Highway Engineering and Material: Understanding Earthwork Materials and Unbound Mixtures

In this assignment we will discuss about highway engineering & material and below are the summaries point:- Earthwork materials for road construction classified into different classes based on grading and composition Various tests are conducted on earthwork materials, including moisture condition value and shear box tests The 800 series of unbound mixtures in the Highway Works Specifications includes Type 1, produced using crushed concrete and other materials.

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HIGHWAY ENGINEERING AND MATERIAL
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Earthwork materials
Earthwork excavation is a very critical process in road construction. It is advisable to
excavate the soil located on site instead of importing from another location. However, when
choosing materials to be used for filling, it is important to consider whether this materials meet
certain requirements for acceptability in construction. Hence, for capping purposes, these
materials are classified into different classes as discussed below:
Class 6F1 fill is a capping layer with fine grading materials. It is made up of any materials or a
mixture of materials other than argillaceous rocks, chalk and unburnt colliery spoil (Reid, et al.,
2008). The aggregates can also be recycled.
Class 6F2 is a capping layer with coarse grading materials. It is made up of any materials or a
mixture of materials other than argillaceous rocks and unburnt colliery spoil (Reid, et al., 2008).
The aggregates can also be recycled.
Class 6F3 is a capping layer material with same grading as 6F5, however, it consist of a 100%
recycled bituminous road planings and asphalt. When 6F3 is used as a specification rather than
road planings, it means that the uniformly graded materials are excluded (Reid, et al., 2008). It is
therefore recommended to use 6F3 as a specification rather than just a road planing. It is
important to note that during hot weather, bituminous road planings may bind in case it is rolled.
Class 6F4 is a capping layer with fine granular materials. Its components are inbound mixtures
that comply with BS 13285 (Reid, et al., 2008).
Class 6F5 is a capping layer that basically contains crushed concrete, crushed bricks or recycled
asphalt. The maximum aggregate size is around 80mm and there is a desirable size distribution

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between the smaller and larger aggregates hence ensuring that there is enough compact between
the aggregates with less voids (Ayan, et al., 2011). This materials have the ability to form
stronger base when rolled.
Earthwork material tests
 Determination of Moisture Condition Value (MCV)
 Determination of Intact Lump Dry Density (IDD) of Chalk
 Los Angeles Tests
 Shear Box Tests
 Triaxial Tests
 In Situ Resistivity Tests
 In Situ Redox Potential Tests
 Plate Loading Tests
Types of 800 Series unbound mixtures
The 800 Series of MCHW of the unbound mixture is part of Highway Works
Specifications. The 800 Series is important for the road pavement with unbound cement and
other hydraulically bound mixtures that relate to the general necessities of the 000 and 100 Series
(Ellis, et al., 2016). There are different kinds of unbound mixtures that can be utilized for sub-
base layers in road development. One of the unbound mixture utilized for sub-base road
construction is Type 1 unbound mixture. Type 1 unbound mixture is produced using crushed
concrete, pulverized rock, squashed slag, and well burnt non-plastic shale which contains 10
percent mass of sand that can pass through 4mm test sieve (Ellis, et al., 2016).

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Table 1: summary grading requirement for Type 1 and type 4 unbound mixtures
Source: (Ellis, et al., 2016)
The Type 2 unbound mixtures comprise of natural sands, crushed rocks, crushed concrete,
crushed slag, and recycled aggregates or properly burnt non-plastic shale. The grading of Type 2
unbound mixtures should comply with the requirements summarised in table 2 below.
Table 2 summary grading requirements for Type 2 unbound mixtures.

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Source: (Ellis, et al., 2016)
The fraction size of Type 2 unbound mixture should be passed through in the 0.425mm size test
sieve. The Type 2 unbound mixtures should have a plasticity index of below 6 percent. The
mixture is then transported, laid and compacted without isolation the moisture content inside the
scope of over 1 percent to 2 percent below the announced estimation of greatest water content.
Type 3 unbound blends are comprised of pulverized blast furnace slag and squashed rock. The
reused concrete aggregates utilized in Type 3 unbound mixtures contains more than 5 percent of
asphalt and not more than 1 percent of other materials (Class X) (Herrador, et al., 2011). The
grading requirement of Type 3 unbound mixtures is outlined in table 3 underneath.
Table3: summary grading requirements for Type 3 (open graded) unbound mixtures

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Source: (Ellis, et al., 2016)
The fraction size of the unbound mixtures is non-plastic and should pass through 0.425mm size
test sieve. After that, the mixture is transported, laid and compacted without drying.
Apart from Type 3 unbound mixture (open graded), the closed graded or Category B is another
type of unbound mixtures. This type of unbound mixture is made from recycled concrete
aggregate or crushed blast furnace slag and crushed rock (Nikolaides, 2011). The recycled
concrete aggregate used in Category B unbound mixture contains less than 5 percent asphalt
(Class RA) and more than 1 percent other materials. The grading requirement of Category B

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unbound mixtures is summarised in table 4.
Source: (Ellis, et al., 2016)
The fraction size of the close-graded unbound mixture should be non-plastic and pass through
0.425mm size sieve test. After this processes, the mixture is then transported, laid and compacted
without segregation. The last type of unbound mixtures is Type 4 (asphalt arisings) unbound
mixtures (Nikolaides, 2011). This kind of mixture is made up mostly of asphalt arisings which
are comprised of smashed slag, squashed concrete, and pulverized rock or well burnt non-plastic
shale of 10 percent mass of regular sand that passes through 4mm size test sieve. The asphalt
arisings are granulated asphalt that ought not to be debased with tar. Type 4 unbound mixtures
have more asphalt (Class Ra) content that surpasses 50 percent and recovered bitumen substance
of more than 10 percent asphalt. The fraction size of the unbound mixture ought to be passed
through 0.425mm size test sieve (Notman, 2011). After the different procedures, the mixture is
then transported, laid and compacted without drying the moisture content. The moisture
substance should be more than 1 percent to 2 percent below the proclaimed estimation of the

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tested water content. The concentration of dampness is controlled by oven drying at a limited
temperature of 45oC to 50oC.

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References
Ayan, V., Limbachiya, M.C. and Azadani, S.M.N., 2011. Investigation of water absorption in
recycled aggregates for application in subbase layer of highway. In Emerging Technologies for
Material, Design, Rehabilitation, and Inspection of Roadway Pavements (pp. 223-230).
Ellis, S., Goodwin, A., Laycock, E. and Hirst, C., 2016. Use of crushed brick in reinforced earth
railway structures. Proceedings of the Institution of Civil Engineers. Construction
Materials, 169(2), pp.93-105.
Herrador, R., Pérez, P., Garach, L. and Ordóñez, J., 2011. Use of recycled construction and
demolition waste aggregate for road course surfacing. Journal of Transportation
Engineering, 138(2), pp.182-190.
Nikolaides, A., 2014. Highway engineering: pavements, materials and control of quality. CRC
Press.
Notman, C.F., 2011. Durability testing of fine grained stabilised soils (Doctoral dissertation,
University of Nottingham).
Reid, J.M., CHANDLER, J., Schiavi, I., Hewitt, A., Griffiths, R. and Bendall, E., 2008.
Sustainable choice of materials for highway works: a guide for local authority highway
engineers. TRL Published Project Report.