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D5385 – Standard Test Method Technical Guide
📐 Specimen Geometry and Preparation
The test substrate consists of precast concrete patio blocks with a minimum density of 2000 kg/m³ [125 lb/ft³] and minimum compressive strength of 14.5 MPa [2100 psi]. Each block measures 191±12 by 394±12 by 57±6 mm [7½±½ by 15½±½ by 2¼±¼ in.] and is smooth-surfaced.
A kerf approximately 3.2 mm [⅛ in.] wide and 44 mm [1¾ in.] deep is cut lengthwise down the center of the block on the side opposite to membrane application. At least three blocks are prepared per membrane. Blocks and all other materials are conditioned at 23±2°C [73±4°F] for at least 24 hours and 4 hours, respectively, before testing. Deviations in test temperature must be reported.
| 🟦 Specification | 📏 Value |
|---|---|
| Block Density | 2000 kg/m³ min [125 lb/ft³ min] |
| Compressive Strength | 14.5 MPa min [2100 psi min] |
| Block Dimensions | 191×394×57 mm [7½×15½×2¼ in.] |
| Kerf Width | 3.2 mm [⅛ in.] |
| Kerf Depth | 44 mm [1¾ in.] |
⚙️ Apparatus and Test Conditions
Required apparatus includes a hydrostatic testing chamber with clamping bracket, gasket, and fasteners. A compressed air source provides pressure up to 690 kPa [100 psi] and is regulated in 103-kPa [15-psi] increments. The conditioning room maintains temperature within ±2°C [±4°F] of the test temperature with forced-air circulation.
The membrane is applied to the prepared block surface after priming and curing per manufacturer instructions. The test detects hydrostatic resistance through a post-formed crack, which forms and widens behind the membrane after application.
💡 Ensure the conditioning room maintains temperature within ±2°C [±4°F] of the designated test temperature for accurate results. Alternate temperatures may be used but must be reported.
| 🟦 Parameter | 📐 Specification |
|---|---|
| Air Pressure Source | Up to 690 kPa [100 psi] |
| Pressure Increments | 103 kPa [15 psi] |
| Conditioning Temperature | 23±2°C [73±4°F] |
| Temperature Variation | ±2°C [±4°F] max |
📊 Significance and Limitations
This test method compares the hydrostatic resistance of waterproofing membranes under standard conditions. It is not intended for systems relying on seam confinement by backfill. The test uses a defined post-formed crack to simulate service conditions.
⚠️ No correlation has been established between this laboratory test and field performance. Results should be evaluated with this limitation in mind.
Key terminology: a post-formed crack is one that forms and widens behind the membrane after application and curing, as defined in the standard.
❓ Frequently Asked Questions
🔍 Scope: What does this test method cover?
It measures hydrostatic resistance of waterproofing membranes under controlled lab conditions, but excludes systems that depend on backfill confinement.
💡 How are test blocks prepared?
Precast concrete blocks are cut with a kerf and conditioned at 23°C for 24 hours. The membrane is applied after priming as per manufacturer recommendations.
⚡ What equipment is needed for this test?
Hydrostatic testing equipment, compressed air source with regulator, conditioning room, cut-off saw, and silicone vacuum grease among other items.
📌 Can this test predict real-world performance?
No, the standard clearly states that no correlation has been established between this test method and field performance.