MASCO Catalog: Concrete Forming & Accessories

237 MASONS SUPPLY COMPANY Oregon (800) 537-3407 ♦ Washington (800) 537-6216 Clackamas | Eugene | West Eugene | Hillsboro | Medford | Portland | Salem | Ridgefield | Seattle | Tacoma | Woodinville M A S C O . N E T GENERAL & TECH INFO CHARTS Fluid or plastic concrete exerts the same side pressure on forms regardless of their width. As you add more fluid or plastic concrete to forms, the pressure will build up toward the bottom at about the rate of 150 pounds per foot of depth. This will be true as long as all concrete remains in a plastic state. Example: Eight feet of fluid or plastic concrete bears on the bottom foot of forms with a pressure of 8x150 pounds or 1200 pounds per square foot. Slab Formwork Design Loads The loadings used in the designs of slab formwork consists of a dead load and a live load. The weight of the formwork plus the concrete is considered dead load while the live load is made up of the with of workers, equipment, material storage and other like items which is supported by the formwork. The tables below tabulate design loads based on the concrete weight for the thickness indicated, and includes 10 pounds per square foot for the weight of forms and a live load of 50 to 75 pounds per square foot as indicated. A live of load of 75 pound per square foot is generally used when motorized carts are used to transport concrete during the placing operation. For a complete explanation of general objectives in formwork design, planning, materials and accessories, loads and pressures, design tables and much more, it is recommended that a copy of ACI publication SP-4 "Formwork for Concrete" be obtained. The current edition is available from American Concrete Institute. PO Box 9094, Farmington Hills, MI 48333. Points To Remember 2" 4" 6" 8" 10" 12" 14 16" 18" 20" 100 110 135 160 185 210 235 260 285 310 2" 4" 6" 8" 10" 12" 14 16" 18" 20" 125* 135 160 185 210 235 260 285 310 335 Slab Formwork Design Load for Uniform Slab Thickness (Includes 50 psf Live Load) Pounds per Square Foot for Indicated Thickness (Includes 75 psf Live Load) Pounds per Square Foot for Indicated Thickness Note: Chart is based on a concrete weight of 150 pounds per cubic foot. * ACI 347 recommends a minimum 100 psf for form design or 125 psf if motorized carts are used. Concrete cures and gains strength faster with an increase in temperature. Example: At 21 o C (70 o F), concrete sets in approximately 1 ¼ hour. At 4.5 o C (40 o F) concrete will set up in about 1 ¾ hour. Plastic concrete exerts the same pressure on forms regardless of their width. (6') (12') (24') (150 lbs) (150 lbs) (150 lbs) Feet PSF KPa 10' 7' 9' 8' 6' 5' 4' 3' 2' 1' 68 136 204 272 340 408 476 544 680 748 150 300 450 600 750 900 1050 1200 1350 1500 1¾ hr 1¼ hr 4.5 o C (40 o F) 21 o C (70 o F) Feet 10' 9' 8' 7' 6' 5' 4' 3' 2' 1' As concrete hardens, lateral pressure on forms decreases. Concrete in plastic state Once bottom foot is cured Once second foot of concrete is cured PSF 150 300 450 600 750 900 1050 1200 1350 1500 136 68 204 272 340 408 476 544 680 748 150 300 450 600 750 900 1050 1200 1350 136 68 204 272 340 408 476 544 680 748 150 300 450 600 750 900 1050 1200 PSF PSF KPa KPa Feet 10' 9' 8' 7' 6' 5' 4' 3' 2' 1'