- How to Build Concrete Docks
- How to Cure Concrete With Burlap
- How to Brighten Concrete
- How to Pour Concrete in the Marine Environment
- How to Remove Self-Leveling Concrete
- How to Cure Concrete With Vermiculite
- How to Make Concrete Caps
- How Long Should You Wait Before Stamping Concrete?
- How to Repair & Level a Cracked Concrete Footing
- How to Make a Concrete Splash Guard
- DIY Concrete Dye
- How to Raise Concrete Under an Exterior Door Sill
- How to Calculate Crushed Concrete
- Why Does New Concrete Crack?
- How to Clean Concrete Pavers
- How to Make a Concrete Garden Urn
- How to Make Aggregate Concrete
- What Causes Concrete to Bubble When It Cures?
- How to Make Concrete Less Slippery
- About Quick Set Concrete
- How to Pour Concrete Around Pools
- Homemade Concrete Mixers
- How to Mark Concrete Without Paint
- What Are the Causes of Carbonation of Concrete?
- Thin Pour Concrete Recipes
- How to Do Thompson's WaterSeal on Fresh Concrete
- How to Install Concrete Formwork
- ASTM Specifications for How to Use a Swiss Hammer
- How to Repair Salt-Damaged Concrete
- How to Fix Chipped Concrete
- How to Use a Magnesium Finishing Trowel
- How Is Concrete Core Testing Performed?
- How to Prime Concrete for Painting
At first, a concrete dock sounds about as practical as a paper car -- after all, if you put cement into water, it will sink down to the bottom before you have time to turn around. However, concrete is much more durable than wood, and if you place concrete around a light material such as polystyrene, flotation becomes possible. By connecting modular pieces of concrete, you can build a dock that will corrode much more slowly than its wooden counterparts.
Purchase concrete forms with polystyrene cores in two different sizes: the larger squares for the top and bottom of each float (no larger than 3 feet square) and the narrower rectangles that will run along the sides. There are specialty construction manufacturers who make these cores, and you can order them to be pre-drilled for your through rods.
Run your through rods between each set of holes and secure with a washer and nut. Attach metal brackets at the appropriate corners or sides of your floats to secure the pieces to your pilings. Drill into the concrete, using a concrete bit, to make the holes for the bracket hardware.
Connect your longer wooden beams to the floats. Your beams serve as the general frame of the dock, running along all sides, while your concrete floats are the pieces. You'll need a beam at every junction point between two concrete floats. You can drill through the wood into the concrete using the drill with the cement bit to create points of attachment.
Attach the walers to the bottom of the concrete floats. Walers are also available from specialty construction retailers and will come with hardware ready for attachment. Use your drill to make holes in the cement and then attach the walers using the provided bolts and nuts.
Soak the burlap bags in water. Flatten the bags out and lay them on the moist concrete in a single layer. Overlap all edges of the burlap by 2 inches to ensure no cracks form between the bags.
Spray the burlap bags with water from a garden hose to ensure they remain soaking wet. Set up a sprinkler along the edge of the concrete.
Turn on the sprinkler and keep it on continuously. Allowing the burlap to dry out and then wetting it again may damage the concrete slab.
Set up more than one sprinkler if you have a large area of burlap and the single sprinkler is not sufficient to keep all the fabric wet. Keep the burlap wet for seven days if your temperatures are around 70 degrees F. If you are in a cooler climate with temperatures closer to 50 degrees F, keep the burlap wet for nine days.
Rent or borrow a power washer if you don't own one. Power washers are available for rent from many home improvement stores for an hourly rate.
Attach the power washer to a garden hose. Start the power washer. Turn on the water and use light pressure to moisten the entire surface of the concrete to be brightened.
Apply a cleaning agent to the surface of the concrete. Use a mix of one part liquid bleach to one part water or laundry detergent.
