Concrete is the most versatile of all garden paving materials. It can have a surface plain and smooth enough for dancing or roller skating, or it can have a rough or patterned texture. These extremes are possible because concrete is a plastic material which will take almost any form and which can be finished in a wide variety of surface textures. Despite these advantages, some homemakers make concrete their last choice as a garden paving material. They claim it is hard, has a cold, industrial quality, and is a difficult material to handle.
Since concrete is a mixture of cement, sand, gravel, and water, its character is determined by the proportions used for these four ingredients. The formula recommended for garden paving is 1 part cement, 2 parts sand, and 3 parts gravel or crushed rock. Add about 5 gallons of water for each sack of cement used. The water should be clean and pure, the sand must be clean river sand, and the gravel or crushed rock should be 1 inch maximum in size.
HOW TO BUY CONCRETE
It is possible to buy concrete for paving in the garden in any of the three ways listed below. The advantages and disadvantages of each are also listed.
Bulk dry materials. You buy the required amounts of sand, cement, and gravel. Unless you have ample storage space, buy only what you need for the project at hand.
Advantages: Buying the materials dry and in bulk is the cheapest way you can get it. You can mix any amount that is convenient for you to use, whenever you are ready to go to work.
Disadvantages: You must have a place where you can store sand and gravel. The cement sacks must be kept absolutely dry. This generally means covered storage.
Ready mix or transit mix. Concrete in this form is delivered to your home, ready to be poured in place.
Advantages: No mixing equipment is needed. The concrete can be prepared according to any specifications before delivery. You get well-mixed concrete every time.
Disadvantages: An extra charge is usually made for delivery of any quantity under 2 or 3 cubic yards. Some plants will deliver as little as ½-cubic yard under this arrangement, but others will deliver nothing less than one yard. There is an extra charge if the truck has to wait a length of time after it arrives on the site. Delivery can be difficult as the trucks are often too large and too heavy for a driveway.
Dry ready-mix. You can buy sacks of all-purpose concrete suitable for most home uses in 50,100, and 150-pound sizes -containing the correct proportions of sand, cement, and gravel. You can also buy a sand-gravel mix to combine with cement.
Advantages: There is no guesswork. All you have to do is add water, mix, and the concrete is ready to use. It is ideal for patching old jobs or doing small piecemeal work.
Disadvantages: Dry ready-mix is relatively expensive. The cost is about three to four times that of either bulk dry materials or transit mix. But, if you don’t have storage space or don’t need large quantities of concrete mix, this is probably the most practical way for you to obtain it.
WORK CAREFULLY TO MAKE GOOD CONCRETE
An important factor in your concrete mix is its ratio of water to cement. Concrete hardens because the powder-like cement and water form an adhesive which locks the sand and pebbles together. Too much water thins or dilutes this adhesive paste and weakens its cementing qualities; too little, and you can’t work it.
If you are working with small quantities, you can mix your concrete on a platform or in a wheelbarrow with a shovel or hoe. An existing concrete slab will do, or you can make a platform out of old lumber or scrap plywood. Measure the quantity of sand, spread it out evenly, and spread the cement on top. Turn and mix the dry ingredients until there are no streaks of color. Add gravel or rock and mix until they are evenly distributed through the mixture. Then make a depression in the mixture and slowly add the water, turning the ingredients until they are thoroughly combined. Use a rolling motion with a shovel to save energy and speed the job. For larger quantities, it is best to rent an electric mixer. There are two standard size mixers available. The smaller one holds about two cubic feet of mix and will fit into the trunk of your car with the lid up. The larger machine holds about three cubic feet and is mounted on a trailer which hooks onto your bumper.
SURFACE TEXTURE IS IMPORTANT
If you are doing your own concrete finishing, you can create an unlimited range of textures. Be sure that the finish you choose is the right one for the service it will perform. Here are two popular choices:
Smooth finish. For the smoothest surface, use a steel trowel. Add non-skid texture by brushing the surface with a broom. Experiment with different bristled brooms for a wide variety of finish. For the roughest ‘smooth’ surface, use a wood float – don’t finish with the steel trowel.
Exposed aggregate. One of the most time consuming surfaces to handle is exposed aggregate. Some craftsmen do the job with a hose and push broom to remove the top surface of sand and cement. Others use a stiff wire brush and a hose.
Make sure that the surface is level -a wood float usually works satisfactorily. Then let the concrete set up until you can walk on it. Then gently try brushing and hosing. If the concrete is too soft, wait another hour or two before exposing the aggregate. Scrub the surface with a solution of muriatic acid and water, which removes some more of the cement and sand.