Having joined the magazine in 2012, Claire developed her knowledge of the industry through the numerous company visits, exhibitions and conferences she attended both in the UK and abroad. A concrete screw should never be inserted into the same drill hole more than once under any circumstances. One of the disadvantages of these systems that must be mentioned is that the durability is reduced in case of heavy constant tensile load. But in a safety critical application this is probably a small extra cost to pay in relation to the whole job. The frictional resistance resulting from expansion forces generated between the anchor and the wall of the drilled hole during setting of the anchor may also be … The introduction of specialist anchor rods with a cone geometry enabled additional applications in cracked concrete. All of the chemical systems offer one major advantage: There is no expanding force when placing the anchors. Some manufacturers have developed faster curing systems bringing curing times for capsules (for use with special anchor rods in cracked concrete) down to as little as a matter of minutes and injection systems, for general purpose anchoring, to half the standard times – while still being slower than standard capsules. Capsule systems have always been less sensitive than injection systems to poor hole cleaning as the spinning action, together with the chunky aggregate, tends to draw some of the dust left on the sides of the hole into the mix, whereas injection systems simply lay the resin against any dust left behind. The curing time is the other bugbear of resin anchors whereas mechanical anchors may be loaded immediately. The first group contains, obviously, anchors that are expanded, some by being tightened – so called torque expanding anchors – such as throughbolts (stud anchors), shield anchors and sleeve anchors and others that are expanded by the displacement of an expander plug (e.g drop-in anchors); while the second group contains undercut and self-tapping screw anchors (frequently referred to as concrete screws) and which are also categorised as a type of undercut anchor. Here's the thing, though: not all objects in which screws are used already have threads. As a rule, mechanical anchors don’t react nearly as badly to drill holes that have been insufficiently cleaned. Epoxy resin chemical systems may offer the best load-bearing capacity, but their curing times are longer and can take up to an entire day in low temperature ranges. Capsule systems are not an option in this case. This is no mean feat, particularly when it comes to safety applications. One part of the mechanical anchor is activated via the torque applied during installation, the so-called torque controlled expansion anchor. The earliest type of ‘resin’ anchor (introduced into the UK in 1970 from Germany) carried all the chemical components (resin, aggregate and catalyst) within a capsule – originally of glass now sometimes of less fragile foil. This allows fixings to be carried out which would otherwise have required a great deal of effort. Mechanical anchors secure themselves by screwing/wedging into the object at the tip. Difference between Rock Anchor Bolts Mechanical Rock Anchors Claire prides herself on keeping readers well informed and up to date with the latest industry news. In order to benefit from their full effect, these anchors must effectively be pressed against the borehole wall, which can result in the formation of depressions in the concrete. Frame fixings are an exception, as the fischer SXRL is suitable for almost any type of anchor substrate. Mechanical vs. Chemical Anchor Fasteners - Which one should you choose? These are rarely used and, in my opinion there is always something better, so, with limited space for this article, I will restrict my discussion to the ‘spin-in’ type. The two zones combine into one long expansion element in solid building materials and aerated concrete, evenly distributing the loads into the subsurface. We provide both stocked and custom anchor bolts, anchor bolt assemblies, threaded rod, bolts, bent bolts, nuts, washers, turnbuckles, clevises … mechanical properties, consist of two figures, one on either side of a dot. Chemical Anchors Foil capsule adhesive anchor HVU & Adhesive anchor system HVU-TZ Page 196-197 ... resp. One part of the mechanical anchor is activated via the torque applied during installation, the so-called torque controlled expansion anchor. Using these anchors in hollow blocks or vertically perforated bricks is rather problematic. Care must be taken to remove all dust and debris from the hole. Other anchors expand by being hammered in using a hammerset tool, these are so-called deformation controlled expansion anchors. For these applications injection resin systems were developed and have largely displaced capsule systems in concrete too. At this point it’s also worth differentiating between different types of chemical anchors. An injection resin of the same basic