Use a long-handled scrubbing brush to thoroughly scrub the surface of the concrete. Make sure to scrub all corners and edges of the concrete well. Repeat scrubbing as necessary across every portion of the concrete.
Rinse away the cleaning agent using the power washer. Low pressure is usually sufficient for this process.
Pre-drill 1-inch holes every 12-inches along the side of 2-by 6- lumber. Lay 2-by 6 lumber to create the length and width of the project, place 2-by 6 lumber directly on the sandy ground; these are the forms that will hold the concrete in place. Lay pieces of lumber across the width of the form so each box within the box is no larger than 6-feet by 6-feet. Wait for low tide to build wood forms, which are bottomless boxes.
Use a sledgehammer to drive 2-foot lengths of rebar through the pre-drilled holes penetrating the sandy surface to hold the forms in place. Rebar is a thick metal rod.
Follow the bag directions carefully to mix specialized seawater manufactured concrete with an aggregate content impervious to salts, in a large trough or wheelbarrow--or schedule a delivery, depending on the size of the project. This type of concrete is available at masonry supply houses or via concrete delivery companies. The concrete mix is thicker than traditional concrete and has a lower air volume.
Bail water from the forms with a bucket or a submersible pump.
Pour the concrete mixture into the forms directly from the concrete truck feed or tip the contents of the wheelbarrow allowing the concrete to flow out.
Use a bull-float, which is a large trowel at end of a pole, to smooth and level the concrete.
Put on the eye and ear protection and the dust mask. Use the concrete saw to cut the floor into sections of concrete that are small enough that they can be physically removed. The size of the sections will be dependent on the depth of the self-leveling concrete floor, with deeper floors requiring smaller sections. All cuts should be through the full depth of the concrete.
Use the sledge hammer to break free any sections that can not be freely removed from the floor. The sections may be adhered to the substrate beneath the concrete floor but since this typically would be loose gravel or crushed stone, the sections should break free after being struck with the sledge hammer. Sections along the perimeter of the concrete floor may be adhered to the walls or forms used to hold the concrete in place while it cured. Striking these sections with the sledge hammer should break them free.
Put on the gloves. Pick up and remove all of the sections of the self-leveling concrete floor.
Determine the ratio of vermiculite to concrete which depends on the job at hand. The base for above ground pools use a ratio of about 7 to 1. A basic ratio which can be used in many different applications is 3 to 1. Use this for walls, garden ornaments, walkways and the like.
Measure out the amount of water you will need and add it to your container for mixing. Then add in your concrete and mix well. Follow package directions for the type of concrete product that you have.
Add in vermiculite. The consistency you are looking for is that of a mud pie. Add more water if needed. Once poured, cover it with plastic sheeting and then allow the concrete to sit and cure.
Place the cap’s concrete molds on a level surface. Moisten the rag with cooking oil. Evenly spread the rag inside of the molds. This will protect the concrete and stop it from sticking.
Put water into the pre-mixed concrete. Use the ratios for measuring that are printed on the side of the package. Remove a single cup of concrete with the bucket at a time. Put the concrete carefully into the molds. Shake them gently in order to settle the molds of concrete. Do this until each of the molds are at their capacity.
Use the trowel’s flat side to level the molds. This will make a smooth surface over the concrete. Allow the concrete to sit for 50 hours. Place a towel on your work area. Turn over each mold individually. Rotate the mods gently until the caps slip out.
Put a tarp over the caps. Allow them to sit for eight days. Use the brush to place a layer of sealer on both sides of the pavers.
Watch the Concrete's Appearance
At least one contractor recommends stamping when the concrete's surface loses its sheen. Then, according to the Stamped Concrete website, you'll stamp with light pressure until the concrete gets harder. On a larger project, your first few stamps will need to be tamped by hand, or your lightest crew member can stand on them. As the concrete dries, use harder pressure or heavier people.
