Materials Conservation – Concrete and Plaster

Carolyn L. Searls Senior Principal, Simpson Gumpertz & Heger

Matthew Bronski Associate Principal, Simpson Gumpertz & Heger

California Preservation Foundation Webinar 16 September 2014

www.sgh.com www.sgh.com 1 Learning Objectives

• Understand the composition and properties of cementitious materials. • Recognize signs of concrete and plaster deterioration and their causes. • Learn reactive and proactive repair techniques for concrete and plaster. • Learn procedures for repairing uncoated, integrally colored plaster and concrete.

2 The Materials: Plaster, Concrete and Cast Stone

• All are made up of binder + aggregates + water • Concrete = Cement (the binder), fine aggregate, coarse aggregate, admixtures and water • Cast Stone = Cement, fine aggregate, crushed rock, admixtures and water, precast in units • Plaster = Mortar applied to a substrate (masonry, concrete, or lath over sheathing or building paper) as a wall finish. Usually cement and/or lime (binder), fine aggregate, admixtures and water

3

Evaluation and Repair of Concrete and Plaster

• Diagnose the problem – field investigation, lab testing, analysis and report. The treatment must be appropriate for the illness. • Design the repair – the right team • Select the correct materials • Construct field mock-ups • Select the right contractor • Provide quality control during repairs

4 Concrete

• Roman concrete structures – lime putty + pozzolan (volcanic tuff rock at Pozzuoli) + aggregates = hydraulic concrete • Natural cement concrete – Erie Canal (1825), Brooklyn Bridge • Portland cement concrete – use in military fortifications in 1880’s in US • Reinforced concrete – 1900 – variety of bar types and placement strategies

5 Overview of Concrete as a Material - Properties

A few key concrete properties:

• Concrete is basically man-made stone (sedimentary) – Strong in compression, weak in tension (roughly 10:1) – Reinforcement provides tensile strength • As w/c ratio decreases (less water, “stiffer” mix) – Strength increases – Density increases – Absorption decreases – Durability increases – But… – “Workability” (by one def.) decreases • Romans understood this, as do engineers today

Cast Stone

• Precast concrete (cement, sand, crushed rock) with fine finish coat • Made to replicate stone or other materials • Used for copings, lintels, sills, ornaments on facades • Can be reinforced or unreinforced • Ability to be mass produced

7 Causes of Deterioration of Concrete

• Environmental effects – water, freeze/thaw, salts (marine and deicing salts), biological growth – Most common problem: corrosion of embedded steel • Inferior materials and poor workmanship – alkali- aggregate reaction (ASR), poor consolidation, poor original quality, cold joints, lack of adequate concrete cover, sulfate attack from soil • Structural design defects – absence of expansion/contraction joints, structural failure • Improper maintenance – lack of maintenance allows water access, poor choice of repair materials, ie, non- breathable waterproof coating

8 Common Signs of Deterioration - Concrete

• Cracks (not shrinkage) • Spalls and incipient spalls • Rust stains and signs of corrosion • Other stains • Deflection • Erosion

ACI 364.1 “Guide for Evaluation of Concrete Structures before Rehabilitation”

9 Corrosion of Reinforcing Steel in Concrete (and Cast Stone) • Reinforcing steel initially protected by passivating layer • Corrosion occurs due to: – Carbonation – Chlorides • Expansion of rust product causes cracking and spalling

10 Methods to Detect Corroding Embedded Reinforcing • Visual observation and sounding for delaminated areas • Locate reinforcing steel with metal detectors and/or GPR • Half-cell potential (copper/copper sulfate) testing • Linear polarization corrosion rate testing • Test concrete for chlorides and carbonation to determine why corrosion is occurring – this will affect your repair

GPR Copper-copper sulfate half cell testing

11 “Reactive” Repairs for Corrosion of Steel in Concrete • Patching • Epoxy injection

ICRI “Guide for Selecting and Specifying Materials for Repair of Concrete Surfaces”

