We have a new concrete slab on grade. The surface is smooth and hard. The surface is beginning to dust or give off a fine white powder. What can we do without removing the slab or installing an expensive overlay? The dust is getting on the inventory and that must stop.
There are many causes for a concrete floor surface to dust. In this case the cause is not the concern. The solution is the immediate need. The best product for the immediate dustproofing of the floor at your property is L&M SEAL HARD™. Seal Hard is odor free and clear. You could apply the Seal Hard and open the floor up to traffic in the same day.
The wise thing to do is a test panel on the worst area of the floor and watch the for the dust free performance. You can then make an informed decision.
We want to apply one of your membrane sealers on a warehouse floor. The problem is that moisture is visible upon the surface of the concrete in early morning. The floor is six months old and we think the moisture is condensation and not moisture vapor from within the slab. What can we do to tell the difference?
Our experience from other, similar circumstances leads us to tell you to use a thin piece of sheet metal and place it on the dry floor surface. The piece of sheet metal should be large (about 20 square feet in size). Tape the sheet metal down with some duck tape in order to seal the entire perimeter edge. Allow it to lay in place at least overnight. Examine the top, exposed surface of the sheet metal the next morning for the presence of moisture. If water is present because of atmospheric condensation, the water will be present upon the top surface of the sheet metal and when you lift the metal sheet, the surface will be dry. There may be a minor amount of moisture under the sheet. This would be from the normal vapor transmission. If, however, the underside of the metal sheet is highly condensed, the problem is probably due to excessive moisture rising through the slab. This may or may not be a problem depending on the origin of the moisture.
L&M LUMISEAL FX™ is an effective, user-friendly membrane that can even be placed over concrete releasing a moderate amount of moisture vapor. L&M LUMISEAL FX is a low-odor, non-yellowing, low-gloss sealer. It has excellent tire marking resistance. If you're not quite sure of your particular application, or the right LATICRETE® product to use to solve your problem, contact us!
We have a concrete block wall with a northern exposure, we have insulated and finished the inside and enjoy the improved looks and warmth the insulation and wallboard provide. We have observed the outside of the wall stays wet or damp for days after a rain or snow melt. Can we improve water resistance of the out side face of our wall? We suspect the water will create problems over time.
The concrete block surface exposed to the water from rain and snow melt will become a problem. Historically, the water will find a way to get to your finished surfaces. We would recommend L&M AQUAPEL PLUS™ as a clear, liquid applied treatment to the exposed face of the block. AQUAPEL PLUS is easy to apply and is odor free. The concrete block wall will repel the water in the future versus letting it soak in and ruin your finished spaces.
We have an expansion adjoining our existing plant. The floor in the existing plant was treated with iron shavings and cement. We can see the iron shavings on the worn parts of the floor. Our existing plant managers told we cannot use it in the new adjoining floor, too much dust from the iron and cement shavings. We have to treat our new floor. What can we do?
Contact your project engineer and discuss this situation with them. The information you are about to see is to be used in combination with the meeting with your project engineer.
L&M SEAL HARD™ is a liquid applied hardener and is totally dust free. SEAL HARD is not an iron hardener and it contains no cement dust. Your plant engineers may have very legitimate reasons for a no dust process.
The construction activities will not be altered. The concrete can be placed as planned and the concrete floor can be finished as specified. The SEAL HARD liquid can be placed upon the finished floor in as soon as the floor is three days old or older. There is no odor associated with it and absolutely no dust. The SEAL HARD treated floor will resist dusting and wear. The color is clear.
We have a beautiful brick paver driveway, walkway and patio. How do we protect it and not change the colors nor make it slippery?
This is an important question. The bricks your contractor used were "interlocking pavers" and are not furnace produced bricks, instead they are cast from cement and sand under immense pressure.
The way we suggest, to protect your investment in your paver pavement, is L&M AQUAPEL™/AQUAPEL PLUS™. It is colorless or clear and will not change the color of your pavers.
You are wise to avoid a treatment that might make the pavers slippery. L&M AQUAPEL/AQUAPEL PLUS soaks down into the pavers and protect from within, and do not make a surface more slippery. You can apply it with a sprinkler can and a sturdy push broom, the result will be a long lasting and protected system for your pavers.
