How to adhere concrete to concrete

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How to adhere concrete to concreteFact: Fresh wet concrete does not normally bond well to existing dry concrete. Do you remember elementary school where one of the subjects on which you were graded was “plays well with others”? Concrete would have gotten an F. There is nothing in basic portland cement that will act as a bonding agent. Portland cement concrete works well in mass and provides great compressive strength but not bond.

Concrete is marvelous stuff but in time it will deteriorate. When it does, you either have to patch it or replace it. Assuming that it is structurally sound the least expensive alternative is to patch it. However patching it requires some attention to detail or your patch will not last. So that you don’t waste too much time or money, we should probably discuss what “structurally sound” means. If your sidewalk has either heaved or dropped at almost every joint, repairing it will not provide a long-term solution. The slabs are likely still moving. If your slab has so much sand and gravel on the surface that despite sweeping and sweeping and squirting and squirting it just keeps coming back, don’t waste your time on repairs. If you have multiple cracks that run so deep that they appear to run through the slab, a repair would only be temporary. The solution to all of these problems involves a jackhammer and bags of one of the Sakrete concretes. Since this discussion is on the best way to bond concrete, we will assume that your slab is good.

There are a variety of Sakrete concrete repair products available to fix concrete that has begun to deteriorate. However, without good surface preparation, none of them are going to perform satisfactorily. All loose sand, gravel, dirt, leaves etc. must be removed. This can typically be done with a garden hose and a good nozzle. Tough areas may require a pressure washer or mechanical abrasion. The two toughest areas to cover are those with oil and tree sap. Both of these will work their way down into the concrete. Simply washing the surface isn’t sufficient. If the stains do not run too deep, you can chip away the concrete using a hammer and chisel. Don’t forget the goggles (not just glasses) as this process will throw concrete all over the place. Also, keep your thumb out of the way. If the spots are too large or too deep for this to be practical, you may need a sealer to cover the stains before patching.

There are two basic methods for bonding a portland cement based product to existing concrete; 1) chemically and 2) mechanically.

Let’s discuss the mechanical approach first since it is really used in both approaches. The most effective way to ensure a really good bond is with a scratch coat. This is simply a very wet coat made up by mixing the repair product with water. Mix up a small amount of the repair material to a soupy consistency. You don’t need to measure the water-just turn the stuff into slop. Then, using a gloved hand or a rag, smear the material onto the area to be patched. Just think finger painting from kindergarten. The technique is about the same. Apply pressure to ensure that as much as possible is shoved into the nocks and crannies. You only need a thin coat. It is not necessary for this scratch coat to dry. By the time you get the repair material mixed it will be ready. Then mix up additional repair material to the proper consistency and apply over this thin scratch coat.

The chemical approach involved mixing up a liquid bonding agent that helps bond new concrete products to old. Products like Sakrete Top ‘N Bond and Sakrete Flo-Coat already contain polymers that greatly improve the bond of portland cement and should NEVER be used with a liquid bonding agent. I know in America bigger is better but it’s just not so with these products. Other products like Sakrete Sand Mix and Sakrete Fast Set Cement Patcher benefit from the use of a liquid chemical bonding agent such as Sakrete Bonder & Fortifier. When using a liquid bonding agent, paint the bonder onto the existing concrete and allow it to dry until it is tacky. This usually takes only a few minutes. Then apply the repair material. Just as in the process described above, after the bonder has become tacky apply a scratch coat and then apply the repair material. The most effective way to ensure that the bonding agent gets into the existing concrete is to apply it directly using a brush or rag. It can be sprayed if you happen to have a sprayer. Although the directions say that you can use it as part of the mix water, direct application works better.

If you are doing a large area and a scratch coat isn’t practical you will need to spray the surface with water before you apply the repair material. On a warm day, the existing concrete surface will be hot enough to suck the water out of the repair material. In addition, some concretes are quite porous and will rob water from your repair material. If too much water is lost into the old concrete there will not be enough water to hydrate all of the cement particles and a lower strength material will be the result. Concrete simply will not bond to all substances. Paint, oil, glue from old flooring tiles are just a few. You must mechanically remove these materials if you want the job to last.

