Uses of Portland Cement Concrete Buildings Bridges Pavements

Uses of Portland Cement Concrete Buildings Bridges Pavements Concrete block buildings

Other Uses of Cementitious Materials Mortar for masonry Grout (protection, leveling, bonding, . . . ) Shotcrete Cement board Soil Stabilization Railroad ties, countertops, moldings. . .

Portland Cement History Egyptian Pyramid of Cheops (3000 B. C. ) n n First Calcareous Cement (Ca. O based) Calcined gypsum Roman and Greek Projects First Hydraulic Cements (100 B. C. ) n calcined limestone and clay

History of Cement 2000 B. C. : Egyptians used cement in mortar when making Pyramids 27 B. C. : Roman cement made of lime and volcanic ash 1756: Smeaton rebuilt Eddystone Lighthouse 1824: Joseph Aspdin discovered and patented “Portland” cement

Isle of Portland Quarry Stone next to a Cylinder of Modern Concrete

Portland Cement History Rotary Kiln w Ransome (1886), Edison (1909) Gypsum and Air-Entraining Admixtures w U. S. (1910 -1940)

Cement is a Manufactured Material Go Animation

Common Sources for Raw Materials Lime (Ca. O) - Limestone, shale Silica (Si. O 2) -Clay, sand, shale Alumina (Al 2 O 3) - Clay, fly ash, shale Iron (Fe 2 O 3) - Clay, iron ore

Portland Cement Production 5/8 rock 1/5 1/10 1/20 Ca. O Limestone or calcareous Si. O 2 Clay or argillaceous rock Al 2 O 3 Clay or Ore Fe 2 O 3 Clay or Ore Ca. SO 4*2 H 2 O Gypsum

Cement Clinker

Shorthand Chemistry C = Ca. O S = Si. O 2 A = Al 2 O 3 H = H 2 O S = SO 3 F = Fe 2 O 3

Clinker: artificial mineral containing: C 3 S tricalcium silicate C 2 S dicalcium silicate C 3 A tricalcium aluminate C 4 AF tetracalcium aluminoferrite

Clinker Micrographs

Finish Grinding Interground with ~5% Gypsum 95% material must pass #325 Sieve

Hydration of Portland Cement C 3 SH 4 Calcium Silicate Hydrate CH Calcium Hydroxide

Hydration of Portland Cement C 6 AS 3 H 32 Ettringite n n stable in SO 4 -2 solution from C 3 A+CSH 2 C 4 ASH 12 Monosulfate n n unstable in SO 4 -2 From C 6 AS 3 H 32 +C 3 A C 3(A, F)H 6 Hydrogarnets

Portland Cement Properties Hydraulic Fineness n 90% finer than 45 m Setting Time n n n Controlled False Set Flash Set

Portland Cement Properties Soundness n Mg. O or Hard-Burned Lime Specific Gravity: 3. 15 Heat of Hydration - Exothermic Reaction n C 3 S & C 3 A LOI SO 3

How are Portland Cements different? Four Main Compounds Tricalcium Silicate (C 3 S) Dicalcium Silicate (C 2 S) Tricalcium Aluminate (C 3 A) Tetracalcium Aluminoferrite (C 4 AF)

C 3 S Tri Calcium Silicate 3 Ca. O. Si. O 2 -“Alite” Provides Early strength development 70% reacts by 28 days Usually present at 40 -70% If >65% difficult to burn

C 2 S Dicalcium Silicate 2 Ca. O. Si. O 2 -“Belite” Provides late strength development 30% reacts by 28 days Present at 20 -40% Under-burning can result in higher C 2 S contents in cement

C 3 A Tricalcium Aluminate 3 Ca. O. Al 2 O 3 -“Aluminate” Provides heat generated in hydration (10 to 15 F per 100 lb. cement) High C 3 A not as resistant to sulfate attack Little contribution to strength

C 4 AF Tetracalcium Aluminoferrite 4 Ca. O. Al 2 O 3. Fe 2 O 3 -“Ferrite” Governs the color of the cement Present at 1 -10% Iron facilitates formation of other compounds-acts as a flux Little contribution to strength

Hydration C 3 S and C 2 S = ~ 75% of the weight of Portland Cement React with Water to form two new compounds: n Calcium Hydroxide n Calcium Silicate Hydrate (CSH) Hydration: C 3 S + H 2 O C-S-H + CH CH + H 2 O Ca++ + OH-

Supplementary Cementing Materials DEFINITION: Powdered or pulverized materials added before or during mixing to improve or change some of the plastic or hardened properties of concrete. • Cementitious • Pozzolans • Nominally Inert

