Question

Mortar is a mixture of: (a) Slaked lime \(+\) silica \(+\mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{CaCO}_{3}+\) silica \(+\mathrm{H}_{2} \mathrm{O}\) (c) Slaked lime \(+\) plaster of paris \(+\mathrm{H}_{2} \mathrm{O}\) (d) Plaster of paris + silica

Short answer

The correct answer is (a): Slaked lime + silica + water.

Step-by-step solution

Understanding Mortar

Mortar is traditionally a mixture used in building construction to bind bricks, stones, or blocks. It generally consists of an adhesive component and water, with slaked lime, sand (silica), and water being the common constituents.

Analyzing Option (a)

Option (a) lists the components as slaked lime, silica, and water. This matches the traditional definition of mortar, where slaked lime acts as the adhesive and silica (sand) is the aggregate.

Evaluating Option (b)

Option (b) suggests that mortar consists of calcium carbonate, silica, and water. Calcium carbonate is not traditionally used as a binder in mortar; thus, this option is unlikely to be correct.

Checking Option (c)

Option (c) includes slaked lime, plaster of Paris, and water. While slaked lime is a component of mortar, the addition of plaster of Paris is not typical for standard mortar mixtures.

Reviewing Option (d)

Option (d) includes plaster of Paris and silica. This combination does not correspond to mortar, as plaster of Paris serves different purposes, often for making mold or casts, not typically in mortar.

Final Step: Selecting the Correct Answer

After analyzing all the options, (a) is the correct composition for mortar: slaked lime, silica, and water. This aligns with the traditional definition of mortar used in construction.

Key concepts

Mortar Composition

Mortar plays a crucial role in construction as the substance that binds bricks, stones, or blocks together. It acts like glue to hold these materials in place, ensuring the stability and longevity of a structure. The traditional composition of mortar includes three key components: slaked lime, silica (often in the form of sand), and water. The combination of these ingredients provides both the adhesive quality and structural integrity needed in construction projects.

Slaked lime serves as the primary adhesive element, responsible for the binding action. Silica, meanwhile, functions as the aggregate, providing bulk and additional strength. Finally, water is essential to activate the slaked lime and facilitate the setting and curing process. The harmonious blend of these ingredients results in a robust and efficient bonding material for construction purposes.

Slaked Lime

Slaked lime, also known as calcium hydroxide, is an essential component of mortar. It is produced by adding water to quicklime (calcium oxide), which initiates a chemical reaction known as slaking. This reaction transforms the quicklime into a more manageable form, specifically suitable for mortar applications.

Slaked lime provides the necessary adhesive property that allows mortar to effectively bind construction materials like bricks and stones. One of its notable features is its ability to set and harden over time as it reacts with carbon dioxide from the air to form calcium carbonate. This hardening process is instrumental in creating a durable and stable bond in construction.

Silica in Construction

Silica, commonly found as sand, is a vital ingredient in mortar and many other construction materials. It mainly serves as the aggregate component within mortar mixtures. As an aggregate, silica offers stability and strength to the overall composite.

In construction, silica ensures that mortar has the necessary bulk to fill spaces between bricks or stones, while also contributing to the overall compressive strength. Without silica, the mortar would lack the physical support necessary to maintain the structural integrity of masonry work. This is why silica is not just an optional component, but a necessary inclusion in mortar mixtures.

Adhesive Components in Building

In building materials, adhesives play a pivotal role, without which structures could not stand firm. The adhesive components in mortar are crucial as they ensure the binding or sticking together of individual building blocks such as stones, bricks, or tiles.

In traditional mortar, slaked lime acts as the main adhesive agent. It provides a smooth, workable substance that can easily be spread over surfaces, creating a tenacious bond as it dries. The drying, or curing process, which involves a slow reaction with carbon dioxide, results in a solid, durable structure. Without effective adhesive properties, the utility of construction materials would be greatly reduced.

Building Materials Chemistry

The chemistry behind building materials like mortar is fascinating and foundational for understanding modern construction practices. It involves the interaction between different chemical compounds that form the mortar mix.

Slaked lime, acting as the primary binder, undergoes a reaction with water to make a paste that can be applied to surfaces. Meanwhile, silica adds strength and stability due to its physical properties and chemical resistance. The study of these interactions provides insights into how these materials can be utilized in designing structures that stand the test of time.

Understanding building materials chemistry is essential for several reasons:

• It helps in improving the quality and durability of construction.
• Enhances sustainability by choosing optimal material compositions.
• Facilitates innovation in creating new materials with better properties.

Such knowledge is instrumental in advancing construction technology, resulting in safer and more efficient building projects.