GENERAL OVERVIEW OF BRICK MANUFACTURING...Brick masonry arches have been used to add beauty and...

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GENERAL OVERVIEW OF BRICK MANUFACTURING

INTRODUCTION

Brick is one of man’s oldest building materials. Although equipment and technology has improved the quality and appearance of

the brick produced, the basic raw material and manufacturing steps remain the same.

RAW MATERIAL

Clay is one of the most abundant mineral materials on earth. However, not all clay possesses the properties to be used in modern brick production. There are three general types of clay used in brick manufacturing.

1. Surface Clay: May be the up thrusts of older deposits or of more recent sedimentary formations. They are formed near the surface.

2. Shale: Clays that have been subjected to high pressures until they have hardened almost to the form of slate.

3. Fire Clay: Usually mined at deeper levels than the other two clays and have refractory qualities.

MANUFACTURING

There are six general phases in the manufacture of brick.

1. Winning: The mining of clay or shale and transportation of it to the manufacturing site.

2. Preparation: Crushing, grinding and mixing the clay into a uniform raw material.

3. Forming: Mixing water with the prepared clay in a plug mill. The amount of water used will determine the plasticity of the clay.

The process used to form the brick will determine the plasticity required.

• Stiff-Mud Process - the clay with 12 to 15% moisture content is extruded through a die to produce a column of clay.

• This column is then cut into the desired sizes.

• Soft-Mud Process - the clay with 20 to 30% moisture content is too soft to go through a die. It is formed in molds. To prevent the clay from sticking, the molds are lubricated with either sand (sand-struck) or water (water-struck).

• Dry-Press Process - the clay with less than 10% moisture content is formed in steel molds under pressure from hydraulic or compressed air rams.

4. Drying: After the wet clay is formed it is dried to remove the moisture through evaporation. The drying time is usually 24 to 48 hours.



5. Firing and Cooling: Firing, one of the most specialized steps in the manufacturing of brick, requires from 40 to 150 hours depending upon kiln type and other variables. Firing may be divided into six general stages: 1) water-smoking (evaporating free water), 2) dehydration, 3) oxidation, 4) vitrification, 5) flashing and 6) cooling. All except flashing and cooling are associated with rising temperatures in the kiln. After the temperature has reached the maximum and is maintained for a prescribed time, the cooling process begins. Because the cooling has a direct effect on color and because excessively rapid cooling will cause cracking and checking of the ware, cooling is an important stage in the flashing process.

6. Drawing: The process of unloading a kiln after cooling and packing the brick for shipment

COLOR

The color of fired clay depends upon its chemical composition, the firing temperatures and the method of firing control. Of all the oxides commonly found in clays, iron probably has the greatest effect on color. Regardless of its natural color, clay containing iron in practically any form will burn red when exposed to an oxidizing fire. A general rule of thumb is the darker the brick, the higher the firing temperature.

TEXTURE AND COATINGS

Many brick have smooth or sand-finished textures produced by the dies or molds used in forming, in the stiff-mud process, many textures may be applied by attachments which cut, scratch, roll, brush or otherwise roughen the surface as the clay column leaves the die. Many plants apply engobes (slurries) of finely ground clay, coloring agents and water to the roughened column. Sands can be rolled into the slurry coating to create interesting and distinctive patterns in the finished products.

BRICK CLASSIFICATIONS

ASTM (American Society for Testing and Materials): ASTM is the world’s leader in the development of voluntary consensus standards for materials, products, systems and services. Its 140 standards writings committees annually publish over 7,000 standards to meet the needs of numerous industries and services.

ASTM C216-04

ASTM C216-04 is the standard specification for Facing Brick.

A The saturation coefficient is the ration to absorption by 24-h submersion in cold water to that after 5-h submersion in boiling water.

B Absorption alternative: The saturation coefficient requirement does not apply, provided the cold water absorption of any single unit of a random sample of fired brick does not exceed 8%


BRICK CLASSIFICATIONS (continued)

EXPOSURE (Weathering) Because of the varying climates throughout the country, and a different application of brick, specific grades of brick are required. Brick must meet a grade of SW or MW based on the weathering index and the exposure of the brick. The weathering index is the product of the average annual number of freezing cycle days and the average annual winter rainfall in inches. The exposure is related to either a vertical or horizontal surface and whether the unit will be in contact with the earth. A higher weathering index or a more severe exposure will require a face brick to meet the SW requirements of the brick. The grade is typically based on physical properties of the brick.

APPEARANCE

Brick types are related to the appearance of the unit, and specifically to limit on dimensional tolerances, distortion tolerances and chippage of the unit. The brick type can be selected depending upon whether: a high degree of precision is necessary; a wider range of color or size is permitted; or a characteristic architectural effect is desired. The three appearance grade for ASTM C216 brick are: FBX, FBS and FBA. (Note: FBA grades is as specified by the purchaser)

1 Smooth texture – die skin finish2 Rough texture – sanded, combed, scratched, wire cut



BRICK SIZES

Bricks are available in many varied sizes and have been called by different names. To eliminate this confusion, in 1993 the Brick Institute of America and the National Association of Brick Distributors, collaborated to establish standard brick dimensions. The established standards represent roughly 90% of all sizes currently manufactured.

