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CHAPTER 2 CONSTRUCTION AND MAINTENANCE OF ROADS IN SRI LANKA INTRODUCTION The National Road Net work of Sri Lanka comprises of nearly 10,900 km of trunk and main roads and has a density of 0.17 km/km2 (IESL 1993 ). Almost all the roads have been built during the colonial period prior to the Independence. The few major roads constructed recently are the Ella Wellawaya road, Mahiyangana-Mahaoya road (Canadian Friendship road). Roads constructed in the Mahaweli Project Area and the Mahiyangana-Victoria road. (Kumaraswamy, 1991) The roads constructed during the colonial period are macadamize roads with one layer of 6" to 9" rubble soling overlaid with IW-3Y*" metal penetrated with 80 - 100 grade bitumen or tar. Subsequently this is given a periodic seal coat of bitumen to improve the durability. Fig. 2.1 shows a typical cross section of such a road. Ex. A4 at Pahathgama - Avissawella. In less important roads the 6"-9" soling has done away with and 2 layers of metal were used as the base interspersed with 3/4" metal and penetrated with bitumen. Ex. A7 at Kithulgala. ( Fig 2.1) These construction methods were mostly labour intensive and were economical at the time as the labour was cheap. The recent advances in construction technology and the escalating labour costs have made these methods uneconomical and obsolete. Mechanized construction methods are being widely used now for the construction and rehabilitation of flexible road pavements. The majority of the present day pavement types can be generally categorized in to 3 main groups, based on the type of pavement construction. They are: 1. Type A; 2. Type B; and 3. Type C. The network of roads built in the colonial era were improved with regard to width, alignment and the carrying capacity up to present time and we have inherited a quite adequate net work of roads. The roads in this extensive network has been categorized by RDA into four groups (Class A, B, C and D). This categorization is based on the relative importance of destination origins linked by the roads. Page 7 PENETRATED 30 /'.CO 31 TV MEN. 22'-0" ROAD CROSS SECTION AT PAHATHGAMA ON COLOMBO-RATH NA PUR A A4 ROAD 30/100 BITUMEN. 3" -f METAL. I LAYER OF 2" METAL. ROAD CROSS SECTION AT KITULGALA ON AV1SSAWELLA-HATTON A7 ROAD FIGURE 2.1 Page 8 lOOOm I 3 330m I 3 350 m i / OOOm_ Shoulder * T * SOmm thick densegraded / •Graded Blended Asphalt concrete machine laid Aggregate Base compacted thickness 5% - ISO mm at 95% De­ 13 selected Gravel Subbase compacted to 150 mm thickness at IOO% 0 0. TYPICAL ROAD CROSS SECTION CAT0G0RY- A Fig. 2 .2 This categorization is found to be inconsistent in the following areas: i) Wearing course material; ii). Pavement Structure or Thickness; iii). Carriageway width; and iv). The Terrain. CONSTRUCTION METHOD With regard to the cost of construction (Specification for Construction of Roads and Bridges RDA, 1991) and cost of maintenance(Maintenance Manual - RDA, 1989) it was found that there is a possibility of forming 3 basic pavement types. These pavement types are described below. 2.2.1 Type A Pavement Most of the major trunk roads in the RDA net work can be brought under this category. The roads are normally 7.4m 6.7m or minimum 5.5m wide and topped with an asphalt concrete wearing course. Examples are : Colombo - Kandy (Al); Colombo - Galle (A2); Kurunegala - Dambulla (A3); and Colombo - Ratnapura (A4) Roads. Construction Procedure After the roadway excavation is completed if the sub grade material is not found to be of required bearing capacity a suitable gravelly material is brought in laid and compacted to 100% Dry Density and to a compacted thickness of 150 mm to form a sub base. Then a mixture of crushed aggregate confirming to a given grading varying in size from 50 mm to Dust is laid moisturized and compacted to 95 % of the maximum Dry Density and to a compacted thickness of 150 mm to form the road base. The crushed aggregate base so laid is then primed with 0.9 to 2.3 It of cutback bitumen (normally MC 30) per square meter and allowed to penetrate for a minimum period of 4 hours and then covered with blotting material (sand or quarry dust). The wearing course of this pavement is normally asphalt concrete. This is laid and compacted to a thickness of 50 mm minimum. In highly trafficked roads the thickness may be increased to 60 mm.