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Q. How long are the concrete blocks in a foundation supposed to last? Some
of mine are deteriorating, and I don't think they are that old.
J.R., Cambridge A. Concrete blocks should last indefinitely, at least 100 or more years. And before you do anything, are the blocks themselves really deteriorating or is it the mortar between the blocks that is coming out and crumbling? If it is the mortar, the blocks can be repointed; that is, old mortar chipped out and new, fresh mortar installed. Sometimes the blocks can spall, or lose fairly large chunks when water gets behind them and freezes; this sometimes happens if they are painted. And, your blocks may be cinder blocks, a block that was made in the 1940s and '50s with cinders rather than crushed stone. They were made to be light in weight, and the cinders may not be standing up as well as stone. Or, the concrete in the blocks is defective. It can happen. So, if the blocks themselves are deteriorating, you could apply a layer of mortar on the blocks, first applying a bonding agent to the old blocks. It is called parging, and is effective. Or, replace the blocks one at a time, chipping out the old, removing all old mortar and putting in new mortar as you set the new block in place. Q. My concrete slab is made of a high-pressure concrete (4,000-pound rating), but I still would like to protect it from road salt. There are also salt marks on the slab. How can I remove them? D.L., Chicopee A. You should be able to hose off the salt marks on the slab. This should take care of the road salt and also effluorescence, which is the leaking out of salts from the concrete by water. Do this as often as it occurs. To help prevent further stains, seal the concrete with a clear sealer. Repeat this once a year. When you repeat the sealing and the new sealer beads up on the concrete, you are resealing too soon. If the new sealer soaks into the concrete, it is a good time to reseal. Q. When drilling into concrete with a masonry bit, should you use a slow, fast, or medium speed? I have quite a few holes to drill. MICHAEL DANA KENNEDY, Needham A. Slow or medium speed is best so you don't burn the drill bit; a burned bit is dull. It will be extremely slow, frustratingly slow. But instead, rent an impact drill; this tool can be rented at a rental store. Am impact drill not only spins, but also punches, like a jack hammer, but with a lot less volience. You will get a clean hole in seconds instead of minutes or hours that a regular drill will take. Q. My concrete stoop has flagstone set in the concrete. It is 15 years old and some of the flagstone is chipping off. How can I stop it? KEVIN BARNEY, North Attleboro A. That chipping is spalling, flat chunks of stone sloughing off, probably due to water action. The flagstone may be sedimentary rock, which is layered, and water got into one of those layers, froze and expanded, popping it off. Salt might have aggravated the situation. A possible cure is to apply a coat of masonry sealer, which will make the stone and the mortar more water resistant. This sealer should be reapplied yearly or every other year. Q. I plan to set up vertical nailing strips on a concrete wall for paneling. Would Liquid Nails be OK to use? R.M., Braintree A. Yes. Liquid Nails is a construction adhesive, and it is amazing what construction adhesive can do. Some people claim that such adhesive will not last very long when it holds wood strips against a cold and sometimes damp surface. Others have pointed out that their wood strips have held onto concrete for years. Go ahead, but I would suggest securing the strips at the top and bottom with concrete nails, partly to secure the strips while the adhesive is curing, and partly to keep holding if the adhesive fails. One thing about concrete nails: They can be driven into concrete with a heavy hammer, but when securing wood strips with them, do not try to drive the nails home; stop when the heads reach the wood. Driving the nails home is likely to break up the concrete. And don't drive nails too close to the edge of the concrete; keep the nails at least 6 inches away. Q. Salt did a job on my precast concrete front steps, creating gouges, fissures and spalled areas 3/4 to 1 inch deep. When I fill them with mortar, would driving small anchors into the sound concrete help hold the new mortar? BRIAN CASHMAN, Londonderry, N.H. A. It sure would; the anchors are a form of reinforcement, always a good thing with concrete or mortar. Drill holes in the sound concrete and insert nails tightly, so they are sticking up about half the depth of the fissures. The new mortar will grab thse nails like crazy and will hold on for dear life. Use Top 'n' Bond as a mortar; it is designed to be applied in thin layers, and is excellent for this purpose. Q. My son is paving a walkway with concrete. How long should the concrete set before steel-troweling it? C.J., Waltham A. You can start steel troweling the concrete 15 minutes to an hour after pouring it and screeding it smooth. It it seems too soft for troweling, wait another half hour or so. Also, put down squares of plywood to use as stepping stones so you can get to the interior of the poured area. Just kneel on the plywood squares; the large area of the