Asphalt paving doesn’t start when trucks arrive on site — it begins weeks earlier in the materials laboratory. Each step, from mix design to compaction, plays a crucial role in determining whether the finished pavement will perform for years or fail prematurely.

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1️⃣ It Starts in the Materials Lab

Before any asphalt reaches the road, engineers test and blend sand, stone, crushed rock fines, and bitumen in varying proportions. This determines two critical factors:

• Optimum aggregate grading (the right particle size distribution)
• Optimum bitumen content (enough binder to coat, but not flood, the mix)

Project specifications dictate these values. Without this foundation, achieving proper compaction later on site becomes nearly impossible.

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2️⃣ Mixing at the Plant

Asphaltic concrete can be produced in two types of plants:

• Continuous plants – material flows without interruption.
• Batching plants – materials are measured and mixed in batches, offering greater control over proportions.

If the optimum bitumen content is missed here, compaction will be compromised. Another concern is contamination. Foreign objects such as plastic bottles, rubber, or leaves sometimes enter the mix, reducing quality. For this reason, trucks should always be inspected and cleaned before loading.

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3️⃣ Transport and Temperature Management

Temperature is the lifeblood of asphalt compaction.

• Too cold (< 300 °F / ~150 °C): wind or rain during transport accelerates cooling, reducing workability.
• Too hot (> 330 °F / ~165 °C): bitumen can strip from the aggregates, preventing bonding and reducing strength.

Covering trucks during transport is essential to preserve the right temperature and protect from weather exposure.

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4️⃣ Laying the Asphalt

On site, the paver spreads the asphalt. Heat may be applied to prevent sticking to the screed, but temperature control must already be correct before this stage. Once placed, the material moves quickly to the most critical stage: compaction.

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5️⃣ Compaction: Three Phases

Compaction is carried out in three distinct stages:

• Breakdown rolling – first passes to achieve initial density.
• Intermediate rolling – consolidates the mat and reduces voids.
• Final rolling – smooths the surface and locks in density.

If rolling is attempted below the minimum rolling temperature (around 200 °F / 93 °C), the asphalt can crack, ravel, or fail to achieve density. The exact threshold varies by binder grade, but the principle remains: once asphalt cools below workable temperatures, compaction success declines rapidly.

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✅ Key Takeaway

Every durable asphalt pavement is the result of a chain of decisions:

• Careful mix design in the lab
• Accurate proportioning at the plant
• Proper temperature control and protection during transport
• And precise rolling practices on site

Break the chain at any stage, and the pavement’s performance is at risk. Get each step right, and the asphaltic concrete could last for decades.