Concrete Technology
Introduction
Prof. Dr. Tek Raj Gyawali
School of Engineering
Pokhara University
Definition and Basic Information
Concrete is a composite material that consists essentially of a binding medium within which are embedded particles or
fragments of aggregates. In hydraulic-cement concrete, the binder is formed from a mixture of hydraulic cement and water
(ASTM 125 and ACI 116).
Cement (Mineral admixtures)+ Water (Chemical Admixtures)+ Fine Aggregates + Coarse Aggregates = Concrete
Should meet the designed target of fresh and hardened state
as well as of durability aspect
Then concrete can be defined in your way:
Concrete is the mixture of water, cement and aggregates (fine and coarse) which are mixed in certain proportions in order to
achieve the required workability, strength, serviceability and durability. Mineral and chemical admixtures are added as
additives in order to enhance the quality of concrete in fresh and hardened state as well as its durability aspect. Mineral
admixtures are part of powder materials and chemical admixtures as part of water.
Requirement for the good quality of concrete
Mixing Each & every cement particle
Cement (Mineral Admix.)
Paste should be coated by water
+ Water (Chemical Admix.) and free water should be
distributed uniformly
Each & every sand particle
should be coated by part of
Paste Paste and rest should be
Mortar
+ Fine Aggregates distributed uniformly among
sand particle
Each & every CA should be
Mortar coated by part of mortar
Concrete and rest should be distributed
+ Coarse Aggregates uniformly among CA
Definition and Basic Information
Paste is the binding medium with composition of cement (also mineral admixture) and water (also chemical admixtures)
including the entrained air
Aggregates consist of fine and coarse aggregates
Paste contributes the strength, due to the hydration process of cement and water, and aggregates, with its own strength, is
bond by the paste to give the desired shape, rigidity and resistance over compression, impact and abrasion.
Concrete is very strong in compression but very weak in tension. It is brittle.
Concrete is the most popular and widely used construction materials in the world.
It is second to the water consumed in the world.
The reasons for being the most popular construction material:
(a) Cheaper than other materials
(b) Its ingredients easily available at every part of the world
(c) High strength (compressive), water resistance capacity (durability) and energy efficient for the production
(d) High temperature and fire resisting capacity than other materials like timber and steel
(e) Can be built to any required shape and size
(f) Maintenance free
(g) Resistance to the cyclic loading
(h) resistance to the bad external exposure like acid, sulphate, salt etc.
(i) Protects steel reinforcement bars from corrosion
(j) Easy on handling and transportation
(k) Better appearance and gives rigidity to the structures
(l) Ability to consume and recycle waste
Use of Concrete in Structures
Disadvantages are:
(a) Very sensitive and difficult in each step of quality control
(b) Very weak in tension and ductility…..so, the tensile reinforcement required in the structures
(c) Problems of shrinkage and creep
(d) Soluble salt in concrete causes efflorescence
(e) Makes structures heavy
Examples of Usage in Structures
Residential, public and commercial buildings
Concrete dams, reservoirs and water tanks
Roads, highways and airports pavements
Tunnels and bridges
Marine structures
Foundation of all structures
Nuclear shielding walls
Refractory: High temperature applications
Culverts and sewers
Slope stabilization with shotcrete/ground retaining structures
Precast and pre-stressed structural elements
Riprap and revetments
Permanent formworks
Parapet and Fences
Railings
Fireproof covering in steel and composite structures
Blocks and tiles
…………etc.
Sequence of Being Structural Engineer
Mathematics A fresh Civil
Engineer
Statics
graduated from
Dynamics any Nepalese
engineering college
Strength of Materials
is supposed to be
Theory of Structure able to design and
Concrete construct the RCC
houses/buildings
RCC as per customer’s
Civil Engineer demand!
No any Significant Difference Between Nepal and Japan
Comparison Between Engineering Study &
Engineering Work
BE Civil Study Civil Work
Mathematics 100% 100% Materials Quality
Statics 100% 100% Mix Proportion
Dynamics 100% 100% Production
Strength of Materials 100% 100% Transportation
Theory of Structure 100% 100% Pumping/Pouring
Concrete 100% 100% Placing
RCC 100% 100% Curing
=
=
Result (Distinction) 100% 100% Concrete Structure
Comparison Between Engineering Study &
Engineering Work (contd.)
BE Civil Study Civil Work
Mathematics 90% 90% Materials Quality
Statics 90% 90% Mix Proportion
Dynamics 90% 90% Production
Strength of Materials 90% 90% Transportation
Theory of Structure 90% 90% Pumping/Pouring
Concrete 90% 90% Placing
RCC 90% 90% Curing
=
=
Result (Distinction) 90% Concrete Structure
?
Comparison Between Engineering Study &
Engineering Work (contd.)
BE Civil Study Civil Work
Mathematics 90% 90% Materials Quality
Statics 90% 90% Mix Proportion
Dynamics 90% 90% Production
Strength of Materials 90% 90% Transportation
Theory of Structure 90% 90% Pumping/Pouring
Concrete 90% 90% Placing
RCC 90% 90% Curing
=
=
Result (Distinction) 90% 48% Concrete Structure
Sequence of Quality Control on RCC Houses
Ground Reality Reinforcement Fabrication
Design Procedure Formwork/skeleton formation
Design Approve Concrete Mix Design on site
(arch., environ.,
struct., cons. proc.)
Concrete Mixing
-National/Regional Auth.
-Owner
Quality Test of Concrete
Material Selection
Transportation/placing/compaction
Assurance of Materials’
Quality on Delivery Curing Finishing
Materials Storing Summarize of QC for QA
Testing of Materials Handover Periodic Maintainence
Structural Design Requirement
Member
Material Analysis
Properties
Member Accurate
Design Design
Requirement for Good Concrete
Workability
Easiness of
Pumping, Placing
Vibrating, Finishing,
Small Etc.
Shrinkage Low Heat
Plastic, Autogeneous Generation
dry, Thermal etc
Good
Concrete
Strength
Durability Compressive,
Chemical Tensile,
Freezing & thawing Flexural
Reasonable
Cost
Effect of Quality Control on Strength & Durability
Particle distribution,
Mix proportion
bonding state with
of each material
each other
Batching Mixing
Type, Free water,
structure, Durability aspect of air content,
material Fresh
chemical structure from its compacting,
constituents state
structure birth to death state finishing
Hardened Early
state state
Porosity, Hydration,
rigidness, micro-structure,
environment environment
Thank You !
