Cold joints are a necessary evil in road construction. They cannot be avoided but they can be planned. Following the correct procedures to work next to them will ensure that the risk of failure of the cold joint is decreased.
Transport Malta’s Standards and Specifications outline the requirements for road construction. Quality Assurance and Quality Control procedures will ensure that if the specifications are met the roads will last longer.
Most underground services need to be accessed to carry out repair and maintenance works. They can be accessed through manholes, which consist of a vertical shaft allowing a person to get into a chamber below ground level. The type and size of manhole depends on the type of action required for repair and maintenance works to the service. Each entity has its own requirements for its own manhole.
Manholes can be divided into two categories:
- Series 1500 Manholes for motorway communication ducts.
- Series 500 Manholes for sewer and storm water networks, including catch pits, inspection chambers and draw pits.
Roads in Malta are designed according to the directive entitled the Standardisation of Pavements for traffic areas a directive written in the year 2000, by Profs. Dr. Ing. Klaus Muller while consulting the Government of Malta on road construction matters. You may download a pdf document of the directive from the official Transport Malta Website.
This directive is based on the German Code of Practice RStO 2000, and takes into consideration Maltese conditions such as climate, available construction materials, sub-grade conditions, and pavement performance.
The main feature of this directive is a chart, which I refer to as the Road Structure Catalog, from where engineers can select the type of road to construct depending on various factors such as:
- Sub-grade conditions and bearing capacity
- Construction method
- Condition of the traffic area
- Present and future traffic loading etc.
Organisation of Road Structure Catalog
The road structure catalog is divided into a series of columns indicating the construction class of a road. The construction class is based on the amount of traffic the road is expected to receive, calculated in millions of equivalent 10 ton axle passes. In the chart this value is indicated by the letter B.
Construction Classes based on Traffic loading
The catalog caters for the following construction classes:
- Class HD for traffic >32 million equivalent 10t axle passes. This type of road is usually constructed for highly industrious areas.
- Class 01 for traffic >10 but <32 million equivalent 10t axle passes.
- Class 02 for traffic > 03 but <10 million equivalent 10t axle passes.
- Class 03 for traffic >0.8 but <10 million equivalent 10t axle passes.
- Class 04 for traffic >0.3 but <0.8 million equivalent 10t axle passes.
- Class 05 for traffic >0.1 but <0.3 million equivalent 10t axle passes.
- Class 06 for traffic <0.1 million equivalent 10t axle passes. This type of road is typically used for a typical road in a village, where traffic is light.
Pavement Construction classes
On the left hand side of the chart, there are 5 rows of different types of pavement construction based on available thickness and sub-grade conditions.
Each pavement construction type in a particular construction class can withstand the traffic loading of its construction class. However, the pavement construction has to be adapted according to the bearing capacity of the sub grade.
The bearing capacity of the sub grade is determined by a plate bearing test. The plate bearing test consists of a steel plate which is loaded at a designated area at the sub grade level. Deformation of the sub grade below the steel plate is recorded when the plate is loaded. The load is then released and deformation under the steel plate is re-measured at regular intervals during the 2nd loading.
This test produces 2 numbers, EV1 and Ev2 from which the ratio Ev2 / Ev1 can be calculated. According to these numbers we may select the type of pavement construction. Ev2 / Ev1 shall always be less than 2.2 in every case.
Interpreting Plate Bearing Test Results
When Ev2 / Ev1 < 2.2, this indicates that the sub grade is well compacted. If Ev2/ Ev1 > 2.2 then it means that the sub grade needs further compaction.
- If Ev2 is greater than 120, then one may choose any of the first three pavement construction classes, depending on the available depth.
- If Ev2 is less than 45, then the sub grade has week bearing capacity. One may choose either pavement construction class 4 or 5, which include the laying of a cement stabilisation layer to improve the subgrade.
How is the selection of the road structure done?
- Carry out traffic counts and determine the equivalent 10t axle passes. From this count, determine the construction class from Class HD to Class 6.
- Excavate pilot holes and check if there are physical hindrances, such as existing cables, water mains, sewer mains etc. Take note of level at which the services are located. The proposed pavement construction should preferably be shallower than the level of the highest service, so that the existing services do not need to be shifted.
- Once the pavement construction is determined scarify the existing surface down to subgrade level and compact it. Carry out plate bearing tests and check the value of Ev2 and the ratio of Ev2 / Ev1, which should be less than 2.2. Consult the structure catalog and check the value of EV2 required for the subgrade.
- If the sub grade is weak, it has to be improved using a 150mm thick cement stabilisation mix.
- If the bearing capacity of the sub grade is achieved then one can proceed with the laying of the type 1 and the asphalt layers according to the sections indicated in the structure catalog.
