- Try to find original drawings or photographs that best depict the original design
- Fads come and go. Consider timeless style for finishes and colors, pick options that are appropriate and blend with surrounding materials.
- Understand performance classifications for windows published by the American Architectural Manufacturers Association (AAMA) and National American Fenestration Standards (NAFS) and how they relate to your building.
- Cold drafts are uncomfortable and energy loss is costly. Select windows that incorporate thermal barriers, double-pane, insulated glass and have been tested and certified by the American Architectural Manufacturers Association (AAMA).
- Outdoor noise from wind, traffic, barking dogs, etc. can be very distracting. Select windows with good acoustical (sound-reduction) properties.
Applying caulk to stop leaks is not always a good thing. Sometimes it makes matters worse by trapping water in the building façade instead of letting it drain. Here are a few areas where NOT to caulk:
*Along window or door head lintels on brick facades – leads to advanced corrosion of the steel support and either rotated/deflected steel or cracked bricks.
*Soffit (ceiling) of elevated concrete slabs (i.e. balconies, parking garage slabs) – traps water in the concrete and accelerates corrosion of the embedded steel and deterioration of the concrete
*Over/covering window weep holes – prevents windows from draining properly
Fiber-reinforced polymer or FRP, is a concrete repair material that has been growing in popularity in the United States for close to 25 years now. FRP, as its name implies, is a polymer material with carbon, glass or steel wires imbedded in a polymer resin. The question is what is it good for? Often, concrete structural elements – slabs, beams, or columns, – that compose a building, will occasionally need to be strengthened due to a change in usage or loading. The typical remediation for such conditions includes the installation of structural steel frames and other elements, to provide additional strength support for the existing concrete. However, FRP is an alternative that is able to provide strengthening effects, with much lower weight. FRP can be applied to the surface of the element to provide support, via two methods. In both methods careful attention to proper surface preparation must be taken, including a primer coating to penetrate the substrate and enhance bonding ability. In some cases, an epoxy putty application is applied to create a more even bonding surface.
- FRP fabric can be applied on site by combining the fibers and liquid polymer resin, and utilizing a wet lay-up process.
- They can also be pre-manufactured off site and arrive as bars, plates, and rods and glued to a structure.
After application, the FRP becomes an integral part of the structural element providing both flexural and shear strengthening, or column confinement and ductility. The increase in structural capacity from FRP is due to the ability of the resin to transfer loads to the fibers, and the fiber’s large capacity to carry tensile loads, varying from 2-5 times the capacity of steel. So why FRP? Despite having a higher material cost than traditional strengthening methods, the reduced installation time, equipment utilization and labor can offset the higher material cost especially in areas with limited access, which would explain the increased usage of FRP over traditional methods.
With the industrial Revolution, concrete began to be an essential piece of United States’ infrastructure. The need of large masonry buildings exploded the natural cement (a hydraulic cement made from limestone) production in the Americas. During the1890s, nearly 3 billion pounds of natural cement were produced and the demand continued to increase.
The most prolific cement production was centered on Rosendaletown, NJ, where cements became known as Rosendale cements. However, due to the high demand of cement, other options such as Portland cement, became available and overtook the market.
In 1976, natural cement became unavailable, and it remained absent for nearly 30 years. Natural cement is now being used as a restoration material of historic structures. Natural cement masonry mortar was used in the restoration of the Washington Monument and the wings of the U.S. Capitol. It also has been used for repointing the historic South Range of the American Museum of Natural History in New York.
The re-emergence of natural cement offers a variety of applications for building restoration processes preserving and protecting the authenticity of historical structures.
Hydrodemolition is a method to remove concrete through the use of high-pressure water jets. This method can be used for horizontal, vertical, overhead, and underwater concrete removals.
One of the main benefits of hydrodemolition over jack hammers is the elimination of the need for a secondary process to remove microcracking related damage to the concrete that is left in place. Several other benefits are that hydrodemolition creates an irregular surface profile for better bonding of the repair material, minimal ground vibrations, and cleaning of embedded reinforcement. Environmentally, hydrodemolition is beneficial because it reduces the amount of harmful silica dust put in the air, and faster concrete removal can reduce construction time.
Although this method has its benefits, there are some negative aspects to it as well. For example, the process can consume a large amount of potable water that will later have to be treated before it can be returned to the storm drain system. Also, containing the runoff from the used water can be difficult, and in freezing temperatures, the water may create hazardous conditions.
Recently, new research has been done in order to test the durability and strength of beams when carbon fiber strips and fabric are added to them. The experiments involved exposure to several environments such as high humidity, freezing-and-thawing cycles, and saltwater exposure.
The data recorded from the durability tests showed that in high humidity environments the bond between carbon fiber plates and concrete degraded over time, but the same conditions did not affect the bond between fabrics and concrete. This would suggest that plates would be better for indoor use rather than outside use
The freezing-and-thawing test results showed that the bond in both the plates and fabric was not affected by the fluctuations in temperature, which suggests that the carbon fiber protects the concrete from getting wet.
