PSI Cementitious Patching Guide

Transcription

1 PSI Cementitius Patching Guide Material Use TuffPatch VOH fr Vertical and Overhead Repairs and TuffPatch DOT fr any Hrizntal r frm and pur applicatins. Use neat materials fr applicatins up t 2 inches thick. Use extended materials fr repairs exceeding 2 inches. Cnsult PSI s technical data t determine minimum thicknesses when determining minimum acceptable thickness, especially when wrking with extended materials. Fr ease f applicatin in vertical and verhead repairs, limit lift thickness t 2 inches. Rughen the surface f materials that will receive subsequent lifts, and ensure substrate is clean and saturated prir t placing additinal repair material. Repair Prcedure Surface preparatin: Remve any damaged r lse cncrete. Avid damage t sund cncrete that is t remain in place. Unless therwise apprved by the Engineer, use nly hand tls r pwer-driven chipping hammers (15-lb. class maximum) t remve cncrete. If mre than 1/2 the perimeter f any mild reinfrcement is expsed r if the expsed bar exhibits significant crrsin, remve the cncrete frm arund the entire bar. Prvide ¾-inch clearance r 1.5 times the largest sized aggregate in the repair material, whichever is greater, between the steel and surrunding cncrete t permit adequate flw f the repair material. NOTE: A gd rule f thumb is that adequate clearance is attained when yu are able t wrap yur fingers arund the bar. Ensuring yu can grab the bar is a simple but highly effective methd f cnfirming there is adequate clearance t permit the repair material t flw arund the expsed bar. D nt chip arund prestressing strands that are expsed anywhere away frm the immediate end f the member. Cnsult the Engineer when patching an area in which prestressing strands have been expsed. When repair dictates that chipping ccur arund

2 expsed strands, the Cntractr must avid striking the strands directly r therwise causing damage that culd lead t wire r strand breaks. Use RustCheck, abrasive blasting r ther apprved technique t remve rust frm expsed steel surfaces. Saw-cut the patch perimeters t eliminate feathered edges and t ensure that the repair material will be applied in depths n less than ½-inch. Handheld grinders r saws may be used t square the patch perimeters. D nt ver-cut the patch perimeters at the crners f the repair areas. When practical, undercut the patch perimeter at an apprximate angle f 30 degrees such that the prfile will help hld the patch material in place. Rughen the substrate t ensure that there will be a mechanical bnd between the patch material and the parent cncrete. Thugh difficult t quantify and measure, Cntractr shuld attempt t attain a minimum surface rughness prfile f 1/8 inch r CSP (Cncrete Surface Prfile) 6 per ICRI. If the damage ccurs at the end f a member and prestressing strand is expsed, recess the strands a minimum 3/8 inch using a trch r ther apprved methd. D nt verheat r damage the surrunding cncrete. NOTE: In the past sme Cntractrs and Fabricatrs pted nt t recess prestressing strands in spalled areas s the prtruding sectins culd serve as dwels fr the patch material. While the strands wuld serve well as dwels in thse circumstances, they culd be expsed t misture and chlrides if the patch fails ver the life f the structure. Fr that reasn, it is mre imprtant that the strand be cmpletely recessed. Install anchrs t hld the patch material in place. Mechanical ties that bind repair material t the substrate can greatly decrease the risk f future delaminatin and spalling. Fr mst intermediate repairs, expsed steel serves that purpse. Hwever, there are scenaris in which n reinfrcement is expsed and thickness f the spall dictates that cementitius repair material be utilized. In such cases it is necessary t install anchrs t help mechanically tie the patch material t the parent cncrete. When n mild reinfrcement is expsed, install anchrs at n mre than 4 inches n center each way r as required by the Engineer. The anchrs must cnsist f ne f the fllwing: Stainless steel expansin anchrs. The Cntractr may prpse t use ther anchrs, such as galvanized r zinc-painted metal lag blts, all thread, cil rd, etc.

