COURSE LEARNING OUTCOMESAt the end of this chapter, students will be able to:CLO 1 - Explain the development of theconstruction sector and its role in national development and thevarious format of the contractor’s organizationCLO 2 - Describe site investigationtechniques and the mixing, compacting and placing of concretemixes
CONCRETE•Freshly prepared concrete till it has not yet is called “wetconcrete”.•After it has thoroughly set and fully hardened it is called “setconcrete”MIXING OF THE CONCRETEGenerally, there are two methods for mixing the concrete:•Hand mixing•Machine mixing
HAND MIXING•In this type, the mixing is done by manual labors. Thismethod is adopted for small construction works.Requirement of cement is more than machine mixing(10%). Normally the mixing time is about 3 minutes.•Construction of platform of bricks, lean concrete or ironsheet.•Spread out-sand evenly, spread cement on it.•Mix till the color of mixing become uniform.•Spread this mixture & spread coarse admixture then mix it.•During mix it remaining water should be added withcontinuation process. Time for mix is generally 2 to 3minutes.
HAND MIXING CONCRETE
MACHINE MIXING•This is similar to hand mixing, only the mixing is carriedout in a rotating drum.•For machine mixing, all the ingredients of concreteincluding water are collected in a revolving drum and thenthe drum is rotated for a certain period.