Cementitious Materials Possess hydraulic cementing properties GGBF slag (by-product of steel industry) Natural cement- Cement Rock Hydraulic hydrated lime

Pozzolans Possess no cemetitious value until finely divided and mixed with water and cement Cherts, clays, shales Fly ash (by-product of coal) Silica fume (silicon manufacture)

Fly Ash Class F (low calcium) - from burning anthracite or bituminous coal, is pozzolanic Class C - from burning sub-bituminous or lignite coal, is somewhat cementitious

GGBFS (Slag) Formed when molten iron blast furnace slag is rapidly chilled (quenched) by immersion in H 2 O Grades 80, 100, 120 Used as a cement replacement

Silica Fume Also known as micro-silica By-product of the production of silicon and ferrosilicon alloys. A small part of silica fume can be used to replace a large part of cement Portland Cement Silica Fume

Types of Cement (ASTM C 150 or AASHTO M 85) Type Type I II IV V Normal* Moderate Heat and Sulfate* High-Early Strength* Low Heat of Hydration High Sulfate Resistance

Performance Cements (ASTM C 1157)

Special Types of Cement Type IP Blended with a Pozzolan* Type IS Blended with a Slag Type I-II Meets Type I and II standards* White Type I or III without Fe Masonry Blended Cements with Lime* Type K Expansive and Shrinkage Oil Well Slow-set, high temp. & press.

Water ·Municipal ·Well ·Heated ·Steam ·Chilled ·Ice ·Recycled

Questionable Water < 2000 ppm of total dissolved solids is satisfactory for making concrete. Water > 2000 ppm of dissolved solids should be tested for its effects on strength and time of set.

Acceptance Criteria for Questionable Water LIMITS ASTM test method _____________________ 7 -day compressive strength, compared to control specimens 90% C-109 _____________________

Acceptance Criteria for Questionable Water LIMITS ASTM test method _________________ Time of set, deviation from control specimens minus 60 min. to plus 90 min. C-191 ________________

w/cm Ratio Parameters Aggregate size: Grading of Aggregate: Surface texture of aggregate Shape of aggregate Cement type and source Pozzolans Air Entraining & Chemical Admixtures Setting Time

The Water - Cement Ratio Law For given materials the strength of the concrete (so long as we have a plastic mix) depends solely on the relative quantity of water as compared with the cement, regardless of mix or size and grading of aggregate. Duff A. Abrams May 1918

Same cement content

w/cm ratio

Water in Concrete Increased water: n n n reduced strength increased shrinkage and creep increases permeability reduced abrasion resistance reduced Freeze-Thaw resistance

Influence of Aggregates STRENGTH Aggregate shape Aggregate size Aggregate texture

Influence of Aggregates DURABILITY Weathering Impurities

Concrete Materials Aggregate is the second most influential ingredient in concrete. Aggregate n n n Occupies 60 -75 % of volume Fine Aggregate is typically 35 -45 % of total aggregate Mortar (Air, water, cement, fly ash, sand) is typically 50 - 65 % of total volume of a mixture

Aggregates in Concrete Fine: Sand or Crushed Stone (< 5 mm) Coarse: Gravel or Crushed Stone (5 -50 mm) Aggregate must be washed in many areas n n Granite & other crushed stone Recycled concrete All must satisfy ASTM C 33

EFFECT OF CHANGING FINENESS MODULUS ON CONCRETE PROPERTIES CONCRETE PROPERTY DECREASING FM (FINE SAND) Water Requirements MORE Water-Cement Ratio HIGHER Strength LOWER Finishability EASY INCREASING FM (COARSE SAND) LESS LOWER HIGHER DIFFICULT Note: Fineness Modulus: Sum of Cumulative % Retained/100. The FM should range between 2. 3 and 3. 1, and not vary more than 0. 2 from the typical value of the aggregate source.

Choosing Aggregate Size maximum nominal size of aggregate n n n 1/5 smallest dimension 1/3 thickness of slab 3/4 clearance between rebars Congestion Shrinkage Mass Concrete

Concrete Construction Significance of aggregate grading n smooth grading curve w (sieve size vs. % passing) n n n more voids will lead to more cement. undersanded mixes tend to be harsh large sizes have less surface area

Near Gap-graded Mix (Meets ASTM C 33)

Optimum Graded Mix Note: Difficult to compact or pump

Compressive Strength n n n fc' (required 28 day compressive strength) fcr' (actual average 28 -day strength of mixture) fc (compressive strength of concrete) fcr' is based on field records and laboratory results n n variations in in materials mixing times and methods transportation time and methods the preparation of test cylinders

Strength (7 day) I > 19. 3 MPa (2800 psi) II > 17. 2 MPa (2500 psi) III > 24. 1 MPa (3500 psi @ 3 days)

Concrete - Fresh Properties Workability: Ease with which a concrete can be handled and placed into forms. n n Slump Kelly Ball Penetration Flow Cone

Quality Concrete A mixture of CEMENTITIOUS MATERIALS, WATER, and AGGREGATES that will meet the requirements under which it is expected to serve.