Components of the structure catalog
Cost comparison of different road structures
Eventually, one must use the most economically feasible pavement structure of a particular construction class.
It would be interesting to come up with a standardised cost of a square metre of a particular road structure, so that the cost of the different road structures can be compared.
For this exercise, I will be using Transport Malta Framework Agreement rates according to CT2003/2013. The following assumptions are made:
- Excavation will be carried out by planar equipment.
- Foreign aggregate based wearing course is used.
- Tack coat is used in between bituminous surfaces.
Transport Malta Framework Agreement Rates CT2003/2013
- Oversite excavation in any type of ground using planar equipment to reduce levels at 20.76 euros per cubic metre excl. VAT.
- Type 1 sub-base material as per series 800, clause 803. Nominal grain size 37.5mm, hard stone (>50kN on 10% fines value in wet condition) , in filling to make up levels, levelling and compacting in layers with a maximum thickness of 300mm as required. Material is to be compacted at the optimum moisture content at 15.88 euros per cubic metre excl. VAT.
- Cement Bound Material CBM2 as per series 1000 clause 1037. The CMB is to achieve a compressive strength between 7 and 12 Mpa after 28 days. This mix is to be used in filling to make up levels , levelling and compacting as required. The Cement Bound Material (also known as cement stabilisation) is used in weak sub grades and can be provided at a cost of 38.14 euros per cubic metre excl. VAT.
- Hot dense bituminous paving mixture in accordance to ASTM D3515 and approved mix designs, including for the necessary bitumen required as per ASTM D3515 and approved mix designs, and the painting of the vertical edges of any joints with hot bitumen:
- 0/25 mm for Base course 80mm thick in carriageway, hard shoulder and hard strip, compaction degree greater or equal to 97%; laid to comply to requirements in TM Standards Clause 901 and 903 @ 24.29 euro / sq.m. excl. VAT.
- 0/19 mm for Binder course 60mm thick in carriageway, hard shoulder and hard strip, compaction degree greater or equal to 97%; laid to comply to requirements in TM Standards Clause 901 and 904 @ 18.21 euro / sq.m. excl. VAT.
- 0/12.5 mm for Wearing course 40mm thick in carriageway, hard shoulder and hard strip, compaction degree greater or equal to 97%; laid to comply to requirements in TM Standards Clause 901 and 906, using aggregates with Los Angeles value less than or equal to 20 and Polished Stone Value greater or equal to 53 @ 15.53 euro / sq.m. excl. VAT.
- 0/19 mm for Combined Base Wearing course 80mm thick in carriageway, hard shoulder and hard strip, compaction degree greater or equal to 96%; laid to comply to requirements in TM Standards Clause 901 and 905 @ 26.06 euro / sq.m. excl. VAT.
- Tack Coat to surfaces to receive bituminous paving mixture @ 1.58 euro / sq.m. excl. VAT. Tack coat is used in between bituminous layers.
Example 1 : Determine cost per square metre of pavement construction type 1 of construction class HD
For easy reference, the road structure for this example is indicated in the image below.
- The road structure is fully composed of asphalt layers, with an overall depth of 34cm which is divided as follows:
- 40mm wearing course
- 80mm binder course
- 220mm base course.
- The structure is laid over a sub grade with a bearing capacity of 120 N per sq.mm.
The cost of 1 square metre of this particular road structure is calculated as follows:
- Excavation (34cm deep)
- Excavation of 0.34 cubic metres (1m x 1m x 0.34m deep) at 20.76 euros per cubic metre excl. VAT. This is equivalent to 7.06 euros per square metre excl. VAT.
- Base Course (22cm deep)
- The rate for base course in the Transport Malta Framework agreement is 24.29 euros per sq.m. for an 80mm thick layer. However, this particular structure requires 22cm instead of 8cm.
- The rate for 22cm of base course can be calculated proportionally as follows:
- 8cm of base course = 24.29 euros per sq. m. excl. VAT
- 22 cm of base course = ?
- 24.29 euros x 22cm / 8cm
- equivalent to 66.80 euros per sq.m. excl. VAT
- Binder Course (80mm)
- The rate for binder course in the Transport Malta Framework agreement is 18.21 euros per sq.m. for a 60mm thick layer. However, this particular structure requires 8cm instead of 6cm.
- The rate for 8cm of binder course can be calculated proportionally as follows:
- 6cm of binder course = 18.21 euros per sq. m. excl. VAT
- 8cm of binder course = ?
- 18.21 euros x 8cm / 6cm
- equivalent to 24.28 euros per sq.m. excl. VAT
- Wearing Course
- The rate for wearing course in the Transport Malta Framework agreement is 15.53 euros per sq.m. for a 40mm thick layer.
- Tack Coat
- Furthermore in between the asphalt layers a tack coat layer is sprayed so that the different layers of asphalt can bond together.
