settling if expansive conditions should occur . The types of slab reinforcement commonly used are :
1 . Synthetic fibers , used as an admixture when concrete is mixed . Can be used with , and is recommended as an addition to , rebar .
2 . Electrically Welded Wire Mesh ( E . W . W . M .), not recommended for architectural concrete due to the lack of sheer value .
3 . Reinforcing steel ( rebar ), the most common size and spacing for normal pedestrian and vehicular architectural concrete is at the very minimum # 3 bar at 18-inch o . c . e . w . to maximum # 5 bar at 12-inch o . c . e . w . Shaw & Sons recommends # 4 bar at 18-inch o . c . e . w .
4 . Steel Dowels , used to connect adjacent pour slabs at construction joints . Always use the Speed Dowel system ( match rebar size and on-center spacing , e . g . for # 4 rebar at 18-inch on-center , use # 4 Speed Dowel 18-inch on-center ). Speed Dowel is a plastic sleeve system that requires an 18-inch long to two-foot long smooth steel dowel ( see the Shaw expansion construction joint , page 152 ). 5 . Rebar numbers indicate the approximate diameter of rebar in 1 / 8-inch increments . Example # 3 rebar is 3 / 8-inch in approx . diameter ; # 4 rebar is 1 / 2-inch in approx . diameter ; # 5 rebar is 5 / 8-inch in approx . diameter .
6 . For topping slabs in extremely thin conditions , use 1 / 4-inch stainless steel dowels .
1 . Verify the load delivered matches the certified Statement of Mix Design for that particular paving finish . Carefully review delivery ticket to ensure correct mix .
2 . Verify that slump is within the stated range ; typically four-inch to five-inch slumps within a +/ - one-inch tolerance ( slump test should be taken at point of discharge ; at the end of the hose if pumped .)
3 . Overall weather and ambient temperature , material conditions , and truck travel time can affect the slump . ( Note : Projects close to batch plants require more on-site mixing time for concrete than concrete brought from plants further away .)
4 . Accepting concrete that falls outside the specified slump may result in weakened concrete and visual variations in adjacent pours ( Shaw & Sons would reject this concrete ).
5 . One gallon of water for each cubic yard of concrete added at the time of pour to increase slump loses approx . 200 PSI to the concrete ’ s strength and will gain approx . one inch in slump ( never exceed maximum design ).
6 . Each delivered load should be mixed at the job site a minimum of 100 revolutions , and must be checked visually prior to dispensing the first yard of each load to ensure a proper mix .
RULE 7
PLACING & FINISHING
There are many steps to placing and finishing architectural concrete . Proper preparation and timing are imperative to ensure a quality slab .
RULE 6 CONCRETE DELIVERY
Placing Concrete :
Before the first concrete load is delivered to the jobsite , coordination efforts should have already been performed between the owner ’ s authorized representative , the designer / architect , concrete contractor , and general contractor . Topics should include mix design , finish elevations , utility coordination , concrete pour sequencing and scheduling , joint layout and finish type . When the first load of concrete is delivered , the following steps should be followed :
1 . Deliver concrete to jobsite . 2 . Deposit concrete as close to its final location as possible to minimize segregation of aggregates .
3 . Deposit concrete at the bottom of a slope and work uphill .
4 . Use an appropriate concrete vibrator to consolidate placed mix . Do not move concrete horizontally with a vibrator ; it will cause segregation .
5 . Do not let concrete free fall more than two feet from point of discharge if the
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