Specification Recommendations
This information is presented to assist the architect/engineer for development of their specifications and construction details. Each project has its own set of circumstances and conditions peculiar to the project:
• Project Location
• Orientation
• Environment
Nothing in this information should be considered as a specific recommendation for any specific project. This information presented can not determine what type of projects for which these guidelines or details are appropriate and should be taken into account by the architect and/or the engineer of record on the project.
It is the responsibility of the architect/engineer to determine the correct specifications and details for the specific project.
Informational Guidelines
ARCHITECTURAL BLOCK
Architectural Block is only a part of the wall. It is part of one of the wall elements—part of the material. However, the wall is made up of various elements, which include workmanship and the skill of the mason. For a wall to perform at its best, it must have these three elements:
• Good materials
• Good workmanship
• Good details
Design Information for Architectural Concrete Masonry Walls
Nature of Product
Architectural Concrete Masonry Units are principally used on the exterior and interior of buildings where they are exposed to a particular design program. They are designed to give structures a single load bearing wall system or a veneer wall system.
Architectural Concrete Masonry Units (as manufactured by members of CCMA) are made from natural and manufactured aggregates, sand, limestone, gravel, cement, and natural and synthetic coloring pigments. These are primarily products of nature varying in size, shape, texture and particle color. Due to the inherent nature of the materials and manufacturing process the Specifier shall have a reasonable expectation of some variables.
Although quality color consistency is a manufacturer's goal, some variations in color, texture and uniformity may be anticipated in the final product. Lighter shades generally exhibit less color variation than do the darker deeper colors. Darker colors seem to accentuate color variations with results appearing more pronounced. Smooth (mold finish) CMU’s will exhibit more variations in reflectivity than split face or other fractured units. This is due to the rich cement content and the cement paste that is brought to the surface by the vibration during the manufacturing process. The surface can be lightly sandblasted or cleaned with detergent cleaners to reduce the paste sheen.
Occasion of efflorescence:
Products of nature have salts that may contribute to efflorescence. Therefore, the occasion of efflorescence might be anticipated. The producers of Architectural Units in the Carolinas use specific care to select aggregates and other ingredients that will not contribute to the development of efflorescence. The producers can include an integral water repellent admixture in Architectural Units; however, even with these safeguards efflorescence may occur under wet weather conditions on unprotected walls.
Architectural Concrete Masonry Units become the exterior and interior facade of the building there are two additional cautions that should be observed:
1) Keep walls clean
Because the finished color of the wall is very important, keeping the wall clean, as the work progresses, will result in a better project and save a lot of cleanup. We strongly advise that the cleaning process be sampled on a sample panel before final clean up, for the architect's approval.
2) Water repellency
There are compounds that seal and reduce water penetration, and/or make the wall more water resistant; in the
manufacture of the Architectural Block, which helps resist water penetration. However, it must be understood that this does not produce a “waterproof” block. Block subjected to hydrostatic pressure requires special consideration.
MORTAR
A colored mortar enhances visual appeal and is recommended when used with colored Architectural Concrete Masonry Units. Coloring material may be added on the jobsite as an add- a-bag system.
Architectural Concrete Masonry Walls require a high level of performance. To increase this performance, consideration shall be given to:
Mortar joints:
Mortar joints in most Concrete Masonry walls represent about 7% to 10% of the wall area. Care must be exercised to achieve a joint that functions properly. It is recommended that a water repellent admixture be added to the mortar at the jobsite. This water repellent admixture should be compatible with Concrete Masonry Units. Care must also be exercised in the tooling of the joints. A concave or “V” groove joint is considered the desired joint for weather tightness. Other joints such as ¼ “ rake joints are common but care should be taken to sweep the joint afterwards to a tight texture. A non-staining tool should be used for the tooling of Architectural joints.
Product tolerances:
The tolerances are detailed in the Architectural Concrete Masonry Specification.
Sample panel:
A 4 ft. tall by 6 ft. wide panel should be constructed on the jobsite for viewing by the owner or architect and is required to be a representation of the material specified and workmanship. It is further recommended that this panel remain on the jobsite until the masonry work has been completed and accepted by the owner and/or architect.
Suggested design details:
Architectural Design details are located on Pages 10-22 of this Section. These Construction Details include the flashing of a single wythe wall and other designs that may be helpful in the detailing of Architectural Concrete Masonry Walls. Please review before incorporating into your documents.
Jobsite Recommendations
THE MASON:
Jobsite co-ordination is important on any project. The mason contractor will place the entire order and co-ordinate the delivery of special shapes as needed.
