Lecture11_concrete_ingredients

Lecture11_concrete_ingredients - Concrete Ingredients:...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
CE Materials, Portland Cement, Page 1 Concrete Ingredients: Aggregates and Aggregates and Admixtures Composition of Concrete ± Concrete is composed: ± Cement ± Water Aggregates ± Aggregates: ± Coarse aggregates ± Fine aggregates ± Admixtures Mixing Water
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CE Materials, Portland Cement, Page 2 Mixing Water ± Water ± Hydrates Portland cement ± Initiates hydration (few minutes) ± Sustains hydration (beyond 28 days) ± Provides workability ± Allows for ingress of deteriorating substances Impurities May Affect ± Strength gain characteristics ± Setting time ± Appearance ± Staining ± Durability ± Aggregate-alkali reactivity, sulfate attack, etc. ± Reinforcement steel corrosion Mixing Water ± Should not (ASTM C94, C109, and C191) ± Affect setting time ± Affect 7-day mortar cube strength ± water distilled f % 90 water le questionab f c c > ± Introduce long term detrimental chemistry ± Common Sources ± Potable water is usually OK ± Well-water may be problematic ± Other sources must be checked
Background image of page 2
CE Materials, Portland Cement, Page 3 Impurities In Mixing Water ± Chlorides ± Carbonates and Bicarbonates (Na/K) ± May cause alkali-aggregate reaction and/or affect setting time and strength ± Sulfate ± May cause expansion ± Salts (Fe, Mg, Zn) ± May discolor concrete or cause strength loss Impurities In Mixing Water ± Sea Water ± Accelerate initial strength, reduce ultimate strength, aggravate alkali- aggregate reactions Suga ± Sugar ± >500 ppm can retard concrete setting and reduce long-term strength ± Can accelerate setting (>.25%) but reduce long-term strength ± Oils ± >2.5% can reduce strength by 20% Chlorides In Mixing Water ± May cause corrosion of reinforcing steel ± Limits ± Prestressed concrete: < 0.06 % ± Reinforced concrete exposed to Cl - : < 0.15 % ± Reinforced concrete dry or protected: < 1.00 % ± Others: < 0.30 %
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CE Materials, Portland Cement, Page 4 Permeability And Porosity ± Permeability ± Measurement of flow through a solid substance ± Porosity ± % of solid that is a void ± High porosity high permeability ± Inverse relationship between porosity and strength Pore Structure ± PCC starts as cement grains suspended in mix water ± Cement hydrates (combines) with water ± Mixing water voids become filled with hydration products ± Becomes hardened cement paste (HCP) ± Voids not filled with HCP = capillary voids (w/c > 0.32) Water In HCP ± Capillary water ± Free water > 50nm ± no shrinkage, loss at RH < 100% ± Capillary tension 5–50nm shrinkage ± ± Adsorbed water ± Physically held by solid particles – hydrogen bonds ± shrinkage at 30% RH
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 15

Lecture11_concrete_ingredients - Concrete Ingredients:...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online