Prestressing
Initial force applied to improve structural capacity by placing concrete in compression before service loads. 【1-9178e2】
| Term | Definition |
|---|---|
Prestressing | Initial force applied to improve structural capacity by placing concrete in compression before service loads. 【1-9178e2】 |
Pretensioning | Steel strands are tensioned before concrete is cast, typically in precasting plants. 【1-9178e2】 |
Posttensioning | Steel strands are tensioned after concrete is cast and has reached adequate strength. 【1-9178e2】 |
Concrete Tensile Strength | Concrete has essentially no useful ability to resist tensile (stretching) forces. 【1-9178e2】 |
Concrete Reinforcing | Steel bars or wires placed along tension zones to resist tensile forces. 【1-9178e2】 |
Rebar | The most common reinforcing material; hot-rolled deformed steel bars. 【1-9178e2】 |
#4 Bar | A reinforcing bar with a diameter of 1/2 inch. 【1-9178e2】 |
#8 Bar | A reinforcing bar with a diameter of 1 inch. 【1-9178e2】 |
Welded Wire Reinforcing (WWR) | Prefabricated welded grids of reinforcing wires or bars, commonly used in slabs. 【1-9178e2】 |
Rebar Congestion | A condition where reinforcing becomes crowded, making concrete placement more difficult. 【1-9178e2】 |
Simple Beam Reinforcing | Includes heavy bottom bars, lighter top bars, and U-shaped shear stirrups. 【1-9178e2】 |
Vertical Bars | Large reinforcing bars placed vertically in columns. 【1-9178e2】 |
Ties or Spirals | Reinforcement wrapped around column bars to prevent buckling. 【1-9178e2】 |
Lap Splice | The overlap between reinforcing bars to transfer loads from one bar to another. 【1-9178e2】 |
Fibrous Reinforcing | Glass, steel, or polypropylene fibers added to concrete. 【1-9178e2】 |
Microfiber Reinforcing | Small amounts of fibers used to reduce plastic shrinkage cracking during early curing. 【1-9178e2】 |
Macrofiber Reinforcing | Higher concentrations of fibers used to resist long-term cracking. 【1-9178e2】 |
Workability | The ease of placing, consolidating, and finishing wet concrete. 【1-9178e2】 |
Normal-Strength Concrete | Concrete with compressive strength up to 6,000 psi. 【1-9178e2】 |
High-Strength Concrete | Concrete with compressive strength greater than 6,000 psi and up to roughly 20,000 psi. 【1-9178e2】 |
Ultra-High-Performance Concrete | Specially formulated concrete with strengths up to 30,000 psi. 【1-9178e2】 |
Water-Cement Ratio (W/C Ratio) | The ratio of water to cement by weight; a key determinant of concrete strength. 【1-9178e2】 |
Lower W/C Ratio | Increases strength and durability but decreases workability and increases cost. 【1-9178e2】 |
Ready-Mix Concrete | Concrete prepared at batch plants and delivered in transit-mix trucks. 【1-9178e2】 |
Slump Test | A test measuring the workability of fresh concrete by its loss of height after a mold is removed. 【1-9178e2】 |
Typical Maximum Slump | Usually specified between 3 and 5 inches. 【1-9178e2】 |
Test Cylinders | Cylindrical concrete samples cast and tested to verify strength. 【1-9178e2】 |
Concrete Placement Window | Concrete should generally be placed within 90 minutes after mixing begins. 【1-9178e2】 |
Segregation | Separation of large aggregate from finer portions of the concrete mix. 【1-9178e2】 |
Consolidation | The process of eliminating voids and air pockets in concrete. 【1-9178e2】 |
Curing | The hydration process in concrete that develops strength and durability. 【1-9178e2】 |
28-Day Strength | The standard age at which concrete strength is typically specified. 【1-9178e2】 |
Formwork | Temporary construction used to hold fresh concrete in shape until it gains strength. 【1-9178e2】 |
