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D1985-13 – Standard Test Method Technical Guide
ASTM D1985-13 (Reapproved 2024) establishes a uniform procedure for preparing concrete blocks used for testing joint and crack sealants for portland cement concrete and asphaltic concrete pavements. It is intended for use by manufacturers, users, and testing agencies to ensure consistent and comparable test results across different laboratories and projects by standardizing the substrate material.
📜 Scope and Significance
The scope of this practice covers the preparation of concrete blocks specifically designed for evaluating sealants used in pavement joints and cracks. By defining a standardized substrate, this practice eliminates variability introduced by different concrete compositions, allowing sealant tests to focus on properties such as adhesion, cohesion, and extensibility. The standard states that values in SI units are to be regarded as the standard. It is developed in accordance with internationally recognized principles on standardization.
🧱 Concrete Block Composition and Mix Design
The mix design detailed in Section 5 of the standard is strictly controlled to ensure uniformity. The aggregates must conform to Specification C33/C33M, with specific restrictions: the coarse aggregate must be crushed limestone (over 95% CaCO₃) with a water absorption of no more than 1.5%. The fine aggregate must also be crushed limestone manufactured from the same parent rock. The cement must be Type I/II conforming to C150/C150M. Table 1 summarizes the exact mix parameters required for the fresh concrete per Section 5.1.
| 🟦 Parameter | 📐 Specification | 📏 Tolerance |
|---|---|---|
| Water-Cement Ratio | 0.49 | — |
| Cement Factor | 335 kg/m³ (6.0 bags/yd³) | ± 30 kg/m³ (0.5 bags/yd³) |
| Slump | 63 mm (2.5 in.) | ± 13 mm (0.5 in.) |
| Fine Aggregate Ratio | 40% (by solid vol.) | Approximate |
| Air Content | 5.0% | ± 0.5% |
⚠️ Critical Aggregates Requirement: The fine aggregate must be crushed limestone from the same parent rock as the coarse aggregate. This is required to provide a consistent, chemically compatible surface for sealant adhesion testing. Natural sand is not permitted as a fine aggregate substitute under this practice.
🌡️ Standard Conditioning and Preparation Procedures
Standard laboratory conditions must be maintained throughout preparation and testing. Per Section 4.1, the laboratory atmosphere must be in accordance with Practice E171/E171M. The concrete itself must be mixed and cured according to the procedure described in Practice C192/C192M. The specified air content is achieved by the addition of an air-entraining agent to the batch. Table 2 provides the official conditioning requirements.
| 🎯 Standard Condition | ⚡ Required Value | 📏 Reference Method |
|---|---|---|
| Temperature | 23 ± 2 °C (73.4 ± 3.6 °F) | Practice E171/E171M |
| Relative Humidity | 50 ± 5% | Practice E171/E171M |
| Concrete Mixing & Curing | Standard laboratory procedure | Practice C192/C192M |
💡 Alternate Block Materials: Section 5.1.1 of the standard does allow for the use of alternate block materials. However, any deviation from the primary materials specified in Section 5.1 must be clearly documented. Users should verify that the specific sealant test method being employed permits the use of alternate block materials.
❓ Frequently Asked Questions
🔍 Why is the fine aggregate required to be crushed limestone?
The standard requires fine aggregate to be crushed limestone from the same parent rock as the coarse aggregate to ensure a consistent, non-reactive surface texture and chemical composition. This eliminates variables in sealant adhesion tests that natural sands could introduce.
💡 What is the purpose of the strict slump and air content tolerances?
The specified slump (63 ± 13 mm) and air content (5.0 ± 0.5%) ensure the concrete block has a consistent surface density, permeability, and texture. This minimizes test variability when evaluating sealant bond strength or extensibility.
⚡ Which ASTM standards are referenced for mixing and curing the concrete?
The standard mandates using Practice C192/C192M for making and curing the concrete test specimens. The cement must meet C150/C150M (Type I/II), and aggregates must meet C33/C33M plus the specific limestone gradation and composition requirements.
📌 What are the standard laboratory conditions required for preparing these blocks?
As per Section 4.1, the laboratory atmospheric conditions must be in accordance with Practice E171/E171M, which specifies a temperature of 23 ± 2 °C (73.4 ± 3.6 °F) and a relative humidity of 50 ± 5%.