CORE CONSOLIDATION OF HERITAGE STRUCTURE MASONRY WALLS & FOUNDATIONS USING GROUTING TECHNIQUES - CANADIAN CASE STUDIES. Paul A.

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1 CORE CONSOLIDATION OF HERITAGE STRUCTURE MASONRY WALLS & FOUNDATIONS USING GROUTING TECHNIQUES - CANADIAN CASE STUDIES Paul A. Jeffs ABSTRACT Damage to masony walls due to deteioation of thei ubble coe can be a majo concen and, in the event that consolidation techniues ae detemined to be necessay, it is impotant that the selected stategy should conside the need to maintain the existing aesthetic uality of the masony, as well as its stuctual integity - both duing and afte the gouting opeations. In paticula, it is geneally ecognized that a estoed stuctue should be able to adeuately accommodate stesses ceated by diffeential movement of components duing changes in tempeatue and dynamic loading conditions. The techniues that ae available fo coe consolidation ae discussed, togethe with Canadian case studies which illustate specific stategies that wee designed to aest deteioation while poviding impoved duability and adeuate movement accommodation. The many factos that wee consideed duing the development of the gouting stategies ae evaluated, including minimum intevention, stuctual stability, investigation methods, desiable popeties of gouting mateials and the impact of placement techniues. Also eviewed is the use of moden nondestuctive methods that wee used to evaluate the condition of the hidden coe and detemine the location of voids. A cement-based cellula foam gout that best matched the citeia of desied popeties and pefomance euiements will also be examined. Key wods Consolidation; Cellula Foam Gout; Coe Rubble Gouting; Foamed Gout; Heitage Stuctues; Gound Penetating Rada; Impact-Echo; Investigation; Lime; Masony; Non-Destuctive Testing; Stone Walls; Restoation; Stabilization PJ Mateials Consultants 11 Wagones Tail, Guelph, Ontaio Canada, N1G 3M9 pjeffs@pjmc.net

2 INTRODUCTION The exteio masony walls of many olde Canadian buildings wee taditionally constucted using dimension stone units built as double wythes with ubble filled inne coes - fo at least the foundation potion. Duing constuction the inne coes wee filled with stone off-cuts, ubble etc., bound with weak, lime-based gouts o motas. Unfotunately, lime bindes feuently fail to adeuately cabonate befoe the mota joints deteioate sufficiently to allow wate to penetate the coe and initiate degadation. Voids can fom as the gout o mota disintegates and subseuently washes out of open joints o accumulates as a loose powde at lowe levels. Ove many yeas, the masony walls can become futhe destabilized as the loosely bound ubble becomes mobile and futhe voids fom. Often the loading conditions and diffeential movement ae sufficiently accommodated by the weakened masony - but, sometimes, the change in distibution of loads can cause concentation of stesses which, in tun, can cause bulging, displacement and/o cacking of masony units. Although gouting voids within the inne coe ubble to stabilize masony walls is a long established pactice, methods have changed ove the yeas - and these have anged fom histoic gavity gouting utilizing hand placement techniues though to the use of moden pumping techniues that include hand and powe-opeated diaphagm pumps, aeated pessue systems and vacuum systems. (1) KEY CONSIDERATIONS The autho believes the following epesent the key factos that affect the success of a gouting opeation and should be consideed duing the development of masony coe consolidation stategies:- Investigation and evaluation Gout mixtue composition - Fluid popeties - Physical hadened popeties Gouting methodology - Mixing euipment - Pumping euipment - Pumping pessues - Gout confinement Method of maintaining masony integity Pehaps the most impotant consideation is the selection of an expeienced specialist gouting company that has a suitably tained wokfoce and the special euipment necessay fo the poduction and placement of the gout in an effective and safe manne. This, of couse, can be a poblem whee expeienced contactos ae not available locally - o when peualification of contactos o sub-contactos is not possible. Howeve, it is undesiable fo this type of wok to be caied out by companies with little o no expeience o expetise.

