Grain Size Analysis (Sieve + Hydrometer) in North Las Vegas

ASTM D422 and ASTM D7928 govern grain size distribution testing, and in North Las Vegas both standards matter equally because the subsurface transitions from coarse alluvial fans near the Sheep Range to fine lacustrine silts toward the Las Vegas Wash. The mechanical sieve captures the sand and gravel fraction, while the hydrometer resolves the silt and clay that control drainage, frost susceptibility, and expansion potential. For a city that added over 100,000 residents since 2000 and keeps pushing infrastructure north of the 215 Beltway, knowing the full particle-size curve isn't optional. Our lab runs both methods on every sample from North Las Vegas so the USCS classification comes out complete, whether the material is a clean sand for a warehouse pad or a borderline clayey silt that needs stabilization. When the hydrometer reading shows more fines than the field log suggested, the Atterberg limits test confirms whether those fines are silt or active clay, and for roadway subgrades the CBR for road design ties the gradation directly to pavement thickness.

In North Las Vegas, a hydrometer curve that shows 15 percent clay versus 5 percent can be the difference between a mat foundation and a deep foundation.

Our approach and scope

A tilt-up distribution center near Losee Road and the 215 sat on a mapped Qal2 deposit that looked like uniform sand in the test pit, but the combined sieve-plus-hydrometer run revealed 28 percent fines passing the No. 200 sieve, all of it low-plasticity silt. That single data point changed the subgrade modulus input for the slab-on-grade. The sieve stack gives us D10, D30, D60, Cu, and Cc in about 48 hours. The hydrometer adds the minus-200 fraction over another 24 hours, reading density at 40 seconds, 2 minutes, 5 minutes, 15 minutes, 30 minutes, 60 minutes, 250 minutes, and 1440 minutes. We run the dispersing agent blank and temperature correction on every cylinder because North Las Vegas tap water chemistry varies enough between Zone 1 and Zone 2 supply lines to shift the readings. For projects that need compaction control alongside gradation, the sand cone density test verifies field density against the Proctor maximum derived from the same material's grain-size curve.

Site-specific factors

We use an eight-inch diameter mechanical sieve shaker with brass frames and stainless mesh, paired with a constant-temperature water bath for the hydrometer cylinders. The bath sits at 20°C plus or minus 0.5°, which matters in North Las Vegas because the lab ambient can swing from 68°F at 7 a.m. to 95°F by mid-afternoon in August. A cylinder left on the bench instead of the bath will give a fines percentage off by three to five points. The hydrometer itself is a Type 152H calibrated at 68°F, and we check the meniscus correction weekly. Skipping the wash-sieve step on a desert soil that looks clean but contains caliche fines is the most common error we see from out-of-town labs. Those fines act as a binder in the field, and missing them leads to an overestimated permeability that shows up later as ponding on graded pads.

Technical data

Parameter	Typical value
Sieve method	Mechanical shaking per ASTM D422 / D6913
Hydrometer method	ASTM D7928, 152H hydrometer, 40 g/L sodium hexametaphosphate
Sieve range	3 in (75 mm) down to No. 200 (75 µm)
Hydrometer range	0.075 mm to approximately 0.001 mm
Sample mass (coarse)	500 g to 20 kg depending on maximum particle size
Sample mass (fines)	50 g dry mass passing No. 10 sieve for hydrometer
Reporting	Semi-log plot, USCS group symbol, D-values, Cu, Cc
Turnaround	3 to 5 working days standard; 48-hour expedited available

Complementary services

Full Sieve + Hydrometer Package

Combined mechanical sieve per ASTM D6913 plus hydrometer per ASTM D7928 on a single split sample. Delivers the complete particle-size distribution curve, D10-D30-D60, Cu, Cc, and USCS classification with group symbol and group name.

Wash Sieve Only (Minus No. 200 Content)

A rapid determination of the percent passing the No. 200 sieve by wet washing. Used for field screening during grading operations when the full hydrometer curve isn't needed yet, typically 24-hour turnaround.

Aggregate Gradation for Concrete and Asphalt

Sieve analysis of coarse and fine aggregate per ASTM C136 and ASTM C117 for ready-mix concrete and asphalt mix design. Includes gradation charts overlaid on specification envelopes.

Standards used

ASTM D422 — Standard Test Method for Particle-Size Analysis of Soils (withdrawn, still referenced), ASTM D6913 — Standard Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis, ASTM D7928 — Standard Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis, ASTM D2487 — Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System), IBC 2024 Section 1803 — Geotechnical Investigations

Common questions

What is the cost of a grain size analysis with sieve and hydrometer in North Las Vegas?

The combined sieve-plus-hydrometer package typically runs between US$90 and US$160 per sample in North Las Vegas. The exact cost depends on whether the material is predominantly sand or contains a high fines fraction that requires extended hydrometer readings, and on turnaround time.

How long does the hydrometer test take compared to the sieve analysis?

The mechanical sieve analysis is completed within 24 to 48 hours including oven-drying. The hydrometer adds another full day because readings continue over a 24-hour period, plus the time for the dispersing agent blank and calculations. Standard reporting is 3 to 5 working days; we offer a 48-hour expedite for an additional fee.

Why does North Las Vegas soil need hydrometer testing if it looks sandy in the field?

Many North Las Vegas soils are alluvial deposits that contain fine silt and clay lenses from historic wash flooding. These fines are not visible to the naked eye in a hand sample but significantly affect drainage, frost heave potential, and the soil's reaction to vibration. The hydrometer quantifies the minus-200 fraction so the engineer can apply the correct USCS classification and design parameters.

Do you report the results using the USCS system?

Yes, every grain size report includes the Unified Soil Classification System group symbol and group name per ASTM D2487. We also provide the semi-logarithmic grain-size distribution plot, the D10, D30, and D60 values, and the coefficients of uniformity (Cu) and curvature (Cc).