Test the Concrete's Firmness
One manufacturer recommends a different approach. An Advanced Surfaces instructional video says to wait until you can stand directly on the stamp without sinking in or making a deep depression. This approach leaves less workable time, so the manufacturer says less experienced installers should do small projects of 400 square feet or less.
Regardless of your method, timing is crucial. The concrete must be firm enough to withstand stamping, dry enough to not stick to the stamp and workable enough to take a good stamp. For these reasons, at least one concrete expert says concrete stamping is not a do-it-yourself job. Chris Sullivan of Concrete Network says concrete mistakes and repairs are too complicated and expensive to risk.
Form a boundary around the slab area by lining it with 2-by-4 boards along the edges. Hammer the stakes into the ground directly against the boards to keep them from slipping while you are working.
Remove large broken pieces, if there are any, from the footing area. When you pour your new concrete, these areas will be filled in.
Sweep the concrete thoroughly to remove all debris.
Paint a layer of acrylic block fill primer onto the concrete. As soon as you have applied it, have an assistant push the acrylic block fill primer into the pores of the concrete with a paint roller. Allow the acrylic block fill primer to dry according to the manufacturer’s directions, which can vary from brand to brand.
Combine the self-leveling concrete in small batches according to the manufacturer’s specifications.
Pour the combined self-leveling concrete over your work area, working from one end of the footing to the other. If large pieces had to be removed, pour plenty of concrete in those areas. The concrete will flow and level as you work.
Allow the concrete overlay to cure for three or four days before putting pressure on it.
Pour 2 to 3 tablespoons of motor oil in the bottom of the pan and wipe it with a paper towel to coat the inside. Set the pan on a steady surface with a 1-inch-thick book under one end, tilting the pan up on that end.
Mix 3 pounds of the concrete with water in a 5-gallon plastic bucket until it has the consistency of peanut butter with no lumps. Pour enough concrete into the pan so that there is a 2-inch-thick layer at the end that is tilted up.
Work the concrete around in the pan with the trowel, similar to what you'd do with cake batter, to remove any air bubbles. Smooth out the surface with the trowel.
Decorate the concrete however you choose. Family handprints pressed into the wet concrete will always be a reminder of the day you made the splash guard. Glass beads, bits of a broken mirror with the sharp edges sanded off, smooth river rocks and other items pressed into the wet concrete allow you to make it a unique yard piece.
Cut away the aluminum pan after 24 hours. Let the splash guard season for a week and then set under the downspout, tilted so that the water drains into the yard after it has spent its energy against the concrete.
Choose the best dye product for your specific application. There are four basic choices: straight dyes, tinted sealers, acrylic stains and acid stains. All are easy to use, but acid stains require more finesse than the others to apply properly. Acid stains are also the most durable, although the others usually last long enough to meet most needs. Finally, all products (except acid stains) are available in water- or solvent-based versions of the compound.
Prepare your concrete to accept the dye by thoroughly cleaning it with concrete cleaner and water. Follow the instructions on the concrete cleaner container so that you get the maximum cleaning power from the cleaner.
Mix the concrete dye according to manufacturer's instructions in a 5-gallon bucket. Always add the dye to the bucket first and add the correct amount of water afterward (this prevents the dye from splashing up accidentally). Wear gloves and eye protection while doing this.
Pour the dye in the pump sprayer and apply the mixture to the concrete. Use consistency in your application. If you are using several colors or shades, allow adequate drying time between applications so that you don't get excessive bleeding when you add the next color.
Put on eye protection, along with work gloves and a dust mask.
Use a chipping hammer with a chisel bit to break up the concrete under the exterior door sill then pull out the rubble by hand. Vacuum out any remaining pieces with a shop vac for a clean surface.
Combine one part Portland cement with three parts masonry sand inside a wheelbarrow then mix up the dry ingredients with a paddle mixer. Wet the cement/sand mixture with a garden hose lightly then mix it again until it becomes the consistency of mud.