squares will prevent them from pushing into the concrete. Steel troweling will make a very smooth surface, and therefore slippery when wet. I suggest instead of using steel, use a trowel with a wood float. You can buy one or make one with a 2-by-6-inch slab with a handle. Wood floating (do it in a semicircular motion) will leave a rough surface, just what you want outdoors. Q. When I took down a tree that was pushing up part of my concrete sidewalk, I also took out the damaged block of concrete, and put in some slate to fill, mortaring it in place. The mortar is much lighter than the concrete. How can I darken it to match the concrete? JOHN BOYLE, West Hyannisport A. Let time do it. The mortar will darken from the weather, and by next spring you probably won't even notice it. For faster results, try rubbing in some mud -- but why bother? Q. I have several concrete birdbaths that are not holding water because of hairline cracks. Is there a way to seal those cracks? J.M., Medfield A. Let me count the ways. 1. Apply several coats of a masonry or tile sealer. This might seal the cracks, but several coats are needed for the sealer to seep into those cracks, into which nothing else will go. No guarantees on this treatment, but I wonder if it will be toxic to birds, because they drink their bath water. When the sealer cures (hardens and sets), it should be safe. 2. Apply a slurry of Portland cement on the inside of the baths. Add water to the dry cement to make a very thin paste, and brush this onto the surface with a scrub brush. 3. Use a cement-based paint, applying it as you would the slurry. 4. Paint the inside with swimming pool paint. Hey, one more brilliant idea: Line the birdbaths with a flexible plastic liner, an aluminum pan, or anything that will fit reasonably well into the birdbath and will hold water. You may know the difference, but the birds won't care. Q. My cellar floor was poured in winter, and now I have a lot of efflorescence (white powder) on the floor. I tried sealing it, and later added an alkyd paint, and it still came through. What can I do? F.Z., Dover, N.H. A. You can sweep it up and throw it away. It will come back, so you repeat the process. The powder is lime leached out of the concrete by water vapor coming up through the concrete. It doesn't matter when the concrete was poured. If there is lime in the concrete and water vapor comes up through it, you will get the powder. No sealer will work against it, because no sealer on the surface of the concrete will stop the water vapor coming through it. If you use the basement for living space, your best bet, and not outrageously expensive, is to put down a wall-to-wall, indoor-outdoor carpet. This won't stop the migration of water vapor -- it is not supposed to -- but it will cover the powder, which essentially is harmless. Otherwise, keep sweeping it up. Q. A carpenter put cedar boards over some crumbling concrete steps, and they are working out nicely, except for one thng: The risers were painted white, and they are really badly scuffed. What can I do to make them look good without having to repaint? B. M., Holliston A. Those scuffed risers are the reason many people put in stair carpet runners. But that is indoors. Outdoors, the solution is masonry. For you, more paint or solid stain will not do the trick; at least it won't look good for long. So, sand off the paint or remove it with chemical paint remover. Then let the cedar weather to gray. The risers will still scuff, but they will not look so bad. Or, stain with a cedar-tone semitransaprent stain. When it scuffs more than you like, reapply the stain. Q. My poured concrete foundation walls are growing a lot of white fur. It gets so thick that it falls on the floor, and I have to vacuum it up. In four or five months I have to do it again. I have not had a drop of water in the basement in 25 years, not even last fall during those big rainstorms, when everyone else had water. What is this fur, and how can I keep it from growing on my walls? FRANK INFANTE, Revere A. The fur is efflorescence -- the leaching of lime out of the concrete by water, depositing it on the surface as that fur, or powder. You mentioned that you don't have water in the basement, but there is some water vapor in the concrete, migrating from the wet earth on the outside. Concrete is impervious to water, but not to water vapor, which then condenses into water in the concrete, leaching out the lime. It also could be from water vapor in the basement penetrating the concrete. The same thing can happen with brick, where you sometimes see a white water mark on the brick. The amount of efflorescence you get indicates there is a lot of lime in the concrete, and a goodly amount of water. It is harmless, only a nuisance. You can vacuum or brush it regularly off the wall to keep ahead of it. As for a cure, I am not quite sure there is one. Possibly a layer of tar on the outside of the foundation would prevent water vapor from penetrating from the outside, but that is drastic, requiring digging down around the outside of the foundation. 