Refer to IS 457: 1957 to ensure quality construction while mass concreting works on your projects
Introduction to IS 457: 1957
IS 457: 1957 is an Indian Standard code for practice for the general construction of plain and reinforced concrete for dams and other massive structures.
The IS 457 covers the selection and proportioning of materials, the design of the concrete mix, the placement and curing of the concrete, and the quality control measures to be followed during construction. It is intended to be used as a guide for engineers and contractors involved in the construction of massive concrete structures in India.
Who published IS 457?
The Bureau of Indian Standards publishes codes like these for the harmonious development of the activities of standardization, marking, and quality certification of goods. BIS prepares these codes with the help of reputed construction companies and organizations across the country doing extensive research. The IS codes are freely available in public resources. They are free to download from the internet.
The IS 457 includes provisions for the design of the concrete mix, including the determination of the water-cement ratio and the grading of the aggregate.
It specifies the requirements for the placement and curing of the concrete, including the methods for placing, compacting, and finishing the concrete.
It outlines the quality control measures to be followed during construction, including the testing of the fresh and hardened concrete to ensure that it meets the required specifications.
Let's take a brief overview of what this code has to offer.
What does IS 457 offers?
The code is divided into 7 sections. Each focuses on a particular aspect of concreting work required for massive structures.
Sections 1 and 2, scope and terminology, explain the extent of the code and provide definitions of the key terms used in the construction activity.
Section 3 is about materials.
The code suggests the use of Portland cement (complying with IS 269 1989), Portland Blast furnace Slag cement (IS 455 1989), and special cement for plain and reinforced concrete work in dams and other massive structures.
It also talks about admixtures, water, aggregates, reinforcement, and storage of materials.
Section 4 is about concrete
This section covers operational procedures for concreting. Here is a review of each:
The general requirement in mass construction work is about the size of aggregate and density of concrete. The code highlights that the maximum size of aggregate should be between 10 cm to 23 cm and cement content ranges from 150 to 235 kg/m3.
In the case of heavily reinforced concrete, the size of the aggregate should be 2 cm, and the cement content of approximately 355 kg/m3 of concrete.
Clause 4.2.1 talks about quality. It focuses on preliminary tests to be carried out in advance, the reference of which is to be taken from IS 456.
Clause 4.3 is about mix proportions. Here, the code gives due importance to the expertise of the engineer-in-charge.
Then, with the guidelines for workability and slump, the code then lays down the process of measuring the materials in clause 4.6
Clause 4.7 is about mixing
In the case of machine mixing, the time of mixing the ingredients is as mentioned in the below table.
Hand mixing is not recommended method of practice by the code.
The code then covers handling and conveying equipment along with their way of use. The equipment includes buckets, chutes, pumps, and belt conveyors.
The next key steps in the concreting of mass structures are preparation for placing of concrete, Placing of concrete, and Compacting, details of which are given in the sub-clauses within the code.
One of the areas of caution is depositing concrete underwater.
Underwater placement of concrete is not recommended. It is preferred to de-water the area if feasible. If not, the code mentions following precautions
- Concrete shall not be placed in water having a temperature of less than 2 degrees Celsius.
- When the temperature of the water is less than 7 degrees, the temperature of the concrete to be deposited should be between 15 to 25 degrees.
- The difference between the temperature of the water and that of concrete shall not exceed 5 degrees.
- The cement content shall not be less than 390 kg/m3 of concrete.
- The limits for the slump be 10cm and 18 cm.
The methods suggested to place the concrete underwater are tremie pipe, drop-bottom bucket, and bags.
Clause 4.13 of the code provides the course of action and precautions to be taken in case of extreme weather conditions.
Clause 4.14 provides guidelines for curing and protection, while clause 4.15 is about repair of concrete.
The 16th clause of section 4 is about finishes and finishing. There are four types of finishes, F1, F2, F3, and F4, each carried out as per the further work to be done on the laid concrete surface.
The three types of finishes for the unformed surfaces are denoted as U1 (unscreeded), U2(floated), U3(trowelled).
The next section of the code is about forms and formwork for concrete where general guidelines are given.
Section 6 is on construction joints. Here four types, horizontal joints, vertical joints, water-tight joints, and emergency joints, are mentioned.
The last section of this code is on tests on concrete, which includes lab tests and field tests. Following this, the structure is successfully erected.
At the end of the code, three Appendices are attached.
Appendix A - Determination of consistency of concrete by Vee Bee consistometer method.
Appendix B -Method of securing hardened specimen of concrete from the structure
Appendix C - Flexural strength of concrete using Simple Beam with Third Point Loading method.
After getting an overview of IS 457, you might ask, what are the applications of this code? Here they are:
Application of IS 457: 1957
Mass concreting can be done for bridge piers, dams, foundations of very tall buildings, canals, and seashore structures.
This type of work is predominant in infrastructure and real estate projects.
If you are into mass concreting, you might know that works like this require top-notch planning and quality control.
Concluding Remarks
In this article, we had an overview of IS 457 and its application. We also learned the structure of the code. Hope you found it helpful. Now, it's time for execution.
Wouldn’t it be great if you have digital tools to make this happen? We at digiQC can help you.
By digitizing your Quality Audit and Quality Control needs, you can reduce paperwork and save costs by automating your processes. With the seamless integration of our mobile-friendly construction quality control software, you get an in-built checklist to ease your site compliance work.
If your organization works in mass construction works, you might be interested in knowing how you can ensure construction quality control at work. We are here to help you. Simply schedule a free demo today to talk with one of our experts.