3 Investigation and Evaluation Befoe it can be detemined whethe o not coe consolidation is necessay, it is impotant that the causes of any masony damage ae fully investigated and identified. The investigation should include eseach into the histoy of the stuctue to detemine whethe events in the past may have had an advese impact on the condition of the masony. (Case Study One povides an example.) If possible, details concening pevious estoation wok should be evaluated - paticulaly if this included coe consolidation wok o below gade watepoofing. If possible, the investigation should attempt to uantify the volume of hidden voids and thei locations - although gouting often takes place by pumping the maximum volume of gout to efusal though unifomly spaced injection tubes (pots).the investigato should also conside the likely impact that changes in masony popeties can have afte consolidation wok has taken place. (Fo example, potential changes in the way in which diffeential movement is accommodated between components.) Gout Mixtue Composition Many diffeent mateials have been used fo consolidation gout mixtues and expets opinions have vaied widely egading what makes the best composition. Some of the mateials that have been incopoated into gouts - o have compised the gout mixtue - include, but ae not limited to:- Lime Mixtues Potland Cement Mixtues Cement/Lime Mixtues Cement/Pozzolan Blends Lime/Pozzolan Blends Bentonite o Gelling Agents Cellula Foamed Cement Gouts Taditionally, consolidation gouts wee based on lime, and even today this binde is still pefeed by many expets. Natually occuing pozzolanic mateials and cushed clay bick have been epoted to povide beneficial flow, anti-segegation/bleeding and stength development popeties when blended with hydated lime, (2) although manmade supplementay cementing mateials such as fly ash and silica fume have also been used o investigated. (1, 4) Fly ash has been epoted to povide beneficial popeties when used with both Potland cement and lime, but was found to be less beneficial when used with lime alone. Howeve, some consideable vaiation between mixes wee also epoted, togethe with inceases in long tem stength. (3) The use of Potland cement as the pimay binde can contibute to geate than desiable stength and shinkage - unless special admixtues o techniues ae used. Bentonite has been used to educe (1, 3) stength and to povide impoved esistance of the gout to bleeding and segegation. The intoduction of soluble salts fom the use of nomal gey Potland cement can be detimental, although this concen can be educed o eliminated by utilizing white cement. Howeve, thee is always a dange that wate injected with the gout can mobilize salts within the masony that could migate to the exteio sufaces. The use of cellula foamed cement gouts will be discussed in Case Study One. Whicheve gout mixtue is selected, the following popeties ae geneally ecognized as being citical:-

4 Plastic Gout Popeties High Fluidity - to povide adeuate flow while using low pump pessues; Good Penetability - to fill small gaps and inteconnected voids; Low Segegation/Settlement - to maintain plastic volume and consistency; Hadened Gout Popeties Low Shinkage - to maintain volume without development of stess o loss of bond and to educe moistue penetation though post-shinkage cacks/gaps; Stength Consideably Lowe than the Masony Units - to absob stesses athe than tansfe them to masony units; Compatibility with Masony Units - to povide adeuate composite movement accommodation, simila moistue vapou tansmission popeties and low mobility of soluble salts; Adeuate Duability - by poviding feeze/thaw stability and low pemeability. The desied stength of the gout will depend on the popeties of the masony units. Vey little published data is available in this egad, although design compessive stengths of less than 2 N/mm 2 28-days have been epoted by some eseaches (2) while othes epot stengths that ange fom 3 to 6.5-N/mm 2 (450 to 950- psi) (4) CASE STUDIES The factos that should be consideed duing the development of estoation stategies can pehaps best be eviewed by examining thee Canadian case studies. Case Study One - Owens At Galley, Mount Allison Univesity, New Bunswick The Owens At Galley is the oldest univesity at galley in Canada. (See Photogaph 1.) Oiginally named The Owens Museum of Fine Ats, it was officially opened on May 28th 1895 to accommodate the School of Fine Ats and Applied Ats within Mount Allison Univesity in Sackville, New Bunswick. The building was constucted using a light olive sandstone stone obtained fom uaies within the neaby community of Rockpot. Photo. 1. Owens At Galley, Sackville, New Bunswick