Pour concrete bonding agent into the exterior door sill area, allowing it to spread over the remaining concrete foundation. Immediately, tilt the wheelbarrow up, allowing the concrete to pour down onto the bonding agent before it dries.
Even and smooth out the wet concrete with a trowel then let it dry and harden for 24 hours before walking on the sill or using the door.
Measure the existing concrete structure. You'll need to measure the length, the width and the depth of the concrete. All measurement should be made in feet. Write these measurements down.
Calculate the volume of the existing concrete. Multiply the length by the width to produce the area. Then multiply the area by the depth of concrete to find the volume in cubic feet. Right this number down.
Calculate the number of pounds of concrete. Multiply the volume by 150. The unit weight for reinforced concrete is approximately 150 pounds per cubic foot. Right this number down.
Convert pounds to tons. Divide the number of pounds of concrete by 2000. Right this number down. Most vendors and trucking companies buy and sell crushed concrete in U.S. tons.
Concrete is a paste prepared by mixing aggregates, such as sand and gravel or crushed stone, with water and a cement, such as crushed limestone, marl, iron ore, shale, clay or fly ash. Freshly mixed concrete is soft; the chemical reaction between the water and cement causes the concrete to harden with time. It takes five to seven days for freshly poured concrete to cure, or harden.
Soft Concrete Cracks
New concrete that has not had the chance to fully cure is susceptible to cracks from two causes. Settlement cracks may develop in areas of the concrete under which dense structures lie, such as steel reinforcements. The soft concrete does not settle as much over dense areas as it does over loosely packed surrounding areas, resulting in settlement cracks. Plastic-shrinkage cracks also occur before the concrete has fully hardened. They result when the surface of the concrete dries faster than the sub-surface concrete. The water from the wet cement below rises, or bleeds, and breaks through the dried surface, causing cracks.
Hard Concrete Cracks
New concrete that has fully cured is also vulnerable to cracking. Although the concrete is hard, it continues to dry; as it dries, it shrinks. According to the Portland Cement Association, concrete shrinks approximately one-sixteenth of an inch for every 10 feet. Placing joints, or manmade cracks, in the concrete at regular intervals not only accommodates the shrinkage but also allows the contractor to control the appearance and location of the cracks in the cement.
Clear the concrete area of any items such as vehicles, patio furniture or other items. You want to clean the entire area properly.
Next sweep the area with the push broom. Make sure to take your small broom around the concrete edges to get up any dirt or debris that may accumulate in the corners.
Fill your bucket with warm soapy water. You will then dunk your push broom in the warm water and scrub at the areas where the concrete is the dirtiest or where something has set into the concrete.
Set your power washer to the recommended setting and spray the concrete with warm water. There is no need for harsh chemicals. Make sure to go across the concrete in slow even strokes to get the concrete clean all over.
Once you have finished cleaning your concrete, make sure to allow it to dry before putting your items back on the concrete. You may also want to give some thought to sealing your concrete once it dries.
Put on protective gear including eye wear, breathing protection and rubber gloves. Concrete is caustic and can harm you if you breathe it or get it in your eyes.
Combine cement and water in a mixing bucket. Stir until it's the consistency of a mud pie.
Add 1 cup of fiberglass reinforcing fibers to the mixture.
Coat the inside of each half of a concrete urn mold with vegetable oil. Assemble the mold by aligning each half and snapping the mold in place.
Pour the concrete into the mold. Soak the mold with water from a garden hose. Cover the concrete mold with a plastic tarp. Allow the concrete to set for between two and seven days.
Open the mold to release the concrete urn. Brush the urn with a wire-bristled brush to smooth out the seams. Soak the urn with water and cover it with the tarp for another seven days to allow the urn to cure and harden.
Mix one part Portland cement, two parts sand and four parts decorative aggregate stone and mix in enough water to make the mixture the consistency of cookie dough. If the decorative aggregate is expensive, the concrete can be made with less expensive gravel and the decorative aggregate seeded on top of the concrete after it is poured.
