Construction Materials: Course Notes Part 2 - PDF

# Chapitre 3: Liants Hydrauliques ## Introduction To build houses or buildings, we need to have strong and solid materials. Stones extracted from the ground and raw or baked clay allows for the creation of stones and bricks that can be stacked to create walls. However, this stacking alone is not...

# Chapitre 3: Liants Hydrauliques ## Introduction To build houses or buildings, we need to have strong and solid materials. Stones extracted from the ground and raw or baked clay allows for the creation of stones and bricks that can be stacked to create walls. However, this stacking alone is not enough to create a stable structure. To create a durable structure, we need to solidify the assembly. This is achieved using a binding material, also known as a mortar. ## Types of Mortar There are two main types of mortar: 1. **Aerial Mortar (Non-hydraulic Mortar)** - Solidifies by drying out due to water evaporation - Requires dryness or even a bit of heat - Examples: air lime, plaster 2. **Hydraulic Mortar** - Solidifies in the presence of water - Often requires water to create a strong structure - Examples: hydraulic lime, cement ## Mortar Categories - **Mineral:** Including both air and hydraulic mortars. This category can be further subdivided into: - **Air Mortar:** Consisting of clay, plaster, and lime - **Hydraulic Mortar:** Including hydraulic lime and Portland cement. - **Portland cement:** Is a specific type of hydraulic mortar used in a wide variety of applications - **Organics:** Including asphalt (for road coverings and waterproofing), resin (resins, acrylics, vinyls, polyester, epoxy) ## Chapter Focus This chapter focuses on hydraulic mortar due to its frequent use in construction. # 3.1 Lime ## Introduction - Lime is a common binding material in masonry, typically found in a powdery white form. - It has been utilized since prehistoric times, with evidence of its use found in early Mesopotamia, Ancient Egypt, Greece, and Rome. - It comes in two forms: air lime and hydraulic lime, differing in their composition and setting mechanisms. ## Properties of Lime - Lime is used to create a mortar permeable to water vapor, allowing for moisture to evaporate and keeping the structure dry. - It is used for interior and exterior wall coatings, or for bonding bricks. - It can also be used to create waterproofing for exterior walls. - Has various applications in agriculture and steel making. ## Types of Lime - **Air lime** - Is a non-hydraulic binder that sets through a chemical reaction with carbon dioxide in the air - Is available in two forms: quicklime (CaO) and slaked lime (Ca(OH)2). - Quicklime is a highly caustic substance produced by heating limestone in a kiln. - Quicklime reacts with water, releasing a significant amount of heat (hydration reaction), forming slaked lime. - Slaked Lime is less caustic than quicklime and is used for plastering and mortar. - **Hydraulic lime** - Is a hydraulic binder that sets through a chemical reaction in the presence of water - Is available in various grades, with varying strengths and setting times. - The hydraulic properties of lime are due to the presence of silica and alumina in the source material. ## Lime Production Process - Starts with limestone (calcium carbonate), which is mined and crushed. - The crushed limestone is then heated in a kiln to a high temperature (around 900 °C), which causes it to decompose into quicklime (calcium oxide) and carbon dioxide. - The quicklime is cooled and mixed with water to produce slaked lime. - Slaked lime can then be mixed with sand and water to create mortar. ## Summary Lime is an essential binding material in construction, available in a variety of forms, each with its own distinct properties. # 3.2 Gypsum ## Introduction Gypsum is another ancient construction material. It is used in its traditional form as a powder mixed with water to create plaster, but also in prefabricated forms, like tiles and panels, for modern construction. ## Uses of Gypsum: - Gypsum mixed with lime and sand forms a mortar used for interior and exterior coatings. - Gypsum can be reinforced with fibers to create a stronger form, known as "armored plaster." - Gypsum reinforced with hemp fibers is known as "staff" and is widely used in decorative works. ## Production of Gypsum: - The production of gypsum is a result of the dehydration of natural gypsum (CaSO4, 2H2O) or industrial byproducts. - Gypsum can be dehydrated to a semi-hydrated form (CaSO4, 1/2 H2O) used to produce plaster, by heating it in a kiln. - Heating the gypsum beyond 180 °C leads to the creation of anhydrous gypsum (CaSO4), which also can be used to produce plaster. ## Properties of Gypsum: - Gypsum behaves differently depending on its hydration state: - **Semi-hydrated gypsum:** Is a fine, white powder that readily absorbs water and sets into a hard, crystalline structure when mixed with water. - **Anhydrous gypsum:** Is a much less reactive form that requires higher temperatures and longer setting times when mixed with water. - Gypsum has a relatively low thermal conductivity, making it a good insulator against heat transfer. - Gypsum is also porous and has good sound-absorbing properties. ## Uses