5 Oiginal constuction documents wee not available at the time of the investigation of the damage that became appaent duing the mid 1990's, but a eview of photogaphs taken duing the oiginal constuction wok confimed that the foundation walls wee constucted as a double wythe with an inteio ubble coe. Reseach also confimed that oof e-constuction wok was caied out duing the ealy 1970's and subseuently this was poved to have contibuted to majo damage of the masony and, in paticula, the inne coe ubble. It also seems likely that the oof e-constuction wok caused an incease in the distibution of loads to the oute wythe and this caused cacking and damage to both units and joints. By 1996, the deteioation and damage caused by the infiltation of moistue though cacks and joints - and the subseuent destabilizing of the inne coe ubble - had become extensive. In paticula, displacement of stones became evident. (See Photogaph 2.) It also appeas that the changes in the load distibution though the masony caused columns suppoting the fiezes that adon the font elevation to become ove-loaded and this esulted in futhe damage. (See Photogaph 3.) Photos 2 & 3: Examples of damage caused by the deteioation of inne coe ubble The pe-poject investigations compised:- Non-destuctive testing to confim the pesence and extent of hidden voids, including impact-echo testing, and fibe-optic inspections; (See Photos 4 & 5) A stuctual evaluation to povide data euied fo the estoation stategy. The stuctual evaluation compised:- A visual inspection of the inteio oof constuction; Removal of a selected masony unit to confim the natue of the vaious wall constuctions; Pull-out testing to confim the stength of the poposed masony tie system; A stuctual analysis caied out by a pofessional enginee.

6 Photos 4 & 5: Using impact-echo (left) and fibe optics to investigate the condition of the inne coe. The stuctual analysis confimed the optimum euiements fo accommodating hoizontal thust foces duing gouting - and thus the design euiements fo the tie diamete, length and spacings based on the poposed maximum pump pessues of 0.03N- (5-psi) and a fluid gout density of 12 KN/m 3 (80-pcf). The maximum desiable lift of gout at any one time was detemined to be 700 mm (28-in) fo the lowe potion of the walls and 500-mm (20-in) fo the uppe potions. In addition, the stuctual analysis confimed that the loading condition on the walls - when acting as a full composite thickness with concentic loading conditions - was uite low. The stuctual analysis also confimed the ove-stessing of the columns and this detemined the need fo tempoay elief of thei loads duing the estoation wok. The confimed low loading on the composite masony walls indicated that acceptable pefomance could be gained once the walls had been adeuately tied and the inne coe ubble stabilised. The stuctual analysis detemined that the use of shea-development anchos to develop load suppot acoss the full thickness of the walls was not necessay. The estoation stategy that was developed fom the infomation povided by the investigation pocess can be summaised as follows:- The elief of load and tempoay suppot of the columns on the south walls duing the anchoing, gouting and epointing wok; the aangement consisted of pe-fabicated steel fames between the columns and the use of hydaulic jacks to deflect the loads fom the columns; the total euied displacement afte settlement of the jacks was calculated to be between 0.3 mm and 0.5 mm (0.012 and ins); deflection gauges wee installed to facilitate monitoing of the load elief and they wee held in position until the loads wee eplaced; Below gade watepoofing to contain the gout and impove duability; Installation of helical stainless steel masony ties between the two oute wythes to povide tempoay estaint duing gouting, and to impove the composite action of the masony;

