masonry cement portland cement

Masonry cement, a specialized hydraulic blend, finds its niche in the world of construction, primarily focusing on masonry applications. Unlike ordinary cement mortar, which boasts strength and setting properties but falls short in workability, water retention, shrinkage control, and extensibility, masonry cement steps in to rectify these shortcomings while retaining the desirable attributes of cement mortar.

What is Masonry Cement?

Masonry cement is a unique blend crafted from specific materials, which, when used to create mortar, amalgamate the favorable traits of lime mortar and eliminate the drawbacks of cement mortar. This cement variant includes precise proportions of air-entraining agents and mineral admixtures to enhance plasticity and water-retentive qualities.

How Masonry Cement is made ?(Composition Matters)

The manufacturing process of masonry cement involves grinding and mixing cement clinker with either pozzolanic or non-pozzolanic (inert) waste materials. Gypsum and air-entraining plasticizers are skillfully added in appropriate measures. Notably, masonry cement maintains a greater fineness than ordinary Portland cement.

Examples of materials conducive to masonry cement production encompass:

  • Pozzolanic materials like Fly ash or calcined clay.
  • Inert materials like Limestone, conglomerates, dolomite, and granulated slag.
  • Occasionally, waste materials such as carbonated sludge and mine tailings can also serve as additives.

The subsequent manufacturing steps largely mirror those of ordinary Portland cement.

Masonry Cement Properties

According to IS 3466-1988, the physical properties of masonry cement are outlined as follows:

Physical Properties Requirements

  • Fineness: Residue on 45-micron IS Sieve, Max (by wet sieving) - 15%
  • Setting Time (by Vicat Apparatus):
  • (a) Initial, Min - 90 minutes
    • (b) Final, Max - 24 hours
  • Soundness:
  • (a) Max. 10 mm Le-Chatelier expansion
    • (b) Autoclave expansion, Max - 1%
  • Compressive Strength: The average strength of at least three mortar cubes of 50 mm in size and made of masonry cement and standard sand in that order.
  • Min at 7 days - 2.5 MPa
    • Min at 28 days - 5 MPa
  • Air Content: Air content of mortar composed of 1 part masonry cement and 3 parts standard sand by volume, Min - 6%
  • Water Retention: Flow after suction of mortar composed of 1 part of masonry cement and 3 parts standard sand by volume, Min - 60% of original flow

Types of Masonry Cement (As stated in ASTM C-91)

In accordance with ASTM C-91 standards, masonry cement is classified into three types, each tailored to specific construction needs:

1. Type N Masonry Cement

  • Type S Masonry Cement
  • Type M Masonry Cement

Type N finds general use in most mortar and stucco applications, while Type M and S are engineered for high-strength requirements, particularly in load-bearing or below-grade walls. These masonry cement types closely adhere to the physical properties stipulated by ASTM C-91.

Storing Masonry Cement

Storage protocols for masonry cement align with those for ordinary Portland cement (OPC). For detailed precautions during cement storage, refer to the guidelines for storing cement.

Delivery Considerations

Masonry cement is typically packaged in various ways, including:

  • Sacking bags made of jute that adhere to IS: 2580
  • Multi-wall paper sacks conforming to IS: 11761
  • Light-weight jute bags conforming to IS: 12154
  • HDPE/PP woven sacks conforming to IS: 11652
  • Woven polypropylene bags conforming to IS: 11653
  • Union bags made of synthetic jute that comply with IS: 12174
  • Composite bags (approved)

Each cement bag should bear the following markings:

  • "Masonry cement"
  • The number of bags (net mass) per tonne or the nominal average net mass Each bag contains a net quantity of 50 kg but is also available in a 25 kg option.

Sampling and Testing

Sampling of masonry cement should occur within 3 weeks of delivery, following the methods and procedures outlined in IS: 3535-1986. Testing should take place within 4 weeks of delivery, adhering to the standard IS: 3466-1988 (Specification for masonry cement).

Applications of Masonry Cement

Masonry cement, when mixed with sand and water, transforms into mortar, a crucial bonding material for masonry construction and plastering. Mortar bridges the gaps between individual masonry units in structures.

Utilizing Masonry Cement

The diverse applications of masonry cement include:

  • Crafting mortar for masonry works
  • Plastering
  • Stucco creation

Advantages of Masonry Cement

Masonry cement boasts several advantages, including:

  • Improved workability
  • Enhanced water retention
  • Production of smooth, cohesive, and strong yet workable mortar
  • Durability as mortar cement
  • Reduced cracks from shrinkage and temperature variations due to low heat of hydration
  • Longer setting time, providing ample working time for masonry construction
  • Ease of handling during masonry projects

Disadvantages of Masonry Cement

However, masonry cement does come with limitations, such as:

  • Limited use exclusively as mortar cement
  • Lower strength compared to OPC, rendering it unsuitable for concrete construction.

Why Masonry Cement Isn't Ideal for Concrete

Masonry cement, designed for masonry works, lacks the potency of concreting cement (OPC). The presence of additional additives like pozzolanic and inert materials, and at times waste materials, makes it unsuitable for concrete projects due to insufficient strength.

Masonry Cement vs. Portland Cement

Comparing masonry cement to Portland cement highlights the former's advantages, including superior workability and water retention. Masonry cement combines the desirable properties of cement mortar with improved attributes.

Concluding Thoughts

In essence, masonry cement, with its tailored composition and specialized properties, serves as a vital component in masonry construction. Its ability to address the shortcomings of ordinary cement mortar while retaining its positive attributes makes it an indispensable choice for various masonry applications.

Frequently Asked Questions

  1. What’s the difference between masonry and Portland cement?

Masonry cement combines the strengths of cement mortar with improved characteristics, making it superior to Portland cement in workability and water retention.

  • Is lime mortar better than cement?

Lime mortar has its merits, but masonry cement excels in combining the best qualities of lime and cement mortars while eliminating their drawbacks.

  • What is masonry cement used for?

Masonry cement finds its application in crafting mortar for masonry construction, plastering, and stucco creation.

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