Binders + Cement + Concrete

Binders types + explanation

● Aerial Binder: Hardens with air (e.g., lime).

● Hydraulic Binder: Hardens with water or underwater (e.g., cement, pozzolanic limes).

Mortar vs Concrete

● Mortar = Binder + Water + Sand (fine aggregate)

● Concrete = Binder + Water + Coarse Aggregate (like gravel) + Sand

Gypsum (Plaster of Paris) everything:

1)made from

2)setting time + temp

3)types

4)limitations

● Made from: Heating gypsum (CaSO₄·2H₂O) to form hemihydrate (CaSO₄·0.5H₂O)

● Setting:

○ 120°C → sets in 1–4 min

○ 180°C → sets in ~20 min

● Reaction: Exothermic (releases heat); reabsorbs water and recrystallizes to dihydrate

● Types:

○ Commercial Gypsum: ~170°C production temp, finess limited

○ Strong Gypsum: ~300°C (used for pavement subfloors), strong but setting

time hight

● Limitations:

○ Not for humid environments → dissolves

○ Not stable >40–50°C○ Not suitable in ammonia-rich air → forms hygroscopic ammonium sulfate

(causes disintegration)

● Fire protection: Non-combustible and releases water when heated

Lime (Aerial Binder)

1)types

2)available as

3)problems

● Quicklime (CaO): Also called burnt lime

● Slaked Lime (Ca(OH)₂): Formed by adding water to quicklime

○ Available as:

■ Powder

■ Putty

■ Lime milk

● Types:

○ Fat Lime:

■ High purity (>95%)

■ Increases 2–3.5× in volume after slaking

■ Uses: plaster, stucco, lime water, bedding mortar

○ Poor Lime:

■ Grey, impure

■ Slow setting, weak bond

● Problems:

○ Popping: Unslaked CaO or MgO reacts with humidity → volume increases →

cracks○ Cracking:

■ Too much binder

■ Support too dry

■ Bad curing (ideal: 5–20°C, 50% RH)

■ Too much sand = poor workability

Pozzolans

● Siliceous/aluminous materials (volcanic ash, pumice, opal)

● React with lime → form hydraulic binders

● Historical Example:

○ Signine Composition: Lime + pozzolan

○ Used in: Roman baths, aqueducts (waterproof and durable)

Mortar Types

● Lime Mortar:

○ Lime (aerial or hydraulic) + sand + water

● Bastard Mortar:

○ Lime + cement

○ Combines workability and strength

Cocciopesto (Roman Waterproof Plaster)

● Lime + ground terracotta (cocciopesto) + sand

● Ratio: 1 part slaked lime : 2 sand : 1 cocciopesto

● Benefits:

○ Waterproof

○ Breathable

○ Colored naturally (no need to paint)

○ Used for bathrooms, damp walls, decorative finishes

● Application Tips:

○ Wet the surface before applying

○ Smooth finish = more waterproof

○ Avoid high firing temperatures (>900°C) to maintain pozzolanic reactivity

The cement industry is responsible for….. of all industrial CO₂ emissions.

25%

rotary kiln

● The rotary kiln is a huge, slightly tilted steel tube (3–6 m wide, >100 m long), lined with

firebrick.

○ It rotates slowly (30–250 rpm) and runs 24/7, only stopping once or twice a

year.

○ It heats raw materials to ~1450°C, producing clinker.

Clinker

● Clinker is the solid, grayish material made in the kiln.

● It contains reactive phases like C₃S, C₂S, C₃A, and C₄AF

● Fast cooling of clinker at the kiln exit is essential to keep the hydraulic (reactive)

phases stable.

Gypsum in Cement

● Gypsum (CaSO₄·2H₂O) is added (3–6 wt%) before grinding.

● It acts as a set retarder to slow down the reaction of C₃A, preventing flash setting.

Grinding Process

● Cement is made by grinding clinker + gypsum in a tube mill.

○ The mill is divided into chambers with steel balls: big (90 mm) in the first, small

(15 mm) in the last.

○ Partitions allow powder to pass but hold the grinding media in place.

Fineness & Hydration

● The finer the cement, the faster it reacts with water.

● Particles >45 μm hydrate slowly, >75 μm may not hydrate fully.

● Typical size distribution:

○ 90% of particles: 2–90 μm

○ 7–9%: <2 μm

○ 0.5%: >90 μm

Hydration Products

● C-S-H (Calcium Silicate Hydrate): Main binding phase, gives strength (80% of

hardened mass).