resin may take typically four times as long. Using classic mechanical anchors in solid construction materials is associated with the risk of the stone splitting. The guide will ensure successful anchoring in solid and hollow cavity materials. Signing up to fastenerandfixing.com enables you to manage your account details. Anyone who is familiar with selecting suitable fixings knows that a large range of various systems are on offer, which can be confusing. As with many mechanical anchors, the disadvantage of these systems is that they can only be used at a set anchoring depth. The closest mechanical anchors get to this degree of flexibility is that many types of throughbolt are available in a variety of lengths – catering not just for different fixture thicknesses, but for different embedment depths and therefore loads as well. It is also quenched and tempered at 800 F leading to its strength. Concrete screws can even be reused, however this only applies to temporary connections on construction sites, for instance when anchoring formwork supports. Grade 8 (SAE J429) is a medium carbon alloy steel with one of the highest tensile strengths available. They are much more sensitive to poor hole cleaning than mechanical anchors and must be allowed to cure before they can be tightened or loaded. While the first mechanical anchors could only be used at a set predefined anchoring depth, anchors are now available that permit multiple or even flexible anchoring depths. While the type of anchor fastener has its own characteristics, the key differences between chemical and mechanical fasteners are listed below: Speed: you can only apply loads to chemical fasteners after the chemical has set, whereas one can apply loads to mechanical fasteners immediately after installation. Chemical bolts: The chemical bolt is used to resist the pull and the bolt itself to shear by the grip and the mechanical bite force between the concrete and the joint of the old and new structure. While chemical anchors could once only be used in temperatures above zero, fixings can now be carried out at temperatures of up to minus 30 degrees thank to high performance systems. Those responsible for choosing fixings for any application – let alone ones that are safety critical – are faced with a bewildering array of fixing systems to choose from and one of the most significant decisions, usually made very quickly by those with experience, is that between chemical and mechanical anchors. There’s only one real problem with mechanical anchors, without which there might be no need for chemical anchors. In most cases, the SXRL exceeds the load values of comparable frame fixings. More Another advantage of mechanical anchors is the fact that the clearance hole required for push-through installation is smaller than that of comparable chemical systems. One of the disadvantages of the mechanical fixings is their expansion behaviour while being positioned. So we’ve established that resin systems can be stronger, work at closer edge and spacing dimensions, and offer a solution for masonry. I need to get something off my chest here. In addition to the capsule systems, the market eventually saw the launch of less delicate film bag and cartridge systems. 1. With a minimum tensile strength of 150 ksi and a minimum yield of 130 ksi, Grade 8 has a higher tensile and yield strength than other steel grades such as Grade 5 and B7. Injection systems are the first choice when it comes to anchorings in masonry, and they are the only choice when it comes to approvals for specific uses. There is no need for a sleeve in solid bricks. To support those stresses you need enough base material around the fixing, so although edge and spacing distances for these fixing types are somewhat reduced compared to expansion anchors they may still be significant if loads are high. The chemical anchor bolt is a new type of anchor bolt that appears after the expansion anchor bolt. 2. If they are aware of the above ‘Pros’ and ‘Cons’ they can make a choice between alternative anchor types that is appropriate to the particular application. Hello Friends!I m MEP engineer working in Dubai. Advantages. There are two types of drilled-in anchors: mechanical and adhesive anchors. The anchor itself as well as the method of clearing the drill hole play an important role. This group includes classic bolt anchors as well as sleeve anchors. Adhesive anchors require a hole to be drilled, cleaned, filled with an adhesive, and then the anchor can be inserted. A step by step guide on how to ensure correct installation of chemical anchor studs and threaded bar and rebar. Difference between stereotyped chemical anchors and ordinary chemical anchors 1. This results in high expansion forces during the anchor’s activation, which requires sufficient component volume around the borehole in order for the concrete to be able to absorb the ensuing tensile stress without damage. 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