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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

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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

Figure 2: Sieve Analysis Envelope for Blended Sands

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

28

44.0 36.2 31.1 44.9 42.6

________________________

* 1 MPa = 145.04 psi

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

28

4.6 3.2 3.2 3.8 3.1

* 1 MPa = 145.04 psi

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