The Edge - Quarter 4, 2008 - (Page 29)

EXPOSED AGGREGATE SURFACES | by Al Rizzo get the desired results. Keep records of your variations for future information. DESIGN MIX FOR SEEDING In designing a concrete mix, a non-seeded base mix should have one part cement to two parts sand to three parts stone. When seeding, your base mix should be designed using less small diameter stone to keep it from coming to the surface and changing the aggregate look. Here is an example: one part cement to two parts sand to one part stone. If using larger stone to seed, such as one inch or larger, decrease the amount of smaller stone in the concrete base mix. To this mix, fiber reinforcing can be added in the same amount that is commonly used in a Stamped-Crete deck. Depending on the weather, as it gets warmer, consider increasing the cement ratio to compensate for extra water. The concrete should be a little on the wet side so that it is easier to seed the aggregate into the surface. A recommended mix when seeding aggregate would be six bags of cement per yard of concrete with a three-inch slump. Factors that are important when ordering slump of three inches or more would be how high the temperature will rise that day and how windy it will get. Both of these will affect drying, so be sure to adjust the mix for that particular day. Here is an example: If temperatures go to 85° or above, add one-half bag per yard of cement to the mix and increase the slump to 4". It would also be recommended to pour less concrete per load. Instead of 10 yard loads, pour six 8-yard loads. Once the concrete is poured, screed the surface (leveling the top). The surface is then bull floated, to fi ll in any voids. Immediately after floating, apply the aggregate by sprinkling it with a shovel or by hand over the entire surface or into a design pattern. Once the surface is seeded, the next step would be to use a Jitterbug Tamper or other methods to compact the aggregate into the surface. Jitterbug Tampers come in different sizes. The striking plate of the tamper has holes in it that allow the seeded aggregate to be compacted. The holes allow the paste to come to the surface. If you are worried about stone adhesion, take the aggregate, put it in a tumble mixer, add a little water and cement – enough to coat the aggregate and tumble it in the mixer until all is coated. Then, sprinkle the coated mixture using the above method. Once the seeded surface has been tamped, use a wooden float to float the surface. This will level the surface. At this point you should accomplish all side and middle joining. WASHING AGGREGATE The tool commonly used to accomplish washing is a garden hose with a high pressure nozzle. Do this when the concrete is set enough to walk on. Don’t try to accomplish the finish wash on the first pass. If it is wet, it may need to be washed a second and third time. In case the surface dries too quickly, a power washer might be needed to wash the surface, and a stiff brush can be used to brush the surface during the washing, depending on the conditions. When washing, expose only 30 percent of the aggregate; if the aggregate is over-exposed it may come loose within a short period of time. The day after the concrete is poured and seeded, give the surface a light acid wash. If time constraints do not allow a return visit the next day, make sure the surface is covered for curing. Then, acid wash the surface within the next three or four days, followed by continual curing for a minimum of seven days. A number of decisions must be made before pouring the concrete. Weather conditions will affect the curing, and the number of craftsmen you have available will affect the amount of area you want to accomplish. In extremely hot weather, retarders are recommended. This will allow time to properly seed and finish the surface. In cold weather, you may want to use accelerators. In areas where it might be difficult to wash the concrete surface, consider pouring every other block the first day, and then fi ll in the empty blocks the next day. Many architects and engineers recommend sealing the surface of the exposed aggregate. There are many different sealants available; a good one will be absorbed into the concrete and will not leave a heavy sheen on the surface. No matter what sealant is used, it will make the surface a lot more slippery and may change the color of the deck to an amber hue. | Al Rizzo is president of the Rizzo Construction Pool Company, Newington, Connecticut. He has been buildings pools in the Northeast for more than 50 years. THE EDGE 29

Table of Contents Feed for the Digital Edition of The Edge - Quarter 4, 2008

The Edge - Quarter 4, 2008 Contents The President’s Message New Pool/Spa Federal Safety Act Worried About the 2009 Market? Treating Hot Water? Project Focus The 411 on UV Disinfection for Pools and Spas The Advantages of Seeding Aggregate Surfaces Pool and Spa Industry Wins Gold Choosing a Retirement Plan To Get Best Coverage at Lowest Cost - Shop Now Index of Advertisers

The Edge - Quarter 4, 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.