12 “Proactive” Repairs for Corrosion of Steel in Concrete • Inhibit moisture ingress – Flash sky-facing surfaces – Cut drip edges – Clear water repellants – Film-forming coatings (elastomeric)

13 “Proactive” Repairs for Corrosion of Steel in Concrete • Chemical treatments to alter corrosion process – Realkalization – Electrochemical chloride extraction – Surface applied corrosion inhibitors

Re-alkalization treatment in process 14 “Proactive” Repairs for Corrosion of Steel in Concrete • Electrical treatments to alter corrosion process – Impressed current (active) cathodic protection – Sacrificial anodes to provide passive galvanic protection of localized repairs

Sacrificial galvanic anode cross section (left) and installed (right).

Images courtesy Vector Corrosion Technologies. 15 Plaster

• Mud plaster – used on interiors and exteriors of adobe • Lime plaster – often mixed w/sand and reinforced w/hair • Gypsum plaster – interior only • Exterior cement plaster (“stucco”) – Cement, lime and sand

16 Exterior Cement Plaster

• Applied as a parge coat to finish masonry or concrete walls – In multiple coats, wide thickness variation – Barrier wall construction • Applied to wood lath or wire lath over a weather resistive barrier and sheathing or open frame construction – Modern: 3 coats, 7/8 in. thick – Expansion joints every 144 sf to reduce cracking – Modified drainage wall construction • Integral color or painted

17 Plaster – Common Signs of Deterioration

• Cracking • Crazing or map cracking • Separation from backing or between coats • Spalling • Crumbling or powdering • Stained • Corrosion

18 Delaminating Plaster

Methods to Detect • Sounding • Infrared thermography • Bond strength (pull off or shear) testing Falling Hazards

19 Plaster Repairs • Analyze existing plaster (remove sample) • Develop possible matches – Match sand • Check against building code = ASTM C926 proportions

20 Plaster Repairs

From PCA, “Repair of Portland Cement Plaster (Stucco)

Patches require moist curing

21 Memorial Auditorium

• Bakewell and Brown, 1937 • Cement plaster over concrete • Campus Landmark • Building envelope assessment

22 Memorial Auditorium Existing Conditions

23 Memorial Auditorium • Condition survey – Samples and laboratory testing – Determined causes of deterioration • Close up survey – Tapping to identify and remove falling hazards – Quantify delaminated areas for pricing • Develop and discuss repair options (eventually used them all): – Clean and remove graffiti – Patch cracks and spalls – Fog coat or paint all or part of plaster – Replace all or part of plaster • Analyze samples, design mix • Mockups • Repair: client expectations

24 Mockups – Graffiti Removal, Patching, Cleaning

Cleaning – Antimicrobial D/2 Graffiti removal – Citristrip (acrylic paint) and Wipe Out (aerosol paint) 25 Repair Gutters and Stains Near Roof

26 Clean and Patch Walls Before After

Considerations • How perfectly do the patches have to match? (skim coat or fog coat vs. patching) • How much of the original fabric should remain? • Is the natural weathered appearance of unpainted plaster OK? • When one area is skim coated, adjacent weathered or patched areas appear imperfect.

27 Garden Walls

Cleaned and patched

Skim coated with plaster (need clean, unpainted surface)

28 Theater Entrance

Mostly skim coated

29 West Side

Cleaned and patched

30 The Southwest Museum

• Built in 1914, Los Angeles’ oldest museum • Local Landmark & National Register • Cast in place reinforced concrete with cement plaster parge coat • Problems addressed – Damage from Northridge earthquake – structural evaluation and repairs – Water infiltration at roofs walls, and windows – Cracking, spalling and

delamination of plaster 31

The Southwest Museum – Exterior Wall Investigation

• Accessed walls using industrial rope access – Tapping and listening for a “hollow sound” to detect delaminated areas – Mapped cracks, delaminated areas, and other damage – Removed cores for materials testing