Bricks are identified by three dimensions: width, height and length.

For additional information visit “Online Tech Notes” on BIA (Brick Industry Association) web site at www.brickinfo.org.



BRICK MASONRY JOINTS

Mortar joint finishes fall into two classes: tooled and troweled joints. In the tooled joint a special tool is used to compress and shape the mortar in the joint. In the troweled joint the excess mortar is cut off (struck) with the trowel with no further finishing.

Of the mortar joints illustrated below only the concave, v-shaped, grapevine, and weathered are recommended for exterior applications.

For additional information visit “Online Tech Notes” on BIA (Brick Industry Association) web site at www.brickinfo.org.



BRICK PATTERNS

Your home can have distinct character when brick patterns are incorporated into the brickwork. Below are the basic patterns which have endless possibilities of applications. Some of the locations where pattern brickwork can be placed are under a feature window, above your garage door(s), on a chimney or fireplace, or on a large wall area which has no windows or openings.



BRICK BOND PATTERNS

There are five commonly used bond patterns – Running Bond, Common Bond, English Bond, Flemish Bond, and Stack Bond as illustrated on this page.

The most common and simplest of patterns is the Running Bond. This pattern consists of all stretchers. The vertical mortar joints between stretchers line up vertically.

The Common Bond also referred to as American Bond is a variation of the Running Bond Patterns with a course of full headers at regular intervals. These intervals may be every fourth, fifth, or sixth course. It may vary even mroe by using a Flemish Header course. Three quarters of a brick must be used at the corner of each header course.

English Bond consists of alternate courses of headers and stretchers with the headers on the stretchers and the mortar joints between the stretchers. The Flemish Bond consists of alternate headers and stretchers with the headers centered over the stretchers in the intervening courses. The English Corner requires a quarter brick closure placed in from the corner. This closure should never be placed at the corner. The Dutch Corner requires a three quarter brick closure.

Patterns may be further enhanced by projecting or recessing certain brick colour, and texture, and types of mortar joints an almost unlimited number of patterns can be developed.

Note: It is important that the corners be started correctly when laying out any bond pattern.

Also referred to as the Block Bond. All vertical mortar joints are aligned with no overlapping of units.



ARCHES

Brick masonry arches have been used to add beauty and distinction to buildings for centuries. The wonder of the brick masonry arch is that it not only is aesthetic but serves a practical purpose. Structurally speaking, under the uniform load of the brick arch, the induced stresses are principally compressive. Brick masonry has greater resistance to compression than it does to tension, therefore making the masonry arch very effective for spaning openings. Arch shapes are created by using tapered mortar joints, tapered brick shapes, or a combination of both.

Illustrated below are a number of different types of arches that have been developed over hundreds of years, which can be used to add distinction to any contemporary structure. By modifying a basic arch, a mason can create many desirable shapes.



BRICK PAVING



MORTAR FOR BRICK MASONRY

Mortar is the bonding agent that integrates brick into a masonry wall. Mortar must be strong, durable, and capable of keeping the wall intact. In addition, it must help in creating a water resistant barrier and it must accommodate dimensional variations and physical properties of the brick when laid. Because concrete and mortar contain the same principal ingredients, it is often erroneously assumed that good concrete practice is also good mortar practice. In reality, mortar differs from concrete in working consistencies, methods of placement and structural performance. Mortar is used to bind masonry units into a single element, developing a complete, strong and durable bond. Concrete, however, is usually a structural element in itself. Mortar is usually placed between absorbent masonry units and loses water upon contact with the units. Concrete is usually placed in non-absorbent metal or wooden forms, which absorb little, if any water. The importance of the water-cement ratio for concrete is significant, whereas for mortar it is less important. Mortars have a high water-cement ratio when mixed, but this ratio changes to a lower value when the mortar comes in contact with the absorbent unit.

Historically, mortars have been made from a variety of materials. Burned gypsum and sand were used to make mortar in ancient Egypt, while lime and sand were used extensively in this country before the 1900’s. Currently, the basic dry ingredients for mortar include Portland cement, masonry cement, hydrated lime and sand. Each of these materials makes a definite contribution to mortar performance.

There are four general mortar types:

Type M. A high compressive strength mortar specifically recommended for masonry below grade and in contact with earth.

Type S. A mortar recommended for use in masonry where maximum flexural strength is required.

Type N. A medium strength mortar suitable for general use in exposed masonry above grade and specifically recommended for parapets, chimneys and exterior walls subjected to severe weathering conditions.