Desired Properties of Fresh Concrete Consistency Workability Uniformity Finishability Low Bleeding

Concrete - Workability cement: too fine of material n n stickiness increased water demand water: too much water n n segregation bleeding water: too little water n n harshness compaction problems fly ash: increases flow n n n ball bearing effect ionic effect reduced water demand aggregate n n n rounded particles flow more easily Too much sand “stickiness” Poor gradation - harsh

Concrete - Fresh Properties Pumpability: Ease with which a given mix can be pumped without segregation or loss of properties n n aggregate: rounded particles pump more easily water: too much - segregation, too little - friction cement: too little - blow through, fly ash: helps prevent segregation, better flow

Concrete - Fresh Properties Compactability: Ease with which a given mix can be fully compacted to eliminate the trapped air. n n harshness gradation Finishability: Ease with which a given mix can be fully finished with the desired texture n n stickiness harshness

Concrete - Fresh Properties Setting Time n n n Cement: different cements have different setting times alkalis, sugars, salts, organics Water: Impurities -sodium carbonate (Na+) rapid set -bicarbonate can accelerate or retard set Aggregate: None

Concrete - Fresh Properties Bleeding: rate of surface water exceeds the evaporation rate. n Water: too much water (severe bleeding), too little water (surface drying) Air Content n n Water: -too much increases entrapped air voids -too little doesn't disperse Air Entraining Agent properly Unit Weight

Concrete - Hardened Properties Compressive Strength: Measure of maximum resistance of a concrete specimen to a compressive axial load. minimum 28 days, fc' * actual any time, fc *

Compressive Strength

Concrete - Hardened Properties Strength Gain n n Normal strength concrete 7 -day fc is 6070% of the 28 -day for Type I 3 -day fc is about 50% of the 7 day. Type III may have 3 -day fc of 60 -70% of the 28 -day Moist cured concrete gains faster than air dried Steam curing is fastest, but. . .

Concrete Strength Tensile Strength: tensile strength can be estimated by 7. 5 fc' / 10% of compressive strength /

Concrete - Hardened Properties Flexural Strength: Measure of cracking strength. n n (pavement and slabs on grade applications) Flexural Strength is generally 7. 5 - 10 fc' Shear Strength 20% of compressive strength

Concrete - Durability Shrinkage: decrease in volume of concrete due to loss of water from pore and capillary structure n n the major cause of cracking in concrete high water content increases shrinkage high aggregate content decreases shrinkage moist curing decreases shrinkage Creep is the time dependent deformation of concrete under load.

Concrete - Durability Freeze-Thaw Resistance is the property of concrete to sustain its strength and surface properties under repeated F-T cycles. n n n Air void structure is crucial in obtaining f-t resistant concrete. Air entraining agents are the only means of getting a good air void structure (4 -7% disconnected micro bubbles at uniform spacing) Low W/C ratio also increases f-t resistance

Concrete - Durability Sulfate Resistance is the concrete’s susceptibility to chemical attack from external sulfate ions. n n ground water or soil are SO 4 sources concrete with low C 3 A cement and pozzolans, low permeability, or protecting it from intrusion.

Concrete - Durability Scaling Resistance is the concrete’s susceptibility to deterioration from surface chemicals or environments. n chloride salts, bleeding, acids Permeability: watertightness or ionic resistance of concrete n n Aggregate: poor gradation increases porosity Pozzolans: reduce permeability

Concrete - Durability Abrasion Resistance n n essential in floors, pavements and hydraulic structures. compressive strength is an important consideration, choice of aggregate. (limestone is not good, gravel is very good) steel trowelling and moist curing surface is best

Assignment Write 1 -2 page paper on concrete related topic with 2 references (one general, one technical) e. g. special material considerations for pumped concrete, concrete sewer pipe, precast colored wall panels, lightweight concrete for crash barriers, concrete design considerations for containment vessels. . . .

