value of modulus of elasticity. However, the 28-day modulus of elasticity
of concrete containing 25% and 35% of clean foundry sand is slightly greater than
that of the control mix.
CONCLUSIONS
The compressive strength values for concrete with 25% and 35% regular sand
replacements with used foundry sand are lower than the concrete with no replacement.
But concrete containing 25% and 35% replacement of fine aggregate with clean/new
foundry sand showed compressive strength similar to that of the control mix.
Therefore, the reduction in the strength for the concrete with used foundry sand
was probably due to the presence of binders. Compressive strength may be increased
by using admixtures, and/or additives such as fly ash. In general, concrete
containing used foundry sand up to 35% as a replacement of regular sand exhibited
compressive strength in excess of 30 MPa.
Based on the results obtained, it can be concluded that structural grade
concrete can be produced using discarded foundry sands as a partial replacement
of regular concrete sand. Test data showed that the mix containing 25% discarded
foundry sand showed about 10% higher compressive strength at 28 days as compared
with 35% used foundry sand. The control mix compressive strength was, however,
about 20 to 30% higher than the mixes containing discarded foundry sands.
The modulus of elasticity data shows that the modulus of elasticity at the
28-day age varies in the range of 2 to 4% from mix to mix.
The two mixes 20-F2 and 20-F3 gave comparatively lower values of entrapped
air content. No marked difference was observed in the density of fresh and hardened
concrete for all mixtures.
FUTURE RESEARCH
The research carried out so far is only the initial stage of this project.
Durability studies have not been done on concrete containing used foundry sand.
Therefore, it is planned to study durability properties like alkali-silica
reaction, freeze-thaw, chloride ion permeability, interaction with air-entraining
agents, fatigue strength, etc., of concrete made with used foundry sand concrete.
REFERENCES
1. Naik, T.R. (1987). "Foundry Industry By-Products Utilization." Center for
By-Products Utilization, UW-Milwaukee.
2. Ishwar P. Murarka (Ed.) (1987). "Solid Waste Disposal and Reuse in U.S."
Vol. 1, 2, CRC Press, Boca Raton, Florida.
3. American Society for Testing and Materials, (1990). Annual Book of ASTM
Standards, Vol. 04.01.
4. American Society for Testing and Materials, (1990). Annual Book of ASTM
Standards, Vol. 04.02.
5. Heine, R.W., Loper, C.R., Jr., Santa Maria, C., and Namninga, N., (1975).
"Solid Waste from Foundry Processes", University of Wisconsin Engineering
Station, A Report of Research sponsored by AFS at the UW-Madison.
6. Greer, B.A., Vonderracek, J.E., Ham, R.K., and Oman, D.E., (1987). "The
Nature and Characteristics of Foundry Waste and its Constructive Use: A
Review of the Literature and Current Practice", a Report for the United
Foundrymen of Wisconsin.
7. American Foundrymen's Society, Inc., (1991). "Alternate Utilization of
Foundry Waste Sand", A report to Illinois Department of Commerce and
Community Affairs.
REP-155A
Figure 1: Sieve Analysis Envelope for Regular Concrete Sand, Falk -Crushed Core
Sand, and Badger - Clean Sand
Table 1: Physical Properties of Type 1 Portland Cement
No.
(1)
Test
(2)
Result
(3)
ASTM Specifications for
Type 1
Minimum
(4)
Maximum
(5)
(a)
(b)
(c)
(d)
(e)
(f)
Air content of mortar
(%)
Fineness specific
surface Air
permeability test
(m2/kg)
Autoclave expansion (%)
Specific gravity
Compressive Strength
MPa (psi)
1 day
3 day
7 day
28 day
Time of setting (min)
(Vicat test)
Initial set
7.9
391
-0.03
3.09
8.6 (1254)
24.2 (3512)
29.1 (4219)
37.0 (5375)
155
--
280
--
--
--
12.4 (1800)
19.3 (2800)
--
45
12
--
0.8
--
--
--
--
--
--
Table 2: Chemical Composition of Type 1 Portland Cement
Oxide
(1)
%
(2)
SiO2
20.25
Al2O3
4.25
CaO
63.6
MgO
2.24
Fe2O3
2.59
TiO2
0.27
K2O
0.80
Na2O
0.2
LOI
0.55
Table 3: Physical Properties of Fine and Coarse Aggregates (ASTM C33)
Gravel : Coarse Aggregate (max. size 19 mm (3/4"))
Sand 1 : Regular Concrete Sand
Sand 2 : Falk - Crushed Core Foundry Sand
Sand 3 : Badger - Clean/New Foundry Sand
As
Received
Moisture
Content
(%)
(1)
Unit
Weight
(kg/m3)
(2)
Bulk
Specific
Gravity
(3)
Bulk
Specific
Gravity
(SSD)
(4)
Apparent
Specific
Gravity
(5)
SSD
Absorption
(%)
(6)
Percent
Void (%)
(7)
Fineness
Modulus
(8)
Material
Finer
than #200
Sieve
(75μm)
(%)
(9)
Clay Lumps
& Friable
Particles
(%)
(10)
Organic
Impurity
for Fine
Aggregate
(11) ASTM
C566
C29
------- C128 and C127 ----------
C29
C136
C117
C142
40
Gravel
0.25
1666
2.75
2.77
2.82
0.7
43
N.A.
