NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

IOOO-IO-L7I6 April 10 , 1953 2335

lublic PROPSRTi:i,S CF 'SFECTRA-GLAZE’'

,

A GLAZED-PAGE CCFCRETE BLOCK

by

D. S. Goalwln, E. W. Bender,

E. R. Oglio, and H, Shirley

Requested by the

Office of the Chief of Engineers

Department of the Army

The publication, re

unless permission is

25, D, C, Such per

cally prepared If f

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

In part. Is prohibited

andards, Washington

port has been speclftjport for Its own use.
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PROPERTIES OP "SPECTRA -GLAZE",

A GLAZED-FACE CONCRETE BLOCK

1. INTRODUCTION

"Spectra-Glaze" is a high-pressure steam-cured, concretemasonry unit with a glazed face* It is made in two types. Type

A, with a sprayed-on, transparent coating, and Type B, a tileface unit made in several colors* At the request of the Engineer

Ing Division, Military Construction, Office of the Chief of

Engineers, Department of the Army, the National Bureau of Standards has performed a variety of evaluation tests on Type B

Spectra-Glaze, a cinder-block unit made by Concrete Pipe and

Products Co, of Richmond, Virginia* There are several other

manufacturers of this product, but it is not known whether

their product is identical with the one tested*

The units tested were three-cell stretcher units, 15 3/h ^

7 3/h X 3 3/h overall dimensions. Three colors were

tested, light green, beige, and blue; some uncoated blocks were

also tested for comparison purposes. It is understood that

other shapes, sizes, and colors are available.

Type B Spectra-Glaze, the tile-face unit, is made by giving

conventional concrete block a smooth, colored facing* Three

coats of "Cermac" glazing compound are sprayed on the block at

l80° F; it is then baked for one hour at temperatures of from

250° to 375° F.

Dimensions of typical blocks as received from the manufacturer are listed in table 1, Sample blocks are shown in figure 1

TABLE 1*

Dimensions of Typical Blocks

Coated Uncoated

Length, in. 15. 6o 15.60

Block thickness, in. 3.70 3.60

Gross area, in^ 57.72 56.16

Shell thickness, in. 1,00 1.05

Web thickness, in. 1.05 1.05

Depth, in.

Proportion of cored

7.65 7.65

spaces, percent 70, 68. — As received from manufacturer*

- 1 -

-2 -

The OCE request for the tests of Spectra-Glaze (letter of

January 9> 1953) asked for an evaluation of the durability of

the material. Tests requested Included determination of resistance to freezing and thawing, to strong cleaning solutions,

to stains likely to be encountered in bathrooms, and to penetration of greases normally encountered in kitchens® Tests we

were also requested to determine whether the coating would be

likely to craze and whether the colors would be unfading.

2. FLAME-SPREAD TESTS

Eight coated units were bolted to each other to form a

specimen 32 by 32 in. Mineral-wool pads were placed between

blocks to simulate mortar joints. The specimens were subjected

to the fire test as described in Federal Specification SS-A-ll8a

for Acoustical Units, Prefabricated, using the standard timetemperature curve for 20 minutes.

Three specimens were tested. The face flamed during each

of the tests but did not touch the angle-iron frame during or

after the tests. This performance requires the classification

of "slow-burning."

3. COMPRESSIVE STRENGTH

Compressive strengths were determined for five coated specimens and five uncoated specimens in accordance with procedures

given in Standard Methods of Sampling and Testing Structural

Clay Tile, ASTM C112-38, and are given in table 2, except that

only three specimens were tested,

TABLE 2.

Compressive Strengths of Blocks

Compressive

strength

Ib/in^

Coated blocks, average 1310

Uncoated blocks, average 1780

Air dry, using gypsum plastic capping mortar.

Average of three specimens.
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ABSORPTION

Absorption data were obtained for two samples, one coated

and one uncoated. The methods used were similar to those

specified in ASTM Specifications for Structural Clay Pacing

Tile, C212-i|9T, except that only two specimens were used and

the absorption by boiling was carried on for five hours rather

than one. The pertinent data are given in table 3*

TABLE 3.