Why did our concrete contractor insisted upon placing our big wide driveway and patio at or near sunset? We live in the desert southwest and we like it, but it seemed odd to require the placement of concrete at the end of the day.
It sounds like your contractor is operating from experience gained in your desert area. We suspect the contractor is wetting the sub grade or soil with water, just prior to placing the concrete in the evening, too. This is all an attempt, in our opinion, to place and finish fresh concrete with a quality approach.
We think your contractor is waiting for the cool of twilight to place the concrete and avoid a rapid surface drying and surface cracking, normally caused by heat and wind. Heat and wind will dewater the surface of fresh concrete and leave many surface shrinkage cracks. This is a situation to avoid. We will speculate, your contractor is also spraying a moisture loss control product upon the surface of the concrete as it is being finished or "smoothed." This moisture loss product is called an evaporation control product (L&M E-CON™).
The next step in giving you a quality concrete project, will be the curing of the finished concrete surface. We prefer to cure with a heavy solids membrane, like our L&M LUMISEAL FX. It cures and seals with the same product.
What can we do to prevent the problems we are experiencing with our concrete in hot weather?
Concrete is a building material that can be used in all types of weather, throughout the year. In hot weather the craftsmen must handle the concrete with enough care and protection as to imitate "ideal" conditions. During hot weather concreting, the temperature is one of problem, relative humidity and wind speed are the other components to the problems in hot weather.
History and experience have alerted us to the effects of hot weather on fresh concrete:
- Increased water demand in the mix
- Rapid slump or workability loss
- Rapid stiffening or actual setting
- Development of surface plastic shrinkage cracks
- Fluctuation in a downward trend of air content.
Approaching this from a contractor's point of view, the water demand and slump loss can be addressed in the preconstruction meeting at the start of the project. Discuss these issues with the engineer and the concrete producer. Request proportioning the concrete as specified to meet the changing environment. Use of ice in the mix is possible, but it is an extreme measure and brings its own burden of cost. Hot weather concreting may have a higher water requirement to maintain the workability. Mainly due to the rapid hydration and evaporation which occurs between batching in hot weather and on site delivery. A mix design performing well in moderate temperatures will need to be proportioned differently for hot temperatures. Remember, if more water is needed, more cement or cementious material will be needed to balance the increase in water.
Speaking to the issue I think you are really asking about, the control of surface plastic shrinkage cracks and surface crusting from rapid surface evaporation, consult ACI 305. It will direct you to a lot of helpful procedures to protect your concrete in hot weather. The one item to focus upon is the use of a monomolecular film on the surface of the fresh concrete. The monomolecular film product is called L&M™ E-CON™. Your crew would apply a repeat spray application of this easy to use liquid. The purpose of the monomolecular film is to reduce early evaporation of the surface water from sun and wind. A simple pump sprayer is the normal device to apply the E-CON. Finishing and tooling are not interfered with and the tools can travel right over the liquid with no consequence.
Summarizing, be proactive and alert the owner and the engineer of your crew are not working in lab conditions, promote the proportioning changes to the concrete for the hot weather conditions. Finally, use the finisher's friend E-CON™ as an insurance to prevent early crusting of the surface and to resist the formation of surface plastic shrinkage cracks. Finally, consider working at a time of the day when the sun and wind are less a problem, early evening or nighttime.
We have a problem with surface crusting on our fresh concrete slabs. Our sites are almost always exposed to sun and wind. Even though we know that "blessing" the concrete surface with a sprinkle of water by the finisher is not the best answer, we have little else to fall back on. What else can we do?
"Surface crusting" is defined as the drying out of the surface of concrete or mortar before setting occurs. This condition gives a false sense of setting. The top of the slab will not have enough moisture at the surface for the finishing operation, which frequently results in a wavy concrete floor surface.
The best independent source is ACI 305, Hot Weather Concreting, (Section 4.2). In this document you will find statements suggesting to the reader a number of practical actions including:
- Avoid placing concrete during the hottest time of the day
- Cool the concrete
- Use a monomolecular film liquid
This last suggestion is, in our opinion, the easiest and most cost-effective step your crew can take to minimize crusting and surface plastic shrinkage cracks that typically go with concrete placements in hot, windy, or dry weather.
