Library of Parliament of Canada - Conservation, Rehabilitation, Upgrade Case Study Presentation

Library of Parliament of Canada - conservation, rehabilitation, upgrade case study presentation

M. Petrescu-Comnene Adjeleian Allen Rubeli Limited, Consulting Structural Engineers, Ottawa, Toronto S.R. Higgins Spencer R. Higgins Architect In c., Toronto

ABSTRACT: The Library of the Parliament of Canada is considered to be the premier heritage building in Canada, and the only surviving building ofthe original high-Victorian parliamentary building built in the 1860's. The building continues to serve its original function as the Parliamentary Library for both the Senate and House of Commons. In 1998, a Consultant Team was retained by Public Works and Government Services Canada to design and oversee a project to conserve, rehabilitate and upgrade the building for a design life span of50 years. The conservation aspect includes an extensive list of structural and architectural elements. The first part of the presentation will address the specific topic of stone masonry rehabilitation and conservation, with an emphasis on issues related to northern climates, i.e. water penetration and freeze- thaw cycling. The second part, will present some structural interventions addressing upgrading of the building to current code requirements and modern environmental control specific to libraries and archives housing valuable historical docllments.

TNTRODUCTION

1.1 History oflhe LibrO/y of Parliament The Library of Parliament (Fig. I) was originally constrllcted in the 1860's and extensively rebuilt in 1952- 56, following a fire. It is the single remain ing original building on Parliament Hill housing the Parliament of Canada. The Library was bllilt to the designs of Fuller and Jones in the form of an English Gothic chapter house, and decorated in an exuberant Victorian manner. It is the premier heritage building in Canada, located on a rugged promontory, high over the Ottawa River. It is linked to the Centre Block (hollsing the Senate and the House of Commons), which was rebllilt in its entirety afier a devastating fire in 1916. Its image is reproduced on Canadian postage stamps and banknotes. Construction of the Library along with the Pari ia ment Buildings began in December 1859. In June 1866 the Parliament opened its first session in the new build ing, however the Library masonry walls were only constructed to a height of 13 m. A temporary roofwas installed over the ring walls. Construction ofthe stone masonry walls restarted in 1871, however the ma in roof structure design was changed from a masonry dome to a wrought iron truss system designed and Figure I. Library of Parliament, c 1875 (NAC, C-I 000 I).

1273 built by Thomas Fairbairn Engin eering Company Ltd., of Manchester, England. The Library moved into the new building in October 1876. In 1888, a cyclone blew away large sections of the original slate roof, and the roofing was replaced with copper. In 19 16 the Centre Block was destroyed by fire, but the Library bui lding suffered only minor damage, being saved by a iron fire door. However, the luck ran out in 1952, when a fire started in the dome of the Library causing significaRt damage to the roof struc ture and extensive water damage to the collections. Mathers and Haldenby Architects of Toronto were retained to prepare plans and specifications for the rehabilitation, repair and fireproofing of the Library. While the exterior appearance of the building was retained, the interior layout and fea tures suffered sig nificant alteration. It was then that the origin al Reading Figure 2. Interi or of Library ofParli ament, photography by Room brick vaulted floor was removed and replaced Williams J. Topley, c.1898 (NAC, PA-8375). by two leveis (basement and sub-basement) of book stacks; a large number ofbags of cement were used for walls also provi de the resistance for lateralloads, i.e. the grouting of buttresses; sanded grout was inj ected wind and earthquake. The walls are founded on large into footings; joints were re-pointed with cement slabs of limestone positioned on limestone bedrock. gauged lime mortar; brick lining walls on the inside The bedrock has significant jointing with variable face of the outer ring wall were removed and replaced directions and angles. with cast-in-place concrete; and the secondary tim The ring walls are of random rubble construction ber roof framing was replaced by steel members. The built to courses with plain ashlarquoins. The outer face Library was re-opened in June 1956. ofthe wa ll was squared and bedded in mortar, and the Between 1956 and 1998 the Library benefited from inner face was built up of coursed random rubble work small maintenance and upgrading projects address grouted up in lifts as the work progressed. The outer ing lighting problems, heating and air conditioning, ring wall is 1200 mm th ick at its base, and reduces to and fi t-up of a rare-book storage room. A number 850 mm above the main floor. The inner ring wall is of studies were completed regarding water infiltra 1500 mm thick below the main floor, and reduces to tion, high humidity leveIs, and the condition of the 1300 mm for the upper secti on. According to the orig masonry walls. In June 1998, Public Works and Gov inai specifications, keystones were placed on a regu lar ernrnent Services Canada retained an Architect Joint pattern to connect the face wythe to the rubble core. Venture Firm as the architects for the Conservation, However, the investigation conducted by the design Rehabilitation and Upgrade Project for the Library of team could not clearly identify the keystones. Parliament. The Joint Venture retained the engineer The area inside the inner ring wall is referred to as ing sub-consultants, as well as specialty consultants. the Reading Room. Originally, it had only one base Construction documents were completed in May 200 I. ment levei, with the reading room rising approximately Construction started in March 2002, and is expected 30 m to the base of the lantern, and up to 4 I m at to be completed in 2005. the lantem. The on ly floor slab had a brick arch sup port, with a concrete, graveI, sand and hydraulic lime morta r topping. The slab was carrying the multi- leveI 1.2 Structural description wooden book stacks (Fig. 2), with eight radial pro The main vertical structural elements of the Library jecting stacks, and access from the perimeter offices are the two concentric masonry wa ll s: the outer ring area. The stacks have a wrought iron framing, and wall and the inner ring wall (Fig. 4). The diameter include two leveIs of circulation galleries to provi de of the inner ring wall is 26.5 m, while the diame access to the shelves and projecting stacks. During ter of the outer ring wall is 45 m. The outer ring the renovations of 1950's, the reading room slab was wall is stiffened by 16 buttresses, with flying but removed and replaced with a 127 mm two way re in tresses arching over to the inner ring wal l. The inner forced concrete slab supported on steel columns on ring wall provides the support for the arched wrought a 2743 mm grid. At the same time, the single base iron truss system supporting the main roof and the ment levei was replaced with two leveis, by sli ghtly lantern. At its lower leveIs, together with the outer 10wering the bedrock and reducing the clear height on ring wall they provide the support fo r the perime each leveI. The steel columns, built up from angles and ter offices slabs (five leveis) and the lower roof. The tee sections, were integrated with the mobile shelvin g

