Concrete

Concrete

Composite l'an made material and is the most widely used construction material in the industry

Composition

Lime or cement, well graded fine and coarse aggregates, water and admixtures

Stages of production

Batching

Mixing

Transporting

Placing

Compacting

Curring

Finishing

Workability

This is the ease with which concrete can be handled

Duff Abraham's law

“For plastic mixtures using neat and clean aggregate, the strength of concrete under specific conditions is governed by net quantity of water mixed per bag of cement “

Gel-space ratio

It is the ratio of volume of hydrated cement paste to the sum of the volumes of hydrated cement and that of the capillary pores

Factors influencing strength of concrete

• Size of test specimen

• Type of stress situation that may exist

• Moisture condition of specimen

• Air voids

• Rate of loading

• Type of testing machine

• Type and age of cement

• Type and size of aggregate

• Degree of compaction

Maturity of concrete

Defined as the summation of product of time and temperature

Factors affecting workability

• Water content

• Mix proportions

• Aggregate size

• Shape of aggregates

• Surface texture

• Admixtures

Measurement of workability

• Slump test

• Compacting factor test

• Vee-bee consistometer method

Durability

A durable concrete is one that performs satisfactorily under anticipated exposure conditions for stipulated life of the structure

Defects

• Cracks

• Segregation

• Bleeding

• Laitance