3 Rebar r threaded stainless steel pins (1/2-inch diameter minimum) anchred in place using TuffPxy 3 FS, TuffPxy 3 r TuffPxy 8 with aggregate. Remve any epxy that leaks nt the patch substrate area after the anchr is placed. If installing expansin anchrs: Drill and clean the hles as required by the anchr manufacturer. D nt use a drill bit that has a larger diameter than that required. Embed the anchr the minimum amunt required by the manufacturer. Hwever, the anchr shuld nt be driven further than necessary. In rder t functin as intended the head f the anchr must prtrude int the repair material. If installing dwels, blts, all thread using structural epxy: Drill a hle 1/8 t 1/4 inch greater than the dwel diameter. Make the hle deep enugh t permit a minimum 2-inch embedment f the dwel r twice the depth f the surrunding patch. Remve any cntaminants frm the hle using a brush r ther mechanical cleaner. Just prir t installing the anchr, clean the hle using a high-pressure air cmpressr equipped with filters t remve all il frm the cmpressed air. Dry the cncrete surface inside the hle prir t installing the dwel. Fill the hle apprximately 1/3 full with structural epxy. Twist the dwel as it is inserted. Ensure that the space between the dwel and the cncrete is cmpletely filled with epxy. Remve all epxy frm the cncrete surface that leaks frm the hle after the dwel is inserted. NOTE: When using epxy, it is difficult t prperly drill and clean the anchr hles and t place a prper amunt f material t keep the anchrs in place. If there is t little epxy, the anchr will nt have enugh pullut resistance. If there is t much epxy, the material can leak ut f the anchr hle and create a bnd breaker n the patch substrate. It is imperative that the Cntractr fllw the manufacturer s instructins and the abve guidelines. Where anchrs are installed, ensure there will be a minimum cverage f 1/2 inch fr stainless steel and 1 inch fr nn-stainless steel after the patch material is applied. Oftentimes anchrs r dwels d nt prtrude far enugh frm the cncrete substrate, leaving large depths f patch material unanchred t the parent cncrete. Cntractr shuld install anchrs with the expsed edge f the patch in mind, nt the utside surface f the parent material.

4 Substrates must be clean and sund. Remve any cntaminants, including laitance, il, dust, debris, r ther freign particles. Just prir t patching, blast the repair area using a high-pressure air cmpressr equipped with filters t remve all il frm the cmpressed air. Mixing: Fr small applicatins (less than 1 cubic yard ttal) use measuring cups r cntainers t determine the prper quantity f each cmpnent per the manufacturer s requirements, then dispense int a clean cntainer. Mix the cmpnents thrughly until they are well-blended (3 minutes minimum) using a lw-speed electric drill ( rpm) and a clean Jiffy type mixing paddle. D nt mix repair mrtar r cncrete by hand. D nt estimate the prper amunts while adding the different cmpnents. Fr vertical and verhead applicatins, Cntractrs ften need t limit the amunt f water r liquid cmpnent in rder t achieve a stiff mix. Cnsult PSI s literature fr minimum requirements. If extending the mrtar t prduce cncrete, add aggregate and mix in accrdance with the manufacturer s requirements. When mixing mre than 1 cubic yard use a mrtar mixer, vlumetric mixer, r ther methd apprved by the engineer. Many cementitius repair materials have relatively shrt wrking times (15 t 30 minutes). D nt mix materials until the surface preparatin is cmplete and the substrate is ready fr applicatin f the repair material. Mix nly the amunt f material necessary fr immediate applicatin. D nt attempt t make the material wrkable by ver-mixing r adding additinal liquid after it has begun t set. Overmixing can reduce the cmpressive strength and increase the permeability f the material. The beneficial prperties f bagged mixes are ften lst when the repair material is retempered.

