08.02.03.053
DESCRIPTION
TRANSCRIPT
Presented by Md Mashqur Ul Alam
Student ID: 08.02.03.053
Department of Civil EngineeringAhsanullah University of Science and Technology
Prestress Concrete Design Sessional CE-416
Concrete : Basic Material Properties
Content
Definition Classification of ConcreteStates of ConcreteMaterial Properties of Concrete
WorkabilityUniformityNon-segregationStrengthDurabilityWatertightness
Admixtures
Definition:
Concrete is a mixture of aggregate and often controlled amounts of entrained air held together by a hardened paste made from cement and water. Although there are other kinds of cement, the word cement, in common usage, refers to portland cement.
Classification of Concrete
Based on unit weight Ultra light concrete <1,200 kg/m3 Lightweight concrete 1200- 1,800 kg/m3 Normal-weight concrete ~ 2,400 kg/m3 Heavyweight concrete > 3,200 kg/m3
Based on strength (of cylindrical sample) Low-strength concrete < 20 MPa compressive strength Moderate-strength concrete 20 -50 MPa compressive strength High-strength concrete 50 - 200 MPa compressive strength Ultra high-strength concrete > 200 MPa compressive strength
Based on additives: Normal concrete Fiber reinforced concrete Shrinkage-compensating concrete Polymer concrete
States of concrete
Concrete has three different states: PLASTIC : Plastic concrete in a relatively fluid state can
be readily molded by hand like a clump of modeling clay.
SETTING: The stiffening of concrete, when it is no longer soft
HARDENING: This is the end product of any concrete design.
Material Properties of Concrete
The Properties of Concrete are its characteristics or basic qualities :
Workability Uniformity Plastic concrete Non-segregation
Strength Durability Hardened concrete Watertightness
Workability
Workability means how it is easy to place, handle, compact and finish a concrete mix.
Facts needed to be considered for good workability:
Proportions of fine and coarse aggregate
Consistency
Amount of slump
Slump Test
Penetration Test
It is a measure of consistency
The ratio of slump to penetration is usually between 1.3 and 2.0
Fig: Kelly Ball Penetration
Nonsegregation
Plastic concrete must be homogeneous and carefully handled to keep segregation to a minimum. For example, plastic concrete should not drop (free-fall) more than 3 to 5 feet nor be transported over long distances without proper agitation.
Uniformity
The uniformity of plastic concrete affects both its economy and strength. Uniformity is determined by how accurately the ingredients are proportioned and mixed according to specifications. Each separate batch of concrete must be proportioned and mixed exactly the same to ensure that the total structural mass has uniform structural properties.
Strength
The ability of concrete to resist a load in compression, flexure, or shear is a measure of its strength. This is the most important property of concrete for engineers.
Concrete strength is largely determined by- w/c ratio in the mixture. Time Curing
Curing
Durability
Concrete's ability to resist the effects of wind, frost, snow, ice, abrasion, and the chemical reaction of soils or salts is a measure of its durability.
Climate and weather exposure affect durability. As the w/c ratio increases, durability decreases
correspondingly. Air-entrained concrete has improved freeze-thaw
durability. Durability should be a strong consideration for
concrete structures expected to last longer than five years.
Watertightness
The watertightness of concrete is judged by the depth of penetration of water forced in under pressure with the mechanism of flow of seepage water examined theoretically and experimentally.
depends on the w/c ratio and the extent of the chemical reaction progress between the cement and water.
W/C ratio should be 0.48 for concrete exposed to fresh water and 0.44 for concrete exposed to salt water.
The watertightness of air-entrained concrete is superior to that of non-air-entrained concrete.
Admixtures
Admixtures are mixed into the concrete to change or alter its properties.
Chemical Admixture:Retarders: sugar, sucrose, sodium gluconate, glucose, citric acid, and tartaric acidAir entrainment agent: LimePlasticizers: LignosulfonateAccelerator: CaCl2, Ca(NO3)2 and NaNO3
Mineral Admixture:Fly ashGround granulated blast furnace slagSilica fumeHigh reactivity Metakaolin(HRM)
Thank You