32 The Southwest Museum – Field Investigation Results • Plaster delaminated on all sides of tower; particularly near top • Up to five layers of plaster over concrete • Plaster appeared “harder” than “soft” concrete beneath • Plaster on rest of building in better condition than on tower

33 The Southwest Museum Laboratory Testing – Petrography & Mortar Analysis • 5 core samples removed - Plaster layers fell off concrete when cores removed even in “sound” areas • Petrographic examination (ASTM C856) and Mortar Analysis (ASTM C1324 – chemical + petrographic) – Composition of materials – Causes of deterioration – Appropriate repairs

34 The Southwest Museum – Laboratory Testing

• 4 to 5 layers of plaster – Two inner layers from original construction (1 cement : 3.5 to 4.5 sand) – Two outer layers (1 cement : 1 lime : 2 sand) – Voids between layers; fractures within layers • High w/c ratio (low strength) concrete beneath

Fractures parallel to surface due to Vertical fractures in outer layer volume changes (temperature & moisture) 35 Southwest Museum – Plaster Repair Considerations • Inherently problematic system – Outer layers of plaster stronger than inner plaster; stronger than concrete beneath – Failures due to defects from original construction + variation in moisture content over time – volume changes, shear stress, warping and delamination of plaster from concrete

• Repair Considerations – How much to remove and replace? – Compatibility of new and existing materials – Matching of color, texture and porosity – Adhesion of repair

36 The Southwest Museum – Mockup Repairs • Plaster repair mockups – Two areas test removing all plaster from the tower – Two areas test patching delaminated areas only • 12 different plaster mixes – 3 coat over metal lath – 1/8” one coat adhered – 2 coat adhered – 3 coat adhered • Varied – Bonding agent – Surface prep (sandblasting, bush hammer, keying, none) • 3 paints

37 The Southwest Museum – Plaster Repair Mockup Evaluation • Testing of plaster mockups – Plaster pull-off (ASTM D 4541 – Portable adhesion tester) – Paint adhesion (ASTM D 4541 + ASTM D 3359 – tape adhesion) • Tested both new plaster and adjacent original plaster

38 The Southwest Museum – Repair Recommendations • Remove existing plaster on the tower only; patch elsewhere • Roughen exposed surface by sandblasting • Apply bonding agent to concrete substrate • Install adhered ½ in. thick, 2-coat plaster system on tower; patch spalls on remainder of building • Paint with breathable elastomeric paint

39 Griffith Observatory – Concrete Repair

40 The Observatory

• History: designed by Austin and Ashley; built in 1933- 1935 • Declared a L.A. Historical Cultural Monument in 1976 • Highly detailed concrete; original design was terra-cotta – Condition: Good – Few Small Spalls – Bugholes on the Concrete Surface – Not as well maintained where access difficult • Paint – Blistering – Peeling – Lead containing

41 Griffith Observatory Restoration and Expansion Griffith Observatory Restoration and Expansion

Excavation Griffith Observatory – Condition Before Restoration

• Concrete detailing important to design • Need to retain crisp edges after repair • Note incipient spall and previous patch

43 Griffith Observatory – Concrete Texture and Finish • Bugholes in concrete • Coating cannot bridge • Water infiltration leads to coating failure

44 Griffith Observatory – Project Goals

• Objectives – To restore the building exterior – To stop leakage to interior – To slow down the deterioration of the concrete ‘skin’ • Primary Forces Driving the Repair – Historical Significance – Aesthetics – Performance of Building ‘Skin’

45 Griffith Observatory – Concrete Repair Procedure • Remove existing paint, carefully • Patch spalls • Install sacking material to fill the bugholes • Install high performance, breathable elastomeric coating

• Mockups especially important – High-profile project – Procedures had to be established before bidding

46 Griffith Observatory Mock up Repairs

• Mock ups constructed for: – Paint removal • Chemical (Peel Away 1, Peel Away 7, PR-40/LEADX) • Low-pressure abrasive blast • Hand scraping – Concrete repair – Sacking – Painting • Mockups evaluated for: – Performance (removal of existing paint, adhesion of new paint) – Aesthetics – Constructability and cost