Once the job is complete, you can do a quick check to see if the bond was successful. Wait at least 24 hours and then tap “gently” on the patch using a hammer or some other dull object and listen for a hollow echoing sound. If you just get a dull thud then the material has bonded well. If you get a hollow sound, the material has not bonded and will crack in time. Which means it is back to the beginning of today’s topic. Here is hoping your concrete work comes across as a dull thud (not like some of my party guests) rather than a hollow endeavor.

For more information on where to buy these products, visit here.

How to adhere concrete to concrete

Michael Holley/Wikimedia/Public Domain

The various brands of cement board, such as HardieBacker, Durock, DenShield, and Wonderboard have become a standard tile backer material for nearly all ceramic, porcelain, and stone tiles for floor, wall, and countertop applications. These convenient panels of cementitious board provide an instant flat, hard surface that bonds with the thin-set adhesives or mortars used to install tile.

Typically, a layer of cement board is screwed to a plywood or OSB subfloor, or to the wall studs for wall installations. While most tile manufacturers do say that their products can be applied directly to plywood, the cementitious surface of cement board provides a better base. And when you are tiling wet locations, such as bathrooms, cement board is not just a good idea—it is necessary.

Cement Board on Concrete?

Normally, installing cement board is not regarded as necessary when you are laying tile onto a concrete slab since this subfloor is already cementitious—adding cement board would be redundant. However, there are three cases where installers are sometimes tempted to install a layer of cement board before applying tile:

  • The existing concrete does not provide an adequate, solid base for tiling.
  • The concrete has been painted over, and paint is not an acceptable surface for thin-set adhesive or mortar.
  • The concrete needs to be raised higher than you can comfortably float a mortar bed.

Would adding an underlayment of cement board help with these problems?

Manufacturer Recommendations

James Hardie Industries, makers of HardieBacker®, and USG, makers of Durock®, indicate that their respective cement backer boards should not be installed over concrete.

  • James Hardie: HardieBacker specifications specifically exclude concrete as a base for installation.
  • USG: Durock does not expressly exclude concrete, but the material is specified only for minimum 5/8-inch exterior-grade plywood or OSB. One source reports that USG will not officially validate the Durock-to-concrete attachment simply because they have not tested it. The lack of testing may be simply because so few customers express a need for applying Durock to concrete.

The View of Tile Professionals

But the manufacturer prohibitions or omissions are warranty issues. The questions remain: Can you effectively pair two cementitious products—cement board and a concrete slab?

There is no problem with the two materials being compatible. The issue, as Bud Cline of The Floor Pro says, is more about how to attach the cement board to the concrete. A powder-actuated nailer is out of the question since nail depth would be impossible to regulate. Concrete screws, Cline says, have heads that are too small to hold down the cement board.

His recommendation: Work with the concrete surface so that it is strong enough and porous enough to accept tile mortar. Portland cement-based fillers can take care holes and cracks. Painted concrete can be sandblasted, sanded, or ground down to bring up a nice, porous surface.

Most tile professionals, including John Bridge, concur: Attaching cement board to concrete is not an acceptable way to surface the concrete prior to tile installation. Thin-set alone will not help the cement board stick to the concrete slab. Screws are the only logical way to do this, but it would entail an extremely tedious and time-consuming process of drilling pilot holes before sinking the screws. Additionally, you would be fighting against the thin-set bed under the cement board when drilling the holes and driving the screws.

Bottom Line

Technically, cement board can be laid over a concrete slab as the base for a tile installation. But doing so is a very laborious, time-consuming process that is likely more trouble than it is worth. A better solution is to prepare and resurface the concrete slab so that it can accept thin-set adhesive or a mortar base onto which to lay tile.

Porch post is generally constructed using wood. A concrete slab forms sturdy and durable flooring for a porch. Each support posts should possess an anchor plates, which include drilled bolt holes. Attaching the bolster posts to the structure of a solid concrete base is not really an easy task. It is necessary for you to drill into concrete and after that fix those anchor posts prior to fitting the railing. You should follow these few steps to fix the posts on concrete. If there is any dampness found in the concrete that will soak up into the post and that may subsequently rot the wood. You have to use the proper hardware for fitting. You will need to install a moisture barricade between your concrete and the post so as to avoid the necessity for its untimely replacement. You should take care while drilling into the concrete that you do not crush or crack the concrete at the position where the rail will be fixed

Tools and Material Needed:

  • Concrete base
  • Wood post
  • Pencil
  • Chalk stick
  • Concrete screw kit
  • Anchor plates
  • Gaskets
  • Rubber mallet
  • Measuring tape
  • Masking tape
  • Power drill
  • Drilling attachment
  • Galvanized screws per post

Step1 – Select the Position for Posts

Mark with pencil the position of the post setting on the concrete slab by placing a post anchor to act as a guide for marking the needed position. Create pencil marks through the mounting holes inside the anchor plates over concrete surface. Take away the anchor plates and place them apart.

