In concrete construction, rebar supports and spacers are critical components for ensuring structural durability and safety. They not only maintain the correct position of the rebar and the thickness of its protective layer, but also directly impact the structure’s impermeability, load-bearing capacity, and service life. Currently, steel supports and plastic spacers are the two most widely used types. So, how should you make the right choice for your specific project? The following analysis will examine material properties, applicable scenarios, and comprehensive benefits to help you accurately grasp the key points of your decision.
What Are Steel Rebar Chairs?
Steel rebar chair also known as a rebar support stool or horse stool, is a rigid support structure made of high-strength steel wire, either welded or cold-drawn. Its core purpose is to provide a stable fulcrum for the upper rebar during concrete pouring, ensuring the rebar grid remains in its designed position and precisely controlling the concrete cover thickness.
Core Features
The rebar chair’s most notable feature is its exceptional compressive strength and structural stability. Its unique “stool” shape evenly distributes the construction load and concrete weight above it, resulting in virtually no deformation or collapse even under heavy loads. This makes it a reliable choice for demanding construction environments, particularly large infrastructure projects such as industrial floors, bridge decks, tunnel linings, and large foundation slabs, where structural integrity and rebar positioning accuracy are paramount.
Advantages and Limitations
Core Advantages: Unparalleled load-bearing capacity, a stable working surface for construction workers, and zero rebar displacement ensured, making it the preferred choice for heavy rebar skeleton support.
Main Limitations: The inherent material nature of the chair increases the risk of corrosion. Without surface anti-corrosion treatments such as galvanizing, or if exposed to moisture or chloride-containing environments for extended periods before concrete covering, corrosion may affect long-term durability. Therefore, it is more commonly used in projects where immediate structural strength is more important than long-term chemical resistance.
Selection
In modern construction, the selection of steel chairs requires comprehensive considerations:
Load Calculation: Accurately calculate the required chair height and specifications based on the weight of the upper rebar and the construction load (e.g., personnel and equipment).
Corrosion Treatment: In humid and corrosive environments, or for projects where structural longevity is critical, hot-dip galvanized steel chairs are preferred to improve their corrosion resistance significantly.
Material Evolution: To address corrosion issues, epoxy-coated steel chairs or composite plastic steel chairs have emerged on the market, offering a balance of strength and corrosion resistance under specific conditions.
What Are Plastic Spacers?
Plastic spacers are concrete supports made from high-strength engineering plastics (such as polypropylene (PP) and polyvinyl chloride (PVC)) through a precision injection molding process. As a key auxiliary material in modern concrete construction, their core function is to precisely ensure the desired concrete cover thickness between the rebar and the formwork, thereby ensuring structural durability and safety.
Core Features
Compared to traditional steel spacers, the core advantage of plastic spacers lies in their superior material properties:
Absolutely corrosion-resistant: Unaffected by moisture, salt, or chemicals, this fundamentally eliminates the risk of rust or damage to the concrete surface caused by spacer corrosion. They are particularly suitable for water conservancy projects, coastal structures, and chemical plants.
Excellent electrical insulation: They effectively prevent electrochemical corrosion caused by stray currents, making them a must-have for projects with special insulation requirements, such as substations and subways.
Lightweight, high-strength, and convenient: Their extremely low weight significantly reduces labor intensity and simplifies transportation and storage. Their standardized design significantly improves installation efficiency.
Diversified Designs and Precise Applications
Plate-type: Suitable for bottom supports of flat structures such as foundation slabs and floor slabs. Wheel/Gear Type: The serrated design of the sidewalls securely “grips” the formwork, effectively preventing slippage and shifting during pouring. Suitable for vertical components such as walls and columns.
Clip Type: Securely fastens to the rebar, preventing displacement under concrete impact and ensuring precise positioning.
This versatility makes it ideal for a wide range of cast-in-place and precast applications, including residential and commercial buildings, as well as large precast components.
Comprehensive Value
By ensuring absolute precision in rebar placement, plastic spacers bring multiple core benefits to projects:
Ensuring Structural Durability: A precise protective layer is the first line of defense against rebar corrosion and is directly related to the building’s designed service life.
Improving Surface Quality: Avoiding missing rebar, rust spots, or concrete surface defects caused by spacer defects.
Optimizing Lifecycle Costs: While the cost per unit may be slightly higher, the advantages in transportation and installation efficiency, as well as the reduced long-term maintenance costs of the structure, result in superior overall cost-effectiveness.
Steel Rebar Chairs vs. Plastic Spacers:
| Feature | Steel Rebar Chairs | Plastic Spacers |
| Material | Welded or cold-drawn steel wire | Polypropylene, PVC, or other high-strength plastics |
| Load Capacity | Very high, suitable for heavy-duty and large-scale structures | Moderate, ideal for residential, precast, and medium-load projects |
| Corrosion Resistance | Low, prone to rusting in humid or chemical environments | Excellent, non-corrosive, and resistant to chemicals |
| Weight | Heavy, requires more effort to handle and transport | Lightweight, easy to carry, and install |
| Cost | Higher initial cost, plus potential maintenance or replacement due to rust | Lower overall cost, minimal maintenance |
| Applications | Large-scale infrastructure, bridges, tunnels, and industrial floors | Residential, commercial, precast panels, pipes, blocks |
| Durability | Strong, but its lifespan may be shortened by rust | Long-lasting with excellent environmental durability |
| Ease of Use | Requires more effort in cutting and adjusting | Simple placement, wide range of shapes for flexibility |
Which One Should You Choose?
The choice between steel saddles and plastic saddles depends on project requirements. For large infrastructure projects like bridges, tunnels, or industrial floors, steel saddles are more suitable due to their strength and load-bearing capacity. However, for most residential, commercial, and precast concrete projects, plastic saddles are often the wiser choice. They are lightweight, corrosion-resistant, cost-effective, and available in a variety of shapes for adaptability. In today’s construction industry, which emphasizes durability and efficiency, plastic saddles are becoming the preferred solution for modern construction and precast plants.
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