Road ConstructionGroup 02

Content of Presentation Introduction to road construction Main segments of road pavement Flexible pavement :Advantages & Disadvantages

Rigid pavement: Advantages & Disadvantages

Selected flexible road project Selected rigid road project Comparative analysis of time and cost Conclusions

Introduction Roads are designed and built for primary use by vehicular and pedestrian traffic. In the past they were constructed using stone, gravel and sand.

All hard road pavements fall into two categories Flexible pavement

Rigid pavement Report includes details, pros and cons of the two types and two selected road construction projects

Flexible Pavement Flexible pavements are composed of abituminous material surface course, underlying

base and sub base course Asphalt is mostly used as bituminous material

The flexible pavement design is based on the loaddistributing characteristics of a layered system.

Advantages Adaptability to stage construction Availability of low-cost types that can be easily built Easy to repair frost heave and settlement Resistance to the formation of ice glaze

Disadvantages Higher maintenance costs Shorter life span under heavy use Weak edges that may require curbs or edge devices

Rigid Pavements Rigid pavement is laid in slabs with steel reinforcement. The rigid characteristic of the pavement are associated with rigidity or flexural strength Rigid pavement is designed and analyzed by using the elastic theory.

Advantages Low maintenance costs Long life with extreme durability Ability to be placed directly on poor soils No damage from oil and grease. Strong edges Disadvantages High initial costs Joints required for contraction and expansion Generally rough riding quality

Selected Flexible Road Project The rehabilitation and improvement of AmbepussaKurunegala-Trincomalee Road From Kanthale to Trincomalee covering a distance of 40km.

Four contractors used: M/s Access Engineering (Pvt) Ltd,Tudawe Brothers (Pvt) ltd, CEC and VV Krunarathna and Company. The existing road is to be widened to a carriageway width of 9.0 m and 0.8 m paved shoulder

Details of Selected ProjectEmployer : Road Development Authority

ConsultantsContractor Contract Sum Duration Date of Commencement Expected date of Completion Type of Contract Conditions of Contract Road Type Road Dimensions

: Road Development Authority (Scott Wilson): Tudawe Brothers : Rs. 824,106,004.73 (Excluding VAT ) : 15 months : 2011-07-11 : 2012-10- 31 : Measure & Pay : FIDIC : Double base bitumen : 10.5km long, 9m wide

Designed Aspects: Flexible Road WATER TABLE 2.0- 2.1m below ground level Vertical band drain installation is used to control the groundwater levels.

SOIL TYPE Main types were peat and clay For Site investigations Wash Boring, Machine Boring and also Standard Penetration Tests were carried out SERVICES Existing electrical services are removed and replaced by the Ceylon Electricity Board

Designed Aspects: Flexible Road CUTTING AND FILLING No cutting and filling done since the road was not over any hilly or mountainous area.

SITE CLEARANCE & EXCAVATION Before starting the work of site all utilities, trees, fence, etc. will be cleaned or removed Initial setting out work for excavation of existing soil is done by referring relevant cross section drawings Removed top soil will be stockpiled at designated locations for reuse

Designed Aspects: Flexible Road DRAINS Located at the low points of gradients On the existing surfaces which are to be overlaid, a level survey is made at sufficiently close centres to enable the gradients to be calculated STAKING METHOD It is the transferring of the design information from the plan to the ground On average reference points were set at least every 70 to 100 meters reference points were placed at points where the centre line alignment can be easily re-established, such as points of curvature.

Flexible Road Layers & FunctionsBASE COURSE Functions include the ability to resist cracking and structural deformation and to spread load Ensures that strength capacities of the weaker sub base and sub grade are not exceeded. BINDER COURSE It is bitumen bound and provides a surface on which to lay the surface course Provides part of the structural strength It also ensures the surface course has a good riding quality

Flexible Road Layers & FunctionsSURFACE COURSE Performs functions such as: Providing a skid resistant surface, Resistant to abrasion, Resistant to indentation, Minimize traffic noise, Protect the underlying road structure, Seals the pavement and pre vents surface water from penetrating and weakening the base and sub-grade Resistant to deformation.

Process of Road ConstructionSite Clearance Establishing the string line/Site Survey Excavation Process Culvert Preparation Shoulder Preparation

Preparing the Sub GradePreparing the Sub base Course Preparing the base course Preparing the Prime Coat Preparing the binding coat

Applying Wearing Course

Equipments Used

Dump Truck

Backhoe Loader

Asphalt Paver

Selected Rigid Road Project Large scale rigid pavement road projects are not commonly found in Sri Lanka Rigid road constructions initiate in sub-urban and rural areas under Maga Naguma- Rural Development Program (MNRDP) Jointed plain concrete pavements Pavement with interlocking cement blocks

Details of Selected ProjectEmployer Consultants Contractor Contract Sum Duration Date of Commencement : Homagama Pradeshiya Sabha : Provincial Road Development Authority : Sunil Contractors (Pvt) Ltd : Rs. 25,106,004.73 (Excluding VAT ) : 1.5 months : 2010-07-11

Expected date of CompletionType of Contract Conditions of Contract Road Type Road Dimensions

: 2010-08- 31: Measure & Pay : SBD 1 : Jointed plain concrete pavement : 600m long, 3m wide and 125mm thick

Process of Road ConstructionSite Clearance Cutting and filling where necessary Establishing the string line

Preparing the base coursePlacing the contraction / expansion joints Placing concrete Texturing and finishing Curing

Equipments Used

Concrete Drum Mixer

Backhoe Loader

Comparing Cost & TimeFlexible Pavements Rigid Pavements

Time AnalysisTakes relatively higher time period to construction Takes lesser time period Can be used after 24 hours from laying the bitumen It takes relatively higher time period to cure the layer concrete road, hence road cannot be used immediately after placing the concrete for traffic movement Life span may be around 4 to 10 years Can be used for 30 years without major defects

Cost AnalysisInitial cost of construction is relatively lowerLife cycle cost is relatively higher, maintenance requirements may arise after 2 to 3 years of project completion The cost of bitumen has a tendency to increase Cost per m2 of a 3m wide 2km long road 3,000.00 Cost per m2 of a 9m wide 10km long road 8,300.00

Initial cost of construction is relatively higherLife cycle cost of rigid roads is lower compared to flexible pavements because wearing of the road is minimum Cement prices doesnt have a trend to Cost per m2 of a 3m wide 600m long road 2,200.00 Cost per m2 of a 3m wide 10km long road 12,100.00

Flexible road has relatively higher carbon footprint Roller compaction is not used, damage to vehicle because of extensive the use of heavy equipment and life cycle cost is less, minimum carbon footprint

Conclusion In Civil Engineering works, road construction has a vital position. Initial cost is generally the major factor in deciding the type of the pavement in design For large scale road construction projects concrete pavements are economical if the subgrade of the area is stable and heavy traffic is expected to move after completion. Minor roads with difficult access for conventional road-making plant, may sometimes be economic to construct in concrete

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