1274 MAIN FLOOR PLAN

Figure 4. Main Floor Plan.

framing and steel deck system. At the same time, the original timber lean-to roof over the perimeter offices Figure 3. Library of Parliament - Cross section. was replaced with a steel framed roof and steel deck. The original timber Lantem structure was com system. The shellacked pine book stacks, refurbished pletely replaced during the 1953 renovations. A new off-site, were reinstalled on the newly constructed slab. structural steel framing system was installecl, spring The perimeter offices area provides office and ing from the compression ring truss. lts structure service space, including four stairs on a diagonally includes cranked steel columns, two leveis of hori opposite configuration. The northeast stair is the Stair zontal diaphragm framing, secondary steel framing, Tower, which extends to the top ofthe inner ring wall, and the central pipe column for the wrought-iron and provides the access to the roof and lantem. It weathervane. contains a stone circular stair within a round stone The Library also includes a number of architectural masonry tower. Ali the perimeter offices slabs were features - pinnacles, stairtower, and chimney. Stability reconstructed in 1953, with a 65 mm reinforced con ofthese masonry elements was addressed by the struc crete floor slab, supported either by a reinforced tural team, and the designers provided the reinforcing concrete skin wall placed against the ring walls, or details. horizontal slots cut into the stone masonry walls. The roof over the Reading Room is carried by 1.3 Struclural challengesfor building upgrade a semi-circular wrought-iron truss system, which is composed of 16 long trusses alternating with 16 short The current conservation, rehabilitation and upgrade trusses (Fig. 3). Ali the trusses are connected at the top project scope-of-work listed a number ofrequirements to a wrought-iron ring compression truss, and are sup set up by the Client. The most challenging tasks from ported at their bases by the inner ring wall. The long the structural engineering point of view included: trusses are the main structural elements as they align (I) conservation of the building for a minimum life with the buttresses. The trusses bear 011 large crys span of 50 years; (2) upgrading of the building to talline limestone blocks set through the walls, between current code requirements (National Building Code of the Reading Room windows. The short trusses bear on Canada 1995), including seismic resistance upgrades; the masonry just above the receiving arches ofthe win (3) construction of an underground link to the exist dows, with additional steel bracing incorporated into ing House of Commons loading docks and material the masonry (their presence remains unconfirmed) handling facility; and finally, (4) construction of a ded transferring their loads to the long trusses. In 1953, icated mechanical room to provide ali the air handling the original wooden strut and purlin system supporting and stringent envirorunental control for the Library, ali the wood deck, was replaced by a mild-steel secondary independent from the Centre Block systems. Of course,