7 Repai of damaged units using a popietay mota designed fo heitage stuctue applications; Raking out deteioated o inappopiate mota and othe mateials within the mota joints and back-pointing with a lime/cement based mota to contain the gout duing estoation wok. The font of the joints wee left open fo about 25-mm (1-in) to facilitate final epointing; Wate-flushing the inne coe ubble using wam wate and low pessue to emove any disintegated binde so that the gout could subseuently be pumped at educed pessues. (See Photogaph 6.) Two way adios wee used between the opeato and a watch-peson within the galley to ensue that leakage to the inteio did not cause damage to finishes, etc. Gouting of the voids within the coe with a cellula foamed cement gout designed to be compatible with the euiement fo consolidation and stability without excessive stiffness; Repointing the balance of the masony unit joints; Coection of othe deficiencies that could have affected the pefomance of the stuctue, such as impovement of stom-wate dainage and flashings. Some five yeas late, the estoation wok appeas to have been successful in accommodating diffeential movement, aesting the deteioation of the at galley and estoing the masony to a duable condition. Cellula Foamed Cement Gout. Cellula foamed cement gout was selected because of the autho s pevious expeiences gained within the mining industy and pincipally because of its lightweight, low stength popeties - as well as its inheent ability to absob stess. These popeties have been well-documented - togethe with the gout s ability to defom consideably unde load at a constant yield stess and edistibute damaging point load stesses. (5) (These uniue popeties also pesent oppotunities fo seismic etofit applications fo histoical stuctues.) The density of the hadened cellula foam gout can be vaied by adjustment of the uantity of foam intoduced into the base gout, as well as by incopoating a fille, such as sand. Geneally, densities less than 400-Kg/m 3 (25-pcf) poduce unstable hadened mateial, while the benefit of foaming becomes diminished once densities exceed about 1600-Kg/m 3 (100-pcf). Fo neat cement gouts this ange of densities will geneally poduce 28-day compessive stengths between 1.5-N/mm 2 and 14-N/mm 2 (200 and 2000-psi) with a elatively easonable linea elationship. The liuid cellula gout, which was designed to have a wet density between 720 and 800-Kg/m 3 (45 and 50-pcf), was poduced by blending a foam into a 0.45 wate/cement atio gout. A methylcellulose-type admixtue was mixed within the cement/wate gout to povide thixotopic popeties to the plastic gout and minimize leakage to the inteio though cacks, gaps, etc. 28-day compessive stengths wee typically between 5 to 7 N/mm 2. (725 to 1015 psi) To poduce the foam, a popietay sufactant-type admixtue was diluted in wate and foced though a nozzle unde pessue using a pupose designed pump. A high-shea colloidal mixe was used to mix the cement/wate gout which was then tansfeed into a standad spial-blade mota mixe. Afte the foam had been blended into the gout, (See Photogaphs 7 & 8) the final mixtue was injected into the coe using a standad Moyno pump fitted with 50-mm (2") diamete lines. (See Photogaph 9.) The nozzle end was fitted with a pessue gauge and a etun line to

8 pemit the nozzleman to contol the flow of gout and pumping pessues. Above gade level the gout contained white cement to educe the level of soluble salts that could subseuently leach to the suface and contaminate the masony units. An estimated 25 cu.m. (900 cu.ft.) of gout was injected into the inne coe ubble voids, which epesented appoximately 7.5% of the total volume of masony. Photos 8: (Top Left) Flushing the coe with wam wate. Photo 9: (Top Right) Pumping foam into mota mixe. Photo 10 (Bottom Left) Tansfeing cellula gout to pump hoppe. Photo 11: (Bottom Right) Injecting cellula gout into inne coe ubble. As aleady discussed, when utilising consolidation gouting techniues, a majo concen is the intoduction of moistue that may cause leaching of soluble salts and staining o damage of masony sufaces. Howeve, a majo advantage of cellula foamed cement gout is the low volume of wate used - in the ode of 50% of that used fo taditional gouts. Povided that the wate/cement atio used fo cellula gout appoaches the figue geneally consideed to be necessay fo optimum hydation - about 0.42(6) - the amount of fee wate that will not be used in the hydation pocess is not significant. (Convesely, it is impotant that the wate/cement atio used is not less than about 0.40, o the cement hydation pocess may consume wate fom the foam - esulting in unstable bubbles.) In fact, although thee wee a few aeas that emained damp fo a while - mainly in shaded aeas - the masony died vey well and no detimental effects wee obseved. A futhe majo advantage povided by cellula foamed gout is the educed weight of mateial that is injected into the masony - theoetically less than the oiginal ubble binde. The dy weight can be designed to be at least 1000-Kg pe cubic mete (1700-lb pe cubic yad) less than a taditional lime o lime/cement gout.

