ASTM C 920 Specification for Elastomeric Joint Sealants

ASTM C920 test method covers the properties of a cured single-or multi component cold-applied elastomeric joint sealant for sealing, caulking, or glazing operations on buildings, plazas, and decks for vehicular or pedestrian use, as well as types of construction other than highway and airfield pavements and bridge. The final results of this method are displayed keeping in view the international standards and inch-pound units.

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ASTM C 920 Specification for Elastomeric Joint Sealants

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Overview
Scope, Applications, and Benefits
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

ASTM C920 defines performance requirements and classifications for elastomeric joint sealants used in construction and structural sealing applications. It ensures sealants provide durability, flexibility, and adhesion under varying environmental conditions.

This standard is widely used in the construction and infrastructure industry to evaluate sealants for joints exposed to movement, weathering, and temperature variations, ensuring long-term sealing performance and reliability.

Scope, Applications, and Benefits

Scope

ASTM C920 covers classification, performance testing, and requirements for elastomeric sealants used in joints subjected to expansion, contraction, and environmental exposure.

It includes evaluation of adhesion, cohesion, durability, and movement capability for different sealant types and grades.

Classification by type, grade, class, and use
Adhesion and cohesion testing
Movement capability evaluation
Weathering and durability assessment
Tensile and elongation testing
Hardness and modulus evaluation
Surface compatibility testing

Applications

Building expansion and control joints
Curtain walls and façade systems
Window and door sealing
Concrete and masonry joints
Bridge and infrastructure joints

Benefits

Provides flexible joint sealing
Accommodates structural movement
Enhances weather resistance
Prevents water and air leakage
Improves durability of structures
Supports long-term performance
Ensures compliance with standards

Test Process

Sample Preparation

Sealant samples are prepared and applied between substrates as per standard conditions.

Conditioning

Samples are conditioned under controlled temperature and humidity before testing.

Mechanical Testing

Sealants are tested for adhesion, elongation, and movement capability.

Evaluation

Results are compared with ASTM C920 criteria for classification and compliance.

Technical Specifications

Parameter	Details
Material Type	Elastomeric sealants such as silicone, polyurethane, and polysulfide.
Classification	Type (single/multi-component), grade, class, and use.
Movement Capability	Typically ±12.5% to ±50% joint movement.
Hardness	Shore A hardness for sealant consistency.
Weather Resistance	Resistance to UV, moisture, and temperature cycles.
Curing Condition	Moisture or chemical curing systems.

Instrumentation Used for Testing

Universal Testing Machine (UTM)
Environmental conditioning chamber
Shore A hardness tester
Adhesion test fixtures
Elongation measurement devices
Temperature and humidity control systems

Results and Deliverables

Sealant classification report
Adhesion and cohesion test results
Movement capability evaluation
Elongation and tensile data
Weathering performance results
Final test certification

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Frequently Asked Questions

ASTM C920 is a specification that defines performance requirements for elastomeric joint sealants, ensuring durability, flexibility, and reliable sealing in structures exposed to environmental and mechanical stresses.

The standard covers elastomeric sealants including silicone, polyurethane, and polysulfide, commonly used for sealing joints in construction and infrastructure applications.

Adhesion testing ensures that the sealant bonds effectively to substrates, preventing failure, leakage, or detachment under stress or environmental exposure.

Type S sealants are single-component, while Type M are multi-component systems, differing in curing mechanisms and application requirements.

The standard includes weathering, adhesion, and mechanical tests to ensure sealants can withstand environmental exposure and maintain performance over time.