- In this particular case, tack coat is used between base course and binder course, and between binder course and wearing course.
- Hence 2 layers of tack coat are used.
- Each layer costs 1.58 euros per sq.m excl. VAT.
- Hence for both layers, the cost is 3.16 euros per sq. m excl. VAT (=2 x 1.58 euros per square m).
Adding all different components forming this road structure we have a cost of 116.83 euros per square metre excl. VAT. This can be summarised as follows:
- 7.06 euros per sq.m. excavation
- 66.80 euros per sq.m base course
- 1.58 euros per sq.m. tack coat
- 24.28 euros per sq.m. binder course
- 1.58 euros per sq.m. tack coat
- 15.53 euros per sq.m. wearing course
Example 2 : Determine cost per square metre of pavement construction type 1 of construction class VI
For easy reference I’m including an extract of the road structure catalog and marking the road structure in caption.
- This road structure consists of a 10cm layer of a combined base wearing course on a sub grade having a bearing capacity of 120 N per sq. mm.
- The cost of 1 sq.m. of such road structure is determined as follows:
- Excavation of 0.1 cubic metres of material at a rate of 20.76 per cubic metre excl. VAT. This is equivalent to 2.08 euros per sq.m. excl. VAT (20.76 per cubic metre x 0.1m deep)
- Base Wearing course 100mm thick at a rate of 26.06 euros per sq.m. for an 80mm thick layer. The cost of a 100mm layer can be calculated pro-rata as follows:
= 26.06 x 100 / 80
= 32.58 euros per sq.m. excl. VAT
- No tack coat is required in this case since only 1 layer of asphalt is being used.
- Hence total cost for this pavement construction is equivalent to 34.66 euros per sq.m. excl. VAT and is determined as follows:
- 2.08 euros per sq.m. excl. VAT for excavation
- 32.58 euros per sq.m. excl. VAT for combined base wearing course
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Before carrying out any trenching works, coordinate with local service providers to mark their underground services in the area where the proposed trench will be excavated.
Services may include water services mains, sewer mains, electricity cables, telecommunication cables, highway communication cables and in certain cases gas/fuel pipelines. Each entity marks their services with a colour coded spray. In Malta, the following colour codes apply:
Go plc. a telecommunication company marks its underground infrastructure in highlighter green. Water Services Corporation uses red spray to mark water, sewer and rising mains. Enemalta, an energy provider, uses highlighter orange to mark its underground cables. Melita plc. and Vodafone Malta Ltd., who are telecommunication companies do not have any specific colour codes to mark their underground services.
Transport Malta Roadworks Permits
#1 Always apply for a roadworks permit before carrying out any works on roads, footpaths, landscaped areas etc. It is illegal to carry out road works without a roadworks permit as stated in LN 29 of 2010.
#3 There are three types of roadworks permits: RWP-1 for Major road works, RWP-2 for Emergency works and RWP-3 for Minor works.
#4 Transport Malta, Local Councils, Service providers and contractors registered with Transport Malta can apply for a roadworks permit. Applications can be submitted online through www.roadpermits.gov.mt.
#5 Transport Malta shall start to review the roadworks permit application only if it is submitted on the prescribed application forms, is accompanied by the relevant fees and all data required has been submitted.
#6 Submittals include the provision of a site plan on a 1:2500 survey sheet of 1988 marking the location of the intervention. The site plan must be signed and rubber stamped by a qualified architect and civil engineer.
#7 Contractor must provide a copy of the insurance policy covering the works.
#8 Contractor must agree in writing that he will backfill and restore the surface of the road to specifications set by the Authority and in accordance with the conditions laid out in the permit.
#9 Once the permit is issued carry out the works as efficiently as possible whilst meeting the required specifications. Backfill and reinstate as indicated in the permit.
#10 Once the works are completed prepare and submit a compliance report to Transport Malta for permit closure.
For further information you may refer to Roadworks Procedure (Permits) on Transport Malta website.
The National Statistics office of Malta issued a News Release on the 2nd August 2013, confirming that as at end June 2013:
- 318,720 licensed motor vehicles are on the island. This is an increase of almost 1% from the previous quarter. The trend is that this increases yearly.
- 416,055 inhabitants live in Malta, according to the last census of 2011 and this number includes children.
- 76% of the population has a motor vehicle. This means that there are 3 vehicles for every 4 people.
If we had to line up all the vehicles one after the other we would need 1,912km of parking space (assuming that each vehicle can fit in a standard 6m parallel parking space). Compare this to the total length of our road network.
The Maltese road network consists of the following categories:
- Arterial roads (4%)
- Distributor roads (4%)
- Rural and Urban Roads with Linking function (92%)
The table below is extracted from NSO publication of 2001 and indicates the length in km of each road category divided between Malta and Gozo.