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Frontage Road Construction 101

Formed Curb & Gutter Before Asphalt Pouring

Did you know?

Utility relocation along the LBJ Express corridor is nearing completion, so frontage road reconstruction has begun in many areas!

Here is what many do not know:

Frontage road construction has a series of steps that must be performed before it can be opened up to traffic.  One would think that it is merely a few layers of asphalt or placement of concrete, however this is not the case.

What are these steps?

1. DRAINAGE INSTALLATION: Before any construction of the actual roadway can be performed, drainage must first be installed underneath the roadway. After the drainage boxes/pipes are installed, the dirt is filled in around the drainage and is 98% compacted for the roadway to be constructed on top of it. This step is vital so that storm water drains properly along the corridor to prevent flooding!

Drainage Pipes to be Installed

2. LIME CURING: After the drainage is installed, lime must be installed and cured. The LBJ Express project lays a total of 24 inches of lime (two 12-inch mixes) for the frontage roads. After the first mix is laid, it must cure for 3 days before any further work can be performed. After the 3 days, the second mix is laid which must cure for 4-9 days before further work can be done.

This process can take up to 30 days to complete one area, and it is one of the most important steps because the lime serves as a stabilizer for the road. The use of lime improves rutting, fracture growth,  moisture resistance and provides an overall  increased durability to the roadway.

3. FLEX BASE GRADING: Once the lime is cured, rock material undergoes compaction so as to provide a smooth “tight” surface for the wearing asphalt to be poured. Both the smooth drum and sheep’s foot rollers  are used in highway construction for compacting the material you’re going to be driving on.  Flex base grading is done in two phases with two 8-inch layers, both of which must be 100% compacted before any further steps can be performed.

Formed Curb & Gutter Before Asphalt Pouring

4. CURB & GUTTER FORMING: The curb & gutters are then ready to be constructed once the flex base is completely compacted. The gutters will allow the storm water to flow into the newly installed drainage below the surface, and the curbs are formed for the safety of the driving public.

5. ASPHALT POURING: After the curbs and gutters are constructed, asphalt can finally be poured! The LBJ Express project uses 3 separate layers of asphalt to construct the permanent frontage roads. These layers provide the final support of the roadway. The lowest, “base” is poured with 5-inch thickness, the middle, “intermediate” layer has a 2-inch thickness, and the top, “wearing course” is 1-inch thick. The wearing course is the smoothest of all the layers which the driving public will travel on!

Once all of the asphalt is poured, the final touches (lane striping, etc.) are performed and the new frontage road can open!

Stay tuned for more updates and insights into the LBJ Express Project!

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