VJeight and Absorption of Blocks

Coated Uncoated

Weight, dry, lb 8,33 8,l8

Moisture content as received,

percent of absorption (2Li.-hr

cold) 23 22

Specific gravity 1,9 lo8

Absorption, 2l4.-hr cold, percent 13*6 13»8

Absorption, 5-hr boil, percent 19.14- 19.5

Saturation coefficient, percent 70 70

5. CRAZING

Two blocks were autoclaved at a steam pressure of

150 Ib/ln^ for one hour in accordance with ASTM Specifications

for Glazed Masonry Units, C126-50T, No crazing was observed.

6. FREEZING AND THAWING

Four specimens, two coated and two uncoated, were subjected

to 2L|.-*hour freezing and thawing cycles. The methods used were

similar to those of ASTM Standard Methods of Testing Brick,

C 67 -l4-Li-. The specimens were stored in air in a chamber at 0

° F

for 17 hours and then thawed and stored in water at 50° F for

7 hours. They were immersed in water for three days prior to

the tests.

The effects of the treatment were based on visual observations and weighings as the test proceeded. The weights of the

specimens after each two days of cycling are given in table I4., The four specimens were carried through 20 freezing and thawing cycles, as shown above, without apparent crazing or other

failure. Some slight spalling was observed in the latter

cycles.

-1+-

TABLE I4..

Freezin,^ and Thawing

Weight of coated sample Weight of uncoated sample

-rfe IrHi

1

! ,U. 1 *•1 irZ

lb ik ik

Dry 8.470 8.214.5 7,985 7.995

12 hour cold 9,700 9.430 9.155 9,240

2 cycles 9,815 9.500 9.275 9.380

6 cycles 9,840 9.525 9,300 9,400

10 cycles 9.375 9.530 9.315 9,410

20 cycles 9.885 9.570 9,340 9,430

After the completion of the 20 cycles, two of the specimens, one coated and one uncoated. were removed from the chamber

and subjected to compressive tests . For comparison purposes,

two similar blocks which had not been subject to the freezing

and thawing cycle were soaked for three days and subjected to

compressive tests at the same time as the above two blocks.

The results are shown in table 5 , TABLE 5.

Effects of Freezing and Thawing

Length ^Width Depth Compressive

strength

Specimans after 72 -hr

soak ZS,

Coated

Uncoated

Specimens oven-dry

Coated

Uncoated

Specimens after 20

freezing and thawing

cycles

Coated

Uncoated

in. in. in. Ib/in®

15 . 65 3.75 7,70 1110

15,65 3.75 7,70 1640

15.65 3.75 7.70 1200

15.65 3.75 7,70 1720

15.65 3.75 7,68 1390

15.65 3.75 7.70 1270

Zi At room temperature
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7 . SPOTTING RESISTANC

Tests were made to determine spotting resistance to some

common kitchen and bathroom, agents. Whenever the supply of

specimens permitted, all three colors, beige, blue, and light

green, were subjected to test. The test conditions are given

in the following sections and the test results in table 6,

7 e 1 C ottonseed oil

Three drops of cottonseed oil of U.S.P, grade

were applied to the coated surfaces at 70-80° F,

covered with a watch glass, and allowed to remain

for periods of 15> and 30 minutes and 5 hours.

At the expiration of each exposure period the oil

was wiped from the surface and the surface rinsed

with carbon tetrachloride. All panels were allowed

to dry for 2I4. hours and exarr.ined at a distance of

five feet for staining,

7o2 Bacon grease

The coatings were tested in the same manner as

described in section 7»1 except that hot bacon grease

(320° F) was used,

7» 3 Sodium hydroxide

The procedure was the same as in section 7«1

except that the coating was exposed to a 10^ solution of sodium hydroxide and the surface rinsed with

distilled water,

7 c4 Dishwashing compound

The procedure was the same as in section 7*3

except that a 10^ solution of dishwashing compound

was used conforming to the requirements of G.S.A,

Specification 207, Type II.

