Concrete Roads: An Invulnerable Solution to Flooding

Reflecting on Malaysia’s “Once in a Century” Flood?

On 16 December 2021, after three days of continuous heavy downpour throughout the East Coast of Peninsula Malaysia, Malaysia witnessed a “once in a century” flood disaster that affected eight (8) states across the country. It was reported that the flood caused concurrent displacement of more than 71,000 residents and affected over 125,000 people overall. Sadly, the flood also left at least 54 dead with 2 more missing.

One of the biggest challenges authorities and volunteers faced after the flood is reaching the victims.?After the flood, many roads and bridges were left damaged. The intention to help victims immediately was delayed due to the inaccessibility of reaching flood-affected areas, with volunteers only able to reach flood victims after roads were cleared and repaired.?

According to a study done a week after the flooding by Department of Statistics Malaysia (DOSM), an assessment of losses due to the floods was estimated to be between RM 5.3 billion to RM 6.5 billion.?Furthermore, DOSM stated that the highest loss out of the total was on public assets and infrastructure, such as roads and bridges, which was estimated to be more than RM 2.0 billion.?However, this estimation is only on losses during the flood, with the loss estimated to be even higher for the maintenance and repair works for roads after the floods.

Roads in Malaysia

Most roads in Malaysia belong to either the federal, state or local government, with each road owner having a limited budget for maintenance. In 2021, although RM3.5 billion was allocated for Infrastructure and Road Projects, only RM 620 million was allocated for road maintenance and upgrading.

It is reported that Malaysia has more than 260,000 km of road network. Out of the total, about 140,000 km (54%) of roads belong to the state government, about 18,000 km (7%) belong to the federal government and about 40,000 km (15%) belong to the local government. 60,000 km (23%) are unpaved rural roads, and only 2,000 km (1%) are highways.?

Figure 1: Total Road Length Data from ASEAN Statistic Data Portal

Out of the 260,000 km of roads in Malaysia, only 23% is unpaved – either laterite earth material or crused aggregate road without any asphalt or bitumen is used as the wearing course or upper layer of the road. The other 77% of road network in Malaysia is made up of paved roads which have asphalt or concrete as its wearing course. Unfortunately, only less than 1% of Malaysia’s road network was constructed using concrete, with a majority of roads in Malaysia constructed using a method called flexible pavement.

Flexible pavement is a type of road that uses unbound materials such as sand and crushed aggregates as the road base and a wearing course of asphalt. On the other hand, rigid or concrete pavement design commonly uses an additional layer on the road base called Cement Treated Base (CTB) as part of its road base.

Road pavement vs flood

During floods, roads are usually the first become inundated by flood waters. This is due to the geometry design and invert level of a road. Once water levels at rivers or monsoon drains rise, storm water from a road’s side drain will overflow directly to the road.?Roads that are submerged under water have a high possibility of getting damaged and will need heavy maintenance works.?

Why do roads deteriorate faster after floods? The answer is simple: water has penetrated into the pavement material. Although the answer may seem simple, explaining it is a little bit more complicated.?As we all know, 99% of the roads in Malaysia have been constructed using a method called flexible pavement that uses an unbound material of sand and crushed aggregates as its road base.?Once water penetrates into the pavement, the unbound road base will get soaked with water. The water will then act as a lubricant to allow the unbound material to move and slide between the aggregates.?The movement in the road base material will make the whole pavement structure unstable, making the road base weak under the top asphalt layer.

Once water fills up the air void, aggregates will tend to move, resulting in weakened optimum strength of the whole pavement structure. ?????

Reinforced Concrete Pavement (CRCP), Jointed Plain Concrete Pavement (JRCP), Jointed Plain Concrete Pavement (JPCP), and Roller Compacted Concrete Pavement (RCCP).?It is common for concrete pavements to use concrete as its wearing course. Concrete pavements also use bound material as its road base, but it is not uncommon for road designers to use unbound material as the road base as well.

However, when we analyse deeper into the usage of cement in pavement, it is not limited to concrete pavements. Cement has been used in several different methods involved in road construction.?The most popular technology that use cement in pavements are:

·????????Soil stabilisation is a construction method that strengthens the existing soil before pavement materials are laid out. By using specialised equipment, the existing soil is mixed with a stabilising agent in-situ and then compacted with a roller. Besides lime, cement is one of the most popular stabilising agents used for soil stabilisation. This method is useful in enhancing the existing strength property of the soil or subgrade, reducing the need to use expensive imported pavement materials.?Soil stabilisation is simple and fast to construct, making it possible to reduce the overall cost of pavement construction.

·????????Cement Treated Base (CTB) or Cement Bound Material (CBM) is a method of construction that mixes crushed aggregates with cement to produce a bonded road base material that comprises of low strength concrete. CTB material is mixed at a central plant, delivered to site, laid with a paver and compacted with a roller. CTB is commonly used as road base for concrete pavements. However, it has grown in popularity and is also used as part of the layers in flexible pavement design with an asphalt wearing course, resulting in composite pavement.

·????????Cold In-Place Recycling (CIPR) is a type of road construction method that is mainly used for maintenance.?CIPR uses specialised equipment that can recycle damaged pavement material with cement. The mix is done in-situ with specialised equipment, levelled with a motor grader and compacted using a roller.?CIPR is the most cost-efficient method for road maintenance and road upgrading works. By recycling the existing pavement material, the mixed material becomes a stronger material compared to the original existing material. CIPR can be used for road base materials as well as damaged asphalt layer.

Cement is the Best Solution for Roads

With the current budget limitations for road maintenance, the impact of the floods puts all parties at a disadvantage. The use of flexible pavements is not a viable solution anymore.

As we know, most flexible pavements requires more frequent maintenance works compared to concrete pavements. It is worth noting that the use of cement does not strictly mean the production of concrete pavements, with many choices of technology that incorporates the use of cement for road construction.?In light of the current situation in Malaysia, cemented material is proven to have better resistance to floods, making it a better solution for road construction in Malaysia.

Historically, the longest concrete pavement in Malaysia was built with a total length of 178 km at PLUS North-South Expressway (NSE). The concrete pavement was built on a CBM road base and has proved its performance over the past 30 years by using less than 1% of the total maintenance cost of the 846 km-long highway. Certain stretches of the highway have also been flooded during several occasions and most recently, a stretch at the ELITE interchange near Shah Alam was closed to traffic after flood waters from the nearby river rose up to 1 meter higher than the road level. This resulted in the whole stretch of pavement being submerged with water for a few days. However, the concrete pavement was open immediately after the water has cleared, with no major maintenance or repair works needed to date.

Another example of incorporating cement in road construction was done on several stretches of federal roads in flood-prone areas in Johor.?The road frequently required repairs works and went through heavy maintenance every year. However, after the road base was stabilised with cement using CIPR, the road sustained for several years without major repair and maintenance.

With flooding in Malaysia being an unfortunately common occurrence, proper use and access to roads is important in ensuring rescue efforts are carried out without delay. To do so, the incorporation of cement in roads may prove to be an invulnerable solution, especially in flood-prone areas, to ensure minimal damage and repairs needed after flooding.