Question

The role of silica in mortar is to (1) form slag with lime (2) make the mass porous (3) give slight acidic nature (4) make it insoluble in water

Short answer

Option 3: give slight acidic nature.

Step-by-step solution

Understand the options

Read the given options carefully and understand what each option implies:

Examine option 1

Option 1 states that the role of silica in mortar is to 'form slag with lime'. Consider the chemical interaction between silica (SiO2) and lime (CaO); they generally form calcium silicates in the mortar, not slag. So this is likely incorrect.

Examine option 2

Option 2 states that silica makes the mass porous. Silica is known for its ability to rearrange and form a dense network, often resulting in a less porous structure. Thus, this option is also likely incorrect.

Examine option 3

Option 3 states that silica gives a slight acidic nature. Silica (SiO2) is mildly acidic, and its inclusion in mortar contributes to the acidic properties. This seems plausible.

Examine option 4

Option 4 states that silica makes the mortar insoluble in water. While silica does contribute to the durability of mortar, it does not specifically make the mortar insoluble in water. This is also likely incorrect.

Conclusion

Considering all the options, the most plausible role of silica in mortar is given by option 3: 'give slight acidic nature'.

Key concepts

acidic properties of silica

Silica, chemically known as SiO2, is a naturally occurring compound found in sand, quartz, and many other minerals. When included in mortar, its most notable role is to provide a slight acidic nature. Silica exhibits mild acidity due to its tendency to release hydrogen ions when hydrated. This slight acidity influences various characteristics of the mortar, primarily affecting its setting properties and durability. Key points to remember:

• Silica makes the mortar slightly acidic due to its chemical behavior in water.
• This mild acidity can impact the longevity and resilience of the mortar.

Understanding this property is crucial for applications requiring specific pH balance and durability in construction materials.

chemical interaction in mortar

In mortar, various chemical interactions take place as different components are mixed together. Silica (SiO2) and lime (CaO) are primary ingredients that react to form calcium silicate hydrates (CSH), which improve the mechanical properties of the mortar. These chemical interactions are vital for the following reasons:

• CSH formation contributes to the mortar's strength and durability.
• This compound also aids in binding other materials together firmly.
• The reaction reduces cracks and increases the load-bearing capacity of the mortar structure.

Understanding these chemical processes helps builders and engineers ensure the proper application and effectiveness of the mortar in various construction projects.

properties of building materials

Building materials such as mortar possess various properties that determine their applicability and performance in construction. Important properties to consider include:

• Durability: Mortar's ability to withstand weathering, chemical attack, and mechanical wear.
• Porosity: The presence of fine pores within a material that can affect its water retention and strength.
• Acidity: The pH level which can influence the material's chemical behavior and interactions.
• Insulation: Heat and sound insulation properties that can be critical in construction.

Careful selection and understanding of these properties ensure that the building materials used will meet specific needs and last over time, thereby guaranteeing the stability and safety of the structure.