|1 Crore+ students have signed up on EduRev. Have you? Download the App|
In a standard California bearing ratio test (sample height is 125 mm), the difference between the initial and final dial gauge readings is found to be 0.125 mm. What is the expansion ratio of this soil?
California Bearing Ratio (CBR)
δ = displacement in mm
Pδ = Load corresponding to ‘δ’ settlement
Ps = Load for standard crushed aggregate:
At 5 mm penetration Standard load Ps = 2055 kg
At 2.5 mm penetration standard load Ps = 1370 kg
The sample height = 125 mm
The change in sample height = 0.125 mm
The expansion ratio of this soil is
The materials not included in highway construction are __________
Petrol is not used directly in highway construction, but by-product like bitumen is used. Stone, dust and soil may be used in subgrade and base.
In angularity number test, the angularity number for aggregates used in construction generally ranges from ______.
It is the absence of roundness. An aggregate particle, which is more rounded, is less angular and vice versa.
Determination of angularity number:
(a) From the solids
(b) From the voids
Where C = weight of the cylinder, W = weight of aggregate in the cylinder, Gs = specific gravity of aggregate
Which of the following test is used for the bitumen?
Various tests conducted on bitumen for testing its various properties are as follows:
Marshal test is used for designing the bituminous concrete for pavement construction, Beckenham Beam Method is used to determine the deflection of the pavement slab.
Bitumen is classified on the basis of either its penetration value or its viscosity.
Classification based on the penetration value of bitumen:
The penetration test is carried out to know the hardness or softness of bitumen used in road construction by measuring the distance in tenths of a millimeter to which a standard needle will penetrate vertically into a sample of bitumen under the stipulated condition of temperature, time and loading.
A bitumen specified as of grade 80/100 means that the range of penetration value of the sample is between 80 to 100 (i.e. actual penetration would range between 8 mm to 10 mm).
∴ Hardest grade of bitumen among the following is 30/40, as penetration would be as less as 3 to 4 mm only.
Note: It can be stated that for a hot climate, lower penetration grades of bitumen are preferred, and for cold climates, higher penetration grades of bitumen are preferred.
For places where there is a passage of flood water then the highway has to be built on __________
If the HFL is more than the formation level of the road which is going to be provided, then it has to be built on embankment.
In the Pensky Marten test for Bitumen, a momentary flash was seen at a temperature of 200° Celsius and the bitumen burned for at least 5 seconds at a temperature of 240° Celsius. The flash and fire point of bitumen is _________ and _________, respectively.
The layer which is constructed above embankment is called __________
The embankment is the lowest layer and it is below the sub grade, base is above sub base, sub base is above the sub grade.
Rapid curing cutback is produced by blending bitumen with
(i) Cutback bitumen is bitumen with less viscosity which, is achieved by the addition of volatile diluent. Hence, to increase the fluidity of the bitumen binder at low temperature the binder is blended with a volatile solvent.
(ii) The viscosity of the cutback bitumen and the rate at which hardness on the road depends on the characteristics and quantity of both bitumen and volatile oil used as diluent.
(iii) Cutback bitumen is available in three types:
(i) MC and SC cutback are used for priming and viscosity increases as the grade increases like RC-0, RC-1, RC-2.
(ii) RT-1 is lowest viscosity used for surface painting but RT-4 may be used for premix in macadam.
(iii) RT-5 is used for grouting which has highest viscosity.
(iv) MC-2 will be thicker than MC-1 but RC-5 and SC-5 will have same viscosity.
The highest CBR number is required for __________
CBR number decreases with an increase in height, the soil requires the highest CBR and the pavement requires the lowest CBR.
Bitumen is a by-product of __________
Bitumen is obtained by burning the petroleum at high temperatures, it is mostly used in the construction of flexible pavements.