Sulfate attack in cement, mortar and concrete. Joined: 23 Nov 2009 Messages: 15 Thanks Received: 0 Location: Cheshire Country: Hi, My fiancee and I have just bought our first house, and were aware from the point of survey that it had problems with the floor slab downstairs. The primary causes of chemical attack on concrete include chloride ion penetration, sulphate attack and carbonation, but technical advances in cementitious coating technology have allowed extended service life solutions to be implemented. This causes the cracks and damage that is commonly seen across Northern Ireland property. The process is to take out and replace the slab but this would be overkill I think. Sulphate attack on concrete is a chemical breakdown mechanism where sulphate ions attack components of the cement paste. Sulfates, chemicals and high acidity can cause expansion, cracking and damage to concrete. Next. (Basically it was going to happen regardless of any membrane being there). Brushed Concrete Specialists . Sulphate attack in concrete or mortar based on Portland cement is generally attributed to the formation of expansive ettringite (AFt-phase) and gypsum. Sulfate attack in concrete and mortar. Upon hydration, the main reaction products are a calcium silicate gels (C-S-H) and calcium hydroxide Ca(OH)2 or CH in cement chemistry. The sulphates react with the concrete causing it to expand. Provides a clean heavy duty Industrial wearing surface. I'd be surprised if it was a concrete floor with no DPM that was then suffering sulphate attack. Sulfate attack in concrete exposed to externally derived sulfates generally causes concrete deterioration due to the expansive growth of ettringite or thaumasite within a concrete surface, often leading to the formation of surface-parallel cracks infilled with sulfate reaction products. You just clipped your first slide! This is where it became common to use what is termed “red ash”. Excavate all the sulfate-bearing fill material. Sulphates react with concrete which causes it to expand. Discussion in 'Building' started by Credulous999, 23 Nov 2009. I deal with sulphate attack in properties from the 50's, 60, and early 70's and the time in which the problem shows itself can vary a great deal. Use of fill material in house construction first became common in mid-1940s. Hardcore containing sulphates is now prohibited from use beneath ground floor slabs. The methods given below can be adopted to protect concrete from sulphate attack. Sulphate Attack >> Sulphate attack is a chemical reaction, affecting the concrete in the floor construction of properties. It all depends on seasonal ground moisture levels, so even from a 50's property, it may be OK one year, but the floor … Clipping is a handy way to collect important slides you want to go back to later. I had an offer accepted yesterday on my first house which also has a known sulphate attack to the ground concrete floors, the price was dropped to more than cover the costs of the repair work. These sulphates react with the Tricalcium Aluminate in ordinary portland cement (OPC) to form Ettringite, a crystal that expands as it grows, in the process often causing substantial damage to the concrete floor slab. Spotlight Project – Sulphate Attack. A sulphate resistant, fibre reinforced shrinkage compensated thixotropic mortar for the repair of concrete – class R4. Providing top quality concrete flooring inside or out. Sulphates present in contaminated hardcore, together with a source of moisture it reacts with the cement in the concrete causing it to expand and crack. 3 posts • Page 1 of 1. by kevpeak » Mon Jul 09, 2007 10:07 am . The most efficient method of resisting the sulphate attack is to use cement with the low C 3 A content. Visually there is no structural damage and the floors don't appear to have cracks or movement. What is Sulfate Attack ? This attack was discovered 9 months ago by the surveyor of a previous buyer who subsequently dropped out due to insufficient funds to rectify the problem. Now customize the name of a clipboard to store your clips. With the presence of sufficient sulphate, the metastable monosulphoaluminate transforms into ettringite. Our recommended procedure is: Remove the concrete floor slab. Microscopic view of Sulphate stals in concrete Sulphate attack is a chemical reaction, affecting the concrete in the floor construction of properties. The sulphate ions intrude into the concrete and react with portlandite Ca(OH) 2 to generate gypsum. Design Sulfate Class (DS Class) - It is a site classification based on the determined sulfate (including Potential sulfate) contents of the ground and/or groundwater. A sulphate attack occurs when the infill material beneath the slab contains sulphates and these are taken up into solution by ground moisture, which then migrates into the concrete which forms the floor slab. Over 35 years of concrete flooring and finishing experience. A sulphate attack occurs when hardcore that contains sulphates was used for a the base of concrete floor slabs in a building. Another serious problem is sulphate attack on ground floor concrete slabs. I have been told that i need to dig out the concrete and the demolition rubble it sits on my approx 450mm. Moisture can carry the sulphates through the concrete slab, causing them to evaporate at the surface, leaving behind salts. A well designed, placed … Quality Concrete. In the immediate post-war period, when construction materials were in short supply, solid floors, comprising a concrete floor slab over fill material, largely superseded suspended timber floors that were typically used in the 1930s. Welcome. 