● Portlandite (CH): Crystalline, does not add strength but keeps high pH (>12.5) to

protect steel it also help with hydration

Ettringite & Gypsum Use

● Gypsum is added in limited amounts, not enough to convert all C₃A to ettringite.

● This creates:

○ ~25% of C₃A → ettringite (C₆AŠ₃H₃₂) → expands but harmless while paste is

soft.

○ Remaining C₃A → C₄AH₁₃ (other hydrated products).

Why not just use calcium silicates (C₃S, C₂S)?

● Raw materials contain impurities like Al₂O₃ and Fe₂O₃.

● These help by:

○ Acting as fluxes (lower melting point → lower kiln temperature).

○ Forming C₃A and C₄AF.

● Purifying them out would raise production costs due to higher kiln temps.

Heat of Hydration

Definition: Exothermic heat released when water reacts with cement.

● Affected by:

○ Cement composition

○ Curing temperature

○ Water-to-cement (w/c) ratio

○ Cement finenes

cold vs hot weather

● Cold weather: Slower reaction, longer setting, heat of hydration helps.

● Hot weather: Faster reaction, shorter setting, heat may cause problems.

Mass Concrete (ACI Definition)

● Large volume concrete requiring special heat control to avoid:

○ Cracking due to temperature gradients

○ Volume changes from differential thermal expansion/shrinkage

Water in Hydrated Cement

1. Capillary water: In pores; evaporates easily

2. Adsorbed water: On surfaces; causes shrinkage on drying

3. Chemically bound water: Part of hydrates; only released at high temp (e.g. fire)

Porosity, Permeability & Properties

● Low permeability = better durability.

● Pore segmentation: Ideal condition where macropores are isolated and connected

only by micropores, slowing degradation.

CE Marking & Cement Types (EN 197-1) “1-5“

● CE mark = Compliance with EEA safety/environmental rules

● CEM Types:

○ CEM I – Portland cement

○ CEM II – Portland-composite

○ CEM III – Blast furnace cement

○ CEM IV – Pozzolanic cement

○ CEM V – Composite cement

Supplementary Cementitious Materials (SCMs)

● Blast furnace slag (GGBFS):

○ Made from rapid cooling of iron slag

○ Needs activation; has latent hydraulic properties

○ At least 2/3 = CaO + MgO + SiO₂

● Natural pozzolanas:

○ From volcanic/sedimentary rocks

○ Need proper chemical/mineralogical composition

● Calcined pozzolanas:

○ Thermally treated shales, clays, volcanic rocks

● Fly ash (byproduct of coal combustion):

○ Siliceous fly ash:

■ <10% CaO → pozzolanic only

■ Free CaO <1%

○ Calcareous fly ash:

■ ≥10% CaO → pozzolanic + hydraulic

● Silica fume:

○ Byproduct of silicon/ferrosilicon production

○ ≥85% amorphous SiO₂○ Very fine, spherical particles

SCMs vs Portland Cement

● Early strength: OPC (CEM I) is stronger

● Later strength: SCMs overtake OPC due to:

○ Pozzolanic reaction using up CH (Portlandite)

● SCMs = Lower heat of hydration → better for:

○ Mass concrete

○ Hot climates

Sulphate-Resisting Cement

● Low C₃A (<5%) → less ettringite → resistant to sulphate attack

Strength Testing Method (EN 196-1)

● Specimens: 40×40×160 mm prisms

● Mortar mix:

○ 1 part cement

○ 3 parts standard sand

○ w/c ratio = 0.50

● Compressive (and optional flexural) strength tested

● First quality check:

○ Normally at 2 days

○ For Class 32.5 only: postponed to 7 days

Setting Time Test (EN 196-3:2016)

● Measured via needle penetration into cement paste

● Initial setting time:

○ Time from mixing until the needle is (6 ± 3) mm from base plate

● Important for timing cast-in-place concrete operations

Soundness Test (EN 196-3:2016)

● Assesses volume stability of hardened cement paste

● Detected via movement of two needles

● Prevents issues from:

○ Unslaked CaO (burnt lime) or MgO

○ These cause expansive slaking reactions when in contact with water →

cracks, instability

Types of Concrete (by use and density)

● By production:

○ Site-mixed concrete

○ Ready-mixed concrete

○ Precast concrete product

● By density:

○ Normal-weight concrete: 2000–2600 kg/m³

○ Light-weight concrete: 800–2000 kg/m³○ Heavy-weight concrete: >2600 kg/m³

● High-strength concrete:

○ Strength > C50/60 (normal or heavy-weight)

○ Strength > LC50/55 (light-weight)

Aggregates

“Granular mineral materials suitable for use in concrete. Can be natural or

recycled

Types of Aggregates

● Natural: e.g., limestone, quartz (just mechanical processing)

● Manufactured: from thermal/industrial processing (e.g., expanded clay)

● Recycled: from construction and demolition waste (CDW)

Classification by Size +Geometrical Characteristics

● Fine aggregate: D ≤ 4 mm

● Coarse aggregate: D > 4 mm

● Shape, Angularity, Size distribution

Physical/Chemical Characteristics

● Density

● Porosity (affects freezing resistance)

● Mechanical properties

● Chemical composition

Shape Effects

● Alluvial (rounded): More workability

● Crushed (angular/edgy):

○ Better paste adhesion

○ Higher strength

Mixing Water

Roles

● Hydration of cement compounds

● Provides workability in fresh state

Key Factors

● w/c ratio

● Chemical composition and origin

Water Types● Potable water: Always suitable

● Natural water (river, lake, sea, lagoon):

○ Fresh/brackish may be OK for non-reinforced

○ Brackish = never for reinforced

● Industrial wastewaters: Use with caution

○ pH < 6 = risk of pollution

○ Chlorides = dangerous (rebar corrosion)

Effects of Excess Water

● ↓ Strength

● ↑ Shrinkage → Cracks

● ↓ Abrasion resistance

● ↑ Porosity → Permeability

● ↓ Durability

● Dusting, scaling

Admixtures

“Materials added in small amounts (<5% of cement mass) during mixing to modify

properties in fresh or hardened state.”

Types

● Water-reducing/plasticizing

○ Improves cement particle dispersion○ ↑ Workability at same w/c ratio

○ Or ↓ water content by 5–12% → ↑ strength & durability

● Superplasticizers:

○ Like plasticizers but stronger effect

● Set Accelerators:

○ ↓ Setting time (useful in cold weather)

● Hardening Accelerators:

○ ↑ Early strength (first days)

● Retarders:

○ Prolong workability (useful in hot weather or long transports)

● Other types:

○ Air entrainers

○ Waterproofing/hydrophobic agents

○ Corrosion inhibitors

○ Water-retaining admixtures

Fresh Concrete Properties

✅ Workability● Definition: Ease of mixing, placing, compacting, and finishing while maintaining

homogeneity.

● Affected by:

○ Water content

○ Aggregate size, shape, grading

○ Aggregate/cement ratio

○ Admixtures

○ Temperature

✅ Consistency

● Related to the flowability of fresh concrete.

● Decreases over time due to:

○ Water absorption by aggregates

○ Evaporation

○ Initial hydration

○ Interaction with admixtures

✅ Tests

● Slump test: Most used method (Abrams' cone, EN 12350-2).

○ Quick and simple; indicates high workability

Fresh Concrete Defects

Segregation● Separation of coarse aggregates from paste.

● Caused by:

○ Too dry or too fluid mix

○ Too much coarse or too little fine aggregate

○ Inadequate compaction

○ High drop height

💧 Bleeding

● Water rises to the surface.

● Caused by:

○ High water content

○ Low cement content

● Effects: Less paste for bonding, reduced strength.

🧊 Honeycombing

● Voids in concrete due to poor compaction or segregation

Placing, Compaction, and Curing

✅ Placing Rules

● Place vertically, close to final position.

● Avoid letting it flow or drop from high (esp. in walls/columns).

✅ Compaction

● Removes entrapped air (5–20%).● Increases density, strength, and bond with reinforcement.

● Compaction must continue until no air bubbles surface.

✅ Curing

● Maintains moisture and temperature for hydration.

● Benefits:

○ Increases strength & abrasion resistance

○ Reduces permeability

○ Improves durability

● Time: Minimum 10 days; ideally 2–3 weeks.

● Methods:

○ Keep water in (water curing)

○ Prevent water loss (covering

Hardened Concrete

📉 Compressive Strength

● Main indicator of concrete quality and structural integrity.