In the final test with saltwater exposure, carbon fiber performed well, but after 10,000 hours the concrete began to weaken, which may indicate that use in a marine environment is not recommended.
This mixed set of results will undoubtedly spawn more research and we will keep an eye on these developments.
A new nano-technology process that layers carbon steel elements with corrosion resistance and strength increasing materials is being tested.
The steel is run through an electroplating bath and various layers of metals are applied to the steel, which is reported to increase the steel strength by up to ten times. High strength and corrosion resistance are a great combination for a material that could be used to repair a steel building.
The following website as more information: http://www.technologyreview.com/news/534796/nano-manufacturing-makes-steel-10-times-stronger/ We will keep an eye out for more developments in this exciting technology.
You’ve probably seen it before in your lifetime, but you may not have known it. Shotcrete is a construction technique that involves spraying concrete through a hose at very high speeds. It is a process rather than a specific material.
Shotcrete is reinforced by steel rods, steel mesh, or fibers. Due to the force with which the concrete leaves the nozzle, the material gets placed and compacted simultaneously. Some properties of hardened shotcrete are high strength, low permeability, and high durability. Because of the manner in which shotcrete is applied (high velocity), it bonds better to most substrates regardless of area or shape.
Shotcrete can be sprayed onto straight, curved, and irregular surfaces and can be applied on vertical and overhead areas too. Some structures where shotcrete is typically applied to for repair and restoration are bridges, parking garages, dams, sewers, and more. In new construction, shotcrete can be used for swimming pools, foundations, and domes
We often specify helical piers for foundation underpinning projects to correct building settlement conditions (see our previous post, “Screw It” http://blog.etc-web.com/?p=83 ), but occasionally we need to use micro piles instead.
As the name suggests, micro piles are small diameter piles (generally 3” to 10” in diameter) that are installed by a drilling process. These piles consist of a steel casing and/or threaded bar that is made of high strength steel. We specify this process when there is shallow bedrock, boulders, or layers of soil that are very hard.
In the past, micro piling was not a highly used process because of cost considerations and a slow installment time. But lately, it has been gaining popularity. The main reason for this are requirement to comply with low noise and vibration regulations that are generally found in urban or highly populated areas. Micro piling is also a useful technique for underpinning at sites with difficult or restricted access, including low headroom interiors and facilities that require minimal disruption to normal operations
Cast-in-place concrete will, more often than not, crack. In a nod to that characteristic, weakened planes (control joints) are formed or cut into conventionally-reinforced concrete slabs and sidewalks to influence where cracks occur. Cracking outside of control joints can indicate shortcomings in concrete placement, finishing, and/or curing, as well as influences from without. Cracks can manifest in a number of forms, most of which are of no structural concern.
Shrinkage cracks are most common and those for which control joints are used. Excessive shrinkage cracks can be caused by high water content in the concrete mix or poor control joint layout.
Plastic-shrinkage cracks are usually shallow and occur when surface water evaporates from the surface of plastic (soft) concrete faster than bleed water from below can replace it. Accelerated evaporation can occur under conditions of low relative humidity, high heat, when wind speeds exceed 5 MPH, or a combination thereof. Plastic shrinkage cracking can be controlled by various methods, including the use of wind breaks, shading provisions, water misting, etc.
Crazing or map-cracking is characterized by interconnected shallow cracks and can be caused by the same conditions that cause simple plastic shrinkage cracks. They can also be caused by poor finishing, particularly on steel-trowel finished concrete. Over-finishing can depress large aggregate and draw excessive paste and fines to the surface. High water content and rapid curing can also produce crazing.
Durability (D)-cracking is caused by the use of porous large aggregates (usually sedimentary materials such as limestone, sandstone, dolomite, shale, etc.) in regions that experience freezing temperatures. It occurs when absorbed water freezes and the resulting expansion (ice occupies about 9% more space than liquid water) breaks the aggregate. The greatest harm is caused by freeze-thaw cycling. The mid-Atlantic region experiences temperatures near the freezing point of fresh water more frequently than most other parts of the country and therefore experiences more freeze-thaw cycles. Deicing agents (such as road salt) creates brines, which have lower freezing points and thereby further increase freeze-thaw cycles.
D-cracking usually occurs near joints and can be partial or full-depth. It will often cause severe spalling and it is considered a terminal, incurable condition.
Displaced or offset cracks are characterized by a height differential on either side of a crack. When they occur at slabs-on-grade, the cause is usually a poorly prepared or unsuitable sub-grade or displacement by tree roots. Significant displacement (one-half-inch, or greater) can present tripping hazards.
Offset cracks in elevated (bridging or cantilevered) slabs could indicate a structural instability. Embedded steel reinforcement would normally prevent displacement and its failure to do so could have serious consequences.