Pour the concrete into the form, screed and smooth with a concrete float as with any other concrete application. If the aggregate is seeded, sprinkle the aggregate on top of the concrete as soon as it is level and use a concrete float to press the aggregate into the top of the concrete.
Spray an even coating of concrete surface retarder on the top of the concrete according to the manufacturer's directions.
Wash the top layer of concrete off the poured concrete when the concrete has set up enough that you can walk on the concrete without creating an impression. Wet the concrete with water from a hose and scrub off the top layer with the bristles of a stiff broom.
Newly poured and hardened concrete needs anywhere from a week to three weeks of curing before applying any stain or sealant. The concrete is in a fragile state and is sensitive to temperature and moisture levels. Curing maintains a specific level of heat and moisture for an extended period of time until the concrete solidifies throughout.
Curing concrete makes the concrete stronger for the duration of its existence. It also makes it less prone to scratching, chipping and dusting due to such conditions as weather, hard contact and erosion. It is a necessary step to ensure the concrete stays pristine for as long as you need it.
Curing allows air and moisture in the concrete to escape until fully hardened. If a homeowner applies a stain or sealant to the concrete before curing completion, then the air and moisture have a difficult time escaping. This causes bubbling in the stain as well as chipping and cracking. Bubbling can ruin the look of the concrete stain.
It's not the actual concrete bubbling, it's the stain on top of the concrete. Fix the bubbling, chipping and cracking by removing the stain with a stain-stripping agent and waiting for the concrete to finish curing. Reapply the stain two to three weeks after the concrete was originally poured and the bubbling will not be a problem.
Clean the concrete surface with industrial solvent and water. Pour 2 tbsp. of solvent and 2 cups of water into the pressure washer. Begin spraying the concrete from one end to the other until fully washed. Rinse with the hose and let dry over night before applying the tape.
Apply the primer to the concrete surface. Pour the primer into the paint pan, roll off the excess on the rippled edge of the pan, and begin covering the concrete with primer. One coat that is not very thick is good enough--about 1/16 of an inch.
Allow four or five minutes of drying time.
Measure the slip-resistant tape. Cut the tape to the correct size and round off the corners. You may need several rolls of tape for the project.
Place the tape pieces on top of the surface to measure and make sure it will be fully covered.
Begin applying the tape. Start at one section, peel the paper backing off of the tape, and press it down. Use the rubber paint roller to add pressure. Continue until the entire surface is covered in tape.
Go over the surface one last time with the rubber roller to help the tape adhesive bond with the concrete primer.
Quick-set concrete is used primarily for jobs where speed is of the essence. It can also be used with normal concrete to add volume (however, this alters the regular setting time). It can also be used for repairing damaged concrete and setting logs, mail boxes, fencing posts and benches.
The key benefit of quick-set concrete is its ability to set faster than normal concrete. In situations where downtime must be kept to a minimum, quick-set concrete is perfect. It also has the benefits of normal concrete in being solid and sturdy for construction and building projects, whether at home or elsewhere.
Some people think that quick-set concrete hardens instantly or that once it's poured, it turns to stone in a matter of seconds. While quick-set concrete is fast, it still can take days to reach maximum strength and consistency.
Quick-set concrete is not suggested for use with aluminum substrates. Quick-set concrete can cause corrosion and wear when in contact with aluminum. Also, as with any concrete and cement, keep the mixture away from your eyes and mouth, and wash your hands repeatedly when in constant contact.
Quick-set concrete should be considered for any projects where time is an issue and you need the sturdiness and strength of concrete and cement, such as setting mailboxes and fencing posts, setting logs into solid positions and securing benches for parks or backyard positioning.
Pouring Concrete around the Pool
Lay down concrete forming panels around the rim of the pool shell to create a barrier around the pool. These forming panels create the shape of the inside edge of your concrete. Fasten these panels to the pool edge with screws.
