Geosynthetic Clay Liner Tips: Types and Swelling Index
Geosynthetic Clay Liner (GCL) is a highly effective waterproofing material mainly composed of high-molecular polymers and natural bentonite. When bentonite particles come into contact with water, they expand and form a dense impervious layer. Whether used as the primary impermeable barrier or as a secondary waterproof layer, it ensures engineering safety.
The key performance indicator of bentonite’s swelling ability is the Swelling Index (mL/2g), which refers to the volume increase of a unit weight of bentonite after free water absorption. The higher this index, the more water the GCL can “block,” and the thicker the “barrier wall” it forms.
(Zhonglong's Sodium Bentonite)
According to the international standard ASTM D5890 and the Chinese construction industry standard JG/T193-2006, high-quality bentonite used in GCLs should have a swelling index of ≥ 24 mL/2g. However, not all bentonite-based waterproof blankets can achieve this swelling index. The comparison is shown in the table below:
Bentonite Types and Characteristics
|
Bentonite Type |
Primary Exchangeable Cations |
Swelling Index (mL/2g) |
Swelling Pressure (kPa) |
Characteristics & Applications |
|---|---|---|---|---|
|
Sodium Bentonite |
Na⁺ (Sodium Ion) |
High, typically ≥ 20;premium products can reach 30-40 or higher |
Very high, can reach hundreds or even thousands |
Best waterproofing performance.The preferred material for manufacturing GCL (Bentonite Waterproof Blanket). |
|
Calcium Bentonite |
Ca²⁺ (Calcium Ion) |
Low, typically < 10 |
Relatively low |
Poor waterproofing performance. Generally used in foundry (molding sand), animal feed, and other fields. |
|
Activated Bentonite |
Artificially processed |
Between Sodium and Calcium bentonite |
Adjustable |
Produced by activating calcium bentonite with soda ash. Performance is inferior to natural sodium bentonite. |
According to this table, different types of bentonite exhibit varying swelling indices. Among them, sodium-based bentonite shows the best performance and is the most suitable for waterproofing applications.
Zhonglong is equipped with advanced GCL production lines, and our products meet the ≥ 24 mL/2g standard, and even up to ≥30 mL/2g in usual test, which fully satisfies the requirements of various waterproofing projects.
（Zhonglong's GCL production lines）
(Zhonglong's GCLs Technical Parameter)
Related product: https://www.zhonglonggeo.com/geosynthetic-clay-liner-1/
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