MASCO Catalog: Concrete Forming & Accessories

235 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 Vibration is more about Quality than it is about Quantity • Over-vibration can cause honeycombing rather than eliminating it. • Under vibrating concrete can cause honeycombing in low slump concrete. • High slump concrete (7-9 inches) requires very little vibration. 'Wet' Concrete and SCC (9 inches and higher) usually requires no vibration. • Over vibration can cause the concrete to lose entrained air, sometimes as much as one half of the air content. • When placing concrete in lifts, be sure to penetrate previous layer with vibrator in order to protect against cold joints. • Use as much vertical angle as possible to maximize effect. • Using the vibrator as a placement tool instead of a consolidation tool can result in sand streaks and an inconsistent surface. CONCRETE TIPS Jointing Guidelines Code Requirements for Residential Concrete (ACI 332) specifying maximum contraction spacing for slabs on grade without steel. Slab Thickness (in) Maximum Aggregate Size less than 3/4 in Maximum Aggregate Size 3/4 in and larger 3.5 8 ft 10 ft 4.5 10 ft 13 ft 5.5 12 ft 15 ft • Saw-cutting should be performed before the concrete starts to cool and as soon as the concrete surface is firm enough not be torn or damaged by the blade. If sawing is delayed, the concrete can crack randomly before it is cut. • Saw-cutting performed too early in the slab curing process can result in pulling out of the aggregate. • Saw cut depths should be a minimum of 1 in and preferably 1/4 to 1/3 of the slab depth where practical. Proper curing can make or break the job Why Cure? Improper curing can reduce the designed concrete strength as much as 50%. A properly cured concrete will have fewer pores in the surface where water can enter and freeze (and crack / scale). Cured concrete will, in general, crack less, have reduced or no dusting, be more durable and achieve increased wear and abrasion resistance. Curing Methods • Membrane curing compounds • Moist / water cure (concrete is kept wet) • Wet curing blankets • Soaked burlap • Plastic sheets • 7 Day ponding When placing concrete in temperatures colder than 70°F, curing times should be increased to protect concrete longer as strength develops more slowly at colder temperatures.