Pilot Survey on the Physical Properties of Hollow Concrete Blocks

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Technical Note (National Research Council of Canada. Division of Building Research), 1961-12-01

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Pilot Survey on the Physical Properties of Hollow Concrete Blocks

Galbreath, M.

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DIVISION OF BUILDING RESEARCH

NATIONAL RESEARCH COUNCIL OF CANADA

'fE

C

1HI N

_][

CAlL

NOTlE

No.

353

NOT FOR PUBL.ICATION

PREPARED BY M. Galbreath CHECKED BY

FOR INTERNAL USE

APPROVED BY N. B. H. DATE December 1961

-PREPARED FOR _{Advisory Fire Group,}

NRC Associate Committee on the National Building Code

SUBJECT _{PILOT SURVEY ON THE PHYSICAL PROPERTIES OF}

HOLLOW CONCRETE BLOCKS

Concrete blocks are widely used by the building industry in Canada. There is also an increasing application of fire resistance ratings as a measure of the performance of buildings in fire. There is therefore a need for more information on the fire endurance of concrete blocks. The number of variables which can be incorporated into a concrete block such as type of aggregate, size and arrangement of cores, makes it difficult to predict their behaviour in fire. The alternative to testing the product of every concrete block manufacturer in the country is the careful selection of a few types of block that may be considered representative of the production as a whole.

In order to do this, a survey of the type and nature of Canadian blocks is necessary. The Division of Building Research and the

Associate Committee on the National Building Code are both interested in this problem and a pilot study was undertaken at the end of 1959 to obtain information and experience which might be applied to a more general survey. A questionnaire (Appendix A) was prepared and

visits were made to three manufacturers of concrete blocks in Ottawa. From this survey, it became clear that a simpler form of questionnair e would be desirable and that it is essential that only those questions that can be readily a!1swered on the spot should be included.

A sample of each type of block manufactured was measured and the number of cores noted. One of the problems encountered was

2

-to decide what measurement -to take. Past fire tests on block walls quote three criteria: 1) percentage core area, 2) minimum face shell thickness, and 3) equivalent volume. The core holes are tapered in their length and rounded at the corner to facilitate' extraction of the moulds. This makes it difficult to measure the area on the job and the area itself varies depending on what part of the block is measured. The minimum face shell thickness is the criterion used in ASTM

standard specifications. This is defined as the minimum face shell for the largest core hole measured at the thinnest point. ('rhis may be the average of the two face shells in the same core;) The minimum permitted dimensions for face shell in ASTMspecifications, are

1 1/411 _{and 3/4}11_{for load-bearing hollow concrete blocks and 1/2"for} non -load -bearing blocks.

Carl Menzel (1) has suggested that the percentage of solid material in the wall thickness is the significant factor. This can

only be measured by displacement of a liquid. Underwdters Laboratories use this method and apply the information in the form of thickness of

equivalent solid block wall as the basis of their estimated fire endurance ratings.

A factor which has to be borne in mind is that although the block-making machines are ｧ･ｮ･ｲ｡ｬｬｹｳｴ｡ｮ､｡ｲ､ｾ the moulds used to

form the blocks wear out fairly quickly and are continually bein.g repaired or replaced by the staff of the plant. There is therefore a probability that there will be some variation in dimensions even in the production of one plant over a period of time. It was noted that one manufacturer in Ottawa was proposing to change the over -all dimensions of his

units to modular sizes by welding steel plates to the faces of the moulds.

Some difficulty was experienced in obtaining an exact des cription of the nature of the aggregate and of the mix used in making the concrete. The first was because the producer is not interested in the nature of the gravel aggregate used and cannot give an exact description. A

geologist's examination at the quarry would appear to be almost essential in view of the importance of this factor in fire endurance. The second difficulty arose because the manufacturer tends to regard his mix as a trade secret and he is afraid competitors may benefit by any

disclosure of his formula. The revised form of questionnaire, Appendix C, has been simplified following the pilot survey. A simple description of the aggregate used is requested and dimensions are limited to those readily obtainable in the field namely over -all size, face shell and web thickness. It is hoped that this will provide the information upon which further study may be based.

