Dawn Lehman Katie Kuder (SU), Jeff Berman, Charles Roeder Guðmundur Hannesson (GSR) High-Volume SCM Concrete in Composite Construction

Overview Impetus and Challenges of Composite Construction and SCM Concretes Evaluation of Binary SCM Concretes Development of Ternary High-Volume SCM Concretes Engineering Properties (time-dependant strength, modulous of elasticity, creep)

Earthquake Damage of Common Structural Components Structural Wall ~ 2% Drift Brace Frame ~ 2% Drift

Goals of PBEE Design Collapse prevention For less severe structural damage states: – Quantifiable damage states – Systems that mitigate damage For functionality-related damage states: – Stiff – Strong

Advantages and Challenges of Composite Construction Engineering Properties – Strong, stiff, efficient – Design models and connections not well established Constructability – Reduced labor, materials – Final properties with time; design for construction loads Seismic Performance – Reduced concrete damage; Reduced steel damage? – Limited experimental testing

Structural Applications – Composite Systems Concrete Filled Tubes for Bridge Construction

Performance of CFT and RC Columns 6% Drift for CFT6% CFT 5.5% Drift for RC 5.5% 3% Drift

Performance of CFT and RC Columns 10% Drift CFT 8.9% Drift RC

Composite Structural Wall (in development) Dual Skin Composite Shear Wall

Low PC, High SCM Concrete Advantages: Sustainability - Minimize Portland cement with High-Volume SCM Concrete Reduce carbon footprint Use waste materials (otherwise land-filled) Reduce virgin materials use Challenges: Material Properties Material variability Slow strength gain Time of set

Sustainable Composite Components Materials SCM characterization Mix design Processing Materials SCM characterization Mix design Processing Construction Construction loads and conditions Construction sequencing Formwork pressure Construction Construction loads and conditions Construction sequencing Formwork pressure Structural Composite system performance Connections Design Models Structural Composite system performance Connections Design Models Time-dependent engineering properties

Experimental Program Binary Mix – Base SCC mix (0.35 w/c ratio) – Four SCMs: 2 slag, 2 fly ash – PC replaced at 20, 40, 60, 80 and 100% – f’ c at 7, 14, 28, 56, 84, 168 days Ternay Mixes – Base SCC mix (0.4 w/c ratio) – Two SCMs: 1 slag, 1 fly ash – PC replaced at 60, 80, and 90% – f’ c and E c at 7, 14, 28, 56, 112, 168 days

f’c vs. time – fly ash Varies by type of fly ash Very low strength at 100% Strength development similar to control for 20 and 40% replacement At 60%, strength development slower, but long term strength is comparable

f’c vs. time – slag Varies by type of slag although variability is less Low strength at 100% replacement Long term strength exceeds control up to 60% replacement Higher early strengths when compared with binary fly ash mix results

High-Volume SCM mixes Fly ash: slower strength development but greater long term Chemical composition appears to have an effect SLAGSLAG FLY ASH

Ternary Mix Design Current Effort: – Develop ternary mix designs – Evaluate concrete properties: strength, stiffness and long-term deformation response (creep) Test Matrix: – Replacement percentages: 60, 80, 90% – Ratios of SL/FA: 25/75, 50/50, 75/25 – C/(S+A) > 1

Ternary Mixes

Predicting Concrete Strength as Function of Time

Comparison with Ternary (solid) and Binary (hollow)

Comparison with Other Data: Percent Replacement

Modulus of Elasticity (ternary)

Comparison with ACI Eqn.

Comparison with Alternative Eqn.

Evaluate response under “gravity” loading (same force on all specimens) Sealed and unsealed Calibration of Bingham-Maxwell creep model Creep Testing Mix Load/ f’ c,target A g TimeStress loading Strength /Stress Ternary 90% Mix: 50% Fly Ash 50% Slag Base E 0 +E 1 Instantaneous Modulus E 0 Modulus at t=∞  Time-dependent Viscous Damper

Creep Data and Model UnsealedUnsealedSealedSealed

Conclusions Strength – 100% replacement does not result in reliable strengths – 60% replacement provides stable results (less uncertainty) – Above 60% replacement must consider chemical composition of the cement and binders Modulus of elasticity – Increases for ternary mixes up to 56 days – Modulus of conventional concrete is stable w/ time – ACI expression underestimates E c. Creep – Loading at 28 days similar to loading at 7 days for conventional concrete (0.1f’c) – Sealed specimens lower creep deformation ~ promising for composite construction application