REINFORCED CEMENT CONCRETE Prepared By Mr. Ashok Kumar Lecturer in Civil Engineering Gpes Meham Rohtak

Chapter-I Introduction The word “concrete” originates from the Latin verb “concretes”, which means to grow together. Roadways/transportation systems Airstrips Infrastructure (bridges, dams, buildings) Harbor protection (break walls) Water distribution (pipes & conduit)

Advantage of Concrete We have the ability to cast desired shapes Arches, piers, columns, shells Properties can be tailored according to need (strength, durability, etc.) Ability to resist high temperatures Will maintain structural integrity far longer than structural steel Does not require protective coatings Can be an architectural & structural member at the same time

Properties of Quality Concrete Workability Durability Strength Chloride Penetration Resistance Abrasion Resistance

The Nature of Concrete It is a composite material Aggregates are 65% - 80% of the volume Fine aggregate: sand Coarse aggregate: stone Cement: General term & applies to any binder Portland cement fly ash ground slag silica fume Water

Concrete Microstructure

The Purpose Of The Aggregates Large aggregates: provide density (fill space) provide strength Fine aggregates: fill small voids between large aggregates Increases strength of the cement binder

The Cement Matrix Cement: Water produces a crystalline structure binds aggregates together Water causes chemical reaction to occur water/cementitious “react” produces workability

What is Portland Cement? Raw limestone, clay & gypsum minerals are ground into powder & heated in kiln (1600 ° C) Minerals interact at that temperature to form calcium silicates (clinker) Available in five types, each with varying performance characteristics and uses

Portland Cement Manufacturing Process

Clinker

Hydration Portland cement becomes cementitious when mixed with water This reaction is referred to as hydration. During hydration, a crystalline structure grows to form bonds Hydration begins as soon as water meets cement Rate of hydration increases with increased cement fineness

In Fact……. Concrete does not gain strength by “drying out” Concrete must have continuous free access to water to achieve its ultimate strength!!

Air Entrainment Admixtures All concrete containes “entrapped” air Large bubbles Large voids are undesirable for durability & permeability Entrained air Bubbles are microscopic in size & distributed through out concrete Increases durability by providing “escape route” for freezing water as it expands

Entrained Air

Water Reducers (Super-Plasticizers) Increases viscosity Water can be reduced Results in higher strength and more durable concrete due to reduced water

REINFOCEMENT MATERIAL steel 1. Physical properties colour –light wave length specific heat – the heat required to raise the temperature of one gram of a substance by one degree centigrade (J/kg K)

density – mass per unit volume expressed in such units as kg/cm 3 thermal conductivity –rate at which heat flows through a given material (W/m K)

Mechanical Properties melting point – a temperature at which a solid begins to liquify electrical conductivity – a measure of how strongly a material opposes the flow of electric current (Ω⋅m)

Mechanical Properties tensile strength – measures the force required to pull something such as rope,wire or a structural beam to the point where it breaks ductility – a measure of how much strain a material can take before rupturing

toughness – the ability of a material to absorb energy and plastically deform without fracturing hardness – the property of being rigid and resistant to pressure; not easily scratched

LOADING ON STRUCTURE AS PER IS 875 Types of Loads on Structures and Buildings In a construction of building two major factors considered are safety and economy. If the loads are adjudged and taken higher then economy is affected. So the estimation of various loads acting is to calculated precisely. Indian standard code IS: 875–1987 and Other Structures specifies various design loads for buildings and structures. Hdfhhhd

Types of load on a structures Dead loads Imposed loads Wind loads Snow loads Earthquake loads Special loads

CHAPTER-2 METHOD OF RCC DESIGN Working stress method Factor of safely for yield stress, allowable stresses are less than ‘fy’. Pure elastic approach for analysis of structures under working loads. Yielding or buckling never occurs at working loads Deformations are evaluated at working loads.

Limit state Method Acceptable limit for the safety and serviceability requirements before failure occurs is called a Limit state

Partial safety factor for material (γm) for yield and ultimate stress. Working loads are factored (increased) as per partial safely factor (γf) causing Limit State of strength. Post buckling and post yielding plays important role in estimating capacity of structural elements at Limit State. Deformations are evaluated at working loads.