Step 2 – Positioning the Anchor Plates

Ensure that the anchor plates are correctly for the support posts prior to drilling. Ascertain this using the measuring tape.

Step 3 – Drilling the Holes

Attach a masonry drill bit to an electric power drill. Keep the working length of the drilling bit half an inch more than the length of anchor bolt sleeves and cover the remaining part of the drill bit by rolling masking tape over it a couple of times.

Drill the mounting holes into the concrete on the every mark made with the pencil for the holes. The masking tape acts as a gauge mark on the drill bit for controlling the depth of the drilled holes for mounting bolts.

If you are staying in a wet place and desire to ensure utmost protection from dampness to the concrete slab, you must install a gasket between concrete surface and anchor to fix the posts to stop any moisture from entering into the posts through holes for anchor mounting. You should take the assistance of a friend to help you for holding the parts in their position while you drill or fasten the posts in their respective places.

Make certain while drilling the holes to maintain the proper depth for putting the anchor bolt sleeve. You should check the hole-depth with the sleeve as well.

Use a rubber or plastic mallet to fix the sleeve into the holes so that you do not damage the sleeves. It is necessary to use protective eye wear while drilling into the concrete to avoid the chips from falling into your eyes and causing injury.

Step 4 – Fixing the Posts

Position the post anchor back on drilled holes and fix in anchor bolts into all holes with a wrench.

Position the post over the mounted anchor ensuring that the post properly fits over the tabs provided on the anchor for fixing the post. Fix the post to the anchor using the galvanized screws with the help of a screw driver or a Phillips head screw tightening bit mounted to on an electric power drill.

How to adhere concrete to concrete

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You can update the look of your concrete deck or patio without tearing up the concrete. Instead, lay concrete stepping stones over the deck for an instant upgrade. Choose colors that complement your outdoor space, and use stepping stones that are uniform in shape and size. Covering your deck with stepping stones means placing them as close together as possible, and oddly shaped or free-form stepping stones can make this problematic.

Sweep all dirt and debris off the deck. Clean the surface of the concrete with trisodium phosphate and water. Rinse well, then let the concrete dry overnight.

Mix the mortar with water in a large bucket. Mortar dries quickly, so only mix what you think you can use in less than an hour. You can mix more later if necessary.

Spread a layer of mortar about 3/4 inch thick along the first side of the deck using a flat masonry trowel. This is usually the side along your house so you can step out of your house onto a full stepping stone. However, you don’t want to box yourself in; if the only way to enter or exit your deck is through the house, start along a side edge.

Press the first stepping stone into the mortar, twisting it a bit to help it adhere. Put the second stone beside the first, keeping it as close as possible. Ideally, there would be a gap of less than 1/4 inch. Continue laying the stones in rows along the deck by laying mortar and twisting the stones in place. If you have stones that aren’t square, you might need to put them together similar to how you would a puzzle. In this case, keep them to rows as best you can, and fill in with smaller pieces. Keep a level handy to lay across the stones; after you install each stone, place a level between it and a neighboring stone, pushing the new one down farther or twisting it up slightly if necessary to make it level. Once you finish a row, test several areas along the row to make sure all stones are level before moving on to the next row.

Cut stones for the edges by placing a masonry blade in a circular saw. Set it to cut 1/2 inch deep, then score the stone with the blade. Change the setting to cut 1 inch deep, then cut along the score mark. Continue until you cut through the stone.

Allow the mortar to dry overnight.

Pour polymeric sand over the top of the stepping stones. Spread the sand with a broom, pushing the sand into the cracks between the stones.

Based outside Atlanta, Ga., Shala Munroe has been writing and copy editing since 1995. Beginning her career at newspapers such as the “Marietta Daily Journal” and the “Atlanta Business Chronicle,” she most recently worked in communications and management for several nonprofit organizations before purchasing a flower shop in 2006. She earned a BA in communications from Jacksonville State University.