1275 ali the work would have to be in conformance with the the perimeter once the accurately laid-out upper wa ll s establi shed heritage conservation principIes in order were constructed. The joints between the blocks have to preserve the historie eharacter of the building. been severely eroded by the flow of water down The rehabilitation and conservation ofthe masonry through the wall and were re-grouted in 1953 using a walls, ring walls and buttresses, resulted in extensive proprielary Portland cement grout. A metallic cemen investigation and research. Despite minor evidence of tilious walerproofing render was applied to lhe inner distress (localized cracking), there was evidence of face of lhe outer wall at the same ti me. The foun major water infiltration problem within rubble core. dation walls were ini tially thought to be in re lative ly Previous investigations had expressed concern regard good condition but ex tensive voiding was later fo und ing cavitations and the disintegration of the hydraulic to exist between the blocks where the bedding mortar lime mortar core, which was possibly effecting the sta was reduced to a sandy consistency. bility ofthe exterior stone wythes. Considering that the The outer ri ng wa ll is constructed of an inner rub deterioration was produced by the freezi ng and thaw ble shale fac ing, a concrete core of hydraulic lime ing of the infiltration water, and further aggravated mortar and limestone rubble, and an outer facing by contamination with de-icing chemicals (salt), the of coursed rubble cream-coloured Nepean quartzite research fo cused on a practical method of cleaning the sandstone trimmed with moulded light brown Ohio interi or cavities ofthe wall ofsilt, and the design ofan sandstone and red Potsdam sandstone. The core mor inj ectable grout with improved resistance to freeze tar consisted of a mixture oftwo-parts hydraulic lime thaw cycl ing and chlorides. With no avai lable space and five parts sand. fo r the required mechanical room, the another major The exterior joints have been repointed in a variety challenge fo r the team was to exeavate into the bedrock of cement-based mortars. In 1953 extensive Portland below the building and to create a large mechani cement pressure grouting of the buttresses and fo un cal room. While maintaining the Reading Room floor dation walls was undertaken to fill voids. The rubble slab in place, including the historical and fragi le book facing of Nepean sandstone was originally pointed stacks, a 21.5 m diameter and 8.9 m deep volume was with adense mixture of equal parts ofbrown hydraulic excavated (Fig. 3). The number of support columns lime, forge ashes and iron scale to provide a blackjoint was reduced by replacing the 2743 mm grid with a ing treatment. Water overflow from the eaves resulted 8230 mm grid. This work was integrated with the con in frost action repeatedly forcing out the jointing in struction of an under-ground li nk to the House of the first few years after pointing. The original point Commons loading dock, extension of the elevator to ing was replaced with a succession ofmixes leading up serve the link and mechanical room leveI, as well as to a recently installed lime-rich Portland cement mi xo extension of another stair to serve as a second emer The joints around the mouldings were pointed with a gency egress route from the new lower leveI. The matching colour mortar. At our initial inspections in mechanical duct work distribution system was routed 1989 th e jointing on the lower walls and butlresses through sloped holes drilled into the rock, to bring the was found to be cracked, loose, missing, moss-filled, ducts from the mechanical room to locations below the damp, delaminating and unsound. There also were vertical air shafts distributed throughout the building. large upper areas oftight, dense, hard Portland cement pointing that was tightly adhered to the stone blocks but obviously stressing the adjacent masonry and caus ing fracturing of arrisses. The Ohio sandstone masonry 2 REHABILITATION AND CONSERVATION window tri m was found to be in good condition at the OF STONE MASONRY upper leve is but was in progressively poorer condition at the lower leveIs, especially at the main doors and to 2. 1 Condition of masonry each side ofthe stair gables where rain water dripped The ring walls are founded on a massive coursed rubble down from the roof and caused serious damage to the crystalline bluish limestone foundation lai d directly masonry. over the leveled limestone bedrock and forms an Behind the pointing mortars of the lower walls the underground leveI base approximately 2 m in height. bedding mortar was found to be seriously damaged The foundati on wall blocks are quite large, approxi with a zone approximately 200 mm deep where the mately 600 mm in bed depth and about 1200 mm longo mortar had been reduced to sand in several locations. The inner and outer foundation ring walls are approx The walling around severa I window surrounds was imately 1200 mm and 1500 mm in thickness. The found to be hollow and sand filled. We determined blocks were apparently laid using imported Engli sh that water infiltration from roofleakage and open wall Portland cement mortar. The wall was constructed joints was percolating down through the wa ll s and dis slightly oversize in plan to accommodate final layout solving and carrying away the lime binder leaving a adjustments to the main walls above, and thi s created sandy residue and allowing the outer core of the wall an irregular ledge about 100- 300 mm in width around to settle slightly and thus compress the outer face ofthe

1276 masonry. During winter conditions the saturated walls better condition than the lower work with the excep and buttresses freeze resulting in the formation of ice tion of the rubblework above the cornice blocks, that lenses in the wall and cracking ofthe outer joints. The has been found to be in seriously eroded condition exterior joints go through some one hundred freeze due to water infiltration at the eaves. Upon remova I thaw cycles each year which progressively cracks and ofthe leaded glass and inner wooden sash the areas of deteriorates the mortar joints within a 100 mm space the Ohio sandstone window jambs concealed behind from the face ofthe walling. When the ice lenses melt the glass were found to be in poor condition due to in the spring the voids fill with silt and sand from the freeze- thaw damage. deteriorated mortar above within the wall, thus pro gressively weakening the assembly and slowly jacking 2.2 Investigations the walls outward in places. Large quantities of rock salt (sodium chloride) is In order to understand the internaI condition of the used in the winter to melt snow on the service road walls a series of investigations were carried out dur ways that run around the base ofthe building. The salt ing the initial stages of the design work on the sprays onto the walls and is absorbed into the joints and Library. A comprehensive set of Design Guidelines masonry. The hygroscopic nature ofthe salt results in had been prepared by the Heritage Conservation Pro a state of continuous dampness in the outer walls and gram staff in which a discussion of previous repairs the salt crystallization cycling results in spalling and and maintenance on the building and an outline of rec delamination of the surface of the weaker Ohio sand ommendations for work were presented. Of particular stone trim. The masonry trim around the main entrance interest was the observation that the building had been has in fact been destroyed by salt action. The quartzite repointed at least ten times and the buttresses had been Nepean facing however is not seriously affected by cement-grouted once in 1953. And the repointing was the salto done when the walls were in poor condition, meaning The masonry is lightly-soiled overall with some that the joints had been open for some time leading heavy accumulations under the sheltered cornices. up to the repointing works and serious deterioration of Most of the soiling was a result of heavy atmospheric the core ofthe walls was inevitable. pollution from the pulp and paper mill that previously A one metre square section of outer ring wall existed directly across the Ottawa River, which the masonry near grade was dismantled to review the con Library overlooks. The sulphuric acid aerosols tend dition ofthe core. The core rubble concrete was found to penetrate the fissured surface of the masonry and to be quite sound but a zone of disintegrated mortar react with the leached calcium carbonate from the lime was found behind the smaller facing blocks. Most of mortal', forming gypsum crystals that disaggregate the facing blocks were tenaciously bonded to the core. the crystal structure and subsequently cause deterio Ten core samples were taken at a range of heights ration of the stone. Pollution reacting with calcium up the sides oftwo adjacent buttresses and wall. As we carbonate has created over time a thin, relatively suspected that significant cavitation of the buttresses insoluble gypsum crust on the surface, laden with had occurred we recommended that the buttresses be black particulate matter. This insoluble gypsum crust partially grouted in the core areas before coring. This seals the capillaries in the stone, retarding normal would stabilize the core where disaggregated and thus evaporation. This permits the fine capillaries to fill allow the remova I of a solid core sample for review. with water and subjects the stone to thermal stressing The core locations were grouted with a proprietary cel when heat is applied, eventually spalling offthe crust lulose stabilized hydraulic lime grout (Unilit B) and and leaving a raw surface. Water comes from internai cured for seven days before coring. Inspection of the vapour and under-roof condensation, and from exte cores and video inspection of the core holes revealed rior joint cracks and roof overflow. Large areas of the that the walls were substantially sound but: (I) the zone Nepean stone have lightly exfoliated and appear clean. behind the face and ilUler lining blocks was seriously A relatively-harmless thin black crust covers most of disaggregated; (2) an extensive matrix of cavitation the upper Ohio sandstone blocks, but the lower blocks was present in many of the areas; (3) traces of the and weatherings are ali covered with adense outer 1953 grouting campaign were found to be solid and crust covering a powdery subsurface zone which is well bonded but did not fill the smaller cavities; and blistering-off through frost, heat and crystallization (4) the core concrete consisted oflarge lumps oflime pressure. stone rubble in lime mortar. An additional core was The interior ring wall is composed of an inner, plas taken without pre-grouting in the upper inner wall. tered brick lining, and a core of hydraulic lime and The conditions were found to be identical to the lower limestone rubble concrete, and a facing of Nepean wall but it was noted that ali the drill water disappeared quartzite sandstone rubble with Ohio sandstone win into the core ofthe wall. dow surrounds and decoration identical to the outer Given that cavitation of the core of the but ring exterior face. The upper masonry is generally in tresses had occurred it was recommended that the

