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Unit Weight: Definition, Test Procedure, and Calculation for Aggregate Materials, Study notes of Chemistry

Morrisville State CollegeChemistry

An in-depth explanation of unit weight, its significance, and the test procedure for determining loose unit weight and dry rodded unit weight. It also covers bucket calibration and adjusting unit weight for moisture. Useful for civil engineering students for determining bulk density values, inventory control, and mass/volume relationships.

Typology: Study notes

2021/2022

Uploaded on 09/12/2022

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UnitWeight
UnitWeight
SignificanceandUse
•Oftenusedtodeterminebulkdensityvalues
usedinselectingproportionsforconcrete
mixes
•Alsousedformass/volumerelationshipsfor
conversionsinpurchaseagreements
•Alsousedannuallyforinventorycontroland
verification
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pf9
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Download Unit Weight: Definition, Test Procedure, and Calculation for Aggregate Materials and more Study notes Chemistry in PDF only on Docsity!

Unit Weight

Unit Weight

Significance and Use

  • Often used to determine bulk density values

used in selecting proportions for concrete

mixes

  • Also used for mass/volume relationships for

conversions in purchase agreements

  • Also used annually for inventory control and

verification

Unit Weight

Definition

  • Unit Weight is the weight per unit volume of a

material.

Unit Weight = Weight of Material

Volume of Material

Example: U.W. = 103.2 lbs = 103.2 pcf

1 cf

Loose Unit Weight

Loose Unit Weight

Loose Unit Weight

Dry Rodded Unit Weight Test Procedure

  • For nominal maximum size of 1½” (37.5 mm) or less, use rodding procedure.
  • For nominal maximum size greater than 1½” (37.5 mm), use jigging procedure.
  • Record weight of empty bucket (to the nearest 0.1 lbs or 0.05 kg).
  • Dry aggregate sample to a constant mass.
  • Fill bucket ⅓ full with dried aggregate.
  • Level surface with fingers.

Dry Rodded Unit Weight Test Procedure

Dry Rodded Unit Weight Test Procedure

Dry Rodded Unit Weight Test Procedure

  • Fill bucket to overflowing.
  • Repeat leveling and rodding procedure.
  • Level final aggregate surface with fingers or a straight edge. - Make any slight projections of larger pieces of aggregate approximately balance the larger voids in the surface.
  • Record weight of bucket and sample.
  • Calculate unit weight and % voids of dry rodded aggregate.

Dry Rodded Unit Weight Test Procedure

Dry Rodded Unit Weight Test Procedure

Dry Rodded Unit Weight Test Procedure

Dry Rodded Unit Weight Test Procedure

Unit Weight Bucket Calibration

  • Volume of bucket must be calibrated at least once per year. - Place a thin layer of grease around the rim of the bucket to prevent water leakage. - Record combined weight of empty bucket and plate glass (to the nearest 0.1 lbs or 0.05 kg).

Unit Weight Bucket Calibration

  • Bucket volume calibration, cont’d
    • Fill bucket with water and cover with plate glass.
      • Leave no bubbles or excess water.
      • Wipe off any overflow water.
    • Record combined weight of bucket, water, and plate glass (to the nearest 0.1 lbs or 0.05 kg).

Unit Weight Bucket Calibration

  • Bucket volume calibration, cont’d.

A = Weight of empty bucket + plate

B = Weight of water‐filled bucket + plate

C = Unit Weight of water at measured

temperature

Bucket Volume = B – A

C

Unit Weight Bucket Calibration

  • Example:
    • Weight of empty bucket + plate = 1.8 lbs
    • Weight of water‐filled bucket + plate = 34.2 lbs
    • Temperature of water in bucket = 70 °F
      • UW of water at 70 °F = 62.301 pcf (from Table 1) Bucket Volume = (34.2 lbs – 1.8 lbs) 62.301 pcf Bucket Volume = 0.52 cf

Adjusted Unit Weight % Moisture

  • Record weight of wet aggregate sample
  • Dry sample to a constant mass
  • Calculate %moisture of sample:
    • %Moisture = (Wet Wt. – Dry Wt.) x 100 Dry Wt.

Adjusted Unit Weight % Moisture

  • Example:
    • Weight of wet sample = 125.0 lbs
    • Weight of dry sample = 117.9 lbs

% M = (125.0 lbs – 117.9 lbs) x 100 117.9 lbs % Moisture = 6.0%