Civil Engineering Materials Department of Civil, Structural and Environmental Engineering Trinity College Dublin Dr. Roger P. West (TCD) And Mr. Peter Flynn (Arup)

Schedule Lectures: Tutorials: Concrete Laboratory: Weeks 1-3(Wed 3-5): Timber, aluminium, glass and pre-cast Weeks 4-9(Mon 10-11, Fri 3-4): Concrete, reinforced concrete and pre-stressed concrete Tutorials: Alternate weeks, weeks 4-9, Thursday 5-6pm, commencing Groups 1-20 in week 4 of term, in Joly Theatre Concrete Laboratory: Each laboratory group on either Monday or Thursday, for one week only, as per timetable

Section A: Concrete A1 Basic Materials: A2 Fresh Concrete Properties: A3 Hardened Concrete Properties: A4 Concrete Mix Design: A5 Reinforced Concrete: A6 Pre-stressed Concrete:

What is Concrete? Concrete is the most widely used construction material in the world Concrete is a construction material composed of crushed rock or gravel and sand bound together with a hardened paste of cement and water.

Concrete History

Concrete History Aquaducts

Concrete History Colleseum

Concrete History Pantheon

Concrete History Eddystone Lighthouse – John Smeaton (1756)

Concrete History Joseph Aspdin Patent (1824)

Concrete History Reinforced Concrete Flower Pot (Joseph Monier 1867)

Concrete History Weavers Mill Swansea (1898)

Concrete History Freysinnet

Concrete History Hoover Dam

Concrete History Astrodome

Concrete History Toronto Tower

Section A.1 Basic Materials 1. Cement 2. Water 3. Aggregates 4. Admixtures

Specialised Portland Cements: Section A.1 Basic Materials 1. Cement Ordinary Portland Cement (OPC) Rapid Hardening Portland Cement (RHPC) Sulphate Resistant Portland Cement (SRPC) White Portland Cement (WPC) Specialised Portland Cements: Masonry Portland Cement Low Heat Portland Cement Hydrophobic Portland Cement Oil-well Portland Cement

Alternative Cement Replacement Materials Blastfurnace Slag Cement (GGBS) Pulverised-fuel Ash Cement (PFA) Metakaolin Rice Husk Ash Silica Fume Cements in Europe are classed as CEM1 (OPC or RHPC), CEM2-4 (OPC with limestone, PFA or GGBS) in varying proportions pre-blended

Section A.1 Basic Materials 1. Cement Chemistry of OPC

Section A.1 Basic Materials 1. Cement Manufacture

Section A.1 Basic Materials 1. Cement Manufacture

Section A.1 Basic Materials 1. Cement Sulphate Resistant Portland Cement Low triacalcium aluminate content (C3A) Achieved by adding Iron oxide to decrease aluminate proportions Resistant to sulphates but not resistant to strong acids Reduced early heat

Section A.1 Basic Materials 1. Cement Pulverised-fuel ash cements (latent hydraulic binder) From burning pulverised coal in power station furnaces Reacts with calcium hydroxide (lime) to from cementitious material Resistant to sulphates but not resistant to strong acids Reduced early heat of hydration Reduced early age strength

Section A.1 Basic Materials 1. Cement Blastfurnace Slag Cements (latent hydraulic binder) By-product of iron smelting, quenched slag forms granuels Generally blended with OPC up to 35% Reduced early age strength Reduced early heat of hydration

Section A.1 Basic Materials

Section A.1 Basic Materials

Section A.1 Basic Materials

Section A.1 Basic Materials 1. Cement Delivery & Storage Usually packaged in 25kg bags or transported in bulk tankers Retail price €5 “Warehouse set”

Section A.1 Basic Materials 2. Water Should be free from impurities Unsuitable if it contains - sugars - sulphates - chlorides Sea water must not be used for reinforced concrete

Section A.1 Basic Materials Hydration Setting and hardening results from a chemical reaction between the cement and the water, not from a drying process. The reaction is exothermic and is irreversible. The heat produced is known as the “Heat of Hydration” C3A and C3S are the compounds primarily responsible. The paste is usually workable up to two hours before it begins to harden Strength gain is initially rapid becoming progressively less rapid Strength gain continues indefinitely provided moisture is present. “Curing”

Section A.2 Fresh Concrete Properties 2. Cement hydration Cement + H2O = Calcium Silicate Hydrate (C-S-H) +Ca (OH)2 +H2O

Section A.2 Fresh Concrete Properties 2. Cement hydration and heat generation

Section A.1 Basic Materials 2. Cement paste strength gain

Section A.1 Basic Materials 3. Aggregates Gravels, crushed rock and sands that are mixed with cement and water to produce concrete. Coarse aggregates are those that do not pass through a 5mm sieve. Fine aggregates are those that pass through a 5mm sieve. Generally make from 50% to 80% of the concrete mix. Used to reduce cost and modify and imporve properties like strength and drying shrinkage.

Section A.1 Basic Materials 3. Aggregates Quality Requirements Durability - Hard - Adequate Strength - No deletrious material Cleanliness - free from chemical impurities - free from organic material - free from dust - excessive washing is not the answer - avoid silica acid aggregates.

Section A.1 Basic Materials 3. Aggregates Aggregate Types Normal density - Most gravels and crushed rock - Divided into coarse and fine Lightweight - Weak porous solids - Good thermal properties High Density - radioactive screening

Section A.1 Basic Materials 3. Aggregates Sieve Analysis

Section A.1 Basic Materials 4. Admixtures Additives to the concrete mix to improve certain properties Must be used with care as excessive amounts can have adverse effects on the concrete

Section A.1 Basic Materials 4. Admixtures Accelerators Increases the rate of strength gain at an early age Most common is calcium chloride (CaCl) but may corrode steel Most common is calcium chloride (CaCl) but may corrode steel Does not increase final strength

Section A.1 Basic Materials 4. Admixtures Water Reducing Admixtures (Plasticisers) Reduces the amount of water required for a given workability Most common is calcium ligno-sulphate Reduces the risk of evaporation cracks Air Entraining Admixtures Generates evenly dispersed air bubbles in the mix Improves durability against frost and marine environments Volume or air entrainment should not exceed 13% of cement paste

Section A.1 Basic Materials 4. Admixtures Retarding Agents Reduces the rate of evolution of heat Necessary for very large concrete pours Water-repelling admixtures Can improve impermeability of concrete in basements and water retaining structures No substitute for sound concrete

Section A.1 Basic Materials 4. Admixtures

Section A.1 Basic Materials Admixtures Foaming Agents Produces highly flowing light concrete Superplasticiser Produces flowing normal concrete with high strength Self-compacting Allows highly flowing cohesive mix with no need for vibration. It can also be self-levelling.