Removal of deteriorated, damaged, porous or defective concrete is a must for any repair work but the extent of this removal cannot usually be determined in the planning stage.
The decision about how much-damaged concrete is to be removed and what level of aging for existing concrete is allowed to remain in place is very tedious.
This decision becomes particularly difficult because the change in properties of concrete occurs gradually along the depth of concrete and there is no hard and fast borderline.
One guideline for the extent of removal in medium and high strength concretes is to continue removing material until aggregate particles are being broken rather than simply removed from the cement matrix.
It is not a good practice to remove material only up to the plane of reinforcement and to have a joint between new and old materials right at the same location. Even in those cases where it is decided not to encase the bars fully, it is better to expose about three-fourth of the bars diameter and to expose the corner bars fully.
Blasting of damaged concrete can produce problems in the surrounding concrete and hence its use must be carefully planned. Use of impact tools may also produce small-scale cracking to the surface of the concrete left in place. The debris removal by some primary means is usually followed by using a secondary method such as chipping, sand blasting (impacting sand with high air pressure) or high-pressure water jetting to clean the surface. For more precise removal of damaged concrete in small areas, saw cutting may be used but the surfaces obtained must be treated with thin layers of materials to improve the feather edge surface.
When exposing narrow but deep areas for repair along cracks, the cavity is better to be undercut to lock the repair material, see Fig.1 for two alternate methods. For large areas, the edges of the area are cut back sharply perpendicular to the face of the existing concrete without any undercut. For large cavities to be filled, the top surface is preferably made sloping towards the interior for easy placement and compaction of the repair material.
The concrete removal techniques in Miami Fort Lauderdale Florida used should be effective, safe and economical, and should produce minimum damage to the concrete left in place. Some removal techniques take much longer time than the others but are environment-friendly.
Some techniques permit a portion of the work to be accomplished without removing the structure from service. A single removal technique may not be the optimum solution for all portions of a given structure. The properties of the concrete to be removed provide important information required determining the method and cost of concrete removal and this information must be made available to contractors for bidding in Miami Fort Lauderdale Florida.
After the removal, the concrete surface is checked by visual inspection and by sounding at the surface, microscopic examination or bond testing for near-surface damage and by taking cores, pulse velocity tests and pulse echo tests for the subsurface condition of remaining concrete. All damaged or deteriorated concrete is to be removed and the quantities must be estimated as accurately as possible in the start.
The broad categories of concrete removal methods are blasting, cutting, impacting, milling, pre-splitting, and abrading. The details of various methods in Miami Fort Lauderdale Florida are given below:
Blasting methods use materials producing rapidly expanding gas confined within a series of bore holes to produce a controlled fracture of the concrete.
Explosive blasting is considered to be the most cost effective and quick way of dislodging large quantities of damaged concrete. A designed quantity of explosive is placed in drilling bore holes that are simultaneously or in predefined sequence detonated.
One technique of controlled blasting is cushion blasting, in which a line of less than or equal to 75 mm diameter bore holes are drilled parallel to the removal face, each hole is loaded with light charges of explosive, the charges are cushioned by wet sand, and the explosives denoted.
This method produces a relatively clean surface with less over break. All phases of the blasting operations must be performed by qualified personnel having proven experience and ability in this field and proper permission from the government departments must be taken in advance.
Following methods can be used to cut the damaged concrete and the selection of the method basically depends on handling and transportation of the cut pieces.
In these methods, repeated striking of concrete surface is done with a high energy tool or a large mass to fracture and spall the concrete. This method may cause micro-cracking in the adjoining concrete particularly if partial depth removal is required. Following equipment are used for this method:
Milling methods are used to remove a specified amount of concrete from large areas of horizontal or vertical surfaces; having removal depth ranging from 3 mm to approximately 100 mm. These methods usually produce a sound surface free of micro-cracks.
Scarifier: A scarifier is a concrete cutting tool that employs the rotary action and its cutter bits cuts concrete surfaces. This equipment can remove deteriorated and sound concrete in which some of the concrete contains form ties and wire mesh, loose concrete from freshly blasted surfaces and concrete that is cracked and weakened by an expansive agent. Scarifiers are available in a wide range of sizes.
High-pressure water jetting is used as a primary means for removal of concrete when it is desired to preserve and clean the steel reinforcement for reuse and to minimize damage to the concrete remaining in place. This method has a high efficiency and disintegrates concrete changing it back to sand and gravel-sized pieces.
Pre-splitting methods use hydraulic splitters, water pressure pulses, or expansive chemicals placed in boreholes drilled along a line to induce a crack plane for the removal of concrete. The direction and extent of the crack planes that propagate depend on the pattern, spacing, and depth of the boreholes.
Abrading blasting removes concrete by propelling an abrasive medium at high velocity against the concrete surface to abrade it. Abrasive blasting is typically used to remove surface contaminants and as a final surface preparation. Commonly used methods include sandblasting, shot blasting, and high-pressure water blasting.
Sandblasting: This method is the most commonly used technique to clean concrete and reinforcing steel, where common sands, silica sands, or metallic sands is used as the primary abrading tool. There are following three methods of implementing this method.
This method is also similar to sandblasting but here metal pieces are projected at the concrete surface at a high velocity. The shot erodes the concrete from the surface and the removed material is collected by a vacuum chamber in the machine. The shot-blasting process is highly efficient and environment-friendly method. A surface cleaning operation is done by using a small-sized shot and setting the machine for maximum travel speed. Removal of as much as 6 mm in a single pass is possible and up to 20 mm thickness can easily be removed.
High-pressure water blasting with abrasives uses a stream of water at a high pressure of 10 to 35 MPa with an abrasive, such as sand, aluminum oxide. This equipment can remove dirt, grease or other small particles exposing the fine aggregate. The abrasive is removed from the water before it is disposed into a storm or waste water system.
In Miami Fort Lauderdale Florida, Concrete Companies are much more than just a concrete contractor. In Miami Fort Lauderdale Florida Concrete Company offers concrete removal services as well. So even if you are just removing a concrete patio, driveway, sidewalk or walkway, we can help!
Often times homeowners and business owners in Miami Fort Lauderdale Florida undergo the process of concrete removal as it is assumed that concrete removal services are expensive. After starting the project, that is when they turn to professional contractors and research the price of concrete removal, ultimately finding that concrete removal is much less expensive and a great deal more convenient than what they had originally thought it might be. So, make certain to check with them about your project before beginning your concrete removal project, an estimate only takes a few short minutes and this way you can make an educated decision before just starting on a project that can be costly and more importantly take much more time than you might have originally expected.
The companies in Miami Fort Lauderdale Florida can help with all of the following concrete removal projects:
Whatever the concrete removal project, in Miami Fort Lauderdale Florida the companies are ready to help!
Miami Beach • Miami Gardens Aventura • Bal Harbour • Bay Harbor Islands • Biscayne Park • Carol City • Coral Gables • Cutler Bay • Cutler Ridge • Doral • El Portal • Fisher Island • Florida City • Golden Beach • Hialeah • Hialeah Gardens • Homestead • Indian Creek • Islandia • Kendall • Key Biscayne • Medley • Miami • Miami Lakes • Miami Shores • Miami Springs • Naranja • North Bay Village • North Miami • North Miami Beach • Ojus • Opa-Locka • Palmetto Bay • Perrine • Pinecrest • Pinecrest / Monroe Co. • South Miami • Sunny Isles • Surfside • Sweetwater • Universal Park • Virginia Gardens • West Miami