of Gypsum: - Plastering - Construction of partitions, walls, and ceilings - Production of various decorative elements, like moldings and cornices - Production of various industrial products, like wallboard, drywall, and plaster of paris - Production of construction materials, like cement, mortar, and concrete # 3.3 Silico-Calcareous Mortar ## Introduction - Silico-calcareous mortar is a hydraulic binder made by mixing lime (either quicklime or slaked lime) with sand and water and then curing the mixture in an autoclave at a temperature of around 180 °C. - This process creates hydrated calcium silicates (CSH), which gives the mortar its binding properties. - It comes in two main types: dense and lightweight. ## Dense silico-calcareous mortar - Made using quicklime only - The mixture is vibrated and compacted before autoclave curing. - Results in a high-density material (1700-2100 kg/m³) with a high compressive strength (6-60 MPa) - Used to produce bricks, blocks, and other construction materials. - Its thermal conductivity is between 1.16 and 12.63 W/mK. ## Lightweight silico-calcareous mortar - Made by mixing lime with sand and adding aluminum powder. - The mixture is cast into molds and preheated to 60°C. - The aluminum powder causes foam formation when heated, making the final product lighter. - The lightweight silico-calcareous mortar is typically used for the production of blocks and panels. # 3.4 Cement ## Introduction - Cement is a hydraulic binder, meaning it sets and hardens in the presence of water. - It is a fine powder made of inorganic materials that are finely ground and mixed with water to form a paste. - This paste sets and hardens through a complex chemical reaction, creating a strong and durable material. - It is the most commonly used binder in concrete construction. ## Composition of Cement: Cement is primarily made of four main components: 1. **Lime (C)**: It is the main component and gives cement its binding properties. 2. **Silica (S)**: It increases the strength and durability of cement. 3. **Alumina (A)**: It accelerates the setting time. 4. **Iron Oxide (F)**: It adds color and influences the setting time. ## Production of Cement: 1. **Preparation of Raw Materials:** The raw materials necessary for cement production are quarried, crushed, and then homogenized. 2. **Burning (Clinker Production):** The carefully homogenized materials are heated in a rotary kiln at very high temperatures (around 1450°C). This creates the clinker, which is the primary component of cement. 3. **Grinding:** The clinker is ground finely along with other materials to create a fine powder. 4. **Mixing:** Various additives, including gypsum, are added to the ground clinker to control the setting time and properties of the final cement. ## Types of Cement: - **Portland Cement:** Is a basic cement type made using only clinker. - **Compound Cements:** Include Portland cement with additions such as fly ash, slag, silica fume, and other materials. ## Cement Classification: Cement is classified according to its composition: - **CEM (Cement European):** Includes a series of five classes (CEM I, CEM II, CEM III, CEM IV, CEM V) representing different types of cement based on the quantities of clinker and other materials added. - **CPA (Cement Portland Artificial):** A French system with various classifications based on the addition of materials to Portland cement. ## Cement Applications: - **Mortar:** A mixture of cement, sand, and water that is used to bond bricks, blocks, and other masonry materials. - **Concrete:** A mixture of cement, aggregates, and water that is used for various structural elements. ## Cement Setting and Hardening: - The setting and hardening of cement depend on a number of factors that include temperature, water content, and the presence of additional materials. - The setting process starts when the cement is mixed with water, resulting in the formation of a pasty mixture that starts to solidify. - Hardening happens as the cement mixture forms hydrated calcium silicate (C-S-H), which is the main binder responsible for the strength of the concrete. ## Cement Strengths: Cement strength is measured in terms of the compressive strength it has after a certain period of time (28 days being the most common). ## Cement Properties in relation to composition: - **C3S:** This compound contributes to faster setting time and higher strength. - **C2S:** This compound contributes to slower setting time and high-strength development over time. - **C3A:** This compound accelerates setting time but can pose problems with expansion due to reaction with sulfate ions, so it is sometimes regulated with the addition of gypsum. - **C4AF:** This compound provides additional strength and contributes to color. ## Cement Usage: - **Normal Cements:** Are the most common types of cement used for general construction purposes. - **Special Cements:** Have specific properties for specific purposes, like those used for marine environments, sulfate-resistance, or to accelerate setting times. ## Summary: Cement is a fundamental and versatile construction material. Its properties and uses are influenced by its composition and the carefully controlled manufacturing processes.