N.A.
0.24
N.A.
Sand 1
0.39
1842
2.43
2.47
2.52
1.0
25
3.57
1.35
0.22
Passes
Sand 2
0.17
1746
2.37
2.45
2.58
3.4
26
2.40
2.70
2.1
Passes
Sand 3
0.09
1746
2.58
2.67
2.87
1.25
33
2.34
0.20
0.10
Passes
Note: kg/m3 = 0.062 lb/ft3
Table 4: Concrete Mix and Test Data for Fresh Concrete
20-F1 Control Mix
20-F2 Mix with 25% Replacement of Regular Sand with Falk Used Core Sand (crushed)
20-F3 Mix with 35% Replacement of Regular Sand with Falk Used Core Sand (crushed)
20-F4 Mix with 25% Replacement of Regular Sand with Badger Clean Sand
20-F5 Mix with 35% Replacement of Regular Sand with Badger Clean Sand
Mix No:
20-F1
(1)
20-F2
(2)
20-F3
(3)
20-F4
(4)
20-F5
(5) Specified Design Strength, MPa
38
38
38
38
38
Cement, kg
362
362
362
362
362
Water, kg
173
173
173
173
173
Sand, SSD, kg
859
644
558
644
558
Used Foundry Sand, kg
0
215
300
215
300
3/4" coarse Aggregates, SSD, kg
1074
1074
1074
1074
1074
Slump, mm
152
32
29
133
120
Air Content, %
2.4
1.8
1.8
2.2
2.4
Air Temperature, C
20
20
20
20
20
Concrete Temperature, C
18
20
20
20
18
Fresh Concrete Density, kg/m3 2467 2499 2467 2435 2499 Hardened Concrete Bulk Density, kg/m3
2450
2435
2450
2450
2450
Note: 1 MPa = 145.04 psi; 1 mm = 0.039 in.; 1 F = 1.8 C + 32;
1 kg/m3 = 0.0624 lb/ft3 = 1.685 lb/cu. yd.
Table 5: Compressive Strength Data for Hardened Concrete (15 cm x 30 cm cylinder)
Mix No.
20-F1
20-F2
20-F3
20-F4
20-F5
Specified Design
Strength, MPa
38
38
38
38
38
% Foundry Sand Replacing
Regular Sand
0
25
Falk
35
Falk
25
Badger
35
Badger
Test Age, Days
(1)
Compressive Strength, MPa*
Actual
(2)
Average
(3)
Actual
(4)
Average
(5)
Actual
(6)
Average
(7)
Actua
l
(8)
Average
(9)
Actual
(10)
Average
(11)
3
3
3
31.0
31.4
22.8
23.6
20.2
19.9
29.3
28.3
31.2
31.2
30.8
25.0
20.0
28.8
31.2
32.3
22.9
19.5
26.8
31.2
7
7
7
37
36.9
28.9
27.9
24.4
26.9
33.2
34.8
38.4
37.8
38
27.3
26.1
35.5
37.8
35.7
27.4
30.2
35.8
37.1
28
28
43.0
43.8
32.3
33.6
30.2
30.7
44.4
43.6
43.0
43.4
44.5
32.3
30.7
41.5
44.6
Table 6: Tensile Strength Data for Hardened Concrete (15 cm x 30 cm cylinder)
Mix No.
20-F1
20-F2
20-F3
20-F4
20-F5
Specified Design
Compressive Strength, MPa
38
38
38
38
38
% Foundry Sand Replacing
Regular Sand
0
25
Falk
35
Falk
25
Badger
35
Badger
Test Age, Days
(1)
Tensile Strength, MPa*
Actua
l
(2)
Average
(3)
Actua
l
(4)
Average
(5)
Actual
(6)
Average
(7)
Actua
l
(8)
Average
(9)
Actual
(10)
Average
(11)
3
3
3
2.6
2.7
1.8
1.8
2.0
2.1
2.6
2.3
2.0
2.1
2.6
2.0
2.2
2.3
2.2
3.0
1.5
2.2
2.1
2.2
7
7
7
3.2
3.2
2.9
3.2
2.4
2.6
3.6
3.5
2.4
2.5
3.2
3.1
2.6
3.5
2.6
3.1
3.0
2.7
3.3
2.6
28
28
4.7
4.6
3.9
3.6
2.9
3.1
4.4
4.0
3.1
3.2
4.4
3.8
3.2
3.8
3.3
Table 7: Modulus of Elasticity Test Data
Mix
20-F1
(2)
20-F2
(3)
20-F3
(4)
20-F4
(5)
20-F5
(6) Age, days
(1)
Modulus of Elasticity, MPa
3
22,000
20,000
17,900
22,700
24,100
3
22,800
22,500
20,700
20,200
20,000
18,400
23,400
23,900
18,600
20,900
3
22,800
20,000
17,300
25,500
20,000
7
25,500
28,400
22,000
26,900
26,200
7
26,200
24,300
23,500
24,500
24,100
23,400
24,100
25,000
28,300
27,600
7
21,400
21,400
24,100
24,100
28,300
28
31,700
31,700
33,100
30,400
33,100
28
32,400
31,700
31,000
31,700
31,000
32,600
36,600
33,400
33,100
33,300
28
31,000
32,400
33,800
33,100
33,800
1 MPa = 145.04 psi