Spread a layer of gravel around the working area and tamp down until it is even and tightly packed. On top of the gravel, lay down the metal grid work. This provides a solid base for the concrete and strengthens its bond when it cures.
Spread mixed concrete evenly around installation area until it forms a smooth and even layer across the work area. Ensure that the concrete does not spill past the forming panels.
Allow the concrete time to solidify. Different brands and mixtures of concrete solidify at varying rates. Consult the concrete manufacture for setting and drying times. Remove forming panels only when the concrete is sufficiently dry.
Wet the concrete frequently with a hose or lay damp burlap over the installation area. This saturates the concrete and strengthens its molecular bond.
Homemade Cement Paddle
When mixing small batches of concrete, you can mix the concrete in a five-gallon bucket using a heavy duty electric drill and a cement paddle. Construct a cement paddle from a 2-foot piece of round bar, 7/16-inch in diameter and a 1-1/2 coils of a car spring. Weld a piece of 1/2-inch flat bar to one end of the rod and then weld the spring to the bar. The other end of the rod connects into the bit end of the electric drill.
Warnings About Drill Speed
If your electric drill's motor speed is too slow it will have to fight to move the heavy concrete and the motor will burn out. If you are using an industrial drill, keep the speed below 650 rpm to avoid air bubbles in the mixture.
Concrete Mixing Drum
If you will be mixing large batches of concrete, you can re-purpose a washer drum. Attach angle brackets to the center tumbler to create mixing blades. Fill the holes on the washer drum with auto body putty. Mount the washer drum at an angle on a steel pipe frame. Rotate the drum by hand so that the blades scoop the concrete and drop it from the top of the drum.
Mark the concrete with chalk. Use different colors of chalk to draw images on the concrete. This method of marking concrete is easily removed with water, making it a non-permanent way to add temporary color to your concrete surfaces.
Color the concrete with markers. Use different colors to make marks or draw images on the concrete. This method of marking concrete is more permanent than chalk but can be removed with a power washer if necessary.
Mark the concrete with a mixture of food coloring and water. Fill a bowl with equal parts food coloring and water, and apply it to the concrete with a paintbrush, stamps or sponges. For more vivid color, use more food coloring and less water.
Stain the concrete. Purchase a concrete acid stain from a home improvement store. Apply the stain to the surface of the concrete with a handheld paintbrush. Pour a mixture of equal parts water and baking soda, and then pour it over the stained concrete. Wipe up the mixture with a mop or sponge, and rinse it with water.
The carbonation process creates calcium carbonate beginning at the surface of the concrete that is open to air and working downward. Several factors affect the penetration rate of carbonation: the density, humidity and porousness of the concrete. The water-to-cement ratio of the concrete changes the carbonation rate: more water means faster carbonation. The same is true for porousness. If concrete is cracked, carbonation will penetrate deeper.
Carbonation improves the compressive and tensile strength of concrete. Carbonation also reduces the porosity of dense and compact concrete, protecting it against water and chloride ion infiltration. Chloride ions can corrode the steel placed in reinforced concrete. These advantages are important to keep in mind because carbonation is an inevitable process for concrete to undergo.
The main danger from carbonation of concrete is the effect on embedded steel. Carbonation lowers the alkalinity of concrete. High alkalinity, however, protects steel from corrosion. At a pH lower than 10, corrosion may begin to occur. Reinforced concrete that has been thoroughly penetrated by carbonation will likely dip below this threshold, exposing the rebar in it to damaging rust.
All concrete that you can see has undergone some degree of carbonation, but it is not possible to tell just by looking at the surface how deep the process has gone. Engineers can drill a small hole in concrete and treat the lower exposed area with phenolphthalein, which turns pink or purple at high alkalinities. Wherever the concrete changes color, carbonation has not yet occurred.