47 Griffith Observatory Paint Removal Mock ups

• Primarily tried various chemical strippers + low pressure sandblast • Hand scraping worked where paint was peeling • High pressure water blasting would be too destructive to concrete • Certified industrial hygienist specified lead paint containment and disposal

Peel Away 7 worked at all locations PR-40/LEADX worked at some locations

48 Griffith Observatory – Paint Removal Mockups Low Pressure Sandblast • 60 psi sandblast • Bits of paint left removed with pressure wash • Surface very abraded Chemical Stripper • Did not remove paint where it was thickest • Bits of paint left came off when surface pressure washed • Peel Away 7 worked best on this paint • Other strippers may work better on other paints

49 Low-Pressure Sandblast (abraded surface)

© 2007 SimpsonChemical Gumpertz & Heger Inc. Proprietary Stripper and Confidential 50 Griffith Observatory – Surface after Paint Removal • Bug holes – too small to get coating inside, but coatings won’t bridge • “Sack” wall to fill bug holes, but do not change crisp edges or surface texture too much

51 Griffith Observatory - Sacking Materials

• Sikatop 121 Plus • Sika Monotop 620 • Edison Coatings Expo 43 • Edison Coatings Thin-Fill 55

Aggregate size and finishing technique influence final appearance

52 Griffith Observatory – Sacking Mock up Results

Sika Monotop 620 rough texture, client preferred

Sikatop 121 Plus – medium size aggregate, bug holes and pour lines read through Sikatop 121 Plus 53 Painting Mock-ups

• Materials – 8 different coatings – 5 elastomerics – 3 acrylics • Substrates – 3 different sacking materials • Application – Roller (2 and 3 coats) – Brush – Spray

54 Griffith Observatory Painting Mockups

55 Griffith Observatory Painting Mockups

• Elastomerics viscous – rolling produces stipple marks • Avoid by increasing # coats, decreasing thickness of coats • Spraying only to avoid texture of stipples • Manufacturers recommend back-rolling • Tested to verify adhesion

56 Griffith Observatory – Anti Graffiti Coatings

• Requirement by City of Los Angeles for first 9 feet of public buildings • Two types of graffiti coatings – Sacrificial – coating must be reapplied after each cleaning – Permanent – more rigid and impermeable than sacrificial coatings • Challenge to find any that work over paint • ASTM D 6578 – Standard Practice for Determination of Graffiti Resistance • Preservation Brief 38: Removing Graffiti from Historical Masonry

57 Griffith Observatory – Anti-Graffiti Coatings

58 Griffith Observatory – Anti Graffiti Coatings

• Coatings tested – both sacrificial – over elastomeric paints – Defacer Eraser SC-1 by ProSoCo – Graffiti Melt by Genesis Coatings • Defacer Eraser system removed graffiti better, but damaged underlying paint more • System selected: Graffti Melt • Stop graffiti coating at a natural break in the wall • Other methods: lighting, security guards, cameras, thorny bushes

59 Concrete Patch Repair Griffith Observatory

• Exterior wall repair systems used: – Patching spalls: Sikatop 123 Plus – Sacking: Sika Monotop 620 – Elastomeric paint: Edison Elastowall 351 – Anti-Graffiti coating: Graffiti Melt Sacrificial Anti-Graffiti Coating by Genesis Coatings

61 Griffith Observatory – Concrete Repair

© Tim Griffith

62 Saving our Cold War Era MC2 Mid-Century Modernist Concrete Facades

Key Points of Presentation: • Intro: – Defining the typology – The Problem of Appreciation/Vulnerability • Evaluation and Repair – Thorough “analysis before intervention” (Athens Charter) needed – Treatment appropriate to the malady – Illustrate through examples

Introduction Mid-Century Modernist Concrete Bldgs • Defining the type: – Typically 1960’s (1958 – ’73) – Facades primarily concrete – Modernist icons, often “Brutalist”

