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Spalling typically occurs as the result of stresses caused by differential movement of building materials that are in contact with one another, or due to a progressive deterioration mechanism, such as corrosion. Separations between the grout and the surrounding concrete, in combination with significant voids within the grout pockets, provided paths for excessive water ingress and created conditions conducive to corrosion deterioration at the post-tensioning tendons and anchorages. Public safety is of paramount importance for engineers and architects designing buildings. This article was produced under the auspices of Pieresearch, manufacturer of quality concrete accessories, exclusively for the benefit of the structural and geotechnical engineering, architectural and construction communities and is copyrighted by Pieresearch 2019. Similar to Structure #1, Structure #2 was located in a busy downtown area and had occurrences of spalled concrete falling from the edges and corners of the balconies. A surface with a smooth finish holds less water on the surface and creates a more durable and less porous surface. The PatchGuard system has been proven to effectively negate the so called incipient anode, or ring anode, effect and significantly extend patch repair life. This is because of salts. It is perhaps obvious, but important enough to note, that the costs of the necessary exterior repairs to these structures far exceeded the costs of proper installation during construction. Failure of an individual post-tensioning tendon may or may not significantly affect the structural integrity of a structure. (5 Primary Reasons), Concrete patios are the summer heartbeat of the backyard the perfect location for dinner parties, chalk-art, and a cold, stiff drink after yourfalse, Methods and Cost of Stem Wall Spalling Repair, Are you concerned spalling will compromise the structural integrity of your foundation? Concrete cover along the balcony edges was not in conformance with either the project specifications or the building code, including areas that had less than 25% of the code-required minimum cover and locations where the cover was less than 1/8. Introduction Just like untreated wood rots, untreated concrete spalls. Corrosion likely exacerbated the concrete fractures and delamination along the length of the reinforcement. This case study illustrates how the deficient installation of post-tensioning tendons and of the grout pockets protecting the tendon ends can cause significant damage and potential safety hazards. 6.) I would like to opt-in to receive email updates, 2022 Concrete Preservation Technologies Limited. The salts mix with the rain and penetrate the porous concrete. The garage experienced consistent daily use and periods of heavy traffic at the start and end of shifts for the hospital staff. If there is a limitation to galvanic anodes it is that the properties of the sacrificial alloy place a ceiling on the voltage available to power the system. Check out our article: Concrete Coatings: Epoxy Vs. Polyurea. Home Gym Surfacing: Why Wet-Pour Rubber Surfacing Emerges as the Winner? A spall is defined as flakes of material that are broken off of a larger solid body. For those unaware, the spalling of concrete, in layperson terms, can be described as flaking or breaking apart of the concrete from its structure, as a result exposing the interior reinforcing materials to the atmosphere. Tendons that are exposed to corrosive elements will deteriorate until they can no longer carry the tension load, at which point they snap. This sudden release of load can cause displacement of the tendon end anchorage, with the failed tendon protruding from the exterior face of the structure. Proper detailing and quality installation of reinforcement, using proper reinforcement support and ensuring proper reinforcement cover and protection, are important for the prevention and mitigation of many of the issues discussed in this paper. The following are examples of how environmental conditions can accelerate the process of The biggest source of spalling we see in the foundation repair industry is rusted rebar. Investigation revealed that a portion of the debris was related to corrosion of reinforcement. Concrete Spalling is the breakdown of concrete via natural weathering and/or chemical reaction that results in sections of cement chipping off the main body often resulting in fractured, compromised concrete. If left unchecked then spalling will tend to accelerate and spread so that, eventually, the structure could become unstable. Structure #1 was a high-rise residential structure, with balconies typical at each floor. In short, spalling can affect anything constructed of concrete but we most often see it in conjunction with foundation failure due to foundation settlement or foundation heave (both of which are caused by expansive soil). To prevent the spalling of concrete in your property, you can follow the tried-and-tested tips shared below. Because of these efforts and with advancements in human understanding of natures forces, the safety of the built environment has improved over time, and large-scale structural collapses of modern buildings are rare. Typically installed at 500mm centres into small drilled holes around the inside edge of the repair, each PatchGuard anode is individually connected, using an integral tie wire, to the exposed steel within the broken out area. For projects where issues related to reinforcement placement have the potential to create potentially unsafe conditions from falling debris, more stringent specifications and additional third-party pre-pour reinforcement