Unit #2 Reinforcing Steel Key Takeaways • Methods of reinforcing concrete • What loads and forces are we trying to counteract • Where is most reinforcing located in a structural element This Unit... • Concrete Introduction • Concrete Components & Properties • Common Tests and Testing Procedures • Concrete Placing Techniques • Concrete Finishing and Curing • Below Grade Concrete Formwork • Concrete Reinforcing • Admixtures The Most Common Method of Reinforcing • …is to use reinforcing steel or rebar http://www.vukasteel.co.za/wp-content/uploads/2012/09/Steel-Reinforcing.jpg Rebar… • Consists of deformed extruded steel rod available in many sizes • Usually cut to specific length, and • Bent into specific shapes • Rebar is available in several different types and grades of steel • A variety of coatings are also available Deformed? •Increases surface area contact with concrete to allow full integration with concrete around it http://www.resteel.com/wp-content/uploads/2014/03/ReSteelReinforcingBar.jpg Strength Rebar is available in grades and specifications that vary in… • yield strength • ultimate tensile strength • chemical composition and • percentage of elongation Strength Rebar achieves its goal of reinforcing concrete only when there is a proper bond between the deformed bars and the fresh concrete. It must be clean (ie. no concrete splatter on it), free of dirt and generally well cared for. Think about how hard that could be when we talk about column and wall dowels sticking out of slabs or footings… Strength http://www.frpdistributors.com/gfrp-vs-steel/gfrp-vs-black-steel Rebar is a Commodity • Rebar is made of steel • Steel is a commodity • Commodity are traded on the stock markets that fluctuate daily (NYSE, TSX, S&P 500, etc.) • How do we buy rebar for large jobs if the price is changing daily? Types •Black •Stainless •Galvanized •Epoxy Coated •Fiberglass http://www.sellwoodbridge.org/files/phase3/blog/20140324a.jpg Black • There are different grades of black rebar • Most commonly used are grades 400R (Regular) and 400W (Weldable). • The grade numbers (400) indicate the minimum yield strength in MPa (megapascals). https://elebia.com/wp-content/uploads/2017/07/rebar-steel-bundles.png Black • The # = Yield strength (Mpa) • The Letter R = Regular (Black steel) • The Letter W = Weldable bar • Most common grade is 400R Rust •Surface rust on black-steel rebar is common and in fact can enhance the bonding of the steel to the concrete •Corrosion will not continue once the bar is in a dry, non-oxygenated environment •Like in concrete for example https://www.gardenguides.com/how_8751855_use-rusted-rebar.html Stainless • Used in highly corrosive areas and non-magnetic applications https://stainlessrebar.com/ Galvanized • Zinc hot dipped ‘galvanizing’ • Emersion process creates a metallurgically bonded protective coating to steel • An alternative to epoxy coated rebar for concrete structures in corrosive environments http://www.midvalleyrebar.ca/gal vanized_rebar.shtml https://www.galvanizedrebar.com/field-handling/ Epoxy Coated •Used in structures exposed to de-icing salts and corrosive environments. •Coated with organic coating known as fusion bonded powder epoxy. •Applied by electrostatic spray. https://precast.org/2015/09/working-with-epoxy-coated-rebar/ https://www.harrissupplysolutions.com/epoxy-coated-rebar.html Fiberglass • Cheaper and technically stronger alternative to steel…has been around since the 1970’s • Some brands are flexible therefore bending can be done on site • Can be more difficult to control location of bar during pouring process due to it’s flexible nature Fiberglass https://img.diytrade.com/seimg/1986782/41085288/FRP_Fiberglass_Bars_Used_in_Concrete_Reinforcement.jpg Bar Sizes https://www.ebay.co.uk/itm/Mild-Steel-REBAR-6-Sizes-available-12-popularlengths-to-choose-from-/362021575460 Common (Canadian)Bar Sizes Common Metric Bar Size Data Bar Markings (www.rebar.org/techincal data) Mills •Producing mills are registered members of the Reinforcing Steel Institute of Canada •See www.rebar.org Bar Bends •Standard bar bends allow consistency •Only the dimensions vary Bar Bends •Are usually done in a manufacturing environment by the rebar supplier and shipped to the site •Bars might also be site-bent… Each Bar… • Must be detailed… • Exact length must be specified • Type of