Why We Cast Starter in Column?

In reinforced concrete construction, every element serves a specific purpose. One such important component is the starter in a column. Though it may appear like a small detail, the starter plays a critical role in ensuring the strength, alignment, and bonding of a column with the foundation. In this blog, we will understand what a starter is, why we cast it, how it’s constructed, and why it is essential for a stable structure.

What is a Starter in Column?

A starter is the initial short height of a reinforced concrete column that is cast along with the footing, plinth beam, or foundation. It is typically around 50 mm to 300 mm in height and is used to ensure the proper positioning and alignment of the full column that will be cast later.

The starter is also known as a kicker in some parts of the world, but in India and most British-standard-following countries, the term “starter” is commonly used in civil engineering works.

Purpose of Casting a Starter

The main purpose of a starter is to prepare the base for the column. It helps in maintaining vertical alignment, provides a rough surface for good bonding, and acts as a reference level for column formwork. Here are some reasons why we cast a starter in a column:

1. Proper Alignment: It ensures the verticality and position of the future column.
2. Ease in Shuttering: The starter provides a base for fixing formwork accurately.
3. Bonding Between Foundation and Column: A rough surface of the starter helps in creating a good bond between the old concrete (foundation) and new concrete (column).
4. Avoids Honeycombing: Directly casting the column on the footing may lead to segregation or honeycombs at the base, which the starter helps to avoid.
5. Prevents Cold Joints: By roughening the starter surface, the new concrete properly bonds with the existing structure.

Construction Process of a Starter

Here’s a simple step-by-step method to cast a starter in a column:

1. Column Reinforcement: Fix the vertical column bars in position and ensure they are tied and plumb.
2. Shuttering for Starter: Use wooden or steel shuttering around the bars to define the starter height.
3. Slurry Application: Apply a bonding slurry or cement paste to the joint area for better adhesion.
4. Concrete Pouring: Carefully pour concrete inside the shuttered portion and compact it thoroughly.
5. Surface Roughening: Once the starter has gained initial strength, the top surface should be roughened for bonding.
6. Curing: Properly cure the starter for at least 7 days to gain the required strength before proceeding with the column casting.

Typical Height of a Starter

The height of the starter depends on the site condition but usually ranges between 50 mm and 300 mm. The starter must be high enough to allow for shuttering of the column and to keep the column steel above ground or plinth level to avoid corrosion.

Importance of Curing the Starter

Curing is essential to achieve the desired strength of concrete. Poorly cured starters may result in weak bonding and may crack when loaded. Water curing or curing compounds are commonly used, depending on the weather conditions.

Common Mistakes to Avoid

• Not roughening the top surface after initial setting.
• Casting the starter without alignment checks.
• Not applying slurry or bonding agent at the base.
• Using weak or insufficient concrete mix.
• Delayed column casting leading to cold joint issues.

IS Code Guidelines

While there is no separate IS code specifically for starters, related practices can be found in:

• IS 456:2000 – Code of practice for plain and reinforced concrete.
• IS 3370 – For concrete structures exposure and curing.

Site engineers are advised to follow proper detailing, alignment checks, and curing methods as per code guidelines and good construction practices.

Advantages of Using a Starter

• Maintains column positioning.
• Ensures good construction joint.
• Reduces errors in shuttering and verticality.
• Enhances structural bonding and load transfer.
• Makes subsequent construction faster and more accurate.

Conclusion🎯

Though the starter might seem like a minor component in column construction, it plays a vital role in ensuring proper alignment, structural bonding, and quality finishing. It is one of those small but significant practices that every site engineer, supervisor, and mason should be well aware of. By following proper methods while casting a starter, we can enhance the overall integrity of the structure and avoid many future issues during column construction.

FAQs

Q1: What is a starter in column construction?
A starter is a short portion of the column (50–300 mm) cast with the footing or plinth to aid in alignment and bonding for the full column.

Q2: Is it compulsory to cast a starter?
While not mandatory by code, it is highly recommended in site practice to ensure quality and alignment.

Q3: What if we don’t cast a starter?
You may face problems like poor alignment, weak bonding, and honeycombing at the base of the column.

Q4: What type of concrete is used for starters?
The same grade of concrete as the structural column, usually M20 or M25, is used for starters.

Q5: Can the starter be cast separately from the footing?
It is ideally cast immediately after the footing or plinth to maintain continuity and bonding.