K. Concrete mix and formulas

A successful concrete pour for a SmartBlockPlus project is a direct result of proper planning and preparation (which you have already done), ordering and receiving the proper concrete mix, placing it in the walls and ensuring good consolidation.

1. Concrete Mix Design

   The best mix design for a typical SmartBlockPlus project is as follows:

   • Strength: 2,500 psi.
   • Aggregate: 0,95- 1.25 cm
   • Slump: 12.5-15 cm. inches out of the pump.
   • Fly ash can be used, as well as super-plasticizers, although they are not required.
   • The volume of concrete you order is determined by the amount you calculated on the Estimating Worksheet.
2. Slump Test

   Once ordered, you must ensure that the concrete you require has been delivered by performing a slump test on each and every truck that arrives on the job. The SmartBlockPlus Installation Manual provides detailed instructions on how to conduct a slump test.

3. Concrete Placement

   WATCH OUT ! All water, ice, or debris must be removed from the forms before placing concrete.This includes the tools, pencils and sandwich wrappers you may have dropped in the walls during construction.
   Concrete can be placed in SmartBlockPlus walls in a variety of ways:

   • Directly from the chute of the concrete truck. An elephant trunk can be attached to end of the chute to better direct the flow of concrete into the walls. To finish one comes to strained(bleached) from concrete as a rule with a resistance of f'c = 250 kg/cm2. The most frequent system is the tremie that consists of straining pouring the concrete in the This procedure must be constant in order to prevent the concrete from setting and for ende there are generated fractures or cold meetings that would reduce the capacity of load .
   • Lifted and delivered with a conveyor truck, if the job site allows for complete access.
   • Pumped through a hose from a trailer pump, which provides a smooth flow of concrete, but requires sufficient labor and/or the guard rail of a roll-around scaffold to move the hose around.
   • A boom pump, which can extend the full range of the project and provide a regulated and direct flow of concrete to the walls on demand. This method requires a reduction in the velocity of the concrete through the hose by attaching a double-90° bend in the hose with a fixture designed to slow the concrete and/or a reducer hose that slows the concrete as it reduces the hose dimension to 7.62 cm. diameter.

   WATCH OUT ! You should always dump the initial solution used to prime the pump, as it is highly liquid and could cause a bulge or blow out in your initial pass.
   Whatever method is used, concrete should be placed in the SmartBlockPlus walls at a rate of 4 feet per hour, with multiple passes being used to reach a typical 8 to 12-foot ( 262-400 cm) wall height. The concrete should be placed uniformly along the wall avoiding the tendency to force the concrete to flow through the crossties. The crossties are plastic and if too much side-to-side pressure is applied the crossties could break causing the form to bulge or blow out.

   The space under windows will be partially filled with the flow of concrete into the walls on both sides. The space directly below the windows should be done after the walls are filled.

4. Consolidation

   Placement of the concrete should begin at a corner and, while working around the perimeter of the project, consolidated by the crew by:

   • Tapping on the wall with a block of wood,
   • Using an orbital sander directly over the attachment studs, without paper attached,
   • Utilizing a 1” “pencil” vibrator, cordless or standard.

   Whichever method is used, two people should be walking the wall below the person placing concrete to communicate the status of the consolidation and to move the placement forward.
   Care should be taken to clean the concrete off of the rebar above the level of the pour to minimize the possibility of voids on the next pass. Extreme care should also be given to achieving good consolidation around doors and windows, as these areas are prone to voids and are structurally dependent on good consolidation.

   If the wall is going to continue beyond the initial pour, stop the pour 4-5 inches below the top of the wall and leave the finish rough, so as to provide a good bond with the next level of concrete.
   If the wall is complete to the top plate, level the top of the wall with a trowel and place anchor bolts, or hurricane straps, into the concrete at the required intervals. Be sure to take the time to clean up your job site when you are finished, including any loose concrete that is left on the surface of the walls. A few minutes spent at this task will go a long way towards improving your image and satisfying your customer.