3

-REFERENCES

-(1) Carl A. Menzel. Tests of the Fire ｒ･ｳｩｳｾ｡ｮ｣･ and Strength of Walls of Concrete Masonry Units. Portland Cement Associ-ation, Chicago 1934.

APPENDIX

A

SURVEY

OF CONCRETE

BLOCKS

PRODUCED IN CANADA

H

IL----W - average

"

Nom. Size of Block: length L,I --IlthiCkness T1 --11height H!.... _ T

]L---I[ "

]L.-_ _

I

Web Thickness

Face Shell Thickness: F. S. - average Over-all Dim. (net):

If) zlf) o ILl -::J: If)<..> Zz ILl -ｾｺ a

Radius of Corner Fillets: R - if corners of cores are curved

Min 11.-__--1 Max Other (describe) Size: De scription Fine Aggregate Cement : Portland

0

Coarse Aggregate: Description If) --I <l D: ILl I-<l :E

-Size: Max Min 11- _

Additives (if used) :

Proportion by weight: Cement

D

r==J

c=J

x

Quantity of Additive %

Water - Cement Ratio

Block Making Machine (describe)

Water

Cement

B

Moulding Process: Curing Process:

Pressed

CJ

c=J

Air-Dried DLow Press. StealnD Autoclave

0

IfAutoclave State Temp. Pressure

APPENDIX B

VISITS TO CONCRETE BLOCK MANUFACTURING PLANTS IN OTTAWA

Visits were made to the three concrete block manufacturing plants in Ottawa as a pilot study for a proposed survey of concrete

blocks produced in Canada. The purpose of the inquiry is to find out

the characteristics of the blocks being prodllced at the present time with particular reference to those factors that influence fire resistance and to establish a suitable form of questionnaire for the survey.

The firms visited wer e:

Frazer Duntile Ltd. , Twin City Dunbrik,

Harry Hayley and Sons, Ltd.

1. Manufactur er

FRAZER DUNTILE CO. LTD., visited 8 December 1959,

Clyde Ave., Ottawa, Ont.,

Plant Manager: Mr. Mitchell,

Bob Bruce in char ge of block making.

2. Materials

a) Coarse Aggregate - Limestone from Clyde Ave. Qual'ry,

b) Fine Aggregate - Sand from Bells Corners, Onto

c) Cement - Portland, d) Additives - None. 3. Mix 400 lb Portland Cement 300 lb Crushed Limestone 3/8" to 1/4" 1100 lb Crushed Limestone 3/16" to 1/16" 2300 lb Crushed Limestone 1/16" to 0

500 lb Sand 50% pass #28 sieve retained #48

50%pas s #48 sieve retained # 100

varies 50/50 to 60/40

4. Machine

Besser Co. ,

Alpena, Michigan. 5. Curing

Low Pressure Stearn. 6. Design of Units

a) Number of Cores - Three b) 1. Height of Block - 7 3/4"

2. Length of Block - 15 3/4"

Wall Width Min. Face Shell, Min. Web Thickness,

Nom. Actual In. In.

4 3 3/4 1 1

6 5 3/4 1 1

8 7 3/4 1 1/4 1

10 9 3/4 1 1/2 1 1/4

12 11 3/4 1 3/4 1 1/8

Also 2 11/16" wide x 7 3/4" high x 15 3/4" long solid block. 7. Remarks

Frazer Duntile operate their own stone crusher which produces a square type aggregate which they claim is superior for block making.

1. Manufacturer

TWIN CITY DUNBRIK, visited 14 December 1959, 158 McArthur Road, Eastview, Ont.,

Office Manager: Harvey Smith. 2. Materials

a) Coarse Aggregate - Stone from Wright Bars. Quarry, Montr eal Road,

Ｎｾ

B3

-b} Fine Aggregate - Sand and Gravel (pit run), A. Charron, Chelsea,

c} CeITlent - Portland - will probably be changing to high

early strength ceITlent in near futu1 e,

d) Additives - Air Entraining Powder; Goodwin Sales,

"Ayrtrap", A. C. Horne.

3. Mix

450 lb Portland CeITlent 800 lb Stone, 3/8" down

2200 lb Sand and Gravel, pit run

12 gallons water approx.

4 oz. Air entraining powder

1 quart Ayrtrap.