1277 compressive stress in the fa cing blocks be determined. A test programme for the development of a suitable Flat-jack testing (ASTM C- I 196) was carried out by grout was developed by our in-house testing labora a testing agency at five locations and it was found that tory. Review of the literature indicated that research the stress leveis ranged from 1. 8- 3.3 MPa. The calcu at lCCROM related to the re-attachrnent of mosaics lated theoretical stress leveIs should have ranged from to lime core walls suggested that a formulation using 0.16- 0.20 MPa. lt was determined that significantly hydraulic lime and fine aggregates might be sui t high compressive stresses were occurring in the outer able. Several formu lations using diatomaceous earth fac ings and ( I) the buttresses were not carrying a prop and a filler to control shrinkage when combined with erly distributed load; (2) loadings on opposite sides of suitable stabilizers and flui disers appeared to be suit the buttresses were not evenly balanced; and (3) any able for use on the Library. A comparison of poly dismantling of buttress facings shou ld be done with vinyl acetate and si li ca fume modified hydraulic lime extreme caution. grout mixes identified in the report were chosen fo r Further evaluation of the core of the walls using evaluation. An outline of formulation development ground penetrating radar was attempted but this methodologies and a summary ofprocedures and tests method was unable to provi de useful information was developed that could be used to verify the char given the relatively complex matrix of materiais within acteristics of these basic formulations to determine the walls. if the lCCROM formulations could be adapted and It was obvious that a method of consolidat made compatible with the mortar core walls of the ing the masonry using a lime-mortar-compatible Library. grout and providing the exterior wall joints with The initial fo rmulations for the grout consisted of a vapour-permeable yet frost-resistant morta r was 4-parts hydraulic li me: 2-parts fine aggregate: 4.5- required to stabi lize the masonry and prevent further parts water. This would be tested with the following deterioration. additive combinations: (I) plasticiser, PVA and expan sive admixture, and (2) superplasticizer, silica fum e and expansive admixture. SI. Astier NHL3.5 hydraulic 2.3 Gra u! research pragram lime was chosen for the initial evaluation, and River lnvestigation into the condition of the masonry walls ton, Jura and Unilit hydraulic limes would be evalu ated of the Library resulted in the conclusion that con after a stable and su itable formulation was developed. sol idation of the core of the wall s was required to The initial performance criteria for the grouts evenly di stribute seismic loading, adhere the inner and were established as follows: (I) Flow (ASTM C-939) outer faces to the core, consolidate the sandy residue less than 25 seconds; (2) Bleed (ASTM C-940) nil; within the walls and stabilize the lower walls to allow (3) lniti al set (ASTM C-953) 48 hours; (4) Shrink underpinning and rock removal operations under the age (QuickMethod) nil; (5) Sand Column Injectability foundations. Inj ection grouting of the core appeared (NF P-18-89 1) 360mm in 60 seconds; (6) Compres to be a method of achieving these aims whilst min sive Strength (ASTM C-942) 1.5 MPa at 28-days; imi zing intrusive rebuilding operations. A review of (7) Splitting Tensi le Strength (ASTM 0-3967) commercially available grouts indicated that achiev 0.15MPa. ing technical performance cri teria matching that found After selection of a final mix for testing the fol in the existing masonry in a grout was not possible. lowing additional performance criteria were tested: (8) Signi ficant bond strength development in the grout Water Retention (ASTM C-94 1) 20 minutes; (9) Com is not required, and the lateral forces on the walls are pressive Strength (ASTM C-942) 5 MPa at 90-days; extremely low, but there is a need to adhere the delam (10) SplittingTensile Strength (ASTM 0-3967) 3 MPa inated inner and outer faces of the walls to the core. at 90-days; (1 1) Vapour Permeability (ASTM E-96) Conventional cement grouts tend to shrink and delami greater than 5.3 gmlm2/day; (12) Shrinkage (ASTM nate from weak core material such as li me mortars, the C-53 1) less than 2%; (13) Rubble Column lnjectabi l grout therefore should be slightly expansive to coun ity (NF P- 18-89 1) 360nun in 60 seconds; (14) Ai r teract shri nkage and possess a degree of tackiness to void Content (ASTM C-457) paste-to-air facto r 4- 1O , adhere to the soft lime mortar during the initial cur specific surface 24-43mm-l , and spacing factor 0. 1- ing processoVerification that adequate bond develops 0.2mm; and (15) Bond Wrench Strength (ASTM within a 90-day cure time was required. As the deteri C-I072) 0.5 MPa. orated interface failed primarily through the action of Grouts were mixed in five litre batches using a lab water flowing through the walls and frost action on the oratory high-shear mixer at greater than 8000 rpm for damp mortar, it was believed that it was essential that six minutes then transferred to a low speed mixer at the grout has good frost resistance. Air-entrainrnent 150 rpm until use. Samples were to be damp cured for of the grout was therefore thought to be essential. seven days in a 98% relative humidity environrnent Verification of the degree of freeze- thaw resistance then burlap-covered and damp-cured at 50% RH for was required. 28-days.