Most commercially available monomolecular films are sold in a concentrated form. The dilution ratio we are most familiar with (L&M E-CON) will provide your crew with up to 50 gallons of monomolecular film liquid from 5 gallons of concentrate. The typical application rate of the diluted material is roughly 200 sq ft/ gallon (5 sq.m/L).
To protect freshly placed concrete, apply the diluted monomolecular film liquid with a durable hand-pump sprayer. It is best when your crew applies it right after the concrete is screeded or bull-floated. Floating and finishing steps will not interfere with the function of monomolecular film liquids. While a finishing tool or finishing machine can pass over the treated surface numerous times without reducing its effectiveness, it is a good practice to reapply if the slab will be left exposed for a long period of time before the next finishing step commences.
Monomolecular films are not curing compounds. They are effective only on freshly placed concrete and last for an hour or two. Subsequent applications can be installed without a problem on difficult concrete pours. In addition to protection of fresh concrete from wind and heat, the installation of mineral and metallic shake-on hardeners is helped greatly with the use of monomolecular film product.
The monomolecular film liquid is named E-CON, short for "Evaporation Control and Economy". A single spray of E-CON will reduce the early evaporation of a concrete slab by as much as 80% in wind and up to 40% in hot temperatures. It is economical, too! At an estimated cost of less than a penny a square foot, no job should be without E-Con's protection. We recommend that you include E-CON in your regular concrete placement regimen to overcome crusting and other problems associated with the rapid surface drying of fresh concrete. The product concentrate comes packaged in 5 gallon, 1 gallon and a convenient one-quart trial size. For more information contact your local LATICRETE representative.
We are an international development company. We specialize in buildings with large areas of concrete floors. Joints in the floors have become a major problem for us. We have a maintenance company on retainer but the repair patch never lasts. Why do we have to have joints at all? Is there a long lasting repair for broken joints?
Our answer has to be divided into sections and each section will address joint types and a repair option when the joint edges break or become a problem. Do concrete floors need joints? Yes, concrete floors should be jointed. Random cracking will develop in concrete floors without joints. Random cracking occurs because concrete shrinks when it moves from its original plastic or wet volume state to its hardened volume. This shrinkage or volume loss of concrete occurs as it hardens. The friction of the base or soil against the bottom of the shrinking concrete restricts the concrete from moving freely, thus cracks develop. This is also true for pipes penetrating the concrete and other embedment. These embedments restrict the movement of the shrinking concrete and a crack will develop near the embedment or support column.
The first joint we can learn about is the Construction Joint. Your floors have construction joints where one lane of concrete was placed and finished and the next day or later another lane of concrete was placed along side of the older lane. Officially, a construction joint is the division between two successive placements of concrete. Reinforcement may pass through a construction joint. (See diagram A). The construction joints in your floors should be straight, and the edges should be unbroken. The way to maintain and repair construction joints is to clean them out and fill them with a rugged polyurea joint sealant. If the joint faces are not out of vertical alignment but the edges are broken or missing, a rugged polyurea joint sealant can also be the proper repair material.
The second joint we can learn about is the Contraction Joint. Your floors should have contraction joints already in the surface. Contraction joints are also called (crack) control joints or saw-cut joints. Contraction joints are cut into the concrete to prevent random cracking due to volume loss or shrinkage of fresh concrete as it hardens. Contraction joint cutting can be accomplished by a jointer hand tool or, more commonly, by a concrete saw cutting blade. Contraction joints are vulnerable to edge breaking or deterioration after the floor is put into service. This vulnerability can be overcome by filling the contraction joints and their deteriorated edges with a rugged polyurea joint sealant. This joint filling is most effective in non-moving cracks and fully cured slabs. For best performance new floors should be allowed to cure for a minimum of 60 days. Deteriorated contraction joints can be cleaned out and rebuilt with polyurea. (See diagram B)
LATICRETE can develop a program for your entire organization and your maintenance contractor to protect new joints in your floors and to rebuild or repair the failed joints. The product we offer is a premium, 2-part rugged polyurea called L&M JOINT TITE 750™. This product is a two-component, self-leveling liquid. The most popular color is concrete gray, but other colors are available. L&M JOINT TITE 750 can be installed in wide range of temperatures and can be opened to traffic in less than an hour. This means that your plant operations will suffer little to no down-time and your material handling machines will be able to roll smoothly across L&M JOINT TITE 750 filled or repaired joints.
