8

Question 1

Specs of exp joints

Answer 1

Expansion joints are about 25 mm for exposed concrete structure and less that 50 m in other structures

Question 2

Why are exp joints used

Answer 2

To prevent the effects of thermal movement and uneven settlement -

Question 3

Principles of expansion joints

Answer 3

1 plan dimensions should not exceed 25 m for exposed and 50 m
2. A mane should be able to pass completely through them
3. Should be placed where there is a large difference in foundation loads or abrupt changes in plan dimensions exist

Question 4

What is concrete made of

Answer 4

Cement (A binding agent that glues aggregates together ), course aggregates (stone), fine aggregates sand and water

Question 5

Manufacturing of O. P.c consists of

Answer 5

Crushing, blending, milling, burning in kiln

Question 6

What are cement extenders

Answer 6

I E, silica fume increases the strength of concrete and reduces is permeability

Question 7

Additive slag

Answer 7

Slows hardening reduces heat and permeability but increases resistance to sulphate and chloride attacks

Question 8

Additive fly ash

Answer 8

Improves workability, retards setting, slows hardening, improves resistance to sulpiliate attacks and alkali reaction

Question 9

Plasticizer and super plasticizer

Answer 9

l. Improves workability without adding more water thus increasing-strength
2. Makes concrete self leveling and flow through condensed reinforcement
Without creating air voids

Question 10

Accelerator and retarders

Answer 10

‘1. Speeds up hardening used in precast prestressed industry
2. Slows down hardening giving more time for transportation and placement

Question 11

Waterproofors and Air entrainments

Answer 11

1 reduce permeability and soriptivity, used in structures which hold water
2. Creates air packets in concrete to improve durability in winter

Question 12

What is curing

Answer 12

Maintenance of hardening concrete by exposing it to adequatemoisture and temperature conditions

Question 13

• Concrete Strengths In parts of building

Answer 13

Foundations, surface beds, suspended slabs - 25 to 30 mp a
Beams and columns - 30

prestressed concrete - 40 to 60

Question 14

What are steel fibers used for.

Answer 14

A n alternative to - steel reinforcement, randomly placed and used in areas of low stress usually fail due to will out so anchorage is important used in surface beds and tunnel turning 13 to 75 mm long

Question 15

Opc is made from?

Answer 15

Clinker (limestone); gypsum and other inorganic materials