Concrete in Your Landscaping Scheme

Concrete used outdoors can provide an extremely durable, versatile and attractive component to any condominium’s landscaping scheme. In our reserve studies we give it a thirty to forty year useful life. It’s a long-range component in your capital reserve fund plan. If you have concrete driveways, patios, walks on your property you know, however, that it does sometimes need some help in achieving that two score and ten goal. Concrete is an engineering amalgam of Portland cement with fine (sand) and coarse (stone) aggregate. The cement paste bonds to the aggregate and bridges across it. It’s that bridging action that provides the strength we all recognize. Where concrete can get in trouble outdoors though is when water is allowed to penetrate the surface.

That saturates the coarse aggregate triggering the damaging freeze and thaw act. The way to combat that is to include entrained air admixture to the concrete at the batch plant. The entrained air admixture provides little bubbles in the cement paste that allow the aggregate to expand without damaging the paste. It’s essential too for durability that the concrete mixture have a low water-cement ratio when placed. When having work done, make sure you pass along those understandings to your contractor. Once the concrete is in service, epoxy based sealers can be used to as added protection against water penetration to the aggregate.

RepairsCracked or heaved sections of condominium concrete walks can be removed of course and new sections formed up to replace the damaged ones. Make sure the sub-base is well compacted before pouring the concrete. If the work is done in hot weather, wet the sub-base to prevent rapid loss of the mix water into the sub-base. The concrete should be misted occasionally as it cures to prevent rapid hydration of the mix water to the air. Concrete is fussy about curing. It takes about 28 days to reach its full strength. It’s the gradual loss of mix water during hydration (curing) that we like to see happen. Driveways require essentially the same precautions with an additional caveat.

They need help accepting the weight of vehicles. Wire mesh is the typical reinforcement used. Reinforcement is also a good idea for walkways. Control joints are cuts or slots provided in new concrete work to weaken the concrete locally. This tells the concrete to crack beneath the cut / groove as it expands during hydration. Otherwise it will crack randomly where it wants to, creating an unattractive piece of work. If your existing concrete is pitted and worn it can be re-surfaced. This amounts to pouring a thin application of topping material over the damaged concrete. The best surface preparation consists of scarifying the existing surface, removal of all loose material and then etching the old concrete with hydrochloric acid. The finish topping coat can provide a skid proof surface suitable for pedestrian traffic. Moss can be removed by washing the area with a solution of household bleach and water.

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