9 Case Study Two - Saint Louis Convent, Wateloo, Ontaio Constucted in 1895, Saint Louis Convent in Wateloo is a bick masony stuctue suppoted on a double wythe foundation wall. Ove the yeas, excessive step-cacks occued within the bick masony walls at many locations - usually adjacent to windows. (See Photogaph 12.) Lack of available funds pecluded a detailed investigation but a peliminay visual study indicated that the most likely cause of the cacking was diffeential settlement/movement of the foundation walls - most likely due to destabilisation of the inne coe ubble. This could be confimed by the condition of the masony at and just below gade level, the knowledge that the below gade potions of the walls had not been watepoofed, and the pesence of debis within the basement that was most likely disintegated coe ubble binde. The poo condition of the below gade foundation walls was confimed duing the subseuent estoation wok. (See Photogaph 13.) The estoation stategy consisted of the following:- To povide the euied estaint duing gouting and a bette composite action between the two wythes, helical stainless steel ties wee installed into the basement inteio. In view of the tough natue of the mainly ganite stones, the ties wee epoxy-esin gouted font and back. The below gade potion of the foundation wall masony was exposed, watepoofed and back-filled - both to contain the gout and to povide impoved potection. The masony joints within the above gade potion of the foundation walls wee cut-out and epointed using a pepackaged lime-based heitage estoation mota. (Had cement-based mota was also emoved fom the face of the stone masony units.) Holes wee dilled into the inne coe ubble fom the inside. Wam wate was used to flush out disintegated binde fom the coe, and the voids wee gouted using simila techniues to those aleady descibed fo the pevious case study. Almost 6.0 cu.m. (200 cu,ft,) of gout was calculated to have been injected, which epesented about 10% of the total volume of masony. The cacks within the bick masony walls wee stitched using the helical stainless steel masony ties. The ties wee dy-fixed into smalle diamete pilot holes fist dilled to the euied depth. The holes wee dilled at 45 angles though the mota joints to intesect the cacks oughly at thei mid-point. The open joints within the bick masony wee then cut-out and epointed using a pepacked heitage estoation masony mota, selected to blend with the existing mota. Afte two sevee wintes and exteme changes in tempeatue ove vey shot peiods, no futhe cacks have become visible and epaied cacks have emained unchanged.

10 Photo 12: (Left) Cacks caused by deteioation of inne coe ubble. Photo 13: (Right) Condition of below gade foundation wall. Case Study Thee - Heitage Complex - Bampton, Ontaio Now a museum and pat of the Heitage Complex in Bampton, the County of Peel Jail was constucted in (See Photogaph 14.) Afte the jail was closed in 1977 a new museum achives building was constucted with potions of the peimete coutyad wall becoming the exteio walls. In the Summe of 2000 it was decided that the exteio masony should be epointed. Duing the old mota cutting out opeations loose stones and the pesence of disintegated mota indicated that the inne coe ubble was in a poo condition and futhe investigation was detemined necessay. (See Photogaph 15.) The investigation consisted pimaily of a suvey using Gound Penetation Rada (GPR) techniues which evealed the pesence of consideable voidage. It is believed that this was the fist time that the techniue has been used fo this pupose in Canada and the esults povided by compute-geneated contou mapping of the esults wee extemely valuable. (See Fig. 1.) The mapping of the voids and suspected loosely bound ubble facilitated the installation of the injection pots and the concentation of gout at key locations. Helical stainless steel masony ties wee fist installed to povide estaint against gouting pessues and to impove the composite action of the estoed masony. Tests wee fist caied out to ensue adeuate pull-out load could be achieved. (See Photogaph 16.) The gout and gouting techniues wee simila to those descibed fo the pevious case studies. (See Photogaph 17.) About 2 cubic metes (70 cubic feet) of gout was used - appoximately that calculated to be euied fom the data povided by the GPR suvey - epesenting about 6% of the total masony volume. Good flow within the ubble was achieved though inteconnected voids and positive contact was made between most of the pots. (See Photogaph 18.)