Form Release Compound | Oil, wax, or coating applied to formwork to prevent adhesion to concrete. 【1-9178e2】 |
Portland Cement | The binding ingredient in concrete. 【1-9178e2】 |
Fine Aggregate | Sand used in concrete. 【1-9178e2】 |
Coarse Aggregate | Gravel or crushed stone providing structural mass in concrete. 【1-9178e2】 |
Admixtures | Added ingredients that improve concrete properties or reduce cost. 【1-9178e2】 |
Aggregates | Coarse and fine materials that make up most of concrete's volume and structural mass. 【1-9178e2】 |
Portland Cement Composition | Primarily calcium silicates with compounds containing aluminum, iron, and magnesium. 【1-9178e2】 |
Clinker | The burned product from cement manufacturing that is later ground into cement. 【1-9178e2】 |
Gypsum | Added to clinker at about 5% to control cement setting time. 【1-9178e2】 |
Type I Cement | General-purpose cement. 【1-9178e2】 |
Type II Cement | Cement with moderate sulfate resistance used for drainage structures, retaining walls, and piers. 【1-9178e2】 |
Type III Cement | High-early-strength cement used for cold weather and precast construction. 【1-9178e2】 |
Type IV Cement | Low-heat cement used for massive structures such as dams. 【1-9178e2】 |
Type V Cement | Cement with high sulfate resistance used in marine and wastewater environments. 【1-9178e2】 |
Air-Entraining Cement | Cement that creates small air bubbles in concrete to improve freeze-thaw resistance and workability. 【1-9178e2】 |
Typical Air Content | Usually 2% to 8% of the total concrete volume. 【1-9178e2】 |
Cement Production Emissions | Manufacturing 10 tons of Portland cement generates roughly 1 ton of CO₂. 【1-9178e2】 |
Supplementary Cementitious Materials (SCMs) | Materials that partially replace Portland cement and improve strength, durability, and sustainability. 【1-9178e2】 |
Pozzolans | Materials that react with hydration byproducts to form additional cementing compounds. 【1-9178e2】 |
Water-Reducing Admixtures | Additives that increase workability while maintaining a low water-cement ratio. 【1-9178e2】 |
Maximum Aggregate Size | The largest aggregate should not exceed 1/5 the form width, 3/4 of rebar spacing, or 1/3 slab depth. 【1-9178e2】 |
Aggregate Grading | The use of varying aggregate sizes to reduce voids and improve workability. 【1-9178e2】 |
Structural Lightweight Concrete | Concrete weighing about 80% or less than ordinary concrete. 【1-9178e2】 |
Nonstructural Lightweight Concrete | Concrete weighing about 60% or less than ordinary concrete. 【1-9178e2】 |
Expanded Shale | A lightweight aggregate produced by thermal treatment. 【1-9178e2】 |
Perlite | Thermally expanded volcanic glass used as lightweight aggregate. 【1-9178e2】 |
Vermiculite | Thermally expanded mica used as lightweight aggregate. 【1-9178e2】 |
Potable Water | Clean water suitable for use in concrete mixing. 【1-9178e2】 |
Hydraulic Cement | Cement that chemically combines with water and remains insoluble after hardening. 【1-9178e2】 |
Roman Concrete | Early concrete made with pozzolanic volcanic ash, lime, water, sand, and rock. 【1-9178e2】 |
Pozzolanic Ash | Volcanic ash rich in silica and alumina used by the Romans in concrete. 【1-9178e2】 |
Joseph Aspdin | In 1824 patented Portland Cement. 【1-9178e2】 |
Joseph-Louis Lambot | Constructed an early steel-reinforced cement boat in 1848. 【1-9178e2】 |
Joseph Monier | Developed reinforced concrete applications and patents between 1867 and 1891. 【1-9178e2】 |
Francois Hennebique | Patented reinforced concrete construction in 1892. 【1-9178e2】 |
First Concrete Bridge | Built in Wiggen, Switzerland, in 1894. 【1-9178e2】 |