a- What do you mean by concrete mix design; what are the major factors that must be considered while designing concrete mixes? [5] b- Name various methods used for concrete mix design worldwide? Which method is commonly used Pakistan?

 

Q#      a-      What do you mean by concrete mix design; what are the major factors that must be considered while designing concrete mixes?                                                                                          

b-      Name various methods used for concrete mix design worldwide? Which method is commonly used Pakistan?                                                                                                                                

Aswer A

concrete mix design

The art of selectig suitable ingrediets of concrete and determining their relative proportions with object of producing concrete with certain minimum strength

Concrete mix design involves a process of preparation in which a mix of ingredients creates the required strength and durability for the concrete structure. Because every ingredient in the mix consists of different properties, it’s not an easy task to create a great concrete mix. It is imperative that all ingredients be tested to determine their physical properties and the bearing capacity of the project location.

The following must be considerd  while designing concrete mixes

Ø  Cost

Ø  WORKABILITY

Ø  COST

Ø  STRENGTH

Ø  DURABILITY

 

1-WORKABILITY

Basic Considerations Workability • The following points related to workability shall be kept in mind while designing concrete mixes. The consistency of concrete should no more than that necessary for placing, compacting and finishing.

2- COST

Ø  Material cost

Ø  equipmentd cost

Ø  labor cost   

cements are several times costliar than than aggregates

cements content need to be minimized

 

3-STRENGTH

Out of all the physical characteristics of concrete compressive strength is often taken as an index. Therefore, the mix design is generally carried out for a particular compressive strength of concrete coupled with adequate workability so that the fresh concrete can be properly placed and compacted. In addition the mix proportions are also checked against the requirement of adequate durability for the type of exposure condition anticipated in service.

 

4-DURABILITY

durability requirements in terms of miimum cement content, maximum w/c ratio and minimum grade of concrete

Durability is the property due to which concrete withstand the enviromental condition to which it is exposed for long period of time

 

ANSWER B 

Name various methods used for concrete mix design worldwide

1- Maximum density method

2 -Road note 4 methods

3- finenes modulus method

4- surface area method

5-ACI method

6-Mix design for high strength concrete

7-Mix design for pumpable concrete

 

 

ACI method and superpave method is used in pakistan commonly