inspections should be considered to reduce the risk of a failure. In short, spalling can affect anything constructed of, but we most often see it in conjunction with foundation failure due to, - Rust can expand the original metal to up to, its original thickness, exerting a tremendous amount of pressure, occasionally resulting in as much as, Patch the pitted area (utilizing a color matching compound), Resurface with new concrete (not the best option if the rust is not addressed first), And, if you do have spalling, get it treated, Why is My Concrete Patio Cracking? Spalling can have wide ranging consequences in terms of health and safety, structural integrity and asset value. Please do not hesitate to contact us atgeneral@cp-tech.co.ukor+44 (0)115 9724 238. CPT have addressed this need by developingDuoGuard,the worlds first hybrid corrosion protection system. In Northern states the use of deicing salts is a prominent contributor to the cause of spalling. The environment into which the concrete member is placed has a significant effect on its performance relative to durability. You can also choose the option of switching to safer material options like rubber, wherever possible, for instance, the driveway leading to your doorstep and your garage and basement floors. How Dangerous is Concrete Spalling? From our UK base CPT manufacture cutting edge corrosion control technology to combat destructive corrosion around the world. These divots vary in diameter and depth but can be thicker than, Improper curing / poor finishing techniques, Electrochemical reactions (such as from de-icing salts), Corrosion/oxidization of reinforcing rebar (due to water exposure), The wear and tear of the freeze-thaw cycle, Without a coating, freezing soaks into the capillaries of the cement and can expand (. 9.) There can be a number of reasons that can cause the concrete in your construction to start cracking and scaling, including the following: Most common in cold climate regions, this is when the water seepage inside a wall freezes and turns to ice. Combine these contaminants with oxygen and water and we have the key ingredients for corrosion. In this article, we are going to touch on: Spall is a verb indicating to break (concrete, rock, stone, or ore) into diminutive sections. 8.) Similar to the salt air, salts used for snow/ice control frequently act as a catalyst to start the reaction between the oxygen in water and the iron in reinforcing steel. The PatchGuard Connect system can be used to mitigate the effects of corrosion in moderately exposed conditions, greatly reducing future maintenance costs. Fun Facts with Brian - Rust can expand the original metal to up to 7 times its original thickness, exerting a tremendous amount of pressure, occasionally resulting in as much as 9000 psi. Ensure that the existing reinforcing steel is cleaned during this process and that the new rebar extends a minimum of 12" beyond the corrosion. The PatchGuard and PatchGuard Connect systems will provide protection for between 10 to 20 years depending on the local environment. 2022 Dalinghaus Construction. All rights reserved. 3.) Separations along the edges of the grout pockets were common. The proper application of the materials protecting the reinforcement, including grout protecting post-tensioning tendons at tendon pockets, may also be critical to the long-term performance of the structure. If corrosion is present on the reinforcing steel, clean rebar and patch void with 9,000 psi non-shrink grout. Most design professionals are diligent in their pursuit of safe structures, carefully calculating the loading conditions, detailing connections and support conditions, and preparing their drawings and specifications. 2021 River Rock Resurfacing. This includes identifying the areas to be repaired. In many cases a purely galvanic system is perfectly adequate and meets the needs of the client by providing long lasting, maintenance free protection. Structure #1 Downtown Residential High-Rise salt-laden air is particularly astringent and exacerbates rust. Contrary to popular opinion, concrete is porous. PatchGuard anodes will slowly, but non-expansively, corrode in preference to the steel. Do you have the tell-tale pockmarks of spalling acned acrossfalse. hbspt.cta._relativeUrls=true;hbspt.cta.load(6780106, 'dbe286fb-8b47-4be2-8d2e-4db6f205287b', {"useNewLoader":"true","region":"na1"}); Spalling can ruin the structural integrity of the concrete and compromise any supported loads. Over the years, this ice-thaw cycle can weaken and crack up the top layer of your concrete resulting in ugly indentations and exposed aggregate. An investigation was performed and it was discovered that other tendon failures existed, including some that exhibited no outward evidence of failure. He has been in the foundation repair industry since 2005. Minimum concrete cover is reduced when the member is cast in plant Along several balcony perimeters, this displaced reinforcement was loose and was sagging at the balcony undersides, with relatively large pieces of concrete delaminating along the reinforcement. When steel is cast into concrete, the naturally high alkalinity helps to protect the embedded steel from corrosion. While not as harmful to one as a threat to life, no one wants to lose the extra income either. More seriously, if the structure is in an area accessed by the public, or by workers, then spalling can be hazardous in terms of falling debris or trip hazards. Playgrounds can also be paved with the same for further safety. Concrete cover varies for different exposures of the concrete member and for the conditions in which the concrete member is formed. Contrary to popular