7 • 5 T incture of iodine

Three drops of tincture of iodine (U.S.P, grade)

were applied to the coated surface at 70-30° F, covered with a watch glass, and allowed to remain for 5

minutes. The solution was then wiped from the surface

with absorbent cotton and rubbed with three successive

alcohol ( 95^ ethanol) -moistened wads of absorbent

cotton. The surface was rinsed thoroughly with the

alcohol, allowed to dry, and examined for staining

at distance of five feet.
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tests.

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The tost was made in accordance with the method

described in ASTM Designation C126-50T, section 17(c),

except that one specimen of each color was used.

8, CLEANABILITY

The coatings were soiled by exposure for 5 hours to cottonseed oil in the manner described in section 7*1* The excess

oil was wiped from the test area and the surfaces subjected

to two cleaning procedures* In one, the surface x-^jas rubbed

with a wad of absorbent cotton moistened and soaped with plain

white toilet soap, using a circular motion. The rubbing consisted of 35 clockwise and 35 counter-clockwise cycles. The

surfaces were then rinsed with warm distilled water (52° C),

allowed to dry for 21]. hours, and examined at a distance of five

feet.

The other cleaning procedure was the sam.e as the above

except that cake grit soap, conforming to the requirements of

F.S, P-5-571, Type A, was used in place of the plain white

soap.

The tost results are given in table 6,

9. WATER-VAPOR TRANSMISSION

Discs, l/2- to 3/l4--in. thick, were cut from the coated

and uncoatcd sections of the beige-coated and green-coated

units and the water-vapor transmission rate determined in

accordance with ASTM Standard Methods of Test for Water Vapor

Permeability, D988-Ij.8T, except that specimens II.I4-6 sq in, in

area and a balance sensitive to 0.01 gram were used.

The test data arc given in table 7i the results arc reported both in grams per square meter per day and in "perms”

The latter was calculated from the following equation:

W

= " Atl’p""

where

:

W = weight in grains of water-vapor transmitted

A = area, in square feet, of specimen

t = time, in hours

^p = water-vapor pressure difference, in inches of

mercury, across the specimen
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The Housing and Heme Finance Agency in their publication

"Condensation Control" has defined a vapor-barrier material

as one having a vapor-transmission rate of less than one perm<

TABLE 7.

yjater-Vapor P ermeance and Color Fastness

Water-Vapor Transmission

at 73±I° F and ^Q±2^ R>H.

Beige coating Green coating

g/m^/day perm g/m^/day perm

Uncoated section

Coated section

66

4

9.9

0.7

89

k

13.5

0.7

Reflectance

Beige

coating

^ Green

V coating

Blue

coating

percent percent percent

Before exposure

After exposure /

a

Change

22.7

22,2

NBS units

o.k

23. ll- 22 r 7

NBS units

0.6

20,9

20.4

NBS units

0.5

Za Exposure consisted of 3^5 hours of accelerated testing,

5l minutes of light and 9 minutes of light and spray

water every hour.

10c COLOR FASTNESS IN ULTRAVIOLET LIGHT

Panels cut from the coated sections of the units were

exposed to 325 hours of accelerated test for durability in a "Type HVKL-X Weather-ome ter" manufactured by the Atlas Electric

Devices Company, Chicago, 111. One carbon arc, centrally

located, with a power consumption of 1,8 KW was used as the

source of radlationc The 60-minute exposure cycle consisted

of 5l minutes of light and 9 minutes of both light and spray

water (demineralized).

Reflectances were determined both before and after exposure using a Hunter Multipurpose Reflactometer with the green

"Tri-stimulus" filter. Change in reflectance was used as the

indication of color change and was expressed in NBS units which

were obtained as follows:

NBS Units = 10(^A - '^)

where: A = reflectance before exposure

B = reflectance after exposure

The test results are given in table 7,
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Color comparison was also made with duplicate panels kept

in dark storage by visual examination from a distance of five

feet. No difference was observed between the e::posed and

unexposed surfaces.

