20.5. Environmental factors

Environmental factors affect the performance of the pavement materials and cause various damages. Environmental factors that affect pavement are of two types, temperature and precipitation, and they are discussed below:

This chunk introduces the concept of environmental factors and their significance in pavement performance. It highlights that two principal types of environmental impacts are temperature and precipitation. Understanding these factors is crucial as they can lead to various forms of damage to pavement materials, affecting overall pavement durability and functionality.

Think of pavement like a car exposed to weather. Just as extreme heat or heavy rain can damage a car's exterior and performance, temperature fluctuations and precipitation critically impact the pavement's integrity over time.

The effect of temperature on asphalt pavements is different from that of concrete pavements. Temperature affects the resilient modulus of asphalt layers, while it induces curling of concrete slabs. In rigid pavements, due to difference in temperatures of top and bottom of slab, temperature stresses or frictional stresses are developed. While in flexible pavement, dynamic modulus of asphaltic concrete varies with temperature. Frost heave causes differential settlements and pavement roughness. The most detrimental effect of frost penetration occurs during the spring break-up period when the ice melts and the subgrade is in a saturated condition.

Here, the chunk explains how temperature can impact two types of pavement—asphalt and concrete. The resilient modulus of asphalt layers is directly influenced by temperature changes, while temperature differences in concrete slabs can cause them to curl. As temperatures fluctuate, flexible pavements also experience changes in their dynamic modulus. Frost heave illustrates another temperature-related issue; it can lead to uneven settlements in pavement, especially in the spring when ice melts and saturates the ground, potentially causing rough surfaces.

Consider how a rubber band behaves. When heated, it becomes more elastic, similar to how temperature changes can affect asphalt. In contrast, think of a rigid ruler bending slightly when heated—this relates to concrete slabs curling. Just as melting snow on a warm day can create puddles, frozen moisture beneath the pavement can cause bumps and uneven areas when it thaws.

The precipitation from rain and snow affects the quantity of surface water infiltrating into the subgrade and the depth of the groundwater table. Poor drainage may bring lack of shear strength, pumping, loss of support, etc.

In this chunk, the focus is on how rain and snow (precipitation) impact the pavement. It describes how water permeates the pavement and seeps into the subgrade (the ground beneath the pavement), while also affecting groundwater levels. If drainage is not adequate, excess water can lead to serious problems like reduced shear strength (the ability of the ground to hold up the pavement), causing issues like pumping (where water forces material upward) and overall loss of structural support for pavements.

Imagine a sponge absorbing too much water. When it gets saturated, it becomes heavy and loses its shape—similar to how poor drainage in pavement systems can lead to structural weaknesses. Just as a flooded street can lead to potholes and damage, excess surface water impacts the subgrade’s ability to support the road.

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