Types S and M
Broco Stucco Cement meets the requirements of ASTM C91 “Masonry Cement” (Table 1) and ASTM C1328 “Plastic (Stucco) Cement for Types S and M.
Broco Stucco Cement consists of a mixture of portland cement, limestone, and chemical admixtures to provide plasticizing properties and other enhanced performance attributes. These components are proportioned at the cement plant under controlled conditions to assure product consistency.
Basic Use: Broco Stucco Cement will produce Plaster Mixes “MS” or “FMS” as defined in ASTM C926 “Standard Specification for Application of Portland Cement-Based Plaster.” Broco Stucco Cement when proportioned and mixed in accordance with ASTM C926 is designed to provide excellent workability and bond.
Limitations: The plaster mortar may be hand or machine applied. The number of coats and the thickness of the stucco should be in accordance to the requirements of ASTM C926, and consistent with industry standards.
When stucco is to be applied to smooth, non-porous solid substrates, an exterior bonding agent meeting the criteria of ASTM C932, or other approved method outlined in ASTM C926 is recommended to be used to ensure adequate adhesion.
Availability: Broco Stucco Cement is available in 79 pound sacks containing a plastic moisture barrier and in bulk via pressurized bulk containers.
Proportioning: The stucco mixture should be produced with sand meeting the requirements of ASTM C926. The stucco mixture shall be proportioned in accordance with ASTM C926 for base coats and finish coats. (Table 2)
Mixing: Approximately two thirds of the water should be added to the mixer with one half of the sand followed by the Broco Stucco Cement. Add the remaining sand and sufficient water to reach the desired consistency and mix for no less than five full minutes.
No admixtures should be used without the written approval of the architect or engineer of record. No additives are necessary, unless specified.
Water: All water should be clean and free from organic material and deleterious amounts of dissolved acids, alkalis and salts.
Application: The plaster coats will be applied in accordance with the requirements of ASTM C926.
The yield or coverage of plaster will vary depending on the thickness of the plaster and the amount of sand used per bag of Rinker Stucco Cement. (Table 3)
Plaster Curing: A light fogging with water two to three times a day for three days will enable cement hydration, strength development, and adequate bond, while minimizing drying shrinkage and cracking. Users should adhere to the curing requirements in ASTM C926.Close
Table 1. ASTM C91 Masonry Cement
|Masonry Cement Type||Compressive Strength 28 Day Minimum||Water Retention Min. %||Air Content Max. %|
Table 2. Plaster Coat Proportions (Parts by Volume)
|Cement Type||Fine Aggregate|
|Plaster Mix||Masonry Cement||Plastic Cement||Scratch Coat||Brown Coat||Finish Coat|
|MS||1||-||2 ½ - 4||3 - 5||-|
|P||-||1||2 ½ - 4||3 - 5||-|
|FMS||1||-||-||-||1 ½ - 3|
|FP||-||1||-||-||1 ½ - 3|
Table 3. Yield Based on Plaster Thickness and Mix
|Area Covered per Bag (Square Feet)*|
|Mixture Volumes||Thickness of Stucco Coats|