The past decade has seen a phenomenal resurgence in the use of Wet Mix Macadam (WMM) as a preferred method of paving roadway surfaces. This trend has raised questions for many about the WMM meaning in road construction or what is WMM in road.
Wet mix macadam (WMM) is a type of construction material used for road surfacing and other civil engineering projects that have become increasingly popular in recent years. WMM is a mixture of crushed stone, sand and water that is compacted to form a strong, durable base for roads and highways.
How Does Wet Mix Macadam Differ from Other Construction Materials?
Wet Mix Macadam (WMM) is a type of construction material used for road construction, consisting of a mixture of aggregate, sand, and binder. It is often referred to as “tar and chip” or “hot mix asphalt”.
WMM differs from other construction materials as it is mixed with water before being placed on the road surface. This creates a more durable and flexible surface that can withstand the wear and tear of traffic.
In addition to its durability, WMM also offers superior drainage capabilities compared to other materials. This makes it an ideal choice for roads located in areas prone to flooding or heavy rainfalls.
What Are The Different Types Of Wet Mix Macadam?
Wet mix macadam is made up of a mixture of aggregates, binders, and water that are mixed together to form a semi-solid mass. The different types of WMM are based on the size and shape of the aggregates used in the mix.
Each type has its own unique characteristics that make it suitable for different uses. Rough aggregate refers to larger crushed stone and gravel used in bituminous mixes, while smoother aggregates are used when concrete has to be poured.
- Rough aggregate includes coarse sandstone and angular pieces that range from rounded shapes to angular shapes with sharp edges that can cause the concrete mix to crack.
- Sandstone is generally easier for workers and equipment to move, break down into smaller pieces, or recycle than coarse gravel; however, sandstone tends not to have as much durability or longevity as gravel does on a road surface.
- Asphalt is typically a mix of aggregate and asphalt binder, which makes it softer than other paving materials. It typically has a high-traction force and better abrasion resistance than other paving materials.
There are seven types of paving materials currently in use in the city: asphalt, concrete, decomposed granite (DG), decomposed granite/composite or cement/aggregate mix (DGC), epoxy-based liquid pavement (liquid sprayed on hot mix asphalt), and pervious pavement.
How To Choose The Right Size And Grading Of WMM?
Choosing the right size and grading of wet mix macadam is an important factor in ensuring the longevity of your project. The size and grading of the material will depend on the environment it is being applied to and its intended purpose. For better application, it is necessary to understand GGR.
Gross Grade Roughness (GGR) refers to the size of the aggregate particles that make up a surface, as well as how sharp or pointy they are. GGR is important when grading land surfaces because it affects how fast water spreads across and through such a surface.
The higher the GGR, the more quickly water will tend to flow and soak into the soil, which can lead to increased runoff. On a paved surface, this means that if you want to prevent water from pooling on your driveway or walkway, you’ll want to use larger aggregate and lower the GGR.
Granite and concrete will have a much lower GGR than a mixture of 40% gravel, 40% sand and 20% silt. Additionally, in terms of the effects on runoff, brick has a similar GGR to granite.
How To Prepare A Proper Sub-Base For The WMM Layer?
Preparing a proper sub-base for the wet mix macadam layer is essential for creating a strong and durable road surface. It is important to understand the process and materials involved in order to get the best results.
Let’s discuss the steps involved in preparing a proper sub-base for the wet mix macadam layer, including the types of materials used, compaction of soil layers, and drainage considerations.
The macadam layer forms a waterproof seal between the sub-base and the road surface. The sub-base should be free of water, liquid petroleum, oil or any other contaminants before laying down the macadam.
The sub-base is compacted by a compactor and should be firm enough to give the required depth for a smooth macadam layer. If necessary it can also be graded with a grader to provide proper depth for this purpose as well.
After the sub-base has been compacted, it is levelled to provide a smooth macadam layer on top. The levelling can be done by hand or with a grader but should not be too steep as this may result in an uneven macadam layer and cause problems with drainage at the surface.
The concrete base is mixed in accordance with standard procedures, usually by adding water and sand to the mix in proper proportions before allowing it to harden into a solid mass.
Then adding cement or other binding materials and additional sand to bind the mix together. In some cases, the concrete is mixed outside of a mixer in a batch plant and is then transported to a location for use.
The Advantages of Using Wet Mix Macadam in Road Base Construction
Compared to traditional methods, WMM offers numerous advantages such as improved drainage, increased stability and strength, reduced dust pollution, and reduced construction costs.
Wet mix asphalt provides many of the same benefits as traditional asphalt, such as longer life, resistance to water and oil penetration, and a wide range of colours and finishes.
One of WMA’s main advantages, however, is its low cost. In comparison, traditional asphalt typically costs three to four times as much.
WMA also has a lower environmental impact, as it does not produce emissions similar to those of oil-based asphalt. WMA can be a more environmentally friendly option than traditional asphalt.
Wet mix asphalt eliminates the risk of accidents that traditional asphalt carry, as it is a non-toxic material. In fact, when properly applied, WMA is one of the safest methods of paving available.
Wet mix macadam offers many advantages over traditional asphalt, the most significant of which is its low cost. WMM is made up of different stone aggregates and the binder can be applied in a variety of ways, making it an ideal choice for a variety of applications.
Wet mix asphalt can be used in a variety of applications, including bicycle and pedestrian pathways, driveways, playgrounds, and parking lots. It is also an excellent solution for roads in urban areas being very environment friendly which is essential in times when we are witnessing the huge impact of climate change.