Green Tech in Construction: Innovative Cement

Innovative Photocatalytic Additive in Concretes

• Reduces pollution by utilizing photocatalytic additives in concretes
• Adds value by enhancing durability and sustainability of concrete structures

Bacterial Self-Healing in Concrete

• Brings added durability to concrete structures through self-healing properties
• Utilizes bacteria to repair cracks and damages in concrete

Investing in Green-tech for Construction

• Consider investing in companies selling innovative cements with sustainable properties
• Request information on the company's environmental impact, durability, and cost-effectiveness

Masonry Blocks and Bricks

• Masonry blocks are larger and heavier than bricks, with different composition (concrete or cement)
• Bricks are made from clay, with different sizes and compositions

Structural Masonry and Veneer

• Structural masonry supports the weight of a building, while veneer is a non-structural layer for aesthetic purposes
• Dry-pressed bricks are more expensive and less porous than soft mud process bricks, making them better resistant to freeze-thaw damage

Unreinforced Masonry Walls

• Not used in seismically active regions due to susceptibility to cracking and collapse during earthquakes

Hydrate Products in Portland Cement

• Four main types of hydrate products: AFm, AFt, C-S-H, and CH
• C-S-H is responsible for setting and final strength
• Tobermorite is a natural mineral used as a structural model to describe the C-S-H structure

Pozzolanic Reaction

• Chemical reaction involving cement chemistry nomenclature
• Limestone is not a pozzolan due to its chemical properties

Concrete Terminology

• Paste: mixture of cement, water, and air
• Mortar: mixture of cement, water, and fine aggregate
• Fine aggregate: small particles such as sand or crushed stone
• Coarse aggregate: large particles such as gravel or crushed rock

Aggregate in Concrete

• Added to concrete for three reasons: to improve strength, to reduce cement content, and to enhance durability
• Excessive water can be undesirable due to three reasons: it can lead to segregation, reduce strength, and increase porosity

Plastic Settlement

• Process where solid particles in a freshly placed concrete mixture settle under gravity, causing cracks to form above a reinforcing bar
• Illustrated through a sketch

Non-Portland Cements

• Two examples: Calcium aluminate cement (CAC) and Geopolymer cement
• CAC has high early strength and fast setting time, while Geopolymer cement has a lower carbon footprint and comparable strength and durability

Steel Reinforcement

• Does not always make for a 'better' concrete, as excessive reinforcement can cause problems such as congestion, increased difficulty in placement and compaction, and reduced durability
• Pre-tensioning and post-tensioning are two methods of prestressing concrete, with different applications and benefits
• Prestressing is mainly used to enhance flexural load resistance, but can also enhance compressive strength
• A passivating film is a layer of oxide or hydroxide that forms on the surface of steel reinforcement, protecting it from corrosion

Concrete Durability

• Plastic settlement is more likely to cause defects on the top surface of a concrete element, especially if it is heavily reinforced or has a high water content
• Chloride can cause corrosion problems in reinforced concretes, as explained through a Pourbaix diagram

Concrete Tensile Strength

• Direct measurement is rare due to difficulties in testing
• Alternative tests and mathematical relationships can be used to determine this material property

Concrete Standards

• EN 197-1 cement types have different clinker contents, with Type I having the highest content and Type IV having the lowest
• Moving from a prescriptive basis to a performance basis in concrete standardization can bring benefits such as increased flexibility, innovation, and optimization of materials and designs