1278 The laboratory testing was carried out by an inde The high porosity of the original hydraulic lime pendent testing laboratory. The initial testing process core morta r indicated that the pointing mortars should identified the following problems with the initial have similar or higher porosity to allow the migration material selection and mixing methodology: (I) air of water-vapour to the exterior. The Nepean quartzite entrainment caused serious foaming problems and was wall facing is relatively impervious and directs most eliminated; (2) PVA emulsions created clumping and water vapour out through the joints and adjacent Ohio retarded set problems and was eliminated: (3) naptha sandstone mouldings. The Ohio sandstone is how Iene sulfonate-based superplasticisers retarded set and ever quite permeable and tends to wick water-vapour were replaced with a polycarboxylate type that pro out through the face of the stone. The molded face vided suitable results; (4) shrinkage reducing admix increases the surface area significantly. Where the tures were found to be unnecessary with a stable grout joints are impervious, this tends to drive ali the water and were eliminated; (5) silica fume required very high vapour out through the moulded window trim, and this speed mixing (15000 rpm) to achieve mix segregation has resulted in extensive failure of the faces of this and stability; and (6) short mixing time is required to relatively weak stone. control mix temperature. A programme of mortar testing was developed Some forty mixes were eventually tested to achieve by a Masonry Group committee consisting of mem a stable and properly performing mixo The slightest bers of the consultant team and technical staff from change to the formulation would lead to extreme vari PWGSC, the Heritage Conservation Program and ation in performance. The final formulation was based the National Research Council of Canada. A test on the following cri teria: water to binding-agent ratio ing agency was retained to carry out verification 0.9; water to fines ratio 0.8; Binding agent to aggregate testing of the following 8- 10% air-entrained mor ratio 7.6; silica fume 1% by weight; superplasticizer tar mixes: (I) NHL3.5/Buff granitic-aggregatel:3 2.3% byweight. The components were Hydraulic Lime ratio; (2) NHL3.5/Black granitic-aggregatel:3 ratio; NHL3.5; Dicalite UF; Force 10000 silica fume; and (3) NHL3.5/Red crushed-brick aggregatel:3 ratio; Grace Adva 100. Two formulations were tested, one and (4) White Portland CementlLime Putty/Buff with entrained air in the hydraulic lime and one with granitic-aggregate 1:2:7 ratio. These mixes repre out. The entrained air mix was about 20% weaker sented the best-guess formulations for each required in compressive and tensile strength but both passed mortar type and a control mix of conventional cement the performance criteria. Questions were brought for gauged mortar. ward related to the acceptability ofthe air-entrainment Ali aggregates were coarse well-graded materi matrix which appeared to be not stable when compared aIs. Hydraulic lime was St. Astier NHL3.5 with to standard concrete evaluation criteria, but this did not a factory-blended aliphatic hydrocarbon insoluble take into consideration that the grout would be mixed (Vinsol) resin. Lime putty was made from a Type SA with sand residues in service. The bond results were (Special!Air-entrained) dolomitic hydrated lime. excellent with the breaks occurring in the grout and Ali mixes were prepared in the laboratory and not at the stone to grout interface. tested in a plastic state to the following standards and Similar mixes were evaluated using Riverton and criteria: (I) Flow (ASTM C-230) 50%; (2) Consis Unilit hydraulic limes with acceptable preliminary tency (ASTM C-780) 20- 25 mm; (3) Water Retention results. The grout was not tested at this time for (ASTM C-230) 80- 90%; (4) Wet Air Content (ASTM freeze-thaw resistance. The tendered grouting package C-231) 10- 12% . Samples were then prepared and contained this formulation and required the successful damp cured and tested in a hardened state to the follow grouting contractor to verify and modify the formula ing standards and criteria: (5) Compressive Strength tion using site equipment to achieve a workable mixo (ASTM C-I 09) 28-day 1.5 MPa and 60-days 3.5 MPa; (6) Air Void (ASTM C-457) 10- 12%; (7) Flexural Bond (ASTM C-1329) 0.3 MPa; (8) Drying Shrink 2.4 Mortar Research Program age (ASTM C-I 148) less than 1%, (9) Water Vapour The Joint Venture Architects recommended to Pub Permeability (ASTM E-96) 5.34 gm/m2/day; and (10) lic Works and Government Service Canada that an Freeze-thaw Resistance (prEN 772-22) intact afier 100 hydraulic lime based mortar be used for ali rebuilding cycles. and repointing work on the Library ofParliament. This Testing indicated that while most cri teria were met recommendation was based upon historic precedent, an wet air-content over 9% could not be achieved site investigation findings and contemporary technical and the dry air-content was in fact only 5%. Flexu performance requirements. Due to the specific nature ral bond was also very low (0.02 MPa) on ali mixes. ofthe colored mortars required for the Library it was And freeze- thaw resistance was poor with ali sam found necessary to verify by testing that the proposed pIes failing the 100 cycle test. The cement-gauged mortar mixes met ali the performance and aesthetic mix performed well and achieved the promised 12% requirements. air-entrainment.