Miami Marine Stadium, 1962, Spillis Candela – Architects include Neutra, Rudolph, Morse & Stiles Colleges, Yale, 1962, (Assessment 2009) Saarinen, Sert, SOM, Kahn, Wright Saarinen (Assessment 2008)

Holyoke Center, 1962-65, Peabody Terrace, 1963-65, Sert Law Tower and Library, 1962, Sert Sert (Assessment 2008-9) (Rehabilitation 2007 - 2012) (Assessment and Rehab. 2010-present) Introduction Mid-Century Modernist Concrete Bldgs The Problem of Appreciation/Vulnerability: • Many now deteriorating • Many just shy of 50 years old • Many not yet landmarked or protected • Difficult to adapt (inflexible plans) • Difficult for many to appreciate • “I just can’t see why some consider this building architecturally significant… I just think it’s ugly”

Today: Holyoke Center, 1962-65, Josep Lluis Sert

65 Introduction Mid-Century Modernist Concrete Bldgs The Problem of Appreciation/Vulnerability: • Beauty and character of the original design can inadvertently be lost and forgotten • Here, soiling and solar window film

• “Okay, now I see it…”

Today (prior to rehabilitation) Then (in its original glory) 66 Evaluation and Repair Mid-Century Modernist Concrete Bldgs Evaluation: • “Diagnosis Before Intervention” (Athens Charter, 1931) is particularly important • Many deterioration mechanisms exist • Need to fully understand the particular illness (deterioration mechanisms) in each case to prescribe treatment

Holyoke Center, 1962-65, Peabody Terrace, 1963-65, Sert Law Tower and Library, 1962, Sert Sert (Assessment 2008-9) (Rehabilitation 2007 - 2012) (Assessment and Rehab. 2010-present) Evaluation and Repair of Modernist Concrete Some (of the many) Deterioration Mechanisms • Corrosion of reinforcement, via – Carbonation front reaching steel – Moisture ingress – High internal chlorides – Externally applied chlorides • External mechanisms: – Impact damage – Sulfate attack (in soil or water) – External chloride application • Internal mechanisms: – Alkali-Silica reaction – Freeze/thaw damage (not common on mid-century modernist concrete buildings in New England) • Treatment must be appropriate for the illness

68 Evaluation and Repair Mid-Century Modernist Concrete Bldgs

• Two BROAD classifications:

• Reactive repairs: – “Fix what’s broken” (spalls, delaminations, etc.) – Always necessary (public safety)

• Proactive (preventative) treatment: – Attempt to reduce the future rate of deterioration – Typically a good idea – Tailor the proactive treatment to the illness (deterioration mechanism)

69 Evaluation and Repair of Modernist Concrete Overview of Preventative Repair Approaches

Treatments to inhibit moisture Chemical treatments to alter ingress: corrosion process:

• Re-alkalization ($$$) • Clear penetrating water • Chloride extraction ($$$) repellant sealer • Penetrating corrosion inhibitor • Metal flashing caps or roofing coating on “sky facing” Electrical treatments (active or surfaces passive) to alter corrosion process: • Film-forming opaque coatings • Passive galvanic protection of (e.g., elastomeric) localized repairs (sacrificial zinc anodes) • Active (impressed current) cathodic protection ($$$) Legend: • Blue = significant visual change • ($$$) = Relatively high cost (compared to other options)

70 Example #1: Peabody Terrace Graduate Student Housing • Designed by Josep Lluis Sert, constructed 1963-65 • Significant work of modern architecture • Winner of AIA Honor Medal, 1965 Peabody Terrace Where they began, pre-2006 • Decades of concrete deterioration • Falling hazards • Reactionary approach to repair – Spalls – Leaks

