SSC JE Civil Engineering 23-Mar-2021 Shift 1 Paper

Question : 169 of 200

Marks: +1, -0

Identify the test to be conducted for the determination of the modulus of subgrade reaction in pavement design.

Solution:

Concept:
The various tests performed on bitumen are as follows:

Test	Characteristics
Penetration test	It is performed to determine the grade of bitumen. Penetration value also gives the idea about the softness and harness of the bitumen Higher the grade of bitumen, softer will be the bitumen.
Plate bearing test	It is done on soil subgrade and it determines the modulus of subgrade reaction. Modulus of subgrade reaction is given by ${\k}={{\p}}/{ \Δ}={{\p}}/{0.125 {\cm}} {\kg} \/{\cm}^{3}$ Where, p = pressure corresponding to settlement of 0.125 cm.
CBR test	CBR value can be defined as the ration of load at penetration of 2.5 mm or 5.0 mm to the standard load (i.e. 1370 kg for 2.5 mm & 2055 kg for 5.0 mm) for same penetration. ${\CBR}={{ \Load \at \penetration \of } 2.5 {\mm} { \or } 5.0 {\mm}}/{{ \standard \load \at \same \penetration }}$ This test is used for determine the thickness of the pavement or subgrade. Greater the CBR value, lower will be the thickness.
Abrasion test	It is performed to determine the hardness of the aggregates used in the pavement. It is performed by Los Angeles, Devel and Dorry Abrasion value ${\AV}={{\W}_{2}}/{{\W}_{1}} ×100$ $\W_2=\weight \of \aggregates \passing \through 1.70 \mm \sieve \and$ $\W_1= \initial \weight \of \aggregates.$ Note:- Abrasion Value should not be greater than 30% for surface and 35% for bituminous concrete.

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