'Tisn't worth it. Perhaps ventilating the basement in spring, summer, and fall would reduce the amount of water vapor there and thus possibly reduce the efflorescence. Incidentally, since I have to look up the spelling of efflorescence every time I use the word, its Latin root is efflorescere, meaning ``to bloom.'' And that fur does seem to flower or bloom. I know this does not add to your solution, but it's interesting. Q. The concrete floor in my basement was covered with 12-inch-square vinyl tiles, but they cracked over an expansion joint in the concrete. Now I have to install new tiles, but what can I use to fill that expansion joint so it won't happen again. Can I use hydraulic cement? A.S., Newton A. Don't use hydraulic cement; it will fill the crack solidly and defeat the purpose of the expansion joint, and, when the concrete expands, the hydraulic cement will crack. Instead, fill the joint with floor-leveling compound, which should be flexible enough not to crack when the concrete moves. Q. The concrete floor in my basement was covered with 12-inch-square vinyl tiles, but they cracked over an expansion joint in the concrete. Now I have to install new tiles, but what can I use to fill that expansion joint so it won't happen again? Can I use hydraulic cement? A.S., Newton A. Don't use hydraulic cement; it will fill the crack solidly and defeat the purpose of the expansion joint, and, when the concrete expands, the hydraulic cement will crack. Instead, fill the joint with floor-leveling compound, which should be flexible enough not to crack when the concrete moves. Q. I would like to bolt a workbench to a concrete foundation wall in my cellar. Can I drill holes in poured concrete? Also, I have a dent three inchetreach horticulturist)s long and about a quarter-inch deep in my hardwood floor. How can I eliminate it? M.S., Norwood A. To make holes in concrete, rent an impact drill, one that hammers like a jack hammer in addition to turning like a drill. Then use lag bolts or other kinds of bolts to hold the workbench to the wall. Frankly, if there is enough room, you'd be better off having a free-standing workbench; get one heavy enough so it won't walk all over the place when you're working on it. Or, set the workbench on the floor for sturdiness, then bolt it to the wall for stability. As for that dent, you could try the old trick of putting a wet cloth over the dent, then a hot iron over that. The steam created will, or should, penetrate the wood and swell it, enough to level off the dent, or nearly so. You will have to refinish this area, because the steam will do a job on the finish. If it is on one board, refinishing that board will be easy to do. The extra gloss of the new polyurethane will dull a bit in a few months. Use oil-based polyurethane varnish; chances are that the original finish is oil based. The new water-based polyurethanes are good, but not good for floors, and may be incompatible with oil-based polyurethanes. If the steam doesn't work, you can always cut out the bad board and put a new one in its place. This is possible, but quite tricky, having to cut very carefully to get a clean, straight joint for the new board to butt up properly against. It's sort of a last resort. Q. A snowplow got rambunctious and knocked two pieces of concrete off the top of my retaining wall. They are about 7 1/2 inches wide, 2 inches deep and 46 inches long, and look as if they were a part of a cap poured on top of the wall. How can I restore the wall? Can I pour new concrete? JOE BARAN, Arlington A. You sure can, and pouring concrete will give the best look. Set up plywood forms against each side of the wall; use 5/8- or 3/4-inch plywood, and secure them by wedging wood posts from the ground against the plywood. Concrete is heavy, so the forms should be secure. Make the top of the forms even with the top of the original wall, so that when you pour concrete to the top, you can strike it off, or screed it smooth, by drawing a board across the top, using the forms as a guide. After 15 minutes or so, can float the concrete; that is, rub it with a wood float (a wood trowel, really) to make a rough but even surface. You're not done yet, either. Now, run an edging tool (inexpensive in hardware stores) between concrete and forms, to round off the edge. If you don't round off the edge, it will be very sharp and will tend to chip. For this small job, use Sakrete concrete mix, which you simply mix with water and pour in place after dampening the top of the wall. Don't make the mix too soupy; just a little crumbly, and it will work nicely. Or, you can mortar in those chips. Buy mortar mix at the same store you bought the concrete mix, mix it with water to a wet, crumbly state, dampen the wall, place the mortar about 1/2 inch thick and set the chip in place. The chip may be a little higher than the top of the wall, but that should be OK. Still another way: Instead of mortar, use thin-set mortar, also sold in hardware and building supply stores, and apply it thinly. It's called thin-set because it can be applied thinly, and will hold better than standard mortar. Thin-set and standard mortar are waterproof. Q. I live in a converted barn 100 years old. The basement laundry was originally a cistern, with cement walls and a cement floor. We painted the floor several times, but each time the paint disintegrates, leaving an ugly, patchy floor. Why does this happen? What can I do that would keep paint on the floor? Mrs. J. M. W., Jamaica