Have You Thought of Using Pozzolana to Save Construction Costs?

Refer to these 7 IS codes on Pozzolana as a go-to guide

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Pozzolana is a type of volcanic ash used for mortar.

As per the definition, "A pozzolan is a siliceous or siliceous and aluminous material that in itself possesses little or no cementitious value but will, in finely divided form and the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds having cementitious properties."

For centuries, the only pozzolana extensively used in India was Surkhi (also called burnt clay pozzolana), however, with advancement in research and owing to sustainability requirements, the use of the term Pozzolana has now extended to industrial wastes such as fly ash, coal ash, etc.

Today, fly ash and surkhi are widely used pozzolanas in the Indian construction industry.

Introduction

Why use Pozzolana?

Pozzolana is used as a part-replacement for cement. If used in appropriate proportions, pozzolana can reduce the cost of construction without affecting the construction quality.

From where Pozzolana is obtained?

There are a large number of pozzolanic clay deposits of stained and impure kaolins, ferruginous or ocherous earth, altered laterites and bauxites, certain shales, etc, available in different parts of the country, which yield highly reactive pozzolanic materials.

The Central Road Research Institute, New Delhi, has extensively conducted an all-India survey of pozzolanic clay deposits. The detailed report of such deposits in each State with suggestions for the mode of industrial use of each of them. The institute published the results in the IS codes, including IS 1344: 1981, and IS 3812: 2013, as we will see below.

Use of Pozzolana

Pozzolana has a wide application and is used to partially replace cement in hydraulic structures, marine construction works, mass concrete, and underground structures like retaining walls, and sewage pipes, and can also be used for masonry works and plastering.

How to use pozzolana to enhance the quality of construction?

No doubt the IS codes, published by the Bureau of Indian Standards, are the best resource to get a good understanding of the use of pozzolana in construction. The BIS is the apex body that researches and documents the relevant useful codes with careful consideration of all the aspects of the specific industry. The BIS also updates these codes as per the latest research. These codes are open-source and freely available on the web.

Let's take a deeper dive into the IS codes on pozzolana.

IS codes related to pozzolana

1. IS 4305: 1967 - Glossary of terms related to pozzolana

This standard covers definitions of words and terms relating to pozzolanas.

As the code suggests, "Pozzolanas find extensive application in this country in the preparation of structural mortar and concrete. Their use is likely to increase further with the availability of industrial wastes and other artificial pozzolanic materials as a result of further industrialization in the country. This has necessitated the formulation of several Indian Standard specifications and methods of tests for different types of pozzolanas."

This code includes several technical terms which require clarifications to give precise meaning relating to various types of pozzolanic materials. The code is used as a reference while drafting a tender that involves the use of pozzolana.

The code covers 32 terms related to pozzolana and is a good source of reference to understand the basic terminologies and constituents of each pozzolanic material.

Once you are aware of the terms, your next task is to figure out a suitable pozzolanic material. to use in your construction project. Here are a few codes that will help yo

2.  IS: 3812 (Part I) -1966  

Specification for pulverized fuel ash. This code is about terms related to fly ash.

3. IS: 1344 -1981

Specification for surkhi for use in mortar and concrete. This code chalks down the specification for calcinated clay pozzolana.

4. IS: 456 -1978

Use of calcined clay pozzolana as part replacement of unblended cement and admixture.

5. IS: 4098 -1967

Lime-pozzolana mixture manufactured by inter-grinding or blending lime and calcined clay pozzolana conforming to this standard.

6. IS: 15388 (2003)

Specification for Silica Fume

7. IS 1489: 1991

IS code on requirements of Portland Pozzolana Cement manufactured either by inter-grinding Portland cement clinker and calcined clay pozzolana with the addition of gypsum or by blending Portland cement and calcined clay pozzolana. In essence, this code contains the raw materials required in selecting the clay for manufacturing, the manufacturing process (obtaining, preparation of raw materials, calcination, grinding), physical requirements, storage, manufacturer's certificate, delivery, sampling, and methods of testing.

Portland-pozzolana cement produces less heat of hydration and offers greater resistance to the attack of aggressive waters than normal Portland cement. Moreover, it reduces the leaching of calcium hydroxide liberated during the setting and hydration of cement. It is particularly useful in marine and hydraulic construction and other mass concrete structures.

For the construction of structures using rapid construction methods like slip-form construction, Portland pozzolana cement shall be used with caution since the 4-6 hour strength of concrete is significant in such construction

  • Part 1 of this standard covers pozzolana cement manufactured by using only fly ash pozzolana
  • Part 2 covers pozzolana cement manufactured by using either calcined clay or a mixture of calcined clay, and fly ash as pozzolana.

Finally, to test the suitability of the pozzolanic material, refer to IS: 1727.

8. IS: 1727-1996

Methods of test for pozzolanic materials (Sixth revision) - This code contains the necessary tests to be carried out to check the compatibility of pozzolana with the concrete mix.

This code covers tests that include:

  • Chemical analysis
  • Fineness
  • Soundness
  • Setting time
  • Lime reactivity
  • Compressive strength
  • Transverse strength
  • Drying shrinkage
  • Permeability
  • Reduction in alkalinity and silica release
  • Specific gravity

The detailed procedure is available in the code, which you can download here.

Conclusion

This article gave you a quick tour of IS codes related to pozzolana. Bookmark this article for future reference. Refer to the codes mentioned to learn more about pozzolana and its application to reduce construction costs.

Rigorously follow the instructions shared in the IS codes.

Your next step would be to maintain the equivalent construction quality control standards at the site. For that, your team needs to follow robust quality practices.

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