Concrete

What is Concrete?  

•      Concrete is a construction material composed of cement, fine aggregates (sand) and coarse aggregates mixed with water which hardens with time.

•      The word concrete comes from the Latin word "concretus" (meaning compact or condensed), the perfect passive participle of "concrescere", from "con-" (together) and "crescere" (to grow).

Composition of concrete

•      Concrete is a composite material composed of fine aggregate ,coarse aggregate and bonded together with a cement paste.

1. Cement

2. Water

3. Aggregates

4. Reinforcement

5. Admixtures

6. Mineral admixtures and blended cements 

   Production of Concrete

•      Concrete production is the process of mixing together the various ingredients—water, aggregate, cement, and any additives—to produce concrete. Concrete production is time-sensitive. Once the ingredients are mixed, workers must put the concrete in place before it hardens. In modern usage, most concrete production takes place in a large type of industrial facility called a concrete plant, or often a batch plant.

     Types of concrete mix plant

•      Mainly Two types of concrete mix plants

1.  ready mix plants

2.  central mix plants

During concrete production different activity which are perform

•     Mixing
•     Mix ratios
•     Workability
•     Curing

v     Mixing

•      Mixing is important for produce  uniform, high-quality concrete.

•      Different types method use for concrete mixing are

1. Manual concrete mixing

2. Machine concrete mixing

v     Mix ratios

•      Concrete Mixes are primarily divided into two types, nominal mix and design mix:

•      Nominal mix ratios are given in volume of {Cement : Sand : Aggregate}. Nominal mixes are a simple, fast way of getting a basic idea of the properties of the finished concrete without having to perform testing in advance.

•      Design mix ratios are decided by an engineer after analyzing the properties of the specific ingredients being used. Instead of using a 'nominal mix' of 1 part cement, 2 parts sand, and 4 parts aggregate , a civil engineer will custom-design a concrete mix to exactly meet the requirements of the site and conditions, setting material ratios and often designing an admixture package to fine-tune the properties or increase the performance envelope of the mix.

•      Design-mix concrete can have very broad specifications that cannot be met with more basic nominal mixes, but the involvement of the engineer often increases the cost of the concrete mix.

v     Workability

•      Workability is the ability of a fresh concrete mix to fill the mould properly with the desired work  and without reducing the concrete's quality. Workability depends on water content, aggregate shape and size distribution, water-cement ratio and can be modified by adding chemical admixtures, like super plasticizer . Raising the water content or adding chemical admixtures increases concrete workability. But reduce the strength of concrete .

•      Workability can be measured by the concrete slump test,  Compacting Factor Test , Flow Test , Kelly Ball Test , Vee Bee Test.

v     Curing

•      Concrete must be kept moist during curing in order to achieve optimal strength and  durability. During curing hydration occurs.

•      Hydration and hardening of concrete during the first three days is critical. 

•      Properly curing concrete leads to increased strength and lower permeability and avoids cracking where the surface dries out prematurely. Improper curing can cause scaling, reduced strength, poor abrasion resistance and cracking.

      Types of Curing

•      Ponding

•      Moist Coverings

•      Membrane Curing of Concrete.

•      Synthetic Resin Curing Compound.

•      Acrylic Curing Compound.

•      Wax Curing Component.

•      Chlorinated Rubber Curing Compound.

•      Steam Curing of Concrete.

•      Curing of Concrete by Infrared Radiation.

Properties

•      Concrete has relatively high compressive strength, but much lower tensile strength.

•      Tests can be performed to ensure that the properties of concrete correspond to specifications for the application properties of concrete are

•      Grades of concrete

•      Compressive strength

•      Characteristic Strength

•      Tensile strength

•      Durability

•      Creep

•      Shrinkage

•      Unit weight

•      Modular Ratio

•      Poisson’s ratio

Use of concrete

1. In construction

1.              Mass structures
2.              Surface finishes
3.              Prestressed structures
4.                  Cold weather placement
5.               Underwater placement
6.               Roads
7.               Energy efficiency
8.               Fire safety
9.              Earthquake safety

Types of concrete

•      Normal Strength Concrete

•      Plain or Ordinary Concrete

•      Reinforced Concrete

•      Prestressed Concrete

•      Precast Concrete

•      Light – Weight Concrete

•      High-Density Concrete

•      Air Entrained Concrete

•      Ready Mix Concrete

•      Polymer Concrete

•      High-Strength Concrete

•      High-Performance Concrete

•      Self - Consolidated Concrete

•      Shotcrete Concrete

•      Pervious Concrete

•      Vacuum Concrete

•      Pumped Concrete

•      Stamped Concrete

•      Lime Concrete

•      Asphalt Concrete

•      Roller Compacted Concrete

•      Rapid Strength Concrete

•      Glass Concrete