Peabody Terrace

• Goals of project – – Thorough diagnosis of underlying causes of deterioration and leakage – Forecast of future needs – Data to inform future planning for the complex – Solutions that respect architectural character Peabody Terrace • Sort categories for collecting survey data • Each of the 9 buildings in complex • N, E, S, W facing exposures • Floors (and pours) • Building elements: – Walls • Exposed slab edges • Exposed columns • Precast panels • Shear Walls – At reveals – Away from reveals – Balconies • Undersides • Topsides • Slab edges

Peabody Terrace

• Our evaluation included:

GPR cover survey Hands-on sounding

Binocular Survey

Data Analysis and Synthesis Corrosion Activity Testing

Petrographic analysis 75 Peabody Terrace

• Assessment – Hands-on survey – Visual/documentation of spalls and delaminations – Hammer sounding – Chain drag sounding

Building Z – Hands-on Survey North South East West Total Away from Reveals 3 3 6 at Reveals 12 4 16 Slab Edge 8 1 9 Wall Building Corner Column 2 1 1 4 Previous Repair Total 2 23 9 1 35 Slab Topside 1 41 42 Slab Underside 2 17 19 Slab Edge 4 22 26 Balcony Column 1 1 Previous Repair 6 6 Total 8 86 94 Peabody Terrace

• In-Situ Testing – Non-destructive measures concrete cover (depth to reinforcement) using Ground Penetrating Radar (GPR)

Cover Statistical Measures (using GPR)

Building Reinforcement Number of Minimum Maximum Average Median Measurements Standard Deviation Z Wall 971 0.558 4.285 1.755 0.553 1.726 Z Wall at Reveal 971 -0.067 3.660 1.302 0.553 1.101 Z Slab Edge at Wall 422 0.973 3.726 2.206 0.558 2.220 Peabody Terrace • In-Situ Testing – Measures of Corrosion Activity: using galvanostatic pulse – Corrosion rate, resistance, and potential (shown)

rd 3 floor, east elev. 5th floor, east elev.

4th floor, east elev. 7th floor, east elev. Peabody Terrace

• In-Situ Testing: Water testing – Leakage only at sealant joints and cold joints – Myth of “sponge”, and “coating solution”

Peabody Terrace

• Laboratory - Petrographic Analysis of cores • Key findings: – w/cm ratio: 0.45 – 0.53 – Air entrainment: 3 – 5 %, max. spacing factor 0.008 “+ – Carbonation depth: ¾” average – Chloride content: 0.12 - 0.95 lbs/cy – No evidence of concrete degradation due to: • alkali silica reaction (ASR) • sulfate attack • freeze/thaw cycling

Peabody Terrace • Assimilating the Data – piecing together the puzzle – Underlying causes of distress – Prognosis for the future – Best value investments

Visual Survey Corrosion Activity Testing

Hands-on Data Analysis and sounding Synthesis - Histograms

Petrographic GPR Cover Analysis Survey

81 Peabody Terrace

0.5 (1) D=Kt (A.M. Neville, Properties of Concrete) Peabody Terrace

0.5 (1) D=Kt (A.M. Neville, Properties of Concrete) Peabody Terrace

0.5 (1) D=Kt (A.M. Neville, Properties of Concrete) Peabody Terrace

0.5 (1) D=Kt (A.M. Neville, Properties of Concrete) Peabody Terrace

• Conclusions – Concrete of reasonably good quality – Carbonation front reaching steel in localized areas of low cover is primary deterioration mechanism – Reveals at walls, balcony slabs greatest concern, and area most in need of preventative treatment – Leakage through sealant joints (not concrete) is the primary path Peabody Terrace

Recommendations: • Reactive: Repair all current damage (e.g., spalls) to concrete – Major cost • Proactive/Preventative: Take measures are taken to mitigate the future rate of deterioration – Consider realkalization of balcony decks (very expensive) – Penetrating corrosion inhibitor everywhere – Coat topside of balcony decks only

87 Peabody Terrace

• Realkalization Trials – In-situ trial re-alkalization of balcony slab – SGH pre and post treatment cores and petro to evalute effectiveness (no fox watching the henhouse) – Restored alkalinity to pH 11-13 at depth of reinforcing steel