4. Machine

Imperial Model 420

The Lithelow Co., Holland, Michigan.

5. Curing

Low Pressure SteaITl

6. Design of Units

a} NUITlber of Cores - Three

b} 1. Height of Block - 7 3/4"

2. Length of Block - 15 3/4"

Wall Width Min. Face Shell, Min. Web Thickness,

NOITl. Actu al

In.

In.

4

/4

/4

/4

/4

Twin City Dunbrik have a parallel production of concrete bricks (Dunbrik)

B4

-1. Manufa ctur er

HARR Y HAYLEY AND SONS, LTD., visited 12 January, 1960,

ｈｵｲ､ｭｾｮｳ Bridge, Ottawa, Ont.,

Office 1vlanager: Mr. Packman,

Branch Manager Eastview: Mr. G1edman. 2. Materials

a) Coarse Aggregate - Gravel from Perkins Mills, Quebec, Pit run, screened before use,

Cinders,

Expanded shale under consideration, hoped to start production in Spring,

b) Fine Aggregate - See above,

c} Cement- Portland, experimenting with high earlY strength cement,

d) Additives - None. 3. Mix

Considered to be trade secret. 4. Machines

Besser Co., Alpena, Michigan,

Gene Olsen Corporation, Adrian, Michigan. 5. Curing

Low Pressure Stearn. 6. Design of Units

a) Number of Cores - Two

b) Eastview Plant, Gene Olsen Machine - 1.

2.

Height of ｂｬｯｾｫ - 7 3/4" Length of Block - 15 3/4"

Wall Width Min. Face Shell, Min. Web Thickness,

Nom. Actual

In.

4 3 3/4 1 1/8 1

8 7 3/4 1 3/4 1 1/2

10 9 3/4 2 1/8 1 3/4

B5

-c) Hurdmans

Bridge,

Modular

2. Length of Block - 15 5/8

Modular

Wall Width Min. Face Shell, Min. Web Thickness,

Nom. Actual

In.

In.

3* 2 5/8 7/8 1 4 3 5/8 1 1 6 5 5/8 1 5/8 2 8 7 5/8 1 3/4 1 3/8 10 9 5/8 1 7/8 2 12 11 5/8 2 1 3/4

*

7. Remarks

Eastview Plant concentrates on lar ger sizes and gravel blocks. Hurdmans Bridge Plant on cinder blocks and 'smaller sizes.

It is intended to convert Gene Olsen Machine to modular dimensions by inserting thicker divisions and welding additional plates to the

mould. Moulds are not obtained from manufacturer but are made

and repaired in the plant. Formerly soft steel was used but

conversion to hardened steel allows production of 8,000 blocks between repairs instead of 3, 000.

APPENDIX C

FORM OF QUESTIONNAIRE

ON PRODUCTION OF HOLLOW CONCRETE BLOCKS

( I ) Manufactur er '..

• • .. • .. .. • .. .. .. • .. .. .. .. .. .. .. • .. .. .. .. • .. .. .. .. t .. .. .. .. .. .. .. .. .. .. ｾ .. .. .. .. .. .. • .. .. • .. .. .. .. • ..

(2) Material

Material Size

Max. Min. (a) Coarse Aggregate:

(b) Fine Aggregate: (c) Cement:

(d) Additives (if any)

.

(3) Mix (a) Cement lb . (b) Coarse Aggregate lb . (c) Fine Aggregate lb . (d) Water gallons . (e) Additives .

(4) Block Making Machine

(a) Description .

(b) Manufactur er .

(5) Method of Curing

,

f

(b) Low Pressure Stearn

CZ

-(c) Autoclave .

If curing is by autoclave state

(i) Temperature .

(ii) Pressure

(6) Design of Units

(a) Number of Cores:

(b) 1.

2.

Height of Block - Nom. :

Length of Block - Nom. :

Exact: Exact:

Block Thickness Min. Face Shell, Min. Web Thickness,

Nom. Exact

In.

In.

7. Standard Specifications

Do the blocks comply with:

(a) A. S. T. M. Standard Specification for Hollow Load-Bearing

Concrete Masonry Units (ASTM C9052)

(b) A. S. T. M. Standard Specification for Hollow Non-Load-Bearing

Concrete Masonry Units (ASTM C145. 52)