How to adhere concrete to concrete

Using adhesive on concrete can be a daunting task for a do-it-yourself enthusiast because you fear that any mistakes you make will be permanent. However, if you put enough planning into the task and choose the right adhesive for the right substance, you can stick whatever needs sticking with confidence!

What Might You Glue to Concrete?

You might wish to put adhesive on concrete to glue carpet, kitchen parts, tiles or masonry. Whatever the task is that you have to do, check the manufacturer’s instructions to make sure that the substance is suitable for the job.

What Kind of Adhesive Sticks?

The type of adhesive you go for will depend on the use you have in mind for it. For example, mortar is appropriate for outdoor building use. It is easy to mix up from a kit you can buy from any hardware store, and can be applied with a mortar trowel where needed.

For real precision jobs, the best adhesive on concrete is a 100 percent silicone caulk. For example, if you need to stick a ceramic kitchen sink into a concrete countertop, the caulk will stick the two substances together well and look good on your work surface. You can get it in a brilliant white color, which is ideal for kitchens and bathrooms. Caulk is easy to apply, often coming in a gun that means that you can position the adhesive with more precision than mortar. It is also waterproof.

If you need to put some adhesive on concrete to lay tiles, then a water-based general bonding agent like polyvinyl acetate emulsion might be more appropriate. It bonds quickly with the surfaces and is very durable.

The other option for tiling and laying carpets is construction mastic adhesive, which is very straightforward to apply.

How Do I Apply the Adhesive Properly?

The first thing to do is to clean the concrete surface thoroughly. It should be free from dust, dirt, grime, and grease. The surface should also be dry.

For the best results, apply the adhesive onto the concrete when the temperature is between 65°F and 95°F. If the concrete is too hot or too cold, the adhesive will not be as efficient.

Read and follow the adhesive manufacturer’s instructions carefully to make sure that you get the best bond between your two surfaces. Then apply the adhesive evenly onto one surface only, using a notched trowel.

Slowly and carefully bring your two surfaces together, clamping them in place if appropriate. If you have split any adhesive it is essential to remove it immediately with a damp cloth before it sets. Next (and this is almost the mort important step), leave the surfaces alone for at least 8 hours, preferably 24 hours. This will ensure that the adhesive on concrete has totally set.

That’s what you need to know about using adhesives on concrete. Remember, when using any kind of chemical, take care to protect your eyes by wearing goggles, and your skin by wearing gloves.

Fastening to concrete looks difficult, but with the proper tools and techniques, its a snap.

How to adhere concrete to concrete

How to adhere concrete to concrete

There are many home-improvement projects that require you to screw or nail into concrete, such as when affixing shelf brackets to a concrete basement wall, screwing down a 2×4 sole plate to a concrete floor, fastening metal conduit
to concrete surfaces, or securing steel post anchors to a concrete patio. Unfortunately for many DIYers, using concrete screws or fasterners can be a frustratingly difficult and almost impossible task. But when armed with the correct tools and a few specialized fasteners, anyone can learn to fasten almost anything to concrete.

Here, we’ll explain four different techniques and types of concrete screws and fasteners specifically designed for attaching to concrete, and most can also be used to fasten into brick, stone, and concrete block as well. Note that before installing most concrete fasteners, you must first drill a hole with a carbide-tipped masonry bit. The quickest, easiest way to drill into concrete is with a hammer drill, which uses both bit rotation and concussive blows to bore the holes. If you don’t own a hammer drill you can use a standard corded electric drill or cordless battery-powered drill, but it’ll take at least twice as long to drill each hole. It’s also important to always blow or vacuum out the concrete dust from the hole before inserting the fastener. That’s because concrete fasteners grip much more securely in clean, dust-free holes.

How to adhere concrete to concrete

When you’re attaching something that’s relatively small and lightweight to concrete, it’s hard to beat the speed and ease of hammer-set anchors. Each anchor consists of an unthreaded pin set into a metal sleeve. Simply drill a hole into the concrete, hold the fixture you’re fastening over the hole, then use a hammer to tap the anchor into the hole. As you drive in the pin, the sleeve expands outward, trapping the anchor in the hole.

Most hammer-set anchors require a 1/4-inch-diameter hole and come in lengths ranging from 1 to 3 inches. A 100-piece box of 1-1/4-inch-long anchors costs about $23.