3 Sulphate Attack Damage to floor slabs indicative of sulphate attack1 is a commonly encountered problem in houses of this age, style of construction and often found on estates developed in the 1950‟s and early 60‟s. Areas of heavy mining, created colliery shale, which often contains sulphate, which can lead to the problematic “sulphate attack”. The most widespread reported failures to concrete floor slabs involve the use of partially burnt colliery shale (Red Shale). Following on from our recent blog on investigating sulphate attack in solid concrete floor slabs; what we didn’t mention in that blog was that we got the lab results back, which proved what we suspected, that there were incredibly high levels of sulphates in the hardcore material and the failed concrete floor slab. A full removal provides complete assurance of future stability and caters for any uncertainty as to the sulfate attack mechanism that may remain after site investigation. The process involves taking a sample of hardcore from the property and having the sample analysed by a reputable laboratory. Mapei Mapegrout T60 is a single component, sulphate-resistant, fibre-reinforced, shrinkage compensated, thixotropic mortar for the repair of concrete and reinforced structures. Concrete Floor with Suspected Sulphate Attack. Previous. Sulfate attack can be 'external' or 'internal'. Sulphate Attacks; Concrete Contractors; Concrete Experts. In the case of flooring it became common to use fill materials below a concrete floor. Sulphate Attack Prevention Sulphate attack is the decline of concrete over a period of time, as a result of a chemical reaction between sulphate ions and the components of hardened concrete. Sulphates present in contaminated hardcore, together with a source of moisture it reacts with the cement in the concrete causing it to expand and crack. The slab needs moisture to activate the attack IIRR so this could wick up from below. I have just been to view a house that is cash only buyers due to it being diagnosed with sulphur attack in the concrete slab floors. Download project PDF. Available from Promain.co.uk . Sulphate attack on concrete floor. It has been found that a C 3 A content of 7% gives a rough division between cement of good and poor performance in sulphate waters. Sulphate attack is caused when sulphates contained within the concrete aggregate contain sulphates or the hardcore sub-base below the concrete contains sulphates. Cement is composed of mainly two minerals tri-calcium silicates (C3S) and di-calcium silicates (C2S). I have a problem with the lounge area of my bungalow built 1960 in that there is a bulge in the floor and cracks on the exterior walls have occurred causing damage to brickwork. Concrete deterioration exists on a global scale and can severely affect the durability of reinforced concrete structures. It can occur when the hardcore beneath the concrete contains sulphates – typically from mining and industrial by-products, quite commonly used between 1945 and 1970 – and these reach the concrete above, typically in the presence of moisture and where there is no damp-proof membrane. Does anyone know how much it would cost to A) dig it all out B) install new hardcore, Visqueen, Kingspan insulation and new concrete slab (100mm) and a … Power Floated Concrete. Sulfate attack is a common form of concrete deterioration. The sulphate in the hardcore infill when combined with moisture (water) can cause the sulphate to migrate into the concrete floor slab causing cracking and possible upward movement of the floor slab and, in extreme cases, cracking and lateral movement of the brickwork below Damp Course level. Apperently it's a common problem in the area The agents have had a quote for £9k to replace the floors. More particularly in industrial areas such as those around Birmingham and associated areas. External: due to penetration of sulfates in solution, in groundwater for example, into the concrete from outside. In damp or wet conditions, the underside of the concrete floor is vulnerable to sulphate attack, with needle-shaped ettringite crystals growing and causing high internal stresses. Internal: due to a soluble source being incorporated into the concrete at the time of mixing, gypsum in the aggregate, for example. Sulphate attack on ground floor slabs is a very serious problem which can cause structural damage to the main walls of a building. It is also dependent on the type of site, presence or absence of magnesium ions, pyrite and for pH less than 5.5 chloride and nitrate ions. Sulphur attack concrete floor. Credulous999. If sulphate attack is in your concrete floor slab a membrane may not be of great relevance. If the floor slab becomes damp then a sulphate attack can occur. We pride ourselves in offering fast, efficient and reliable service. The downstairs of the house … Blythe Building Consultants have specialised in Sulphate Floor Testing for over 25 years and have carried out over 16,000 tests. The house that we have just bought has got sulphate attack so all the ground floor has expanded, cracked and pushed my walls out. But it may be argued if sulphate attack inherent in the slab when laid the membrane is a red herring. Sulphate attack occurs when the contents of the hardcore fill material that has been used beneath the floor slab contains Sulphate and there is enough moisture in the fill to cause them to attack the concrete floor slab causing heave. Sulphate attack is a major difficulty which has a local effect on the constructional materials, specially the concrete. Use of Sulphate Resisting Cement. The problem occurs when the fill material (hardcore) beneath the slab contains sulphates and these migrate into the concrete. 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