bend and bend dimensions • Exact location of each piece must be noted • Each bundle of bars is tagged and cross referenced to bar placement info • Check out the sample going around the class… Lapping •Continuous bars must either •Lap or be coupled together •Lapping is generally more economical •Minimum lap distance for any bar is 12” •Lap length changes based on size of bar Lapping http://8.gregvan.com/images/foundation12302009%20014.jpg Couplers • Couplers are used to make large, continuous structural elements of a building (think about columns in a highrise) without lapping. Lapping takes up space…think about it…to the white board • Several different types of couplers are available • Threaded • Mechanical (Bolt-on) • Wedge Couplers Couplers • Threaded https://www.aleono.com/wp-content/uploads/2017/03/Aleono-Tapered-Thread-Rebar-Coupler.jpg http://image.made-in-china.com/2f0j00RCKTnsYdEvhG/Rebar-Coupler-001-.jpg Couplers • Mechanical (Bolt-On) https://i.ytimg.com/vi/oIPDGiuHdII/hqdefault.jpg https://www.ancon.co.nz/system/uploads/content/summary_image/1660/open_graph/mbt_rebar_coupler-ce8d0e.jpg Couplers • Wedge Couplers https://www.erico.com/catalog/variants/PH1465m.jpg Tying Rebar • Rebar laps and intersections must be tied to hold the bars together during the concrete placing process http://www.bnproducts.com/wpcontent/uploads/2015/05/Depositphotos_152741646_l-2015.jpg Tying Hand Tying Machine Tying Rodbusters • Who are they? • What are their work hours? • Why? Tie Wire • Low carbon steel • Very flexible yet strong • Must use appropriate wire for the steel being tied… https://cdn.shopify.com/s/files/1/0006/2275/5901/products/tie-wire-epoxy-coated_530x@2x.jpg?v=1523983377 https://www.wallywiremesh.com/wp-content/uploads/2017/12/rebar-tie-wire-1-2.jpg Chairs and Supports • Come in many different types, materials, sizes etc. • Used to keep rebar in place during placing process • On big projects chairs may even be bent out of rebar itself if their size necessitates Chairs and Supports https://images.homedepot-static.com/productImages/22e1d7e2-b31c-482c9c3c-98baaf24c308/svn/hercules-rebar-remesh-912-64_1000.jpg Welded Wire Mesh •Pre-welded mesh products are available for light reinforcing to slabs on grade •Comes in various configurations •Comes in sheets or coils(rolls) Welded Wire Mesh (WWM) https://victoria.meshstore.com.au/wp-content/uploads/sites/4/2017/09/W025GB.jpg Various sizes available The Rebar Drawing Process • Considering all of the components and types we’ve just discussed, who is typically responsible for determining size, quantity, location of rebar and accessories? • What is the flow of information for this process (who-who-who-who)? • How long does this process (prior to even getting the steel fabricated and delivered to site) take? The Rebar Installation Process • Once all rebar has been installed as per the ________________and ______________ drawings • The inspection firm working for the ____________ or the ____________ must be called to perform an inspection and sign off the rebar before the concrete is poured. In the event the structure fails, this signoff is your only proof it was done correctly. Concrete Cover on Rebar • Concrete cover is the specified amount of concrete that must be between the outside face of the concrete element and the outside face of the rebar within it. • It is prescribed by the_________________ and is require to prevent ________________ and protect against _______________ • It may be different for different areas of the building or structure because __________________ Concrete Cover on Rebar •ACI says… https://www.eng-tips.com/viewthread.cfm?qid=433795 Concrete Cover on Rebar • In mm for Canadians … RCC = Reinforced cement concrete PSC = Prestressed concrete (more next semester) https://theconstructor.org/wp-content/uploads/2013/02/clip_image002.png Concrete Cover on Rebar http:/www.acivilengineer.com/2017/04/concrete-cover.html/ Rebar Video • Click Here for Below Grade Rebar Installation Video • What did they do that we like? • What did they do that we didn’t like? WWM Video • Click Here for Welded Wire Mesh Concrete Pour with In Floor Heating Video • What did they do that we like? • What did they do that we didn’t like? • What must you remember when using WWM? Recommended Reading More Studying…this is a big test…30%...take it seriously
