aggregate quality tests batching plant
Quality Checks for Batching-Plant Aggregates: Sieve Analysis, Specific Gravity, Absorption, LA Abrasion, Soundness and the Supplier Test Certificate
Sieve analysis, specific gravity, absorption, LA abrasion and soundness for batching-plant aggregates, and what a supplier test certificate must show.
Aggregates make up most of the volume of a cubic metre of concrete. When a plant's strengths drift, its yield comes up short or its slabs crack, the aggregate is the first place to look. This guide explains the core tests, what the numbers mean in the mix, how often to run them, and what a supplier's test certificate has to show before it is worth the paper.
Why aggregate testing pays for itself
A batching plant buys aggregate by volume or weight but sells concrete by strength, slump and finish. Gradation and fines drive water demand, slump loss and shrinkage. Specific gravity and absorption drive yield and the moisture corrections that keep the water–cement ratio where the design put it. Abrasion and soundness drive durability: dusting, pop-outs and scaling in pavements and exposed slabs. Testing is cheap next to a rejected pour.
Sampling: the test is only as good as the sample
Follow ASTM D75 for field sampling and ASTM C702 for reducing the sample to test size. Take increments from several points around and into the stockpile, not from the segregated toe or the crusted surface. For a truck delivery, sample during unloading or from the pile immediately after, and record the truck, date, source and stockpile; most disputes between plant and supplier start with two different samples.
Sieve analysis and fines
Tests: ASTM C136 (AASHTO T 27) for gradation, with ASTM C117 (AASHTO T 11) to wash out the material finer than 75 µm first.
What it gives: percentage passing each sieve, the fineness modulus for sand, and the fines content.
What to compare it to: the ASTM C33 envelope for the size number or for fine aggregate, or the requirements of the DPWH aggregates item named in the contract. ASTM C33 requires the fineness modulus of successive sand deliveries to stay within 0.20 of the value used in the mix design.
What a drift means: more passing 4.75 mm in the gravel means an over-sanded mix and lower slump for the same water; fines above the limit mean higher water demand, weaker paste bond and shrinkage cracks. The method and the specification envelopes are in the guide on aggregate gradation for DPWH specifications.
Specific gravity and absorption
Tests: ASTM C127 (AASHTO T 85) for coarse aggregate; ASTM C128 (AASHTO T 84) for fine aggregate.
What it gives: relative density (specific gravity) on an oven-dry and a saturated-surface-dry (SSD) basis, apparent relative density, and absorption as a percentage of dry mass.
Why the plant needs it: the mix design converts masses into volumes using the SSD relative density. A wrong value gives a wrong yield: a cubic metre that is really 0.97 m³ shows up as short loads. Absorption is the base for the daily moisture correction: sand delivered at 6% moisture with 1% absorption carries 5% free water that must come out of the batch water.
Reading it: values vary with the rock type; a high absorption is a durability warning and should prompt a soundness test.
Los Angeles abrasion
Test: ASTM C131 (AASHTO T 96) for coarse aggregate smaller than 37.5 mm; ASTM C535 for larger sizes.
What it does: tumbles a graded sample with steel balls in a drum and reports the percentage that breaks down to finer than the 1.70 mm sieve.
Limits: ASTM C33 allows up to 50% loss for concrete coarse aggregate. The DPWH concrete and base course items set their own limits, which are tighter for concrete; take them from the item in your contract.
Reading it: a high loss means the aggregate breaks down in handling and mixing and wears faster in pavements. Note the test grading used (A, B, C or D); results from different gradings are not directly comparable.
Soundness
Test: ASTM C88 (AASHTO T 104), sodium or magnesium sulfate, five cycles of immersion and drying.
What it does: simulates weathering by growing salt crystals in the pores and reports the mass lost.
Limits: ASTM C33 sets a weighted average loss of 10% (sodium sulfate) or 15% (magnesium sulfate) for fine aggregate and 12% or 18% for coarse aggregate. DPWH concrete items carry their own soundness limits; read the contract item.