Hammer-set anchors, also known as nail anchors, are perfect for attaching metal electrical boxes, wood furring strips, metal conduit, and shelf brackets to concrete, block, and brick. Keep in mind that hammer-set anchors aren’t easily removable.

How to adhere concrete to concrete

The soft-metal shield is one of the oldest and most effective concrete fasteners available. It’s little more than a ribbed, slightly tapered hollow metal sleeve that fits into a hole. The shield is made from soft, almost lead-like material that accepts a sheet-metal screw.

When installing a soft-metal shield, it’s important to drill the proper-size hole. If the hole is too large, then the shield will spin in the hole. If it’s too small, the shield will crush when you tap it in. Also, you must clean all the dust out of the hole prior to hammering in the shield.

Soft-metal shields are commonly available in lengths ranging from 3/4 to 1 1/2 inches, and in three different diameters for accepting screw sizes from No. 6 to No. 18. Expect to pay about $15 for a box of 100 No. 6-8 shields; you must purchase the sheet metal screws separately. Soft-metal shields are suitable for fastening to concrete, block, and brick.

It’s worth mentioning that there’s another type of soft-metal shield, called the lag shield anchor. Lag shield anchors are larger than soft-metal shields and accept big lag screws for extra holding power for heavy objects. A 20-pack of 3/8-inch-diameter x 1¾-inch lag shields goes for about $14. Items secured by either soft-metal shields or lag shields can be easily removed, if necessary.

How to adhere concrete to concrete

Concrete screws provide a quick, easy and incredibly strong way to fasten to concrete. And best of all, there’s no hammering required or anchor or shield to install. All you do is drill a hole and drive in the screw. That’s it. You don’t even have to blow out the hole.

Concrete screws, commonly known by the tradename Tapcon, look like wood screws, but feature high–low threads that bite tightly to the sides of the hole. To ensure a solid attachment, it’s important to use the drill bit recommended by the screw manufacturer, and bore the hole about 1/4 inch deeper than the screw length to avoid bottoming out when you put in the screw.

Concrete screws come in 3/16- and 1/4-inch diameter, in lengths up to 3-3/4 inches. Both hex-head and Phillips-head styles are available. They can be used in poured concrete, concrete block, and brick. Expect to pay about $15 for a 100-count box of 1¾-inch-long screws.

How to adhere concrete to concrete

If you don’t think fastening to concrete can be fun, then you’ve never used a powder-actuated fastener. This tool is essentially a .22-caliber pistol that fires hardened nails into concrete. How cool is that? (Some tool manufacturers also offer .25- and .27-caliber models.)

Powder-actuated fasteners are ideal for securing 2×4 sleepers to floors, furring strips to walls, and plywood subfloors to concrete slabs. They provide an incredibly strong and fast way to attach to concrete—but you can’t remove the nails once they’ve been fired in.

The gun accepts a wide range of nails, called pins, ranging from about 1/2 to 3 inches, and various charges, also known as loads. The larger the load, the more gunpowder it contains. Loads are numbered and color-coded for easy identification, ranging from Gray No. 1 (least powerful) to Purple No. 6 (most powerful). Which load to use depends on several factors, including the nail length, thickness of material being fastened, and hardness of the concrete.

Warning: A powder-actuated fastener is a potentially dangerous tool. Use it only to fasten to poured concrete—never to concrete block or brick. Keep people well clear of the work area, and always wear safety goggles and hearing protection.

Powder-actuated fasteners come in a wide range of prices, starting at about $85. You can also rent one for about $40 per day, not including pins and loads. Expect to pay about $12 for a 100-piece box of 2-inch pins, and about $12 for 100 Yellow No. 4 loads.

Finally, it’s worth mentioning that for about $30 you can buy a manual powder-actuated fastener

that you hit with a hammer to fire the load and drive the pin.

Choosing and Using a Concrete Screw

How to adhere concrete to concrete

Concrete screws are the easy way to anchor objects to concrete. When building your storage shed you may need to install a screw in the concrete slab to attach something to the shed floor, like a bike stand or table saw. This article shows you how to drill a holes in concrete or masonry and then how to choose and install concrete screws.

