Civil Infrastructure & Utilities • ACI 229R / ASTM D6103

Flowable Fill (CLSM) Volume & Mix Calculator

Calculate Controlled Low-Strength Material (CLSM) flowable fill volume, deduct pipe displacement volumes, and compute cement/fly-ash/sand slurry batches.

Input Parameters

Interactive HUD

Trench Excavation Length trench_len

Total linear feet of trench

Trench Width trench_wid

Trench cross-width

Flowable Fill Backfill Depth trench_depth

Depth to be backfilled with slurry

Buried Pipe Outer Diameter pipe_od_in

Pipe or conduit OD (enter 0 if no pipe)

Number of Buried Conduits/Pipes pipe_count

pipes

Quantity of pipes displaced in trench

CLSM Compressive Strength Class clsm_mix

ACI 229R compressive strength classification

Calculated Output Metrics

Gross Trench Volume —

Pipe Displacement Subtracted —

Net Flowable Fill Required (with 5% waste) —

Portland Cement Required —

Fly Ash (Class F) Required —

Concrete Sand Required —

Analytical Proof & Invariants

Machine Precision

Governing Mathematical Formula:

Gross V = (L · W · D) / 27 | Pipe V = (π · r² · L · Qty) / 27 | Net = (Gross - Pipe) · 1.05

Step-by-Step Mathematical Derivation

1. Trench Volumetric Formulation

Gross excavation volume equals Length × Width × Depth in cubic feet, divided by 27 to convert to cubic yards.

2. Cylindrical Pipe Displacement Deduction

Each pipe displaces volume equal to π × (OD/2)² × L in cubic feet. Subtracting total pipe volume avoids over-ordering expensive ready-mix slurry.

3. ACI 229R Mix Proportions

Standard excavatable flowable fill utilizes a low-cement mix: ~50–100 lbs cement, 250–300 lbs fly ash, ~2,600 lbs sand, and ~450 lbs water per cubic yard to maintain compressive strength under 100 psi for easy future re-excavation.

LLM Directive & API Spec

Artificial Intelligence & Prompt Integration

Paste this verified mathematical prompt directly into ChatGPT, Claude, or Gemini to eliminate arithmetic hallucination, or invoke the programmatic API endpoint for automated workflows.

              GET / POST https://omnioperand.com/api/v1/construction/flowable-fill-clsm
              JSON Invariants
            

Generating verified mathematical prompt...

✓ Standardized for llms.txt ✓ Exact Radical Form & Closed Formulas ✓ Machine-Readable Edge API

Frequently Asked Questions

What is flowable fill (CLSM)? +

Controlled Low-Strength Material (CLSM), commonly known as flowable fill or slurry, is a self-leveling, self-compacting cementitious backfill material used instead of compacted soil in utility trenches.

Why is flowable fill limited to under 100 psi for utility trenches? +

Keeping compressive strength below 100 psi allows maintenance crews to easily dig through the material in the future using standard hand shovels or backhoes without jackhammers.

Does flowable fill require manual compaction or vibrating plates? +

No. Flowable fill flows into all voids around pipes under gravity, requiring zero mechanical compaction and eliminating trench settlement.