Basic concrete composition requires cement, water and sand. Some concrete also has granite or aggregate stone added to lower the overall cost and add additional texture. Standard concrete has 1 part cement, 2 to 3 parts sand, 2 parts gravel and 1/2 part water.
Smoother, thin pour concrete often leaves out granite and aggregate. Thinner concrete recipes also use more water. A basic thin concrete recipe includes 1 1/2 parts cement, 1 part water and 2 parts sand. The finished product has a consistency like pancake batter, whereas a regular concrete recipe has a consistency like a thick brownie batter.
As with any concrete recipe, you should add the water a little at a time to form the desired consistency. Too much water will make the finished product weaker, and extremely thin recipes will often produce concrete that is not suitable for load-bearing purposes. Additionally, using damp sand instead of dry sand reduces the amount of air holes in the finished concrete.
Sweep up debris from the concrete with a broom and remove all objects.
Fill a paint tray with concrete degreaser and apply the degreaser to the concrete surface with a paint roller. If the concrete surface is vertical, apply from the bottom of the wall to the top.
Wait 15 minutes for the degreaser to break apart any oil stains on the concrete and then scrub the concrete down with a nylon brush.
Rinse the concrete surface with a garden hose. Wait 24 hours for the concrete to dry fully before continuing. Make sure that the air and surface temperature of the concrete is above 40 degrees Fahrenheit before moving on to the sealing process.
Fill a pump sprayer with Thompson's WaterSeal and prepare the sprayer for use as directed in the user manual.
Spray a single coat of the sealant onto the concrete using long, slightly overlapping strokes. If the surface is vertical, work from the bottom to the top of the wall.
Wait two to four hours for the sealant to dry before using the concrete surface.
Measure out the length and the width of your concrete slab area.
Cut a 2-inch by 12-inch board that is equal to the length of one side of your intended concrete area.
Pound two 2-inch by 4-inch stakes into the ground in the corner of the intended slab area. Nail the 2-by-12 to the two stakes.
Set up a builder's level and use it to level the 2-by-12.
Place 2-by-4 stakes every 2 feet along the board to brace the 2-by-12.
Cut a second 2-by-12 to the width of the concrete slab. Nail one end to the other 2-by-12 end. Calculate the diagonal for 90 degrees and run a measuring tape from one end of both 2-by-12s to make sure the form is straight.
Add the other two sides of the formwork in the same manner.
Test the Swiss hammer against the test anvil. Press the plunger end (with the plunger retracted) at a 90-degree angle against the test spot of the anvil until the internal hammer fires. Holding it against the anvil, check the gauge for the rebound number. If you move the hammer away from the anvil, the gauge will reset to zero, so be sure to check it before you move the hammer. Check this rebound number against the label on the test anvil to ensure your hammer is measuring accurately.
Smooth the test spots on your concrete surface with the abrasive stone. A rough surface texture can affect your results negatively. It does not need to be absolutely smooth, but any obvious tool marks or ridges should be ground down to the level of the main surface.
Using the same method as on the anvil (holding the hammer firmly at a 90-degree angle to the surface), test several spots on your concrete. Write these down on a piece of paper to keep track of your test numbers, always rounding to the nearest full number. Check with the manufacturer for the rebound numbers of your particular concrete mix to ensure your concrete is as strong as it should be.
Sweep the damaged concrete with a stiff-bristle push broom, using vigorous motions to dislodge any remaining chips and crumbles from the concrete. Push this material into a dust pan and then into a trash can.
Turn on a garden hose and spray the entire concrete area with a light spray of water until all of the concrete changes color but there are no water puddles on it.
Fill a bucket with 1 to 2 cups of concrete, or more if you are repairing a very large area such as a driveway. Slowly add water to the mixture until it is the consistency of paint. Stir the solution well with a paint stirrer, and then use a paintbrush to apply a thin layer over the entire damaged area of concrete.