Plain A. Forget about the paint. It is impossible to keep paint on a concrete floor because water vapor is constantly coming up through the floor, and pushes the paint right off. Well, not exactly impossible, because some epoxy paints do resist the force of water vapor. You have to remove all the paint by scraping and a chemical paint remover before applying the epoxy. But there is a better way: Use a concrete stain. It is sold in paint stores, in seven lovely decorator colors, including white. It will not peel, but, like the epoxy, it must be applied to bare concrete. Q. I'd like to get my basement concrete floor as clean as possible before putting down wall-to-wall carpeting. What is the recipe for cleaning concrete? WENDY PEARSON, Hanover A. No secrets. Just plain old Spic and Span, or any similar detergent. For heavy-duty washing, I prefer the granular (not liquid) Spic and Span. Make a double-strength mix. Add a cup of bleach to the bucket. Wear skin and eye protection when working with bleach. Apply this solution, let it stand for two to five minutes, scrub, rinse and let dry thoroughly before putting down the carpet. Nothing else is needed. Q. I am building concrete balusters for an outside wall. I want them white, so I was thinking I would have to treat them with a cement-based paint. I would like to skip this step; can I buy white concrete? D.D., Wellesley A. I think white concrete is sold, but you can also make it yourself with Portland cement, white sand and crushed white stone (usually marble). If you can't find these materials or find white concrete, you could instead paint the gray concrete with a white, solid latex stain. This should be easier to do than using the cement-based paint, and should last for many years without peeling. And remember, no matter what paint you use, thin coats are important, in fact essential, to success. Q. I would like to stain my concrete basement floor, but now I understand the standard concrete stain is not available anymore. I don't want to paint because of possible peeling. I saw in Home Depot a Behr product, a concrete stain. Would that work? JILL Cox, Leominster A. You're right. Benjamin Moore used to make a concrete stain, and it was a cure for tough concrete floors. I think the Behr may work, but double-check to make sure it is not a solid-type stain that could peel. The whole idea of a concrete stain is that it will not peel. If you're worried about peeling, then I suggest this: Choose a semitransparent stain, one that normally goes on cedar clapboard or shingles or other outdoor wood. If you ever spilled such stains on concrete, you know they seem to last forever, so why not do it on purpose. Use lots and lots of ventilation when using such stains, and apply sparingly. Only one thin coat is needed, but the odor is strong and will take a while to dissipate even with full ventilation. Q. I redid my basement, but when I sprayed some furniture with a black spray paint, a lot of it go on the new concrete floor, an area of about eight feet square. How can I get rid of that black spray paint? R.K., Beverly A. Good question, big problem. Chemical paint remover or grinding with a concrete grinding machine is the only way. And since this will be very tedious, I suggest you put down a wall-to-wall indoor-outdoor carpet instead. If you don't like the idea of a carpet, then wait until the black paint wears off. Then remove the rest, and leave the concrete bare, or if you want a color, apply a semitransparent stain. Such a stain must go on bare concrete. Semitransparent stain is designed to go on shingles or clapboards outside, but I think it will work on a concrete floor. If you ever spilled semitransparent stain on concrete, it never goes away, it seems, and that is why I think it will work on concrete. Benjamin Moore used to make a concrete stain, but it was outlawed for environmental reasons. Q. I ran out of concrete when I poured concrete for a project. Can I pour the rest the next day, as much as 3 inches? Should I drive in a few nails for the new concrete to hold? M.S., Ashland A. Your idea of the nails in the old concrete is good; if what you poured is less than a few days old, you should be able to drive ordinary nails in the old concrete. When you pour the new concrete, the nails will hold everything together. In future projects, if you run out of concrete, you could throw in several larger rocks immediately to try to bring up the level. The Handyman did this once when he was running out of concrete. The kids in the neighborhood helped out, bringing up small- to medium-size rocks, and dumping them in the mix. It worked. You should have seen all those kids and the Handyman scrambling around, in a hurry to get the job done before the batch set up and hardened, which would have made it unworkable. Q. My four-year-old house has a farmer's porch supported by concrete Sonatube piers. The concrete is eroding at the top, and fasteners holding the wood posts to the piers are losing their hold on the concrete. How can I fix that? R.M., Stow A. Four years is a short time for a concrete pier to erode, so I think it is defective concrete. There are several things you can try. One of those things depends on how high the concrete piers are sticking above the ground. If the piers are