belief, concrete is porous. As with Structure #1, the concrete cover at the balconies of Structure #2 was deficient with respect to the project specifications and with respect to the requirements of the building code. This is not a particularly prevalent issue for Southern Californians or Central Arizonians however, wed be remiss not to touch on the subject. There are a number of reasons why spalling occurs including freeze thaw cycling, the expansive effects of Alkali Silica Reaction or exposure to fire. Corroding steel can expand up to ten times its original volume, exerting stress on the surrounding concrete. Due to the severity of the damage to the tendons, the long-term integrity and durability of the structure was compromised. There are many causes of concrete spalling; they include the improper placement of concrete and its reinforcing, electrochemical (galvanic) reactions between embedded metals within the concrete matrix, and corrosion of embedded reinforcing steel due to exposure to water and/or chemicals. So, what exactly is spalling? If poured and cared for correctly, concrete can last a very long time long enough to survive a couple generations of bloody knees and chalk art. Materials are available for either hand placed, flowable or spray application, determined by the size and geometry of the application. vs. cast in the field (better quality control). Our technologies are complimentary with each other and are often used side by side on the same structure. When exposed to both of those elements, a chemical reaction takes place wherein iron oxide (rust) is produced. 11.) The good news is that this can be easily controlled by the installation of CPTPatchGuardgalvanic anodes. The falling of broken concrete debris on people, as well as objects below, poses the threat to ones life and property. 4.) If you live in Southern California or Central Arizona and would like one of our foundation specialists to come out and inspect your cement, click the link below . Concrete cover is the thickness of concrete between the outside edge of the concrete member and the steel bar, which covers or protects the steel from exposure to the outside elements. Upon detailed evaluation and by performing destructive testing, it was discovered that the grout pockets protecting the tendon ends had been poorly installed. These variations in cover acknowledge the fact that concrete is porous and that greater concrete cover will significantly decrease the rate of steel corrosion and the subsequent concrete degradation. This also means a direct fall in the value of the property. The parking garage was a post-tensioned concrete structure, with post-tensioning tendons used as the primary reinforcement for the beams and slabs of the garage. The primary function of the grout that fills the pockets at the ends of post-tensioning tendons is to prevent the ingress of water and to provide long-term corrosion protection from the elements. Most engineers and architects have likely observed some degree of spalling at the surface of a reinforced concrete structure or element. There is a whole slew of risks involved with the breaking off of concrete walls and floors and proper care is required on a regular basis to eliminate them. The reinforcing structure upon which a building stands, when exposed to the atmosphere, becomes highly susceptible to corrosion, once the concrete starts flaking. While the damage done to property can be reimbursed, there is no compensation one can offer for a lost life or a disabling injury. A portion of the repair material, reportedly installed during the original construction, had debonded from the concrete substrate and had become loose. However, despite best intentions, concrete patch repairs often fail prematurely due to on-going corrosion around the periphery of the repairs. Usage of good quality tools along with monitoring each step of the process like reviewing the concrete mix is a good start in that direction. 2.) An additional consideration is that both delamination and spalling offer increased access of air and water to the reinforcing steel within that member; thus creating a cycle of corrosion and increased access of the corrosive elements exacerbating the process with each subsequent cycle. For the last 15 years CPT corrosion control solutions have been installed worldwide. Spalling or as it is popularly known as flaking concrete is when the concrete construction starts cracking and breaking off the structure, thus exposing the reinforcements used in its internal structure. The DuoGuard system can be used to stop areas of active corrosion in aggressive environments before expensive and disruptive spalling occurs. Falling concrete debris was noted by occupants when the building was only a few years of age (some of the residential units had not yet been completed or occupied). This can lead to the weakening of the constructions strength. Because of the nature of post-tensioning tendon installation, tendon replacement was difficult, and the estimated cost of repairs was significant when compared to the original construction cost for the parking garage. A portion of the reinforcement intended to be placed in the top portion of the cantilevered balcony slabs was not properly supported prior to concrete placement and had displaced such that portions of the reinforcement were ultimately located near the bottom of the slab. This is perhaps especially true for a high-rise residential structure located in a popular downtown area. The design life of a DuoGuard system is typically 20 years plus. 1.) In currently sound but contaminated areas of concrete, CPTPatchGuard Connect anodes can be installed to prevent further spalling.