11. SUMNIARY

Although there are no standard specifications for products

of this t^rpe, their performance can be compared with the performance of similar products in applicable tests from specifications such as ASTM Standard Specification for Hollow NonLoad-Bearing Concrete Masonry Units, C129-39, ASTM Tentative

Specifications for Glazed Masonrj^ Units, C126-50T, and ASTM

Tentative Specifications for Structural Clay Facing Tile,

C212-I|9T.

The performance of the coated faces of the blocks classified them as ’’slow-burning" in the flame-spread tests.

Compressive strengths of both coated and uncoated blocks

were roughly equivalent to "standard" tile in ASTM Specifications for Structural Clay Facing Tile, C212-I4.9T, which requires

a minimum average compressive strength of llj.00 Ih/ln^ for endconstruction tile.

Absorptions were roughly equivalent to the requirements

of C212-I4.9T for typo FTS tile, which specifies the 21i-hr cold

absorption as not exceeding 13^ and the 1-hr boiling absorption

as not exceeding l6%. The moisture content of the blocks, as

received, was better than the requirements of ASTM Specifications for Hollow Non-Load-Bcaring Concrete Masonry Units,

C129-39, which requires that the moisture content as received

not exceed l\.0% of the total absorption.

Resistance to crazing was satisfactory when tested in

accordance with ASTM Specifications for Glazed Masonry Units,

C126-4Li.T,

Freezing and thawing da.ta on comparable materials are not

available. However, the results may be considered to have been

satisfactory in that the blocks did not break, did not lose

weight as compared with the original conditions, and showed an

increase in compressive strength after 20 freezing and thawing

cycles

.

Of the reagents used, cottonseed oil appeared to produce

the most pronounced staining of the coating. Some of the reagent appeared to be retained by the matt surface of the coating after the five-hour exposure test and was not completely

removed by the solvent. In the 5”; l5~^ and 30-minute exposure
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tests staining was no worse than barely visible. Although

staining was discernible when bacon grease was used, it was

not as pronounced as that produced by cottonseed oil. Except

on the green coating, staining was slight. In the tests with

iodine and ink, the only pronounced staining occurred with the

former on the green coating. Sodium hydroxide and the dishwashing compound did not affect the appearance of any of the

coatings

,

Although standard requirements of performance for products

of this type do not exist, perhaps the most nearly applicable

one is ASTM Designation C126-50T (Tentative Specifications for

Ceramic Glazed Structural Clay Pacing Tile, Facing Brick and

Solid Masonry Units) which permits a slight discoloration of

the surface on matt finishes when ink is used as a reagent.

If this is used as a criterion, the product may be considered

satisfactory in spotting resistance to all reagents used in

the tests except tincture of iodine (green coating only) and

five-hour exposure to cottonseed oil.

The stain was not completely removed in every case by the

cleaners in the tests, but in only two Instances (blue and

green coatings, cleaned with cake grit soap) were the residual

stains classed as greater than slight.

The test results showed that the coating was effective in

reducing the rate of water-vapor transmission of the cinderblock units under the test conditions. Assuming that the rate

of water-vapor transmission is proportional to the water-vapor

pressure difference across the specimen, the coated units can

be classified as vapor barriers under the present HHFA definition.

Close examination uf the coatings revealed a large number

of light spots about the size of pin points distributed over

the entire surface of the panels after exposure to ultraviolet

light and water. However, when examined at a distance of five

feet, these spots were not visible. The comparatively small

changes in reflectance, as well as comparison of the exposed

specimens with duplicates kept in dark storage, indicate that

no significant color changes occurred during these tests.

This Bureau has no data correlating the specification requirements given above for other materials with the performance

in service of the subject material. The fairly satisfactory

performance of this material in the laboratory tests, although

informative, does not necessarily indicate that the performance

in service would be equally satisfactory.
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