Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D5971 – Standard Test Method Technical Guide
ASTM D5971/D5971M−16 establishes the standardized procedure for obtaining a representative sample of freshly mixed Controlled Low-Strength Material (CLSM) as delivered to a project site. This practice is essential for verifying compliance with project specifications and ensuring material quality before placement.
🎯 Scope and Application of D5971
This practice details the method for taking representative samples of freshly mixed CLSM. It specifically covers sampling operations from revolving-drum truck mixers and agitating equipment used to transport central-mixed CLSM. The procedures outlined in this standard are fundamentally based on Practice C172 for sampling freshly mixed concrete, adapted here for the unique rheological and material properties of CLSM.
The standard emphasizes that composite samples are required unless specific test procedures governing uniformity of consistency or mixer efficiency dictate otherwise. It is recommended that random sampling techniques be employed to determine overall specification compliance effectively. The values stated in either SI units or inch-pound units are to be regarded separately as standard, and combining values from the two systems may result in non-conformance.
⚠️ Safety Warning: Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure. Appropriate safety and health practices, including the use of gloves, eye protection, and skin coverings, must be strictly followed during all sampling operations as noted in the standard.
⚙️ Sampling Procedure and Equipment Requirements
To ensure a truly representative sample, the standard mandates the collection of a composite sample obtained from several portions of the batch throughout the discharge process. The entire procedure is heavily reliant on the principles established in Practice C172. Practitioners should note that this practice does not describe the procedures used to select specific test batches, but rather focuses strictly on the method of obtaining the representative sample from the delivery equipment.
The following table outlines the key ASTM standards referenced within D5971 that support the comprehensive sampling and testing framework:
| 🟦 Designation | 📏 Role in Sampling and Testing |
|---|---|
| Practice C172 | Primary basis for the sampling procedure of freshly mixed concrete adapted for CLSM. |
| Test Method D4832 | Specifies the procedures for the preparation and testing of CLSM test cylinders from the sampled material. |
| Test Method D6023 | Provides the gravimetric method for determining density (unit weight), yield, cement content, and air content. |
| Practice D3740 | Defines the minimum requirements for agencies engaged in the testing and inspection of soil and rock. |
💡 Tip for Practitioners: When sampling, remember that composite samples are the standard requirement. However, tests specifically designed to determine the uniformity of consistency or mixer efficiency may require individual or separate samples. Always verify the specific test requirements for the material being placed before conducting the sampling.
📊 Key Terminology and Material Properties
Understanding the precise definition of Controlled Low-Strength Material (CLSM) as presented in D5971 is critical for proper sampling. CLSM is formally defined as a mixture of soil, aggregates (sand, gravel, or both), cementitious materials, water, and sometimes admixtures. It is designed to harden into a material with a higher strength than the native soil, but with a strict upper strength bound. The table below summarizes these critical definitional parameters:
| 📐 Parameter | 🎯 Specification / Limit |
|---|---|
| Maximum Strength Threshold | Less than about 8400 kPa (1200 psi) |
| Primary Constituents | Soil, aggregates, cementitious materials, water, admixtures |
| Intended Application | Replacement for compacted backfill in structural fills |
| Physical Placement States | Typically placed as a slurry, a mortar, or a compacted material |
❓ Frequently Asked Questions
🔍 Upon which standard is the ASTM D5971 sampling procedure based?
The sampling procedure in ASTM D5971 is directly based on Practice C172, Standard Practice for Sampling Freshly Mixed Concrete, but it has been specifically adapted for the unique fluid and material characteristics of CLSM.
⚡ What is the specific upper strength limit that defines a material as CLSM?
According to the terminology section of the standard, CLSM is defined as a material that hardens to a strength higher than soil but strictly less than about 8400 kPa (1200 psi).
💡 Is a single “grab” sample sufficient for standard quality assurance compliance testing?
No. The standard explicitly requires composite samples for compliance testing unless the specific test being performed (e.g., uniformity of consistency or mixer efficiency) dictates otherwise. A composite sample ensures a representative average of the entire batch of delivered CLSM.
📌 What types of delivery equipment are specifically covered under this sampling practice?
This practice specifically covers sampling from both revolving-drum truck mixers and agitating equipment used to transport central-mixed CLSM to the project site.