11 Photo 14 (Top Left) Fome County of Peel Jail - the gouted coutyad wall is to its left. Photo 15 (Top Right) Example of inne coe ubble deteioation afte emoval of stone masony unit. Figue 1 (Middle Left) Computeized contou image poduced by GPR - The dake aeas epesent solid masony. Photo 16 (Middle Left) Pullout testing a masony tie. Photo 17: (Bottom Left) Pumping cellula gout though an injection pot. Photo 18 (Bottom Right) Contact is made between pots. CONCLUSIONS In an ideal wold, estoation stategies should be designed to include the least intusive methods and they should be evesible. Wheeve possible, they should also attempt to use taditional mateials that ae simila to those used fo the oiginal constuction - and compatible with the masony in tems of movement accommodation, etc. Howeve, although competent design and pactices can almost always ensue that gouting opeations do not impact on the aesthetic uality of the building fabic, these

12 philosophies ae difficult to obseve when the oiginal mateials did not pove to be adeuately duable and the techniues to be employed ae unavoidably pemanent. It is theefoe the autho s opinion that the use of cellula foamed cement gout povides an acceptable compomise - paticulaly in view of the sacificial and beneficial popeties that the mateial povides. Thee ae many heitage stuctues and olde buildings that ae no doubt suffeing fom the effects of deteioated inne coe ubble - most of them pobably emain undiagnosed, with deteioation poceeding at an acceleated ate. Often, estoation stategies addess the esult of the poblems without fully undestanding the cause. Consolidation and stabilisation of the walls using gouting techniues should be an essential pat of a estoation stategy fo these buildings - povided that the oiginal cause/s of acceleated deteioation - wate infiltation though joints above and below gade, cacks, poo watepoofing and flashing details, etc., - ae also addessed. ACKNOWLEDGEMENTS The Autho would like to thank Mount Allison Univesity, St Louis Paish Chuch and Region of Peel fo poviding pemission to publish details egading the pojects used as case studies. The Stuctual Enginee fo Case Study One was Mak Kantzbeg & Associates, Toonto. Impact-echo and GPR testing was povided by Tekon Sevices Incopoated, Mississauga, Ontaio. The Contacto fo Case Study One was Jones Masony Limited, Havey Station, New Bunswick. Fo Case Study Two the Masony Contacto was Empie Restoation Limited, New Hambug, Ontaio and fo Case Study Thee the Geneal Contacto was Roof Tile Management, Mississauga, Ontaio. The specialist gouting contacto fo Case Study One and Two was Geotec Contacting Limited, Maple, Ontaio, and fo Case Study Thee it was Undegound Sevices Limited, Bolton, Ontaio. REFERENCES 1. Ashust, J & N., English Heitage Technical Handbook Pactical Building Consevation Volume 1.Stone Masony. Published by Gowe Technical Pess. 2. Penelis, G., Kaavezioglou, M., & Papayianni, J., (1993) Gouts fo Repaiing and Stengthening Old Masony Stuctues, Poceedings, Thid Intenational Confeence, Stuctual Studies Repai and Maintenance of Histoical Buildings, pp Jones, M.C, (1994) Coe Consolidation of Heitage Masony Walls and Foundations Using Gouting Techniues unpublished pesentation at Restoation & Consevation of Heitage Stuctues semina, Guelph, Ontaio, Technical Univesity of Nova Scotia. 4. Toumbakai, E.-E, van Gemet, D., & Tassios, T.P., (1999) Methodology fo the Design of Injection Gouts fo Consolidation of Ancient Masony, Poceedings, Intenational RILEM Wokshop on Histoic Motas: Chaacteistics and Tests, Paisley, Scotland, pp Skinne, E.H., (1990) Stuctual Uses and Placement Techniues fo Lightweight Concete in Undegound Mining, U.S. Depatment of the Inteio, Bueau of Mines Repot of Investigations, RI-9266, Aïtcin, P.-C., Neville, A.M., and Acke, P. (1997) Integated View of Shinkage Defomation, Concete Intenational, Septembe, pp 35-41