1500 - E117 - 30 - Considerations for Concrete Durability.

Concrette Tech C hnolog gy and Codes s Considerations for Concrete C t Durability D bilit Why concrete problems occur? Avoiding Problems      Designg Constructabilityy Mix Design Materials Selection Placement Procedures Environment Workmanship Design Environment Discussion: Desired Durabilityy  Concrete Specifications  Mix Design Requirements  ACI 318-08 Updates- CH   Evaluating Concrete Performance Designing Concrete Mixtures Objective: To determine the most economical and practical combination of readily available il bl materials t i l to t produce d a concrete that will satisfy the performance requirements under particular conditions of use Concrete Durabilityy  M-21 M 21 / Plaster Creek Ability of Concrete to Resist Weathering Action, Chemical Attack, and Abrasion While Maintaining its Desired E i Engineering i P Properties ti Durability Considerations • • • • • • Abrasion Freeze-Thaw, Freeze Thaw, Scaling Carbonation Corrosion Reactive Aggregate – ASR Chemical Attack – DEF – Sulfate Attack Factors Impacting Permeability    Water:cement ratio Curing Material fineness   Paste/aggregate ratio    Aggregate Gradation Cement content Aggregate-paste Aggregate paste bond Barriers Porosity 100 60 50 50 40 Capillar porosity Capillary porosit → 30 Cap pillary Porossity (%) Degree e of Hydrattion (%) ← Degree of hydration 20 0 10 20 30 40 50 60 Curing time (days) Young et al 1998 Cement Content PCA RD129 Low-Permeability Concrete Low-Corrosion Resistance    PermeabilityASTM C1202 Less than 2000 Coulombs Effect of test age? Crackingg vs Durabilityy Volume StabilityStabilityLow Shrinkage Concrete   Low Shrinkage Concrete ASTM C157 Less Than 400 millionths Surface Blemishes vs Defects I it a Durability D bilit Issue?? I ?? Is Acceptance Criteria  General Acceptance p criteria-Architecturally Architecturally acceptable concrete surfaces should be aesthetically compatible with minimal color and texture variations and minimal surface f defects when viewed at a distance of approximately 20 ft (6m) or more as agreed upon by architect, owner, and contractor, or as otherwise specified QA/QC    Preconstruction meeting Prequalification of finishing crew Test panels, Mock ups Specify Curing Regime When not otherwise specified (ACI 301):  Concrete shall be maintained above 50° F and in a moist condition diti ffor att lleastt th the fi firstt days after placement High High-early early strength concrete shall be maintained above 50° F and in a moist condition for att least l t th the fi firstt d days  Cement Hydrates in Layers… • Concrete cures from outside in Be Clear on Desired Outcome  Specify enough “hoops” to jump through to get the performance you require for service conditions Caution Requirements that Bind Contractors Hands   Means and Methods Materials Types State the Obvious  If it isn’t in the Specification, it probably b bl won’t ’ h happen  Ex: Curing Regime ... Environment Discussion: Desired Durabilityy  Concrete Specifications  Mix Design Requirements  ACI 31 8-0 8 Updates- CH   Evaluating Concrete Performance Designing Concrete Mixtures Objective: To determine... strength of 35Mpa (5000psi) for Very Severe (S3) Sulfate Exposure Resistance to Sulfates Expansion Test- ASTM C1012 Moderate- Class- S1 < 0.10% 10% at months  Severe- Class- S2 < 0.05% at months... l to t produce d a concrete that will satisfy the performance requirements under particular conditions of use Concrete Durabilityy  M-21 M 21 / Plaster Creek Ability of Concrete to Resist Weathering