Table from Bromfield Peabody Terrace • Repair Mock-ups – Aesthetic matching of concrete repairs critical • Aggr, aggr, aggr – Developed a special “dry-pack” site mixed repair material – Technical durability critical • Bond pull-off tests – Concrete repairs and paint colors of balconies approved by Cambridge Historical Commission • Archival research on balcony railings and screen colors

Peabody Terrace

• Dry-pack concrete repair procedure – Packed by hand proud of surface – brief set – “Shave” level w/ metal trowel – Moist cure w/ Burlene ten days – Sandblast finish

Example #2: Holyoke Center, Cambridge, MA Sert, c. 1962-65

Conclusions: • Concrete quality very similar to Peabody Terrace, but Holyoke concrete has fewer problems • Why??? Better cover!

Recommendations: • Technical - very similar to Peabody Terrace • Aesthetic – cleaning and other measures could easily restore appearance

91 Example #3: BU Law Tower and Pappas Law Library, Boston

• Designed by Josep Lluis Sert • Completed 1962 • C.I.P. walls and structure • Exposed aggregate precast: – Fins – Sills – Panels – Scuppers

92 BU Law Tower and Pappas Law Library

Conclusions:

• Concrete quality is relatively good • No indications of: – Internal distress (e.g.,ASR) – Freeze/thaw damage • Primary Deterioration Mechanisms: – Cast-in-Place Concrete: • Carbonation (carbonation front reaching the reinf.) – Precast Concrete: • Carbonation, and high chloride concentrations in some elements – Sky-Facing Surfaces (e.g., sills, ledges): • Moisture ingress , carbonation

93 BU Law Tower and Pappas Law Library

Preventative Recommendations:

• All concrete: – Penetrating corrosion inhibitor • Additional treatments: – Precast Concrete only: • Clear silane water repellant – Sky facing surfaces • Cap with flashing or roofing coating – Underside horizontal surfaces • Saw-cut drip edge where absent

94 Concrete Repair Mix Design (Mock-up process)

Cast-in-Place Concrete Repair Mock-ups Cement Aggregate Water Admixture Fine Medium Coarse Mica

Grace Daravair Mix Iron Clad Type I - Lafarge - Type 1 - Iron Clad White - Quikrete All Vitacrete Pea A.A. Will River A.A. Will Brown Conproco Potable - (lbs) 1000 - Liquid - Buff - (lbs) Gray - (lbs) (lbs) Purpose Sand - Gravel - 3/8" Stone - 3/8" Sand - (lbs) (teaspoons) (teaspoons)

Date installed 1152 (lbs) A.A. Will Coarse washed - (lbs) washed - (lbs) Concrete Sand - (lbs) C1 8 0 0 12.8 0 0 0 0 8 2.4 8 C2 6 0 2 12.8 0 0 0 0 8 2.4 8 C3 4 0 4 12.8 0 0 0 0 8 2.4 8 C4 8 0 0 12.2 0 0 0.6 0 8 2.4 8 C5 6 0 2 12.2 0 0 0.6 0 8 2.4 8

C6 4 0 4 12.2 0 0 0.6 0 8 2.4 8 C7 8 0 0 12.2 0 0 0.3 0.3 8 2.4 8 ROUND 1 4/26/2013 C8 6 0 2 12.2 0 0 0.3 0.3 8 2.4 8 C9 4 0 4 12.2 0 0 0.3 0.3 8 2.4 8 C1A Proportions by volume are - 1 part C1 mix: 1 part A.A. Will River Stone C1B Proportions by volume are - 1 part C1 mix: 1 part Vitacrete Pea Gravel C1C Proportions by volume are - 1 part C1 mix: 1/2 part A.A. Will River Stone : 1/2 part Vitacrete Pea Gravel C1D 8 0 0 0 0 12.8 0 0 8 2.4 8 C10 8 0 0 9.1 3.1 0 0 0.6 8 2.4 8 C11 8 0 0 6.1 6.1 0 0 0.6 8 2.4 8 C12 8 0 0 3.1 9.1 0 0 0.6 8 2.4 8 ROUND 2 5/15/2013 C13 2 6 0 12.2 0 0 0 0.6 8 2.4 8 C14 4 4 0 12.2 0 0 0 0.6 8 2.4 8 C15 6 2 0 12.2 0 0 0 0.6 8 2.4 8