1279 A second series oftests was undertaken using NHL5 no experi ence with hydrauli c lime grout. A suitable hydraulic lime and additional ai r-entrainment to pro mix was developed afier five sessions of multiple vide 12- 15% air-content. A wet air-content of 15% was tests. The following issues were noted: (I) high speed achieved on ali mixes but it was found that the bl ack (3000 rpm) high-shear equipment with a large mix granite aggregate mix only achieved a dry air-content ing rotor (300 mm) and a ten minute mixing time was of 6%. Ali the mixes passed the freeze-thaw test required to disperse the silica fume and produce a sta with no surface erosion. The bond strength improved ble mix; (2) fi nding a stable mix that will penetrate a marginally (0. 1 MPa) but still was poor. lt was later sand column was di fficult as variations in any com found that the freeze- thaw specimens were intimately ponent will create major changes in characteristics; bonded after testing at 90-days and required a chisel (3) different types of hydraulic lime performed dif and hammer to break lhe joints. fe rently; (4) factory blending of the final mix was We determined that: (I) sign ificantly higher leveIs essential to provide consistency of mix in the field; (1 5%) ofwet ai r-entrainment are required to produce and (5) ai r-entrainment of a grout with good penetra frost-resistant mortars; (2) higherfiow and consistency tion qualities is not possible. The final test results using (25- 30 mm) values are required to achieve good ini Riverton NHL2 were as follows: (I) Flow: 12 seconds; tial bond; (3) prolonged damp (50-70% RH) curing (2) Expansion and bleed: nil; (3) Set time: 4 days; (4) 3 is required to develop carbonization and hardening LinearShrinkage: 0.2%; (5) Unit Weight: 1557 Kg/m ; of the li me; (4) significantly lower dry air-content (6) Compressive Strength: 7-days 1.6 MPa, 60-days va lues are found in mortars that have been worked; 8.7 MPa; (7) Air Content wet 0.7%, dry 2.4%. (5) compressive strengths afier one year are approx Field verification of the mortar mixes by the con imately three-times the 28-day result; (6) prolonged tractor resulted in the following modi fications: (1) damp curing of hydraulic lime mortars is essential to factory-blended pre-bagged ai r-entrained hydrauli c limit shrinkage and develop bond; (7) good permeabil lime and aggregate mixes was used for quality control; ity values are achieved with hydraulic lime mortars; (2) hand-held high speed mixers were used to prepare (8) ASTM bond testing methods are toe aggressive for 20 litre batches of mortar on the scaffold as required. new HL mortars; (9) air-entrainment va lues of over 12% are required to ensure good initial freeze-thaw resistance; and (10) NHL5 hydraulic lime is required to 3 STRUCTURAL ASPECTS OF THE provide frost resistance afier a 60-day laboratory cure. UPGRADING Testing indicated that high permeabili ty and moder ate strength could be achieved through the use of ei ther 3. 1 Underground mechanical room a Portland cementlLime Putty/Aggregate mix in the Construction of a mechanical room below the Read ratio of I :2:7 or an Hydraulic Lime/Aggregate mix in ing Room slab required excavation of a large vol ume the rati o of 1: 3 while still maintaining adequate tech of rock, and a significant reduction in the number of nical performance including excell ent freeze- th aw columns supporting the ground fioor slab. lt was deter resistance and low compressive strength. The recom mined at an early stage th at the Reading Room slab mendation was made to use an hydraulic lime-based must be retained in place to avoid removal ofthe frag mix primarily on the aesthetic basis that hydraulic lime il e book stacks, and also to all ow conservation an d mortars age more gracefully than Portland cement rehabilitation work to proceed above thi s leveI dur gauged mortars and al50 are historically appropriate. ing the construction of the Mechanical Room below. Tt was also decided to in crease the head room in the 2.5 Conclusions two basement leveIs of the building in order to meet Altho ugh the in itial site evaluation testing ofthe walls current code requirements and allow a more effi cient indicated that the core of the walls was in good use of the space. condition, further investigation indicated that serious The fi rst design decision was to increase the column voiding and dissaggregation of the core of the wa ll s grid from 2743 mm to 8230 mm, this way reducing the had occurred. Field work subsequently revealed that number of col umns from 76 to 12. A new steel beam the cavitati on problem was systematic throughout the grid was specified below the slab on a 2743 mm grid, walls and the voiding was in excess of8% by vo lume, all owing this way to maintain the same support points almost three times the pre-construction estimate, and for the concrete two way slab, and retaining the slab as has required over 180 tonnes of grout to consolidate. found. The new columns were placed at the locations Consolidation ofthe masonry was essentia l as the seis ofthe existing colum ns, which created some additional mic analysis had found the stability ofthe structure to temporary shoring challenges, but allowed mainte be marginal whi le assum ing a masonry wall of sol id nance of a regular grid. Eight ofthe new columns (the construction. perimeter columns) were placed elose to the inner ring Field verification testing of the grout mix design wall, on a rock ledge just below LeveI O slab (approx proved to be difficult as the grouting contractor had imately 2000 mm below the underside of the ring