sticking up maybe 6 to 12 inches or so, you might be able to cut off the pier to expose sound concrete, then fasten a pressure-treated wood block to the sound concrete, then the post onto the wood block. Another trick is to drill deeper into the concrete until you reach sound concrete, and insert a steel bolt or rod into the concrete and also into the wood post. For all these things, you have to shore up the porch, supporting it temporarily, so you will have some working room, and keep it from collapsing as you remove the existing support. And, if the piers are eroding down to their bottoms, then hire a pro to pour new ones. In fact, it would be a good idea to hire a pro for any of these projects unless you are confident -- and quite confident -- that you can do it yourself. Q. I have a crack, an eighth of an inch or less, in a concrete sidewalk. How can I fill it? C.K., Reading A. Why bother? It might get bigger when water gets into it and freezes, but for a sidewalk, that's not too bad, except cosmetically. If you really want to fill it, you have to chip it out wider, and as deep as practical (at least an inch), and fill it with hydraulic cement. But the patch will show more than the crack. Another way, but it will take a lot longer, is to apply masonry sealer to the crack; do it every time you think of it, and eventually, with some luck, it may fill the crack, making a much less invisible crack. But it will take many applications. I know of people who have filled a hairline crack in a concrete birdbath with sealer, and they swear it stopped the birdbath leak. While the crack in your sidewalk may not be hairline, the sealer still might fill it, if you apply enough coats. Q. I'd like to get rid of a long concrete walk from the porch to the driveway, and maybe put in some brick. A landscaper suggested using stamped concrete, a technique of applying new concrete and stamping or forming it into a pattern of brick, stone, or other stylish paving. Would this work? TOM O'NEILL, North Andover A. Such a concrete treatment can work, and can look pretty good. It's new, but there are several outfits who are doing it. Some of the operators who do it with newly laid concrete are Decorative Concrete of Whitman, phone 781-447-9444 or 800-236-1322; Concrete Impressions of Center Harbor, N.H., phone 603-536-1650, ext. 112; and Increte Systems by N.E. Decorative Concrete of Northwood, N.H., phone 603-942-9273 or 800-972-9273. And there is an outfit, CTI New England of Groton, Conn., phone 800-737-4284, which resurfaces old concrete with a pattern and colors. If you want to put in brick instead, that too is possible, right on top of the old concrete. But instead of mortaring it onto the old concrete, you could do this: Drill holes in the concrete for drainage, set up borders along each side to contain the brick, and install brick dry (not with mortar). This will raise the walk, but it will provide a good, no-maintenance brick surface. I think it would be better than trying to mortar in the brick, but you do need that border. You can make the border of pressure-treated timbers, 2 x 8s or 2 x 10s, concrete patio blocks, or soldier bricks, i.e., bricks on their long ends. A final possibility, still using the borders, is to regrade the earth against the new walk so that the walk is flush with the earth instead of sticking up 2 or 3 inches. Q. My concrete front steps are still in pretty good shape, but the concrete has become pockmarked. Can I trowel on a thin coat of concrete to smooth out the treads? BILL SPATRICK, Peabody A. Yes, and hope springs eternal that it will work. Trowel on a thin coat of Top 'n Bond, a type of mortar (more mortar than concrete because it has no stones) designed to go down in thin layers, without the need for a bonding agent. The handyman has had pretty good luck using this stuff on small projects. After troweling it on and waiting about 15 minutes, rub the surface with a wood float, a type of trowel that is wood rather than steel, and which makes a rough, skid-resistant surface. If you try to smooth it out with a steel trowel, you will get a supersmooth surface that will be slippery when wet, an added hazard on stairs. The rougher the old concrete, the better the Top 'n Bond will hold. And, it won't hurt to put a bonding agent (sold in hardware and building supply stores where you buy the Top 'n Bond) on the old surface before adding the Top 'n Bond. Q. The concrete deck around my pool is getting badly pitted. What can I put on it to smooth it out and make it look better? It is quite an extensive deck, some 500 square feet, so any repair work would be a lot of work. J.M., Lynnfield A. There are several things you can do: Anything you do will be a lot of work on an extensive deck around the pool. In other words, there is no easy way, unless you pay for it. 1. Trowel on a layer of Top 'n Bond, a special mortar designed to go on in thin layers, up to 1/2 inch thick. If you use this material, be sure to give it a rough, anti-skid surface. To do this, float it with a wood float 15 minutes or so after laying the mortar. Floating means rubbing the surface with a wood trowel, called a float. If you did this with a metal trowel, you will get a smooth and very slippery surfaces. 