Type 0. A relatively low compressive strength mortar suitable for limited exterior use and general interior use in load bearing and non-load bearing masonry. Type 0 mortar should not be used where it will be subject to freezing in the presence of moisture.

No single type of mortar is best for all purposes. The basic rule for the selection of a mortar for a particular project is: Never use a mortar that is stronger (in compression) than is required by the structural requirements of the project.

Type N Portland cement-lime mortar is recommended for brick veneer, except that Type M Portland cement-lime mortar should be used for brick veneer below grade where the brickwork is in contact with earth. The Portland cement-lime mortar is recommended because they have a long history of proven performance in brick veneer construction.



MORTAR FOR BRICK MASONRY (continued)

Mortar is perhaps the last building material in history that is still manufactured at the project site. The following on site practices should be followed to insure the quality of mortar meets the required specifications:

1. Cementitious materials and aggregates shall be stored in such a manner as to prevent deterioration or contamination by foreign materials.

2. The method of measuring materials for the mortar used in construction shall be by either volume or weight, and such that the specified proportions of the mortar materials can be controlled and accurately maintained. Measurement of sand by shovel shall not be permitted. Table 1 list proportion requirements of the various mortar types. Note that a Type N masonry cement may be combined with Portland cement to produce Type S or Type M mortar.

3. All cementitious materials and aggregate shall be mixed for at least 3 minutes and not more than 5 minutes in a mechanical batch mixer, with the maximum amount of water to produce a workable consistency.

4. Mortars that have stiffened because of evaporation of water from the mortar may be retempered by adding water as frequently as needed to restore the required consistency. Mortars should be used and placed in final position within 2-1/2 hours after initial mixing.

5. When coloring mortar, use the minimum quantity of pigments that will produce the desired results; excess may seriously impair strength and durability. The maximum permissible quantity of most metallic oxide pigments is 10 percent of the cement content by weight. Although carbon black is a very effective coloring agent, it will greatly reduce mortar strength when used in greater proportions. Therefore, limit carbon black to 2 percent of the cement by weight.



BRICK CLEANING

The bucket and brush cleaning is the most widely used method of cleaning newly constructed brick walls in both small and large jobs. A minimum amount of equipment is needed and workmen do not need to he highly skilled.

This method may be used for cleaning all colors and textures of brick. However, care must be used in selecting the proper cleaning solution for the job.

The safest way to determine the proper cleaning solution for a given type of brick is to ask the brick manufacturer for his recommendation. Listed below are some of the recommended commercial cleaning compounds:

Sure Klean 101, 600 and Vanatrol Superior 800 series

Goldblatt Brick Bath

Diedrich 200, 202, 202 Vana-Stop

Formulation of most commercial cleaners is so complicated that the users should rely on the chemical manufacturers’ recommendations as found on the containers and on the recommendations of the brick manufacturers.

The Detering Company DOES NOT recommend the uses of muriatic acid for the cleaning of any brick lines they represent.

THE FOLLOWING PROCEDURES ARE RECOMMENDED FOR CLEANING BY THE BUCKET AND BRUSH METHOD;

1. Schedule cleaning at least seven days after the brick masonry is completed. Mortar must be thoroughly set and cured. Prolonged time periods between the completion of the masonry work and the actual cleaning should be avoided when possible.

2. Remove large mortar particles by hand with wooden paddles, non-metallic scrape hoes or chisels.

3. Protect metal, glass, wood, limestone and cast stone surfaces. Mask or otherwise protect windows, doors and ornamental trim from cleaning solutions.

4. Presoak or saturate the area to be cleaned. Flush with water from the top down. Saturated brick masonry will not absorb the cleaning solution or dissolved mortar particles. Areas below should also be saturated in order to prevent absorption of the run-off from above.

5. Starting at the top, apply the cleaning solution. Use a long handled stiff fiber brush or other type as recommended by the cleaning solution manufacturer. Allow the solution to remain on the brickwork 5 to 10 minutes. For proprietary com-pounds follow the manufacturer’s instructions for application and scrubbing. Wooden paddles or other non-metallic tools may be used to remove stubborn particles. Do not use metal scrapers or chisels. Metal marks will oxidize and cause staining.

6. Heat, direct sunlight, warm masonry and drying winds will affect the drying time and reaction rate of cleaning solutions. Ideally, the cleaning crew should be working on shaded areas to avoid rapid evaporation.

7. Rinse thoroughly!! Flush walls with large amounts of clean water from top to bottom before they can dry. Failure to completely flush the wall of cleaning solution and dissolve materials from top to bottom may result in the formation of “white scum”.

8. Work on a small area. The size of the “wash down” area should be determined after a trial run. This will permit the cleaning crew to examine the work for initial results.



MANUFACTURER’S SPECIFICATIONS


GENERAL OVERVIEW OF BRICK MANUFACTURING...Brick masonry arches have been used to add beauty and...

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