Our team is trained and ready to assist you in helping you with your concrete floor problems. Contact us to help solve your concrete floor problems.
What is the purpose of a "vapor barrier" under a concrete floor, does it make the bottom weak?
A vapor barrier does not make the bottom of the concrete weak. There are excellent curing conditions in the bottom section of a concrete slab and these tend to make the concrete stronger. We suspect your question sprang from hearing someone say the bottom of a concrete slab was soft or plastic, when laid over a vapor barrier. This is true for a comparative short time. The comparison is to the top section of the concrete slab. The top section of a concrete slab generally stiffens faster than the bottom section. Both regions will harden, but at differing rates.
The purpose of a vapor barrier is to eliminate rising dampness from the subgrade. Concrete is a stiff and structural material, it is also porous to water or water vapor. Compared to the atmosphere above a slab, the interior of a concrete slab is a high pressure area. Moisture vapor can travel through the interior pore system of the concrete and reaching the surface, condense into liquid water under the floor coverings.
Floor coverings do not perform well when underlain with a minute but persistent supply of liquid water. Carpet dampens, vinyl tile losses its bond, urethanes age due to the high pH of the rising water and epoxies can become cloudy in appearance. Waterproof vapor barriers are intended to prevent any rising dampness from the surface.
Occasionally, we are called to repair spalled and scaling concrete on either new or old concrete placements. We've tried mixing our own repair material, mostly “moose milk” (acrylic latex) with Portland cement and fine sand and have had some success, but not always. We are looking for a more reliable way to repair eroded surfaces in concrete work. Call backs are eating up our profits. Any suggestions?
This is a very common need and the answer is a product named L&M DURACRETE™. This product was a long time in development, because everyone knows that a “half fast” repair failure causes more dissatisfaction than the original complaint. L&M DURACRETE is a single component, dry polymer-reinforced, cement based patching and re-surfacing mortar. This product has been formulated to repair, slope or level, and to resurface structurally sound interior or exterior concrete surfaces that are pitted, worn, spalled or scaled. In addition, this product can be “sculpted” to repair vertical and horizontal concrete members, curbs, and deep voids.
The secret to L&M DURACRETE's performance is twofold:
- Is “strength matched” to normal concrete. With over 65 years of experience, LATICRETE has found that patching materials which more closely match their compressive strength to the strength of the concrete substrate adhere better and last longer. In other words, high compressive strength repair materials are generally not better.
- It contains a technologically advanced, dried polymer, reinforcing and bonding component. At the same time, L&M DURACRETE reduces waste, simplifies installation, and ensures outstanding freeze-thaw durability in colder climates. This particular polymer is key to your search. Once this product is properly bonded to the base concrete, it stays there.
Picture in your mind a scaled driveway surface. The L&M DURACRETE repair approach would be to power-wash the entire driveway with a high-pressure water blaster and selectively apply a de-greaser liquid to any oil stains. Allow the standing water to dissipate, yet maintain a damp surface. Fill in all prepared spalls, voids, and scaled areas with a stiff, mortar-like consistency of L&M DURACRETE. Allow to harden for an hour or so. After setting for a few hours, broom a thick coat of semi-self-leveling L&M DURACRETE, prepared to a slurry consistency, similar to thick buttermilk over the entire area. At this time, your crew can broom, trowel, or even texture the surface with stamping or geometric shapes. Application thickness can range from very thin to many inches thick.
L&M DURACRETE is available in a standard portland cement gray color or in white, which comes job-site ready to accept pigment. Re-build curbs or smooth out dips in gutters with L&M DURACRETE. Your crew will soon become masters at repair! Your “call back” will turn into a nice encounter for your company and the property owner at the same time. Please contact your LATICRETE sales representative for more details on L&M DURACRETE and its almost unlimited repair uses.