Properties of concrete: durability, shrinkage, creep, grade & tensile strength | Property of concrete | properties of fresh concrete | property of reinforced concrete | elastic properties of concrete | elastic modulus of concrete.
Property/ properties of concrete
Today in construction of concrete structures project you will require necessary to know about property of concrete, it’s importance to design of structural that is play a important role in concrete strength and control the properties of strength, behavioural property of concrete with its constituents cement, sand, aggregate, water that is chemically inert particulate materials such as fine aggregates and coarse aggregate is bonded together by cement and water, cement is consisting in powder form ,act as binding agent mixed with water and aggregates .
Property of concrete are especially the basic introduction of development in concrete technology that is mostly used in construction of structures for longer life which is controlled and influence by various fector for examples wide varieties of admixtures and the availability of additional Pozzolanic materials have play a important role to increased the importance of properties of concrete.
In recent development, required a good knowledge of property of concrete that is permitted the acheive highly strength and durability for construction of the structures which is consist the grade of concrete, compressive strength, characteristics strength, durability, creep, shrinkage etc.
Concrete used in design of structure and pavements is expected to have long life and low maintenance ,in fact that property of concrete must have good durability to resist exposure conditions .
Properties of concrete
1. Grade of concrete
2. Characteristics strength of concrete
3. Tensile strength of concrete
4. Modulus of elasticity of concrete
5. Creep in concrete
6. Shrinkage of concrete
7. Durability of concrete
Grade of concrete
Grade of concrete is consist the basic properties of concrete that is effluent factor of design property of concrete which is measured by standard test on concrete cube.
Grade of concrete is denoted like as M25, which means the M is important to mix or mixing and 25 characteristics compressive strength in 28 days that is expressed in MPa or N/mm2.
Grade of concrete is three types normal strength concrete M10, M15, M20, M25, M30 standard strength concrete M35, M40, M45, M50, M55 and high strength concrete is above M60.
Characteristics strength of concrete
Characteristics strength of concrete is defined as the phenomenon of strength of materials below which not more than 5% result are expected to fall,for example if we consist the 20 test result during the compression test on cube specimen in laboratory that is not 1 in 20 tests result fall below the characteristics value.
If grade of concrete is M20 then it’s characteristics strength is 20 MPa or N/mm2, also grade of concrete M 25 then it’s characteristics strength is 25 MPa or N/ mm2, it is expressed in fck.
Characteristics strength of concrete variation is described in terms of standard deviations that is related to each other in the form of formula
Fm= fck+1.65 s
Where Fm term is denoted the target mean strength, fck is characteristic strength of concrete and s is standard deviations, standard deviations s value is depend on grade of concrete which is consist the 3.5 for grade of concrete M10, M15 and 4.0 for grade of concrete M20, M25 and also consist the standard deviations 5.0 for grade of concrete above the M30.
Tensile strength of concrete
Tensile strength of concrete is a test which is associated with direct tension test, splitting test and three point method test, this strength value of concrete is 7 to 15% of characteristics compressive strength of concrete .
Tensile strength of concrete is consist the modulus of rupture that is the theoretical maximum tensile stress reached in extreme fibers which is expressed in term as fcr and according to IS code it’s empirical formula is fcr= 0.7 root fck
Modulus of elasticity of concrete
Modulus of elasticity of concrete is described as the term in Ec which is stress/ strain in case of normally short term elastic strain that means as the presences of instantaneous load and long term elastic strain which is consist the creep and shrinkage properties of concrete
The modulus of elasticity of concrete is constant at the low stress and starts decreasing at the higher stress level as a result cracking developed in concrete structures.
Modulus of elasticity of concrete is having property of brittle materials, non elastic and non linear but only the initial portion of curve is consist the linear,this is play a important role in behavioral properties of concrete.
According to ISI-2000empirical formula of modulus of elasticity of concrete
Ec= 5000 under root fck
Where the Ec is modulus of elasticity of concrete and fck is characteristic compressive strength of concrete.
Creep is defined as the phenomenon of time dependent of total strain that is expressed as thita and its value is play a important role in design of structures which is consist the creep coefficient value is different for according to days of construction of structures
Creep= creep strain at time t/ instantaneous strain
According to IS code creep value as follows-:
1. Creep coefficient for Design is 2.2 for 7 days
2. Creep coefficient for Design is 1.6 for 28 days
3. Creep coefficient for Design is 1.1 for 1 year
Shrinkage is a property of concrete that is associated with the shrinks of concrete means it’s hardened state of concrete due to loss of moisture by evaporation.this properties of concrete is consist the dry shrinkage and differentials shrinkage.
Behavioural properties of dry shrinkage in concrete is a state of reduction of volume of concrete having similar property of creeps which is develop the tensile stress and a important cause of lead to cracking.
Behavioural properties of differential shrinkage in concrete is a state of due to moisture or thermal gradient placed reinforced steel in beam which is associated with the induced internal stresses, curvature and deflection.
Concrete structures surface dries due to water evaporates from the void between the particles as a result this water dissipates ,the movement of particles close together, then cracking is developed in concrete structures such as slabs, residential foundation walls that is called as shrinkage of concrete.shrinkage of concrete during the fresh concrete surface is known as plastic shrinkage and consequence of chemical bonding is known as chemical shrinkage.
Behaviour of srinkage of properties of concrete is important which is affect the long term strength and durability, minimize the shrinkage by keep the total water content of the concrete mix as low in practicalble for the requirements of application and addition of high range water reducing admixtures.
Durability of concrete
Durability of concrete is defined as the phenomenon of the capable property of concrete to resist the strength and maintain the desired engineering properties in weathering action, abrasion and chemical attack that is depend on the environment exposure conditions.
Durability of concrete is affected by the some factors such as water quality, concrete compaction, curing period, moisture, permeability, temperature, cement content etc.
Effective behavioral properties of concrete is durability of concrete is mostly effluent factor to serve the purpose for increases the lifetime during the design of construction of structures.some factors are effectively increase the durability of concrete
1. Providing the adequate clear cover to embedded steel
2. To use coated steel in construction of structures
3. To use effective grade of concrete according to environmental exposure conditions that is highly affect the durability of concrete