Does the presence of cracks indicate a structural problem?
In most instances, the answer is no. Very narrow “hairline” cracks are superficial and do not indicate any structural problem. Cracks that have movement where one side of the crack moves relative to the opposite side should be evaluated by a professional engineer.
Why should I choose concrete over asphalt when asphalt is less expensive?
Consider the cost of the driveway over its lifetime. A good quality concrete driveway will last more than 30 years with little maintenance. Asphalt driveways need regular periodic sealing coats to retard age-related cracking. Deterioration of even properly constructed residential asphalt driveways will occur more quickly due to environmental influences than due to vehicle traffic. If you factor in the cost of surface and crack sealers and the shorter life-span of the asphalt, concrete will cost much less over the life of the structure. Furthermore, the concrete structure will not harden in sunlight, resulting in a more consistent surface over time.
What finish should be used for a sidewalk, patio, or driveway?
Brooming of the concrete surface provides a safe, attractive, non-slip surface for exterior concrete flatwork. Broom finishes are created by pulling a special dampened, stiff-bristle concrete texturing broom across freshly floated concrete, and can be applied in many ways, including straight, curved, and wavy lines.
Most broom finishes for concrete sidewalks and driveways are straight-line textures broomed at right angles to the anticipated traffic direction. Broom finishes are not incorporated into most decorative concrete finishes.
What does it mean to “cure” concrete?
Curing is one of the most important steps in concrete construction, because proper curing greatly increases concrete strength and durability. Concrete hardens as a result of hydration: the chemical reaction between cement and water. However, hydration occurs only if water is available and if the concrete’s temperature stays within a suitable range. During the curing period-from five to seven days after placement for conventional concrete-the concrete surface needs to be kept moist to permit the hydration process, new concrete can be wet with soaking hoses, sprinklers or covered with wet burlap, or can be coated with commercially available curing compounds, which seal in moisture.
What Is a mechanic’s lien? (What you don’t know could cost you thousands!)
Mechanic’s liens exist to provide collection rights to contractors and material suppliers who supply construction services or materials for improvements to real property. Waiver-of-lien forms provide protection for homeowners who pay their home improvement bills.
With a mechanic’s lien, the concrete supplier or concrete contractor has the right to serve the homeowner with notice of lien and to record it as part of the county land-title records, should payment not be made for materials or services provided. A lien is a claim of partial ownership of your home. If the mechanic’s lien is not paid, the material supplier or contractor can commence court proceedings to foreclose the lien and sell the property in payment of the obligation.
A waiver-of-lien form provides a homeowner proof that subcontractors and material suppliers have been paid and relinquish their right to serve the homeowner with a notice to place a lien on the home. The case history that follows, taken from the Wisconsin Department of Agriculture, Trade, and Consumer Protection web site, explains why lien waivers are important to homeowners:
Mr. Jones signed a contract with ABC Contractors for the construction of an addition to his home. When the work was done, Jones paid the contracted price and started enjoying his new addition. A month later, he received a “Notice of Intent to File I Claim for Lien” in the mail from the lumberyard where ABC Contractors obtained building materials. What happened? Although Jones had paid his bill, ABC Contractors did not pay the lumberyard. The law allows a subcontractor or supplier of materials to place a lien on the property where the work was done, if the contractor doesn’t pay his bills. This can happen even if the homeowner has paid the contract in full.
What is air-entrained concrete?
Air-entrained concrete contains billions of microscopic air cells per cubic foot. These air pockets relieve internal pressure on the concrete by providing tiny chambers for water to expand into when it freezes. Air-entrained concrete is produced through the use of air-entraining portland cement, or by the introduction of air-entraining agents, under careful engineering supervision as the concrete is mixed on the job. The amount of entrained air is usually between 4 percent and 7 percent of the volume of the concrete, but may be varied as required by special conditions.
Why does concrete crack?
Concrete, like all other materials, will slightly change in volume when it dries out. In typical concrete this change amounts to about 500 millionths. Translated into dimensions-this is about 1/16 of an inch in 10 feet (.4 cm in 3 meters). The reason that contractors put joints in concrete pavements and floors is to allow the concrete to crack in a neat, straight line at the joint when the volume of the concrete changes due to shrinkage.
Why do concrete surfaces flake and spall?
Concrete surfaces can flake or spall for one or more of the following reasons:
In areas of the country that are subjected to freezing and thawing the concrete should be air-entrained to resist flaking and scaling of the surface. If air-entrained concrete is not used, there will be subsequent damage to the surface.
The water/cement ratio should be as low as possible to improve durability of the surface. Too much water in the mix will produce a weaker, less durable concrete that will contribute to early flaking and spalling of the surface.
The finishing operations should not begin until the water sheen on the surface is gone and excess bleed water on the surface has had a chance to evaporate. If this excess water is worked into the concrete because the finishing operations are begun too soon, the concrete on the surface will have too high a water content and will be weaker and less durable.
Will concrete harden under water?
Portland cement is a hydraulic cement which means that it sets and hardens due to a chemical reaction with water. Consequently, it will harden under water.
How do you control the strength of concrete?
The easiest way to add strength is to add cement. The factor that most predominantly influences concrete strength is the ratio of water to cement in the cement paste that binds the aggregates together. The higher this ratio is, the weaker the concrete will be and vice versa. Every desirable physical property that you can measure will be adversely effected by adding more water.
What are the decorative finishes that can be applied to concrete surfaces?
Color may be added to concrete by adding pigments-before or after concrete is place-and using white cement rather than conventional gray cement, by using chemical stains, or by exposing colorful aggregates at the surface. Textured finishes can vary from a smooth polish to the roughness of gravel. Geometric patterns can be scored, stamped, rolled, or inlaid into the concrete to resemble stone, brick or tile paving. Other interesting patterns are obtained by using divider strips (commonly redwood) to form panels of various sizes and shapes rectangular, square, circular or diamond. Special techniques are available to make concrete slip-resistant and sparkling.