Fill another bucket with a mixture of three parts gravel, two parts coarse sand and one and a half parts cement. Mix the solution with a trowel and add water until it is the consistency of peanut butter.
Scoop up 1/2 cup of the mixture on the trowel and place it in the damaged areas of the concrete. Smooth the top of it out with the back of the trowel until it blends in with the surrounding undamaged concrete.
Place an old board on top of the concrete patch, and move it from side to side over the surface until the gravel sinks down and produces a smooth upper surface.
Fixing Chipped Concrete
Clean the area around the chip by clearing away any debris. If there's a lot of dirt or dust in or around the chip, you may want to clean the area with water.
Load the caulk into the caulking gun. This can be done by first pulling the plunger of the gun all the way back, inserting the caulk tube, and then slowly pushing the plunger back. Most caulk gun plungers will snap into place when they are far enough in.
Cut the end of the caulk tube so that the tip is the appropriate size for the chip. The closer you cut to the base of the tube, the bigger the tip will be and the more caulk will come out at once. A utility knife is recommended because it will make a cleaner cut than scissors.
Slowly spread the caulk over the chipped area so that it fills the chip.
Wipe the filled chip's surface with a clean rag dampened with mineral spirits. This will clean away excess caulk. Let it sit for a few hours to ensure the caulk has set in. If the concrete is outdoors, you will want to cover the repaired area with a weighted sheet of plastic to ensure nothing damages the repair before it sets.
Place concrete in the forms you created. Depending on what is being poured, the concrete will be reinforced with rebar.
Screed out the concrete. A screed will remove the excess concrete as well as fill in any low parts in the concrete. Screed only 3 to 4 feet at a time.
Float the concrete with magnesium trowel to settle, slightly, the larger aggregate (stone) and bring up the fines (sand). The weight of the magnesium trowel makes this tool ideal for this process.
Allow bleed water to settle out. Use a magnesium float, a long, flat tool, to level the concrete. Make sure the front edge of the float is up so as not to dig into the concrete. A magnesium float is lighter weight than a steel float, and will pass over the surface of the concrete easily.
Finish concrete as it begins to set up and support light weight. Use a steel trowel in this process. Tilt the trowel slightly to give the concrete a smooth surface.
Allow the concrete to set overnight before putting any weight on it.
Create testing samples during construction by molding the concrete in cylinders. Cure the cylinders at 60 to 80 degrees Fahrenheit for one day and in a moist environment for another seven to 28 days. If the strength of test cylinders is low, in-place core testing may be indicated.
Use a rotary cutting tool with diamond bits to obtain a cylindrical test specimen. Describe and photograph the specimen, observing factors like the distribution of aggregates and compaction.
Drive probes into the specimen to test concrete quality. Space the probes at least seven inches apart and keep them away from the edge. Measure the exposed portion of the probe accurately to analyze the results. You can also use a rebound hammer to test the specimen's strength.
Factors like the presence of transverse steel reinforcement and the size of stone aggregate may reduce concrete strength.
ASTM International publishes detailed standards and procedures for concrete core testing in print or PDF versions that are available on-line for $39.00.
Clean concrete surface with a broom or vacuum. Remove all debris and mop if necessary.
Remove all grease stains or other spills on the concrete. Scrub with a brush and degreaser if the grease stains are particularly stubborn. Use a scraper to remove any other materials that have adhered to the concrete.
Patch and repair all cracks with a concrete patch product. Follow the manufacturer's instructions paying particularly close attention to recommended drying time.
If the concrete has been sealed, you are ready to start the primer process. To test for sealant, tape a piece of plastic wrap onto the concrete. If after 24 hours there is condensed water on the wrap, the concrete will need to be sealed with a masonry sealer.
Apply the primer using the roller pan and brush. Let it dry thoroughly, then apply another coat. Once the second coat of primer has completely dried, you are ready to start painting.