Reading it: a high loss identifies aggregate that will spall, pop out or disintegrate under wet–dry cycling, the normal condition of a slab in the tropics. Soundness is the durability test most often missing from a certificate, and the one most worth insisting on for pavements and exposed work.
Other checks that catch real problems
| Check | Standard | Why it matters |
|---|---|---|
| Unit weight and voids | ASTM C29 | Volumetric batching and yield checks |
| Moisture content | ASTM C566 | Daily batch-water correction |
| Clay lumps and friable particles | ASTM C142 | Weak spots, pop-outs; C33 limits by exposure class |
| Organic impurities | ASTM C40 | Retarded set and low strength from humic matter in sand |
| Flat and elongated particles | ASTM D4791 | Harsh mixes, low strength; limited by some specifications |
| Water-soluble chloride | ASTM C1218 | Corrosion risk from sea-derived sand |
| Alkali–silica reactivity | ASTM C1260, C1293, C295 | Long-term expansion in reactive aggregates |
How often to test
A workable schedule for a plant in continuous production; on government work follow the contract's minimum testing requirements where they are stricter.
| Test | Frequency |
|---|---|
| Moisture content | Daily, or per shift when weather changes |
| Sieve analysis and fines | Weekly per stockpile, and on every delivery from a changed source |
| Specific gravity and absorption | On qualification of each source and every 3–6 months |
| LA abrasion and soundness | On qualification of each source and at least annually, or per volume interval in the specification |
| Chloride, ASR | On qualification of coastal or unfamiliar sources; as the designer requires |
Plot results over time. A gradual drift toward a limit is the signal to talk to the source before the stockpile fails.
What a supplier test certificate should show
A useful certificate answers who tested what, from where, when, how and against which limit. At minimum:
- Laboratory identity and accreditation. For government work, a laboratory accredited by DPWH through its Bureau of Research and Standards; DPWH's own laboratories offer the same tests (grading, material finer than the No. 200 sieve, specific gravity and absorption, abrasion, soundness, organic impurities, unit weight) under a published schedule of fees.
- Report number and date of issue.
- Client and source: the supplier, the quarry or river with its location, and the permit holder where applicable.
- Material description: product name, nominal size and intended use, matching the delivery receipts.
- Sampling details: date, location (stockpile, truck or crusher belt), method and who sampled.
- Test methods by designation and year.
- Results with units, alongside the specification limits and a pass/fail statement for each.
- Test grading for abrasion and the salt used for soundness.
- Signatures of the technician and the reviewing engineer, and the laboratory's seal.
- Lot or stockpile identification tying the certificate to the deliveries it covers.
That is the standard to hold a certificate to, not a description of what every source has on the shelf. Some yards hold a full recent set, some hold one old sieve analysis, and some hold nothing. Ask which of these reports exist for the product you are buying, and how recent they are, before the order — a missing result is a test to commission and pay for, not a formality to waive.
Reading a certificate: red flags
- No sampling information. A result with no sample date, location or method may describe a different pile.
- Old date. A certificate from a previous year describes the source as it was then; sources change with the quarry face and the river.
- Unwashed sieve analysis on a material with a fines limit, or specific gravity without absorption.
- Only the tests that pass. A certificate for pavement aggregate with no soundness result is incomplete, not clean.
When a certificate raises questions, split a sample and test it at a laboratory of your choosing.
How Stone Depot Trading helps
Stone Depot Trading coordinates B2B sourcing and supply of limestone, sand, gravel and fly ash through trade partner companies from General Santos City. State the tests and limits your specification requires up front — for example "sieve analysis, abrasion and soundness from a DPWH-accredited laboratory, dated within six months" — and that requirement is put to the partner source before quotation rather than after delivery (see aggregates for a concrete batching plant).
