Department of Civil Engineering Sep 20, 2010 Concrete (CE-107) By: Engr. Muhammad Abbas Qureshi Department of Civil Engineering

CE- Properties of Concrete What is Concrete?. Concrete is word of Latin derivation ( con – together ) ( crete – to grow ) and its history can be charted from 3000 BC. It is a composite material that consists essentially of a binding medium (Cement, Lime) within which are embedded particles or fragments of aggregate(Coarse & Fine Aggregates). Concrete is often looked upon as “man made rock”. Section cut from Hardened Concrete 2018/12/1 CE- Properties of Concrete

CE- Properties of Concrete Concrete Ingredients Cement /Lime - Binder Aggregate - sand, gravel, crushed rock Fine aggregate ----- Sand Coarse aggregates ----crushed rock Water Admixtures - when necessary 2018/12/1 CE- Properties of Concrete

CE- Properties of Concrete Cement A mixture of inorganic materials that sets and develops strength by chemical reaction with water by formation of hydrates and is capable of doing so under water. Cement Bag Cement Powder 2018/12/1 CE- Properties of Concrete

CE- Properties of Concrete Cement Binds the aggregates into a solid mass Imparts strength to concrete Makes concrete impermeable by filling up voids in fine concrete 2018/12/1 CE- Properties of Concrete

CE- Properties of Concrete Aggregates Granular materials, such as sand, gravel, crushed stone used with cementing medium to form concrete or mortar. Aggregates act as a relatively inexpensive inert filler, providing stability against volume changes and influencing strength. Fine Aggregate Diameter< 4.75mm Coarse Aggregate Diameter > 4.75mm 2018/12/1 CE- Properties of Concrete

CE- Properties of Concrete Aggregates Sand Fills the voids within coarse aggregates Assists in hardening of cement by allowing water to seep through its voids Minimizes shrinking and cracking of concrete Economizes concrete by varying its proportion for strength Coarse Aggregate Acts as main filler, forms the main bulk mass Binding material adheres on its surface Imparts volumetric stability and durability to concrete Increases crushing strength, resistance to wear and tear, and water tightness of concrete Economizes concrete since it is cheaper than cement 2018/12/1 CE- Properties of Concrete

CE- Properties of Concrete Water It reacts with the cement to form binder that hardens and bonds the aggregates together Lubricates the fresh concrete enabling it to be placed into position and compacted. Good water is essential for quality concrete. It should be good enough to drink--free of trash, organic matter and excessive chemicals and/or minerals. The strength and other properties of concrete are highly dependent on the amount of water and the water-cement ratio. 2018/12/1 CE- Properties of Concrete

CE- Properties of Concrete Concrete Ingredients Admixtures They are chemicals that can be added to the concrete immediately before or during mixing and significantly change its fresh, early age or hardened state to economic or physical advantage 2018/12/1 CE- Properties of Concrete

CE- Properties of Concrete Concrete Ingredients Admixtures Retarding agents – delay setting time Accelerators – set and acquire strength rapidly Air entraining agents Water proofing agents – pore filling, water repelling Pozzolanas – non-cementing, but forms lime compounds which are cementing Pigments Workability agents 2018/12/1 CE- Properties of Concrete

CE- Properties of Concrete Cement Concrete Coarse aggregate acts as a filler. Fine aggregate fills up the voids between the paste and coarse aggregate. Cement in conjunction with water acts as a binder. Admixtures aid the mobility of the mixture by regulating the setting environment and time. (Setting & Hardening) 2018/12/1 CE- Properties of Concrete

Advantages of Concrete Concrete is the most widely used construction material in the world. It has relatively high compressive strength. It has better resistance to fire than steel, wood etc It has long service life with low maintenance cost. In some type of structure such as dams, piers and footing it is most economical structural materials. It can be cast to take the shape required making it widely used in pre-cast structural components. It yield rigid member with minimum apparent deflection. Concrete can be finished to produce surfaces ranging from glass-smooth to coarsely textured, and it can be colored with pigments or painted. 2018/12/1 CE- Properties of Concrete

Disadvantages of Concrete It needs mixing, casting and curing all of which affect the final strength of concrete. The cost of formwork used to cast the concrete is relatively high. It has very low tensile strength. It has low compressive strength as compared to steel which lead to large section of structural members. Minor crack develops in concrete due to shrinkage. It requires skill labor and supervision from mixing to finishing. 2018/12/1 CE- Properties of Concrete

CE- Properties of Concrete History Concrete 2018/12/1 CE- Properties of Concrete

Qualities of Good Concrete Fresh Concrete Workability – easily workable Volume stability Hardened Concrete Strength – compressive and tensile Durability – wind, rain, frost, temperature, chemicals and salts Density – 3,000 kg/m³ well compacted Water tightness – avoid corrosion of inside steel and leakage, seepage in hydraulic structures Resistance to wear and tear – abrasive action in floors and roads 2018/12/1 CE- Properties of Concrete