5 Applicatin: Ht and cld weather applicatin: The temperature f the patch material and the cncrete substrate at the time f applicatin must be between 40 F and 95 F. Cntractr must als adhere t manufacturer limits if they are mre stringent. D nt apply patch material when the ambient temperature in the shade is belw 40 F and falling. Patch material may be placed when the ambient temperature in the shade is 35 F and rising r abve 40 F. Shade the repair material cmpnents and the patch substrate if the ambient temperature is abve 100 F. In almst all cases, the repair material shuld be applied ver a Saturated Surface Dry (SSD) substrate. Obtain an SSD cnditin using ne f the fllwing methds: Hrizntal: Pnd water ver the substrate fr a minimum f 24 hurs if pssible. Vertical: Several minutes befre patching, apply high-pressure water blast t the surface fr a brief perid (1 r 2 minutes depending n the prsity f the cncrete). An SSD cnditin is achieved if the surface remains damp until the patch material is applied. Surface may be damp, but must be free f standing water. D nt use a prprietary epxy bnding layer in lieu f an SSD substrate unless apprved by PSI. If use f a bnding agent is authrized/required, mix it in accrdance with the PSI s requirements. If trwel-applying the repair material: Apply ver a bnding layer, which typically cnsists f a scrub cat brushed int the SSD substrate. The scrub cat cnsists f a thin layer f repair mrtar that is pushed int the surface using a stiff brush, cmpletely cvering the substrate and filling all vids. Ensure that there is nt an excess amunt f water n the brush used t apply the scrub cat. D nt dilute the scrub cat material with additinal liquid. Apply the repair material while the bnding layer is still wet (scrub cat) r tacky (prprietary bnding layer). Apply in minimum 1/2-inch and maximum 2 inch lifts unless therwise apprved by PSI. Fr multiple lift applicatins, rughen the surface f the preceding lift befre it has reached initial set. Wait until the preceding lift has reached initial set (30 minutes minimum) t prevent sagging prir t applying the next lift.

6 Wet the surface just prir t applying the subsequent lift. If patching, using a frm-and-pur methd: Prepare and install the frms prir t mixing the repair material. Ensure that frms are tight enugh t prevent grut leakage. Place the repair material in the frms while the bnding layer is still wet (scrub cat) r tacky (epxy). Cnslidate the material by rdding, vibrating, and/r hammering the frms. D nt ver-vibrate the mix. If required by the Engineer, determine the cmpressive strength f the patch material by making cncrete test cylinders r mrtar cubes. Curing: Failures ften ccur in cement-based repair materials due t inadequate curing. Large plastic shrinkage cracks can develp if rapid misture lss ccurs befre the patch has the capacity t resist tensile lads that develp as a result f the shrinkage. Drying shrinkage can lead t elevated stress levels that cause cracking within the repair material r at the bnd line between the patch and the parent cncrete. It is paramunt t the lng-term success f the repair that prper mist curing cmmences as sn as pssible after applicatin f the repair material, and that it cntinues fr a sufficient amunt f time thereafter. After placing repair material, use TuffCure P nn resin based curing cmpund r mist cure expsed patch material surfaces fr a minimum f 72 hurs using wet mats, water spray, r pnding. D nt use any resin r acrylic curing cmpunds in lieu f mist curing unless apprved by PSI. If use f anther curing cmpund is authrized, any remaining residue must be cmpletely remved after the required curing perid. TuffCure P requires n preparatin befre applying any tp cating r paint. In frm-and-pur applicatins, leave frms in place fr a minimum f 72 hurs after placing the repair material. Place wet mats n expsed sectins and ver the penings used t place the material. The Engineer may reduce required curing time in sme cases, such as when there is a need t return the member t service quickly r when CFRP will be placed ver the patch material. D nt allw cncrete surfaces t becme dry during the specified mist curing perid. Ensure that wet mats are kept wet during the entire cycle r reapply TuffCure P.

7 Insulate the patch material t ensure that there is adequate heat fr curing if ambient temperature is expected t fall belw 50 F. If using artificial heating methds, d nt heat the air arund the repair material t abve 130 F. Finish Ensure the patches clsely resemble the surrunding cncrete. Blend in the repair area if after cmpletin, the patch material des nt clsely resemble the surrunding cncrete. The Cntractr may use a slurry cat finish t blend in the patch. Patches shuld nt be easily discernible if viewed frm mre than 25 feet away.