Concrete Basics and Techniques

Concrete

• A construction material made by combining Portland cement, aggregate, and water
• Normal-weight concrete typically weighs 140-160 lb/cu ft
• Lightweight insulating concrete can weigh 15-90 lb/cu ft with a 28-day compressive strength of 100-1000 psi
• Mass concrete is used in structures like dams; its weight provides structural strength
• Heavyweight concrete is made with heavy aggregates (barite, magnetite, steel punchings) and used for shielding
• Refractory concrete is cast into shape before placement
• Leveling refers to bringing a concrete surface to the desired grade
• Edging smooths off the edges of slabs to prevent chipping
• Screeding involves moving a straight edge to create a smooth concrete surface
• Jointing uses premolded inserts to control cracking due to shrinkage
• Bleeding is the tendency of dry materials to settle at the bottom of concrete and carry mixing water to the surface
• Troweling is done on exposed slabs to prepare them for finishes like carpet or paint
• Scaling is the breaking away of hardened concrete surface, typically occurring in the early stages of a slab

Harbor, Ports, and Waterways

• A protected water area used for safe ship accommodation, cargo handling, and repairs.
• Natural harbors are protected from storms by the land's shape.
• Artificial harbors are protected by breakwaters or dredging.
• A port is a sheltered area for receiving or discharging cargo, including approach channels and anchorage positions.
• A fairway is a navigable channel for ships.
• A wharf is a structure along a waterway for ships to dock or load cargo
• A pier is a structure extending into water where ships can dock or be moored.
• Jetties are structures alongside waterways.
• Dolphins are mooring structures for ships at sea.
• A significant wave is a hypothetical wave with mean height and period.
• The highest wave is the highest in a wave group.
• A mean wave has height and period equal to the mean of all waves in a group.

Wave Types and Levels

• Deepwater waves are those where the water depth is at least half the wavelength.
• Mean Sea Level represents the average sea water level over a 19-year period.
• Mean Low Water is the average lowest water level over a 19-year period.
• Mean Lower Low Water is the average of the lower low waters over a 19-year period.
• Storm surge is an abnormal rise in sea level during storms, caused by reduced atmospheric pressure and wind.
• Tsunamis are extremely long-period waves often caused by underwater earthquakes.
• Seiches are abnormal water oscillations with periods of a few minutes to a few tens of minutes.
• Seal coat is a very thin bituminous surface treatment for roads.
• Tack coat is the initial application of bituminous material onto existing surfaces.
• Prime coat is the application of liquid bituminous material onto untreated road bases.

Construction and Materials

• Traffic signs convey information using words and symbols for regulating, warning, or guiding traffic
• Regulatory signs inform road users about traffic laws and regulations
• Warning signs warn of road conditions and hazards
• Guide signs provide directions, distances, and points of interest
• Roadwork signs alert users to temporary hazards
• Overhead signs provide information on wide multi-lane roads
• Plate line capacity refers to the bucket volume contained within the bucket
• Struck capacity is the bucket capacity when the load is flush against the sides of the bucket
• Water line capacity assumes a material level flush with the lowest bucket edge
• Heaped volume is the maximum volume that can be placed in a bucket without spillage
• Grade resistance is a component of vehicle weight acting parallel to the inclined surface
• Rolling resistance is the resistance due to tire flexing and penetration
• Total resistance is the combination of grade and rolling resistance
• Aggregate is used in concrete to reduce costs and shrinkage
• Water is essential for concrete hydration
• Hydration is a chemical reaction between cement and water to create hardened cement
• Water-reducing agents increase the workability of concrete by altering the amount of water required without affecting consistency

Concrete Additives

• Retarders slow the hardening rate of concrete.
• Accelerators decrease setting time and increase early strength.
• Pozzolans reduce heat during hydration, increase workability, and reduce segregation.
• Plasticizers increase workability.
• Batching is the process of proportioning cement, water, aggregates, and additives before concrete mixing.
• Admixtures are materials other than cement, aggregates, and water that are added during mixing to alter properties.