2. Apply a bonding agent to the concrete, then cover it with two inches of standard concrete, then wood float it. This won't work without the bonding agent, which is a sort of glue designed to hold the two components together. 3. Have an epoxy covering applied professionally. This might be slippery. 4. Build a cedar boardwalk over the concrete. This is the biggest job but may in the long run be the most satisfactory. It would require installing 1 x 4 cedar sleepers on the concrete, spaced 12 inches apart, then applying cedar floor boards on the sleepers, spaced enough for drainage, and parallel to the length of the deck. With luck this will last 15 years. Or, use Trex or other artificial ``wood'' made of ground-up wood and ground-up plastic milk cartons. It is more expensive than the cedar but is likely to last longer. Neither the cedar nor the artificial wood needs staining, sealing, or painting. This wood deck would raise the deck by 1 1/2 to 2 inches or so, but you might be able to live with that. Q. A water tank broke in my basement, flooding the floor. When the water dried up, it left a large white spot. The tank has been fixed, but nothing seems to take off that white spot. I tried washing and it came back. I tried washing with soap and it came back. How can I get rid of that stain? S. R., Beverly A. That stain is efflorescence, the leaching of lime out of the concrete by the water. Washing even without soap or detergent should have removed it. You could try scrubbing it dry with a scrub brush. If that doesn't work, buy muriatic acid (sold in hardware and building supply stores), and make a solution of one part acid and five parts water. Always pour the acid into the water, and wear skin and eye protection when working with acid. Apply this solution to the stain and you'll probably see the stain fizz up; after the fizzing stops, rinse the floor and let dry. The acid attacks the lime wherever it is, dissolving it.
Q. My garage roof is a flat concrete slab, 70 years old, and it has been leaking badly and damaging the cars under. A contractor sealed the holes, then applied a clear sealer. It did not help. Another man put in two inches of concrete which also did not work. Still another man took off the concrete and sealed the roof, also without success. Now what can I do? LEE BURNS, Medford A. After spending a small fortune for all thsoe unsuccessful patches, consider moving the cars out for a while until the roof is fixed, once and for all. And this might be the once-and-for-all fix: If the roof is relatively intact, I suggest hiring a roofer to put on a rubber roof. But be warned that you cannot walk on this rubber roof, even if it is on concrete. In fact, I know of no roof that can be walked on (with added stress of furniture, etc.) that is waterproof. If you want to use the roof as a patio, you have to build a deck above it; a few inches above it will do. Q. A mason filled the space between the patio and the house foundation with mortar. It works well in keeping water out of that space, but he left a film of mortar on the concrete patio. How can I remove it? FLORENCE MISITE, Needham A. The mason should have cleaned up his sloppiness. But you can do it without too much trouble. Buy muriatic acid in a hardware or paint store. Mix equal parts acid and water; always pour acid into water. Paint this solution on the mortar film. It will fizz up; when it stops fizzing, scrub if necessary with a bristled scrub brush, and rinse. Repeat if necessary. Wear skin and eye protection when working with acid. Q. A bag of cement got very hard after being stored for two years. I broke it up a little and it worked to make concrete. Will that cement be OK to make more concrete? PAUL ANDERSON, Melrose A. It can work if you can break up the cement (which got hard because of moisture) and pulverize it back into powder. But it is so inexpensive that it is probably worth buying new Portland cement rather than risk the old cement not working. Remember, cement is Portland cement, and is only a part of concrete, which comprises cement, sand, and gravel. If the bag was a concrete mix (with cement, sand, and gravel), breaking it up completely may work, provided some of the mix has not become concrete, which is virtualy impossible to break up and reconstitute. But again, the cost of these bags is so low that it is hardly worth the effort to break it up. Q. You mentioned a dry material that is used to fill wide cracks in concrete, but I forget what it is. I have a half-inch-wide crack between my foundation and walkway; unfortunately, the walk slopes toward the foundation and I get water running into the crack. Anyway, I would like to fill it. R.R., Woburn A. Anything dry that I mentioned was soil cement, using Portland cement and earth rather than sand and crushed stone. I don't think it would work very well in the crack. So, I suggest ordinary mortar. Dig out any old patching material, and as deeply as practicable; several inches would be better than an inch or so. Or, instead of mortar, use hydraulic cement, which expands as it sets and will make a tighter joint. If that doesn't work, you could try regrading the walkway with more concrete so it slopes away from the foundation. That may be impossible, but it's worth thinking about.
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