STOCKING THE JOB:
The General Contractor for unloading and staging the CMU’s should provide adequate space on the jobsite. The mason should stock the job blending the units from three or more cubes. CMU’s delivered to the jobsite should be single stacked. CMU’s may have pallet covers applied on the jobsite as covering units may reduce the amount of dirt and other adulterants that the units might be exposed to.
LAYING ARCHITECTURAL BLOCK:
The mason should take care not to place into the wall any block exhibiting cracks through the outside face shell in any climate area subject to wind driven rain.
CLEANING:
The mason should maintain a clean wall. Cleaning should be done daily. Additionally, the mason should clean the Architectural Block walls with a solution of mild detergent prior to the application of any water repellent sealer.
SURFACE APPLIED SEALER:
If an integral water repellent system is not used, it is recommended that a sealer be applied to protect the completed wall assembly. This process provides an additional safety feature to your project protecting the wall(s) from the elements. Your Concrete Masonry Manufacturer can recommend specific sealers that have been found to perform in acceptable fashion.
Clear Sealer: Architectural CMU’s should have a clear coating of a non-yellowing hydrophobic acryloid base product, or a suitable siloxane compound applied to protect the completed wall assembly.
Guideline Specification
ARCHITECTURAL BLOCK
Because Architectural Block is normally used differently and is expected to perform differently than the normal gray block, it is expected that a more stringent “guideline specification” would be appropriate to the requirements of this enhanced building material. It is in this spirit that the following three pages are submitted as a guideline specification appropriate to Architectural Block.
CAROLINAS CONCRETE MASONRY ASSOCIATION
Per ASTM C-90 – Modified for Architectural Concrete Masonry Units in the Carolinas
This guideline specification was developed by the Florida Concrete and Products Association and modified by CCMA as a recommended standard for Architectural Concrete Masonry Units in the Carolinas.
1. Scope
1.1 This specification covers hollow and solid Architectural masonry units. There are three classes of Architectural Unit (1) normal weight, (2) medium weight and (3) lightweight.
1.2 Concrete masonry units covered by this specification are made from lightweight or normal weight aggregates or a combination of both.
2. Reference Documents
2.1 ASTM Standards
C33 Specification for Concrete Aggregates
C90 Specification for Load-Bearing CMU’s
C140 Sampling and Testing Concrete Masonry Units
C150 Specification for Portland Cement
C270 Specification for Mortar for Unit Masonry
C331 Specification for Lightweight Aggregates for Concrete Masonry Units
E514-90 Test Method for Water Penetration and Leakage Through Masonry
C595 Specification for Blended Hydraulic Cements
C618 Specification for Fly Ash and Raw or Calcined Natural Pozzolan for use as a mineral
admixture in Portland Cement Concrete
C989 Specification for Ground Blast Furnace Slag for use in Portland Cement Concrete
3. Classification
3.1 Types – There is one type of Architectural Concrete Masonry Unit. It is described as exhibiting higher strength, greater density, lower permeability, and greater ability to resist efflorescence than regular concrete masonry units.
3.2 All architectural concrete masonry units covered by this specification will be manufactured to ASTM C90.
3.3 Block submitted for approval shall meet or exceed the requirements of ASTM C 90.
4. Materials
4.1 Cementitious Materials – Materials shall conform to the following applicable specifications:
4.1.1 Portland Cement – ASTM C-150
4.1.2 Blended Cements – ASTM C-595
4.1.3 Pozzolans – ASTM C-618
4.1.4 Blast Furnace Slag Cement – ASTM C-989
4.2 Aggregates – Aggregates shall conform to the following specifications, except that grading requirements shall not necessarily apply:
4.2.1 Normal Weight Aggregates – ASTM C-33
4.2.2 Lightweight Aggregates – ASTM C-331
4.3 Integral Water Repellent Admixture
4.3.1 All Units shall be manufactured with an integral water repellent admixture, applied at the dosage recommended by the admixture manufacturer. The mortar shall have the recommended dosage to complete the system.
4.3.2 The integral water repellent admixture shall be certified, by the admixture manufacturer, with the wall showing no visible water when tested in accordance with E 514-74. (the test is a controlled environment procedure)
4.4 Other Constituents – Air entraining agents, coloring pigments, integral water repellents, finely ground silica, and other constituents shall be previously established as suitable for use in concrete masonry and shall confirm to applicable ASTM Standards or, shall be shown by test or experience to be not detrimental to the durability of the concrete masonry units or any material customarily used in masonry construction.
5. Physical Requirements
5.1 CMU’s – After 28 days from the time of manufacture the units shall conform to the physical requirements prescribed in
Table 3.
5.2 All units shall have a minimum age of 7 days prior to delivery to the jobsite.
5.3 Face Shell (FST) and web (WT) thickness for hollow units shall conform to the requirements listed in Table 2:
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