Maintenance

IT MAY BE INACCURATE to apply the term "maintenance" to such permanent installations as masonry projects, but there are times when some touch-up work is in order. The most common fault that will appear in concrete—this, despite the most careful preparation of mix, installation and curing—is a crack. If this is due to a poor subbase the crack can become quite serious, especially if uneven settling causes a portion of the slab to sink below the grade level of adjacent areas. Many times it is necessary to crack up the nuisance area, remove the old concrete and repour. But this sort of major repair job will become necessary only if you neglect the procedures outlined or skip some of the steps in an effort to hurry the job.

Although concrete is one of the most durable building materials known, easy-to-make minor repairs may be needed

A sealer (Thiolastic is one) can be used in joints between precast concrete blocks and to fully seal the joints between brick and masonry units and other materials. Since sealer adheres to almost any material, it forms a permanent, weatherproof seal.

Most of the time the crack will be isolated—across a corner or into an expansion or contraction joint. When it is too bad to walk on or too unsightly to tolerate, it can be easily repaired. The first step is to remove the bad concrete. If the crack is wide and deep you can often get a pry bar under the piece and lift it right off the sub-base. If the repair area is in the center of a slab or walk, use a wide chisel and hammer to remove the bad material. Be sure all edges are clean even if you have to chip off a little concrete from adjacent good areas.

Clean the section thoroughly to remove all dirt, dust and any foreign matter. Oil or grease will make it difficult for the new patch to adhere to existing concrete; if any is present, remove it by washing with a solution of 8 oz. of tri-sodium-phosphate in 1 gal. of hot water. Scrub the surface thoroughly with the solution and rinse with clean water.

Allow excess moisture to drain off and paint the area with pure cement adhesive. Coat the bottom of the cavity as well as all edges. When this coating is sticky to the touch it is ready to take the pour.

Cement adhesive should also be used in the mix you make for the repair job. Fif­teen oz. of dry mix cement adhesive prod­uct, an equal amount of water and a 60 lb. sack of concrete makes a good repair substance. The ingredients should be thor­oughly mixed and then mixed again with enough additional water to get a good flowing concrete. Cement adhesive prod­ucts may differ, so be sure to read labels carefully and follow directions.

Apply the mix to the prepared, tacky surface and work it in just enough to fill all crevices. Finish with float or trowel to match adjacent areas. As soon as the patch has hardened on the surface so it won't mar, sprinkle it with water and cover with paper or canvas or an old burlap sack and keep the surface damp for at least three days. If the weather is hot or if the repair job will be exposed to bright sunlight, it is a good idea to cover and keep moist for an even longer period.

Repair jobs that require ap­plication of a thin lacing to sides or surfaces of new or old concrete should not be done without the application of cement adhesive (see left). This can be one of the new epoxies but be sure to follow the manufacturer's instructions.

Usually the adhesive is used in pure form on the area to be patched and also in mix that will be applied. When you don't have special adhesive, try mixing white wood-working glue in the patch concrete. It does a surprisingly good job.

Caulking Small Cracks

Where the size or location of the crack does not justify a complete repair, it is usually advisable to seal it with a suitable caulking material to prevent it from col­lecting water.

In brickwork or concrete block, cracks may occur at door and window openings. They can be caused by settling of the house and/or foundation, or even by moisture in a joint which, in freezing weather, ex­pands the joint and forms a crack. Repair is simple—just a matter of cleaning the crack and refilling it with fresh mortar.

Sealer may also be used for cracks around sinks, tubs. etc. Available is a kit which contains a caulking-gun cartridge, simplified loading device.

Thiolastic sealer is mixed, then loaded into car­tridges for use in "grease-gun" type device. It's good for most small-scale sealing, caulking jobs.

Use compound to seal masonry cracks, openings between masonry and doors, windows. Best adhe­sion occurs when working surfaces are clean, dry.

With brickwork, dig out any loose, crumbly mortar. Work carefully with a small cold chisel to avoid damaging the brick. The new joint should be at least 1 in. deep. It is very important to remove loose material so the new mortar will be able to bond with a solid substance. After chip­ping, clean put the joint with a small brush and wet the opening inside and out with a fine spray from a garden hose or by splash­ing water on with the brush. If the area is very dry, repeat the wetting a few times at ten-minute intervals. A weak repair will result if the brick sucks too much moisture from the new mortar.

Use one part portland cement to one part lime to five or six parts sand for the mortar, or buy a ready-mixed, packaged "point­ing" mortar. Use just enough water to make a smooth, plastic mix that will easily pene­trate to the deepest part of the new joint. If necessary, use a slim piece of wood to pack in the mortar, but be sure the area is completely filled. Lei the mortar set a while and follow with tooling to match ex­isting joints. Carry out the same procedure for repairing a joint in a block wall. Where the joint under repair is not between blocks or bricks but between the masonry units and another material or structure such as a window or door, it is a wiser course to use a sealer such as Thiolastic instead of mortar. Such a sealer, applied with a caulking gun, can be used on expansion joints, around flashings and gutters, for floor cracks, around pipes and posts that sit on or come through concrete—in fact, any maintenance or repair job that requires a permanent, leak-proof, flexible seal.

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