Remember to wear eye and ear protection when drilling concrete!

step 1 Choosing The Right Concrete Screw

How to adhere concrete to concrete

There are several ways to attach a screw to concrete. You can use an actual concrete screw that screws directly into a hole you have drilled in the concrete or you can use a metal or plastic anchor that is inserted into a drilled hole and then a regular screw is screwed into the anchor. Both systems work well. Try the concrete screw first and if it does not grab in the hole you can make the hole larger and insert a plastic or metal expansion shield and install a regular screw to the shed floor.

Length of Screw: Try to get the concrete screw to go at least an inch into the concrete. If you are attaching something heavy to concrete, like a handrail, you will need to install the concrete screw farther into the concrete.

Diameter of The Screw: The diameter of concrete screws gets larger as the screw gets longer. If you are securing heavier objects to the shed you will need to use a larger diameter screw

Tapcon Concrete Screws “Blue Screws”: The brand name of the blue concrete screws is Tapcon. These screws come in two diameters and two head types. Many of the larger packs come with a masonry drill bit. If you plan on drilling alot of holed you will want to use a rotary hammer drill bit instead of the one sold with the Tapcons. These are the screw and driver sizes provided by Tapcon.

The bit to use with each size of TapconВ® are:

  • 3/16″ diameter TapconВ® = 5/32″ bit
  • 1/4″ diameter TapconВ® = 3/16″ bit

The drivers to use with the different head style Tapcons are:

  • #2 Phillips — 3/16″ Flat TapconВ®
  • 1/4″ Socket — 3/16″ Hex TapconВ®
  • #3 Phillips — 1/4″ Flat TapconВ®
  • 5/16″ Socket — 1/4″ Hex TapconВ®

Metal Expansion Anchors: Metal expansion anchors or shields are inserted into a hole in the concrete and then a screw is driven into the shield. The insert expands and presses against the concrete which creates holding power. Metal expansion shields work well for heavier screw applications.

Plastic Expansion Anchors: Plastic expansion anchors work just like the metal expansion anchors. The work well for lighter duty applications like hanging window shutters on the brick exterior of the shed.

step 2 Mark The Hole Drilling Location

Use a permenant marker to put a dot or x on the spot where the hole will be drilled.

step 3 Set The Depth To Drill The Hole

How to adhere concrete to concreteDrill the hole for the concrete screw at least 1/4″ deeper than the depth the screw will enter the concrete to allow space for any concrete dust in the bottom of the hole. Find the depth of the concrete screw by:

  1. Measure the length of the screw
  2. Subtract the thickness of the material you are screwing to the concrete
  3. Add 1/4″

The result if this is your desired depth. Either set the depth gauge on the drill to this depth or use masking tape wrapped around the drill bit to mark the depth.

step 4 Drill The Hole

How to adhere concrete to concrete

Use a hammer drill to drill into the concrete or masonry surface. A hammer drill is a drill that rotates like a normal drill and it hammers the concrete at the same time. The hammering breaks up the concrete or masonry and the rotation removes the concrete dust.

  1. Place the hammer drill on the mark on the concrete and turn it on.
  2. The hammering will start when you press the drill into the concrete. Press the drill hard enough to get dust coming out of the new hole. Pressing too hard on the spinning drill bit will cause excessive heat and damage the bit.
  3. Pull the drill out of the hole about every 10 seconds to pull out concrete dust.
  4. Stop drilling when the depth gauge touches the surface of the concrete or the drill bit gets to the tape you wrapped around it or when you know that you are deep enough.

For more information on drilling in concrete or masonry read the article How To Drill Concrete.

step 5 Attach The Concrete Screw

Tapcon Screws: When using Tapcon concrete screws it is best to use a drill with the proper driver head for your screws, either phillips head or 1/4″ or 5/16″ socket. It is important to maintain a fair amount of pressure on the head of the screw so the bit does not slip, this is especially true when using phillips head screws.

How to adhere concrete to concrete

Regular Screws In Plastic Expansion Anchors: If you are driving a wood screw into a plastic anchor you can use a phillips head screw driver if you wish but a drill with a phillips driver works best.

How to adhere concrete to concrete

Regular Screws In Metal Expansion Anchors: Metal expansion anchors will allow larger screws like lag screws with a hex head. Determine the size of the screw head and either set up your drill or use a wrench to drive the screw into the anchor.