C16 4 4 0 6 0 6 0 0.8 0 2.4 8

C17 4 4 0 0 0 12 0 0.8 0 2.4 8 ROUND 3 REMOVED C18 4 4 0 0 0 10 0 2.8 0 2.4 8

C16 4 4 0 6.1 0 6.1 0 0.6 0 2.4 8

C17 4 4 0 5.1 2 5.1 0 0.6 0 2.4 8 7/31/2013 ROUND 3.1 C18 4 4 0 4.1 4 4.1 0 0.6 0 2.4 8 C19S 8 0 0 6.1 0 6.1 0 0.6 0 2.4 8

C20S 4 4 0 12.2 0 0 0.6 0 0 2.4 8 C21S 4 4 0 0 0 12.8 0 0 0 2.4 8

ROUND 4 8/14/2013

Law Tower and Pappas Law Library

Mock-up process for determining concrete repair mix design:

• No pigment in any samples! • Varied constituents: – Cement (3 types) – Sand (3 types) – Medium and course aggregate (2 types) August 2013 above. September 2013 below. – Trowel type for installation • Looking for best long-term match

96 Example #4 Morse & Stiles Colleges, New Haven CT • Designed by Eero Saarinen • Constructed 1958-62 • Large boulders as course aggregate

Morse & Stiles Colleges, New Haven CT

Conclusions: • In very good condition, but… – Avg. Chloride ion content 1.4 pcy – 1-2% air • Concrete is worse quality than other examples - Why in so much better condition? – Much better cover! Morse & Stiles Colleges, New Haven CT

Preventative Recommendations: • Cap sky-facing surfaces that aren’t already capped • (Don’t bother with penetrating corrosion inhibitor)

Example #5: Miami Marine Stadium • Designed by: – Hilario Candela, Architect – Jack Meyer, Engineer – 1964 • Significance: – Structural (64’cantilever) – Architectural – Rare type (purpose built) – Cultural • Elvis “Clambake”, Richard Nixon, Sammy Davis Jr., Jimmy Buffet, etc • Endangered Watch Lists: – World Monuments Fund – National Trust for Historic Preservation Miami Marine Stadium

Conclusions: • Poor condition, except roof is good – Galvanized rebar in roof only • High chlorides – Everywhere, particularly topside of deck – Severe exposure, & – Used for target practice by fireboats!

Miami Marine Stadium

Preventative Recommendations: • Multiple options, generally: • Roofing on topside of roof • Coating on topside deck • No coatings on underside deck • Penetrating corrosion inhibitor throughout

Saving our Cold War Era MC2 Mid-Century Modernist Concrete Facades

Summary - Key “Take-aways" : • MC2 are particularly vulnerable historic resources – Often significant works of modernism, YET • Often lack protection and appreciation • Often have serious deterioration, falling hazards • Inflexible to modify in plan • Evaluation and Repair – Thorough “analysis before intervention” (Athens Charter) needed • Involves putting together many pieces of data and to understand the whole picture – Treatment must be appropriate to the malady • Can and should be tailored to the malady, even within a single building

Mid-Century Modernist Concrete Facades • Thank you

Miami Marine Stadium, 1962, Spillis Candela Morse & Stiles Colleges, Yale, 1962, (Assessment 2009) Saarinen (Assessment 2008)

Holyoke Center, 1962-65, Peabody Terrace, 1963-65, Sert Law Tower and Library, 1962, Sert Sert (Assessment 2008-9) (Rehabilitation 2007 - 2013) (Assess. 201, current Rehab.)