1280 PERIMETER OFFlCES

( M ) COCM:1[~WE1[II CQ.LIWM C/W"ft.IIIOA Sltl1..PIP(lO/9'OIII~ <».-

Figure 6. Mechanical Room excavation.

of the base plate to allow placing of the concrete into

ME CHANIC AL ROOM the caisson. Concrete was placed only after the final alignment ofthe colunm, and included both the caisson Figure 5. Typical section - New Mechanical Room . and the interior of the steel pipe colurnn. A lean con crete mix was placed between the steel column and the rock, in order to provide lateral stability for the column wall foundation). The remammg four colurnns (the during the following phase of construction. central columns) would extend through the Mechani The following phase of construction was the instal cal Room, with an approximate length of 14.4 m plus a lation ofthe Reading Room slab support grid, spanning 2 m socket into the rock. The totallength ofthe column between the 12 new colurnns. Some of the new steel below the as found rock elevation would be around beams were cambered to compensate for the calculated 9m (Fig. 5). deflection. AI! the beams were installed with tempo Construction started with the removal of the origi rary shoring ofthe slab. Support plates were installed nal slab on grade (LeveI O) , and shoring ofthe existing between the beams and the underside of the exist slabs LeveI I and Levei 2 (Reading Room levei) around ing slab exactly where the cast-in steel pl ates were the location of the new colurnns. The existing steel left behind afier removal ofthe original colurnns. The colurnns were removed, and a 2700 x 2700 mm open loading was transferred from the temporary shoring ing was cut in the Levei I slab. The excavation for to the new steel grid by jacking at pre-determined the perimeter colurnns was carried out by traditional locations until the calculated deflection was induced mechanical rock removal techniques, and a 2 x 2 x 2 m into the new beams. The slab movements and book pit was created for each COlUmJ1 and its foundation. stacks above the slab were monitored at ali times. This A structural steel colurnn was placed to the under operation was followed by the demolition of LeveI I side elevation ofthe steel grid to support the Reading slab, and installation of temporary lateral braces for Room slab. the four central colunms, from a location just above The four central colurnns have a central struc the top of the rock (above the future LeveI O slab) tural steel section which provided the support during to the new steel grid below the Reading Room slab. the excavation and construction stage, and which During this time, book stack woodwork conservation was encased in concrete with the construction of the activity continued above in the Reading Room in an air underground slabs. They are supported by concrete conditioned space, with plaster and stone conservation caissons socketed into the rock. Construction started activities continuing within the dome space above. with 762 mm diameter shaft, pre-drilled for each col The next phase was the excavation of the new urnn, to the elevation of the underside of the colurnn's Mechanical Room (Fig. 6), a circular space ofapprox caisson (approximately 9 m long). The lower section of imately 21.5 m diameter and 8.9 m deep. This exca the steel column is 324 mm diameter (7 m long), with vation was part of a long list of similar items which the upper section only 219 mm in diameter. The col included the loading dock link, elevator extension, unm was assembled on site from sections as they were new stair access, and mechanical distribution shafis. lowered into the shaft, with fuI! penetration welds, The excavation, rock stabilization and monitoring due to limited headroom. The caisson reinforcing was was designed by the geoteclmical consultanl. Ali the welded to the underside ofthe column's base plate, and excavation was by mechanical means: dril!ing, rock a 100 mm diameter hole was provided in the middle splitting, hoe-rarnn1ing. The rock faces, the Library

