Cours 3 - Les granulats -Matériaux de construction

What Are Granulates and Their Importance in Civil Engineering?

Introduction to Granulates

• The video introduces granulates, explaining their significance as the fundamental components in most civil engineering projects, such as roads and buildings.

• To create concrete, a mixture of sand, gravel, cement (sometimes with additives), water, and air is required. Additives are not mandatory except for specific types of concrete.

Definition and Composition of Granulates

• Granulates are defined as inert materials that form the skeleton of concrete, constituting approximately 80% of its total volume.

• The production of granulates reached 329 million tons in 2016. They play an economic role by reducing the amount of cement needed due to its high cost.

Benefits and Properties

• Economically and ecologically beneficial, granulates help limit dimensional variations in concrete since they are more rigid than cement paste.

• The contraction dimensionally caused by chemical and physical phenomena is addressed through proper granulate selection during manufacturing.

Manufacturing Process

• The process begins at quarries where blocks are fragmented using explosives or machinery before being transported for further processing.

• After fragmentation, screening is performed to classify the material into different granular classes. Secondary or tertiary crushing may follow to refine sizes further.

Classification of Granulates

• Granulates can be classified based on origin: natural (from quarries), artificial (produced from thermal transformation), or recycled (from existing structures).

• Natural granulates include crushed rock from hard stones; examples include limestone aggregates characterized by their rough texture.

Types of Natural Granulates

• Rolled granulates result from natural erosion processes like water flow or wind action; they have rounded shapes suitable for various applications.

• Artificial granules come from industrial processes like blast furnace slag; these serve as co-products in construction materials.

Recycled Granulates

• Recycled aggregates originate from demolished structures after treatment processes yield usable materials for new concrete mixes.

Size Classification

• Granulate classification also considers size: small grains (minimum diameter represented by lowercase letters), large grains (maximum diameter represented by uppercase letters).

Examples:

• Granule Classifications:

• A class labeled "8/15" indicates a range between 8 mm to 15 mm in diameter.

Density Classification

• Further classification includes density categories where common aggregates have a bulk density ranging around 2 to 3 tons per cubic meter.

Utilization of Lightweight Aggregates in Construction

Overview of Lightweight Aggregates

• The unique absolute density of lightweight aggregates is approximately 2.7 grams per cubic meter, which makes them suitable for construction projects requiring biological protection against radiation.

• These aggregates are essential in the production of lightweight concrete, contributing to reduced overall weight while maintaining structural integrity.

• The discussion highlights the importance of these materials in modern construction practices, particularly in environments where weight reduction is critical.

• The speaker mentions specific types of lightweight aggregates and their applications, emphasizing their role in enhancing building safety and efficiency.

• Acknowledgment is given to the audience for their attention, indicating a conclusion to this segment on lightweight aggregates.