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You are here: Home > Topics > Ask a Pro > Does concrete adhere to concrete…?

  • This topic has 32 replies, 16 voices, and was last updated 6 years, 6 months ago by How to adhere concrete to concretesvensshutters .

Let’s say you have a post set in concrete and it’s leaning badly. If you dig out around it and add more concrete and plumb up the post, will the newly poured concrete adhere well to the old concrete? There’s obviously going to be some dirt/clay stuck to the existing concrete but I would clean off what I could.

Would it be better to remove the post & concrete, demo the concrete off the post with the awesome DH1020VC and reset it in new concrete?

Resident Sign Guy

I think what you’re thinking would work fine. The surface of the old concrete is so rough that the new should key into the old and help lock it in place. That along with friction and I think it would be good.
Removing it completely is always the best thing but a lot of work. Keep us updated.

I like Dirty’s answer, You didn’t say what the post is for?

I’ve done that with good result, but like DWB said.. best to remove completely and start fresh. I did a fence post 3 years ago and it’s still good

I like Dirty’s answer, You didn’t say what the post is for?

It’s a sign for handicap parking. I think it’s 3″ square aluminum tube with a 12″x18″ face attached to it. The problem is, whoever set the post, poured the concrete until it was above grade. So it’s all loosey goosey.

It just seems like it would be a whole lot easier for them to just provide a new post and for me to remove the existing (easy with the remover I built), set a new post properly and attach the new face.

Otherwise, I would have to chip away what I can with the demo hammer so it’s below grade but also dig next to it and pour new concrete.

I think given the labor involved, the first option would be cheaper.

Resident Sign Guy

It just seems like it would be a whole lot easier for them to just provide a new post and for me to remove the existing (easy with the remover I built), set a new post properly and attach the new face.

Sometimes it is easier to just redo it right. Get rid of the old put in the new. This way you know it’s right rather than getting a call 6 months from now to fix it again because the old concrete failed and it’s now your responsibility (no money being paid).

Automotive Pro
Fayetteville, NC

My thoughts exactly. I do everything I can to avoid call backs and I can see this turning into one if I try to short cut it.

Resident Sign Guy

I think what you’re thinking would work fine. The surface of the old concrete is so rough that the new should key into the old and help lock it in place. That along with friction and I think it would be good.
Removing it completely is always the best thing but a lot of work. Keep us updated.

How would this apply to a sidewalk? I have two sidewalks that run up to a building that I have to fix. The sidewalk is about 3inches lower than the door threshold and the local ADA requirement is for a 1/4 drop. This leaves me having to hammer up a couple of sections to slope the sidewalk properly, or add concrete over the existing .

I’ve wondered about that as well – pouring concrete on top of existing, smooth concrete.

Resident Sign Guy

I’ve wondered about that as well – pouring concrete on top of existing, smooth concrete.

I’m not confident in the long term results in my particular situation. This is mostly because I will be sloping fom 3 inches to zero and I seriously doubt the thinner end will have much strength. It will probably crumble before long…I think I’m talking myself into a bit of demo.

How would this apply to a sidewalk? I have two sidewalks that run up to a building that I have to fix. The sidewalk is about 3inches lower than the door threshold and the local ADA requirement is for a 1/4 drop. This leaves me having to hammer up a couple of sections to slope the sidewalk properly, or add concrete over the existing .

It will crack at the parting line. BTDT. When you pour new concrete over old concrete especially when trying to level it as it slopes to join the new concrete at the thinnest point it will crack. If you’re going to do it dig it out so the two pieces have vertical edges then join the two pieces with a new piece in between.

Automotive Pro
Fayetteville, NC

Just from what Ive heard, but concrete won’t easily adhere to concrete. Any one here do concrete for a living, no’s your time to shine.

With the sidewalk situation I would rem9the walk, concrete ever works well to a feather edge.

For the post most likely it will be fine. For some extra grip to the existing concrete, run some tapcons into the old concrete leaving them protrude an inch or so. Use a few. This allows something more for the new crete to lock to.

If the sidewalk is in excellent shape but just low it can be done too. If the 3″ is a consistent pour you should be good. If it tapers to something thinner I wouldn’t. Pressure wash the old and paint a bonding agent on the slab according to the directions for the bonding agent. Form the new top and mark where the existing cuts are. You will need to make the cut line up to avoid unwanted cracking.