1281 and the adjacent historical buildings were moni tored Increasing the number of mechanical risers signif at ali times for movement and vibration leveis. Moni icantly reduced their size, and good overall coordina toring equipment included extensometers,jointmeters, ti on within the design team limited the impact on both strain gauges, convergence monitors, inclinometers, the heritage structure and on the space functionality. tilt beams, piezometers. For the Mechanical Room, the excavation proceeded in 2 m deep concentric lifts. It was coordinated with local underpinning of the 3.3 Underpinning ofstone masomy walls inner ring wall, and other excavation items. Finally, New floor leveis were constructed below the Reading the inclined distribution shafts were drilled, by the Room (Levei O and Levei 1), while the fl oor leveis raise bore technique, for the mechanical distribution of the perimeter offices were retained. Used as book system. storage, these two new leveis required leveled access The fi nal construction phase included construction to the elevator. Therefore, the slab in one quadrant of of the reinforced concrete wall s of the Mechanical the perimeter office space, on LeveI O and Levei I, Room, placing of a reinforced concrete jacket around was lowered to match the new interior space. While the columns, and constructi on of Levei O and Levei 1 reconstruction ofLevel 1 slab at lhe new elevation did reinforced concrete slabs. The temporary lateral braces not result in any structural complications, th e new ele ofthe central columns were removed after the pl acing vation of Levei O slab was below the underside of the of Levei O slab. inner and outer ring walls. In addition, the crawl space for the mechanical distribution system had to be main tained. This required an overall excavation of up to 3.2 Mechanical distribution system 2 m below the bearing levei ofthe masonry walls. The Finding appropriate routes for the mechanical distribu condition of the rock was found to be weakened by a tion system was a major challenge for the entire team. large number ofjoints, and significant fragmentation. The build ing contains four climatic control zones, each Therefore, it was concluded that the inner ring wall, with strict temperature and humidity requirements, with excavation of both faces must be underpinned, plus the compli cation of getting air to optimum loca while the rock below the outer ring wall could be sta tions within the Reading Room open space. Levei O bilized with pre-reinforcing dowels and ti e back rods. and LeveI I over the Mechanical Room are fed directly A 1-2-3 underpinning sequence was specified by a standard vertical mechanical shaft. The Read (Fig. 7). A trench was excavated in the mi ddle section ing Room is supplied by a large number of flat ducts located in th e narrow space availab le between the book stacks and the inner ring wall, bringing air to the top of the stacks, with the return system located in the slab, and built into the furniture. The most challenging system was for the perime ter office space. Seven diagonal shafts drilled into the rock (diameter between 800 and 1200 mm) together with seven vertical shafts (1500 mm diameter) pro vide the connection between the Mechanical Room and the perimeter offices space. They host ductwork, sprinklers, plumbing, and other mechanical and elec trical systems. The diagonal shafts were drilled from outside the building using raise-bore equipment, up to the meeting point with the vertical shafts. From this location, the ductwork is placed on the rock, in a crawl space below the lowest floor leveI (the lowest floor levei is a structural suspended slab). With no headroom fo r a horizontal distribution duct work system, the ver tical supply risers are distributed unifo rmly throughout the floor plan - with one semi-recessed shaft behind every buttress, in the tension zone of the buttress. The majority of the shafts are recessed only in the concrete Iiner placed in 1953, therefore with minimal impact on the stone masonry walls. The buttresses were pressure grouted before cutting any slots. The return air ducts were partially recessed in the brick masonry wa ll s, at each side of the four stair shafts. Figure 7. lnner ring wall - underpinning.

1282 along the perimeter office, while the inside area was The construction of the new Mechanical Room lowered as part of the Mechanical Room excavation. required extensive coordination, review and detailing Trenches perpendicular to the inner ring wall were of step by step construction activities, and on going extended to the face of the wall on both sides, not quality control and supervisiono Good communication exceeding 1200 mm width. Needle beams at 400 mm with the General Contractor's team, Fuller Construc centers were installed in cores drilled into rock just tion (Ottawa), ensured a smooth implementation ofthe below the underside of the walls, and hung from designo the underside of a steel beam bearing each side of Underpinning of large loadbearing masonry walls the trench. Considering significant deterioration ofthe is possible only with a good understanding of actual wall rubble core, it was a concern that pre-grouting soil conditions. The procedure ll1ust be tailored to such would not be sufficient to ensure the integrity of the conditions, and must ensure full control ofthe wall, or wall and sections of wall might fali into the excava sections of the wall, at ali times. It is a good practice tion. Afier the installation ofthe needle beams, the rock that any tell1porary support element be removed from below the wall section was removed and replaced with the wall after the completion ofthe work. unreinforced concrete. The joint between the top ofthe concrete and underside of the wall was dry-packed a few days after placing ofthe concrete, in order to allow ACKNOWLEDGEMENTS for the initial shrinkage. The procedure was repeated for the stage 2 and 3 sections. Architect Joint Venture: Ogilvie & Hogg Architects (Ottawa), Architects Desnoyers Mercure et Associés 3.4 Conclusions (Montreal), Spencer R. Higgins Architects (Toronto), and Michael Lundholm Architects (Toronto) Remodeling and upgrading of heritage buildings to Structural Engineers: Adjeleian AlIen Rubeli Lill1ited meet modern code and functional requirements is pos (Ottawa) sible. It requires a team approach within the design Geotechnical Engineers: Golder Associates (Toronto) teall1, as well as continuous supervision and collabo Testing Agency: ArconTEST (Toronto) and Labo SM ration during the construction phase. Architects, con (Montreal) servators and engineers of different specialties ll1ust work together, understanding each other requirements, and search for innovative ideas in order to satisfy the REFERENCE Client's needs. Design assull1ptions must be confirll1ed by further exploratory work and confirmation ali the Ferragni, D.1984 Injection Grouting of Mural Paintings and time during the construction phase, as a variety ofsite Mosaics. Adhesives and Consolidants: Reprints of the conditions are revealed. 1984 Paris llC Conference (llC London 1984) 110- 116.

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