Freshers civil Engineer must know these Topics

Filling operation:

Filling shall be placed in layers. The compacted thickness of each layer shall be 300mm for large areas and 200mm for smaller areas. Each layer shall be properl ywatered and compacted to the requirements given below:

Fill shall be compacted to achieve 90% of modified Proctor density or 95% of standard Proctor density at optimum moisture content when tested as per any one method given in IS 2720 (part 28, 29 and 34). The in-situ moisture content of the compacted fill shall be determined as per one of the procedures given in IS 2720 (part 2).

Granular material which does not exhibit well defined moisture density relationship shall be compacted to at least 80% relative density when tested according to IS 2720 (part 14).

NOTE : -Field density testing should be performed for every 250 square metres per layer for small areas measuring up to 2000 square meters. For larger areas one test shall be performed for every 500 square metres per layer of compacted fill. At least one test shall be performed on every layer of fill. Until the required density is achieved, further placement of fill shall not be permitted.

Why Crank Bars are Provided in Slab :

A bent-up bar called as crank bar is provided to make RCC slab safe from compressive stresses.To resist negative bending moment, resist shear force which is greater at supports and to reduce the risk of a brittle failure of slab-column connection.

Why Hook Is Provided In Stirrups :

Hooks are provided for to resist seismic movement. To prevent it from buckling of column and prevent it slippage of steel from the concrete.

what If on-site slump test fails :

If concrete slump comes more than maximum range, put the concrete mixer on site for 7-10 minutes to have more mixing and to reduce the slump.

If concrete slump comes less than minimum range put some admixture (super plasticizer) to mixer on site it will surely maximize the slump.