(Specification for Construction of Roads and Bridges - RDA, 1991) A sketch of the construction is shown as Fig. 2.2 and the detailed construction cost for such a pavement is given in appendix A. The life time of this road is considered to be 15 years with no maintenance. Page 10 2.2.2. Type B Pavement Most of the roads in Class B of RDA classification falls into this group. The minimum width is 5.5 m but the wearing surface is inferior to that of Type A. The wearing surface is either Single Bituminous Surface Treatment (SBST), Double Bituminous Surface Treatment (DBST) or Seal Coat. Examples are: Negombo - Giriulla Road and Madampe - Narammala Road. Construction Procedure In this type of construction a gravel sub base of 150 mm compacted thickness is laid as described earlier under type A. The base consists of two layers of 40 mm single sized metal laid and rolled with one operation interspersed with 20 mm metal. Penetrated with hot bitumen of 80 - 100 grade at a rate of 2 lt/m2 and blinded with sand of quarry dust. This is left open for traffic for 48 hours and broomed to remove loose dust and a second application of bitumen at the rate of 0.75 lt/m2 in made followed by blinding.(Specification for the Construction of Roads and Bridges -RDA 1989) This surface treatment is popularly known as (DBST) Double Bituminous Surface Treatment) Fig 2.3 A detailed Bill Of Quantities (BOQ) for this type is given in appendix B and a sketch of the construction is shown in Fig.2.3 Normally this type of road needs major improvement or rehabilitation every 8th years. Page 11 Final sand sealing Top layer ot 20 mm metal rolled 2nd coat of bitumen at OTQlt/m* 2 Two layeis of 40mm metal rolled Sub base of selected gravel 150mm compacted thickness TYPICAL ROAD CROSS SECTION CATOGORY - B Fig. 2.3 -L—iogo 1 3 330m 3 350m | I QOOm 1 -t- J Shoulder T I Sand seal surface treatment 20mm Metal layer 40mm Metal layer Compacted sub base TYPICAL ROAD CROSS SECTION CATOGORY-C Fig. 2.4 2.2.3. Type C Pavement The least important paved roads in the RDA net work can be grouped in to the type C. Where the base thickness is minimum and the wearing surface is inferior to the earlier two groups. Construction Procedure The roadway excavation is followed by a layer of gravel sub base compacted to 100 % maximum dry density and 150 mm compacted thickness. The base is built with blended aggregate 40 mm down to dust confirming to a grading envelop specified. This base is watered and compacted to 95 % dry density and compacted to a thickness of 150 mm. Mechanically or manually broomed top is primed with MC 30 at a rate of 0.9 to 2.3 Lt/m2and allowed to penetrate . This is followed by either SBST or DBST surface treatment. (Specification for Construction of Roads and Bridges - RDA, 1982). Surface treatment is carried out by DBST on SBST as mentioned in 2.2.2. A typical cross section is shown in Fig. 2.3 and a detailed BOQ for this type is given in appendix C. The time between subsequent major rehabilitations is 6 years. MAINTENANCE OF ROADS 2.3.1. History The maintenance of the road network of the country has been the responsibility of the government. This task has been carried out by various agencies of the government in the past. Irrespective of the type of the road all roads were maintained by the Public Works Department (PWD) from the colonial era up to 1969. With the transformation of PWD in to Highways Department in 1st October 1969, roads maintenance was done by Highways Department. Then with the formation of T.C.E.O. (Territorial Civil Engineering Organization) in February 1971 all the roads in a division were maintained by the T.C.E.O of the area. After abolishing the TCEO in February 1978 again the Highways Department took the maintenance responsibilities of trunk roads, namely class A and class B roads in RDA classification leaving the class C and D roads for the local government authorities. The Highway Department managed these activities by employing direct labour or through selected sub contractors (RMCs). With the Page 14 transformation of the Highways Department in to Roads Development Authority (RDA) in Feb 1986 and with the setting up of the semi government organization Roads Construction and Development Company (RCDC) in 1987, the government assigned the RCDC to carry out all maintenance activities carried out by RDA previously. RCDC is paid a fixed payment per kilometer per year irrespective of the actual work carried out by RCDC. 2.3.2. Maintenance Procedure Road Development Authority classifies the maintenance activities into four major categories (Road maintenance manual - RDA 1989) they are 1. Routine maintenance; 2. Recurrent maintenance; 3. Periodic maintenance; and 4. Urgent maintenance. 1. Routine Maintenance These are considered the activities required for the general upkeep of the road network.

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