What comes back is an answer, not a promise made in advance. Which reports a source can supply depends on the material, the source, the supplier, your project specification, the testing arrangement and the agreed order requirements, and a test that has not been run has to be commissioned and paid for. That answer is given before you order, so the documentation position is known while it can still change the decision.
FAQ
Which aggregate tests are essential for a batching plant?
Sieve analysis with washed fines, moisture content, specific gravity and absorption, and for durability, LA abrasion and soundness. Add chloride and reactivity tests for coastal or unfamiliar sources and long-life structures.
What is a good LA abrasion value?
Lower is better. ASTM C33 allows up to 50% loss for concrete coarse aggregate; DPWH concrete items set a tighter limit, and many plants prefer a comfortable margin below whichever limit applies.
Why does specific gravity matter if I batch by weight?
Because the mix design converts weights into a cubic metre using the relative density. A wrong value means short yield or wrong proportions even when the scales are perfect.
Can Stone Depot Trading provide test results?
Not of its own: it runs no laboratory and issues no certificates. Tell us which tests and limits your specification requires and the source is asked what it holds or can produce, with the answer given before you order. Availability depends on the material, the source, the specification and the testing arrangement. See the FAQ for other common questions.
Request a quote
Send the material, the size or gradation, the tests and limits required, the quantity, the delivery location and the schedule through the quote form, by email to cjandulana@stonedepotph.com, or by call or Viber to +63 945 643 5233. Submitting an inquiry starts a sourcing conversation; it does not create a binding order.
Sources
- ASTM C33/C33M, Standard Specification for Concrete Aggregates — ASTM International (https://store.astm.org/c0033_c0033m-18.html)
- ASTM C136/C136M, Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates — ASTM International (https://store.astm.org/c0136_c0136m-19.html)
- ASTM C117, Standard Test Method for Materials Finer than 75-μm (No. 200) Sieve in Mineral Aggregates by Washing — ASTM International (https://store.astm.org/c0117-23.html)
- ASTM C127, Standard Test Method for Relative Density (Specific Gravity) and Absorption of Coarse Aggregate — ASTM International (https://store.astm.org/c0127-15.html)
- ASTM C128, Standard Test Method for Relative Density (Specific Gravity) and Absorption of Fine Aggregate — ASTM International (https://store.astm.org/c0128-22.html)
- ASTM C131/C131M, Standard Test Method for Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine — ASTM International (https://store.astm.org/c0131_c0131m-20.html)
- ASTM C88/C88M, Standard Test Method for Soundness of Aggregates by Use of Sodium Sulfate or Magnesium Sulfate — ASTM International (https://store.astm.org/c0088_c0088m-18.html)
- ASTM D4791, Standard Test Method for Flat Particles, Elongated Particles, or Flat and Elongated Particles in Coarse Aggregate — ASTM International (https://store.astm.org/d4791-19.html)
- ASTM C1218/C1218M, Standard Test Method for Water-Soluble Chloride in Mortar and Concrete — ASTM International (https://store.astm.org/c1218_c1218m-20.html)
- Department Order No. 69, Series of 2015, Revised Schedule of Fees and Charges for Laboratory Testing of Construction Materials — Department of Public Works and Highways (https://web.archive.org/web/20160127155720/http://www.dpwh.gov.ph/doing_business/accreditation/pdf/mat_test_lab/DO_069_S2015.pdf)
- Application for Assessment as DPWH Accredited Private Testing Laboratory (BRS Form No. 1) — DPWH Bureau of Research and Standards (https://web.archive.org/web/20120816121113/http://www.dpwh.gov.ph/doing_business/accreditation/mat_test_lab/GUIDELINES_lab.pdf)
- DPWH Standard Specifications for Highways, Bridges and Airports, Volume II (2013 edition) — Department of Public Works and Highways
Disclaimer
This article is general information. Final suitability of any material must be confirmed against the buyer's project specifications, the approved mix design, laboratory test results and the project engineer's requirements. Stone Depot Trading coordinates sourcing and supply; it does not certify materials or guarantee acceptance by any agency.