Admixtures • DEFINITION: Admixtures are any ingredients in concrete other than: • Water Aggregates Cementitious Materials Fiber Reinforcement • Added to the batch before or during mixing

Why Use Admixtures? To Modify fresh concrete properties • decrease water content • increase workability • retard or accelerate setting time • reduce segregation • reduce the rate of slump loss • improve pumpability, placeability, finishability • modify the rate and/or capacity for bleeding

Why Use Admixtures? To Modify hardened concrete properties • improve impact and abrasion resistance • inhibit corrosion of embedded metals • reduce plastic shrinkage cracking • reduce long term drying shrinkage • produce colored concrete • produce cellular concrete

Current Admixture Standards (AASHTO Designations in parentheses) Air Entraining ASTM C 260 (M 154) Chemical ASTM C 494 (M 194) Calcium Chloride ASTM D 98 (M 144) Foaming Agents ASTM C 869 Admixtures for shotcrete ASTM C 1141 Flowing Concrete ASTM C 1017 Grout Fluidifier ASTM C 937 Pigments ASTM C 979

Air Entrainment DEFINITION: Air-Entraining Agents are primarily used to stabilize tiny bubbles generated in concrete to protect against freezing and thawing cycles.

Chemical Admixtures Dispersing Agents n Water Reducers, Superplasticizers Accelerators Retarders

ASTM C 494 Chemical Admixtures (AASHTO M 194) Type Type A - Water-reducing admixtures B - Retarding admixtures C - Accelerating admixtures D - Water-reducing and retarding E - Water-reducing and accelerating F - High range water reducing G - HRWR and retarding

Water Reducers DEFINITION: Water Reducers are used for the purpose of reducing the quantity of mixing water required to produce a concrete of given consistency.

Accelerators DEFINITION: Accelerating admixtures are added to concrete for the purpose of shortening set time and accelerating early strength development.

Retarders DEFINITION: Retarding, and Water-reducing and retarding admixtures are used to offset acceleration and unwanted effects of high temperature and keep concrete workable during placement and consolidation.

Shrinkage Reducing Admixtures DEFINITION: Shrinkage Reducing Admixtures are used to minimize drying shrinkage cracking in concrete.

Corrosion Inhibitors DEFINITION: Corrosion Inhibitors are used to mitigate corrosion of reinforcing steel in concrete.

ASR Inhibitors DEFINITION: ASR Inhibitors (primarily Lithium) are used to mitigate alkali-silica reactivity in concrete.

Specialty Admixtures Coloring Admixtures Workability Agents Bonding Admixtures Damp-proofing Admixtures Permeability. Reducing Grouting Gas-forming Anti-Washout Foaming Pumping Aids

The Effectiveness of an Admixture Depends on: Type & Brand Amount of Cement Water Content Temperature Aggregate Shape Proportions Mixing Time Consistency of the Mix Sequencing

Concrete Mixture Pre-Design Engineer Architect Contractor Concrete Supplier Define strength, congestion and durability properties Defines color, texture, Defines workability, setting time, . . Defines aggregates, cement, fly ash, admixtures. .

Concrete Mixture Design Discussion of defined needs Negotiation on conflicting needs Negotiation on economics Conflicts defined Trial Solution determined n n Engineer Accepts Mixture Proportions n trial batching

Mixture Design Procedures Step 1: Choose Slump PCA Table 7 -7 3” foundations, footings and slabs 4” beams, columns & reinforced walls 2” mass concrete 3” Pavements (add 1” for nonvibrated concrete)

Mixture Design Procedures Step 2: Select Aggregate Local Availability Large Aggregate reduces water demand max size of aggregate n n n 1/5 minimum size of form dimension 3/4 minimum rebar spacing 1/3 the slab thickness

Mixture Design Procedures Step 3: Choose Air Content PCA Table 7 -6 mild exposure 3 -4. 5% non-freezing and nonchemical environment moderate exposure 4. 56. 0% air exposed members not subjected to moisture saturation & chemicals severe exposure 5 -7%

Mixture Design Procedures Step 4: Estimate mixing water PCA Table 7 -6 Step 5: Estimate w/cm ratio PCA Tables 7 -1, 2, 3 Lb. Of water per yd 3 Function of: - Slump - Air - Max Aggregate Size Typically = 0. 45

Mixture Design Procedures Step 6: Choose Cement Type Portland Cement n n Types I-V Generally type I or II Pozzolans Fly Ash n Blast Furnace Slag n Silica Fume * Decrease PC demand n

Mixture Design Procedures Step 7: Calculate the cementitious content

Mixture Design Procedures Step 8: Estimate Coarse Aggregate Content PCA Table 7 -5 Calculate the Coarse Aggregate Step 9: Calculate the Fine Aggregate Coarse Agg. Factor (CAF) = % Agg. in concrete volume CAF*DRUW*Vconcrete Affects workability Vconcrete - Vconstituents

Mixture Design Procedures Step 10: Admixtures Air entraining agent water reducer ? accelerator ? retarder ? other

Mixture Design Procedures PCA Procedure is widely applicable No first trial is perfect Initial trial batch…… Determine Adjust mix design Repeat as necessary n n slump, air content strength