ABOUT CONCRETE. What does it mean to "cure" concrete? Why does concrete crack? What does 28 -day strength mean?

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1 What does it mean to "cure" concrete? ABOUT CONCRETE Curing is one of the most important steps in concrete construction, because proper curing greatly increases concrete strength and durability. Concrete hardens as a result of hydration: the chemical reaction between cement and water. However, hydration occurs only if water is available and if the concrete's temperature stays within a suitable range. During the curing period-from five to seven days after placement for conventional concrete-the concrete surface needs to be kept moist to permit the hydration process. New concrete can be wet with soaking hoses, sprinklers or covered with wet burlap, or can be coated with commercially available curing compounds, which seal in moisture. Why does concrete crack? Concrete, like all other materials, will slightly change in volume when it dries out. In typical concrete this change amounts to about 500 millionths. Translated into dimensions-this is about 1/16 of an inch in 10 feet (.4 cm in 3 meters). The reason that contractors put joints in concrete pavements and floors is to allow the concrete to crack in a neat, straight line at the joint when the volume of the concrete changes due to shrinkage. What does 28 -day strength mean? Concrete hardens and gains strength as it hydrates. The hydration process continues over a long period of time. It happens rapidly at first and slows down as time goes by. To measure the ultimate strength of concrete would require a wait of several years. This would be impractical, so a time period of 28 days was selected by specification writing authorities as the age that all concrete should be tested. At this age, a substantial percentage of the hydration has taken place. For additional information on concrete, visit 1

2 HOW TO CARE FOR YOUR NEW CONCRETE LANDSCAPING EDGING CURING Your edging will be dry to the touch within 2 hours. At this point it can withstand rain. Your edging can be damaged if you bump it within the first 24 hours. Please take care to make sure pets, children and guests do not step on your edging. If your edging is damaged by rain, we will repair it at our cost within 20 days. If your edging is damaged otherwise, it will be repaired at a minimum charge of $200. Concrete is considered fully cured after 28 days. If your edging was covered with plastic, it can be removed and disposed of after 24 hours. During the dry season you may be asked to water the edging for three days after the first 24 hours. Overly dry ground conditions will absorb moisture from the concrete, which may lead to cracking. STAINING OR SEALING Most stains and sealers are applied after 28-day curing process. Be sure to follow the manufacturer s instructions when applying stain or sealer. If your edging was sealed at the time of installation, we used a special curing product that will last about 6 months. We recommend that you reseal your edging after 6 months and then annually. When selecting a sealer, you want to look for a U.V. stable sealer with a solid content of 20% or more. The more solid content the sealer has, the better the sealer. 2

3 PREVENT DAMAGE Your concrete edging will give you years of enjoyment with little care. It is important to understand that while extremely durable, your edging is not indestructible. Pushing a wheelbarrow full of rock over your edging may cause it to crack. If you need to get rocks inside your bed, then use a ramp to keep the weight off the edging. Running it over with a truck could cause it to crack. Stepping on it or rubbing your shoes on it less than 48 hours of installation may damage A heavy-duty truck ran over curbing the surface of your edging. Warn your landscaper not to scrape the deck of his mower on the side of the edging; it will leave unsightly scratches that diminish the beauty of edging. A string trimmer should be used to trim the grass around your edging. Over time tree roots may lift and break your edging. We put more control joints closer together in areas that trees are a factor. We do this so that any cracking will hopefully occur at the control joints as tree roots lift the edging. This allows you to lift the section out and remove or shave the tree roots back down with a chain saw or hatchet and replace the section. Fortunately this will not happen for many years and with this information, you will be prepared if it does occur. EFLORESCENCE OR COLOR FADING We offer a curing sealer and recommend that it be applied at the time of installation. This immediately provides protection for your edging. Sealing is especially important when using colored concrete. Calcium carbonates deposits may form on the surface of the edging due to a natural reaction between carbon dioxide and the free lime in the cement of ten referred to as efflorescence. As a result, colored edging may appear faded. While efflorescence can be cleaned using a solution of 1-part muriatic acid to 5-parts water, we feel it is better to prevent the initial buildup. Curing sealer will appear glossy at first but it will result in a matte finish. To obtain a shinny appearance, a high gloss sealer, containing at least 25% solids can be applied after the 28-day curing process. CLEANING To remove mold and mildew, spray the edging with a strong bleach and water solution to kill the mold/mildew spores. Wait 24 hours then wash off with a spray nozzle attached to your hose. Pressure washing your edging is not recommended. A stiff scrub brush may be needed for stubborn areas. Sealing or staining your edging will help prevent recurring growth. It closes the pores of the concrete giving mold or mildew nothing to hold onto. 3

4 Warranty CARE AND WARRANTY FOR YOUR NEW CURBING Concrete takes time to cure and harden!! Do not allow any contact with water for 5 to 8 hours. Do not allow children or pets near curbing for at least 24 hours. It will take the concrete a full 30 days to completely cure. During this time take care to avoid excess pressure, to prevent cracking (do not walk on curbing or place anything heavy on curbing). Avoid contact with sharp or heavy objects, to prevent gouging or chipping (weed whackers, lawn mowers, pitchforks, shovels, etc.). Excess concrete along front and back of curbing is normal. This will provide an extra root barrier. In about a month, grass will normally grow back up against the front of the curbing. Control joints have been placed in curbing to avoid random cracks. Hairline fractures may occur normally in the drying process. The color of your new curbing will lighten throughout the drying time until it has completely cured. We take care in the installations of your new curbing. With your new decorative concrete curbing, lawn and landscape chores should diminish. Your home property value will increase. Both beauty and value will be added to your home for many years to come. 4

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