Christ the Light CathedralOakland, CAOur TeamAdam OjedaSteve Bourne Christian MartinezFrancisco MartinOverview• Replacement for St. Francis de Sales– Damaged by Loma Prieta earthquake• $131M total cost; $20M concrete• Includes:– Cathedral– Mausoleum– Rectory/Chancery– Gift shop– ParkingSite PlanArtist RenditionFeaturesArchitectural elements– Concrete–Wood–Glass–Steel• Earthquake resistance– Supported by 36 friction pendulum double concave bearingsFeatures (cont.)• Cathedral “floats” on bearingsConcrete overview• Normal– Slabs, floors, non-architectural concrete• Shotcrete– Retaining wall• Self-Consolidating Concrete– Vertical architectural elements– Thin vertical walls– Mix design/testingConcrete overview (cont.)• 27,000 cu yards total concrete volume• Rebar reinforcement– No pre/post tensioning– Regular grade 60 steel – Cover: 2” ext., ¾” int.• Extensive admixtures– Slag/fly ash– HRWR, VMA, stabilizers (SCC)Concrete overview (cont.)• W/C ratio dependent on desired strength– Slabs: 4,000 psi– Walls: 5,000 psi– Sanctuary floor & isolator system: 8,000 psiAggregates• Coarse aggregate– Sechelt, British Columbia– ½” crushed • required due to rebar congestion• Fine aggregate– RMC Eliot, Angel Island• Reduced coarse/fine ratio for SCCCement and cement replacements• Portland cement– Type II/V cement – Source: RMC/Cemex• Blast furnace slag– Up to 50% cement replacement– Source: Calaveras Cement• fly ash–Used for SCC– Up to 25% cement replacement– Source: Phoenix CementChemical admixtures• HRWR/super plasticizer– BASF Glenium 3000NS• Polycarboxylate-based water reducer• Viscosity modifier– BASF Rheomac VMA• Adds cohesiveness • Stabilizer– BASF Delvo Stabilizer• Increases working time for SCC• No intentional air entrainmentTechnical issues• Heavy/dense rebar• Thin elements• Odd shapes/dimensions• Architectural finish• Solution: SCC!SCC benefits• Lower costs– Labor, equipment• Excellent finish– Smooth, defect free• Difficult elements– Thin, rebar-congestedSCC mix issues• New to contractor; needed mix evaluation– Required extensive mix testing– Mixes tested on non-critical components– Segregation, bleed, and flowability monitored• Admixture balance– HRWR, VMA, stabilizer; balance is critical• Aggregate balance– More fines (sand); coarse/fine ratio low– Proper balance improves flowSCC quality control• QC based on tested/accepted design mix– Required spread test every truck• Inverted slump cone spread test • Only used to confirm basic properties– Goal: 26” spread w/o segregation/edge bleed– Sample (for strength testing) as normalSCC form design• Full hydrostatic load design• Forms must be water-tight (<1/4” gaps)• Special, smooth form surfaceSCC placement• Placement primarily via pump– Some also placed with bucketForm removal/curing• Three days before form removal– Reshoring used until full strength developed– Spray-on curing compound after removalWhat we learned• SCC is very helpful with some projects– Thin walls/rebar congestion– Odd shapes/smooth finish requirements– Placement difficulties/costs• SCC mix design and monitoring is critical• Cement replacements becoming commonOur thanks go to…Frank Haase, PEProject ManagerEric PetersonSenior SuperintendentHarry GoularteCentral ConcreteTodd MercerProject Director(no
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