● Depends on:

○ w/c ratio (lower is better)

○ Compaction quality

● Measured at 28 days unless specified.

📏 Characteristic Strength (f_ck)● Strength below which 5% of samples may fall.

● EN 206-1:2013 standard:

○ Initial production: First 35 tests

○ Continuous production: At least 35 tests over ≤12 months

Jobsite Control Types

● Type A (≤300 m³):

○ 3 samplings (each max 100 m³)

○ Each sampling: 2 specimens, 28-day cure

○ Mean strength: R_cm ≥ R_ck + 3.5 MPa

● Type B (≥1500 m³):

○ 15 samplings minimum (1/day)

○ Mean strength: R_cm ≥ R_ck – 3.5 MPa

Deformation Behaviors

🔻 Shrinkage

● Plastic Shrinkage (fresh concrete):

○ Due to water evaporation, chemical shrinkage, formwork absorption.

● Drying Shrinkage (hardened concrete):

○ Due to moisture loss from fine pores.

○ Affected by RH, wind, and temperature.

🕒 Creep● Time-dependent deformation under sustained load.

● Influenced by:

○ Load magnitude

○ Age & strength of concrete

○ Loading duration

● Reduced by:

○ Dense, non-absorptive aggregates

○ Well-graded coarse aggregates

📏 Elastic Deformation

● Instantaneous response under load (Hooke’s Law).

📈 Inelastic Deformation (Creep)

● Time-dependent strain increase under constant load

Precast Concrete

● Definition: Concrete unit cast/cured off-site.

● Benefits:

○ Fast on-site assembly, weather-independent.

○ Aesthetic and design flexibility (textures, colors, long spans via prestressing).

○ Durability and high quality from factory control.

○ Cost-effective with reusable molds and repetitive production.

Prestressed Concrete

● Purpose: Internal stresses counteract service tensile stresses.

● Steel role: Active in prestressed; passive in reinforced concrete.

● Methods:

○ Pre-tensioning: Steel stressed before casting; ideal for small, transportable

elements.

○ Post-tensioning: Steel stressed after casting; allows curved tendons and longer,

thinner spans.

Self-Compacting Concrete (SCC)

● Definition: Concrete that flows under its own weight, without vibration.

● Use: Complex shapes, congested reinforcement, precast and cast-in-place.

● Composition: Superplasticizers, viscosity modifiers, supplementary cementitious

materials (up to 70%).

● Properties: Flowability, segregation resistance, filling/passing ability, stability.

● Testing Standards:

○ Slump Flow (EN 12350-8): Measures filling ability.

○ J-Ring (EN 12350-12): Assesses passing ability (with obstacles).

○ V-Funnel (EN 12350-9): Assesses viscosity (<10s preferred).

○ L-Box (EN 12350-10): Measures flow/passing via horizontal distance

(T200/T400)

Lightweight Concrete

● Density Range: 800–2000 kg/m³ (vs. normal: 2000–2600 kg/m³).● Types:

1. Lightweight Aggregate Concrete: Uses porous aggregates like LECA.

■ LECA: Expanded clay, 1150°C in rotary kiln → 5× volume expansion.

2. No-Fines Concrete: Omits fine aggregate → porous, drainable (1200–1900

kg/m³; strength 1.4–10 MPa).

3. Aerated/Cellular Concrete:

■ Foamed Concrete: Uses protein/synthetic foam (≥25% air); made via

generator or admixtures.

■ Autoclaved Aerated Concrete (AAC): Uses aluminium powder to create

H₂ bubbles; cured via steam pressure (block/panel form)

Fiber-Reinforced Concrete (FRC)

● Purpose: Enhances crack control, toughness, durability, and impact resistance.

● Applications: Industrial floors, tunnels, hydraulic works, fire-resistant structures.

● Benefits:

○ Improves flexural strength, fire resistance, crack distribution, and early-age

shrinkage resistance.

● Fiber Types: Steel, plastic, glass, carbon, cellulose; various forms (round, flat, crimped).

● Note: Does not replace rebar; used as supplementary reinforcement.

High-Performance / High-Strength Concrete

● High-Performance: Emphasizes durability features (chloride, abrasion resistance).

● High-Strength: Focuses on mechanical strength (compressive).● Design Features:

○ Portland cement + Pozzolans/GGBFS.

○ Low water/cement ratio (0.2–0.35).

○ Superplasticizers.

○ Controlled porosity and selected aggregates