Long Term Pavement Performance Project Laboratory Materials Testing and Handling Guide

Protocol P46
Test Method for Resilient Modulusof Unbound Granular Base/Subbase Materials and Subgrade Soils (UG07, SS07)

APPENDIX A
SAMPLE PREPARATION

The following provides guidelines for reconstituting the material to be tested so as to produce a sufficient amount of material needed to prepare the appropriate sample type (Type 1 or Type 2 sample) at the designated moisture content and density.

1. SAMPLE CONDITIONING

If the sample is damp when received from the field, dry it until it becomes friable. Drying may be in air or by use of a drying apparatus such that the temperature does not exceed 60°C (140°F). Then thoroughly break up the aggregations in such a manner as to avoid reducing the natural size of individual particles. Moderate pressure and a 4.75-mm (No. 4) sieve have been found to be adequate to break down clay lumps.

2. SAMPLE PREPARATION

2.1 Determine the moisture content (w₁) of the sample as per LTPP Protocol P49. The sample moisture content shall weigh not less than 200 g (0.44 lb) for samples with a maximum particle size smaller than the 4.75-mm (No. 4) sieve and not less than 500 g (1.1 lbs) for samples with a maximum particle size greater than the 4.75-mm (No. 4) sieve.

2.2 Determine the appropriate total volume (V) of the compacted specimen to be prepared. The total volume must be based on a height of the compacted specimen slightly greater than that required for resilient testing to allow for trimming of the specimen ends if necessary. Compacting to a height/diameter ratio of 2.1 to 2.2 will provide adequate material for this purpose.

2.3 Determine the weight of oven-dry soil solids (W_s) and water (W_w) required to obtain the desired dry density (Υ_d) and moisture content (w) as follows:

• W_s (pounds) = Υ_d(pounds per cubic foot) ¤ V (cubic feet)
• W_s (grams) = W_s (pounds) ¤ 454
• W_w (pounds) = W_s (pounds) ¤ w (÷/100)
• W_wo (grams) = W_w (pounds) ¤ 454

2.4 Determine the total weight of the prepared material sample (W_t) required to obtain W_s to produce the desired specimen volume V at dry density Υ_d and moisture content w.

• W_t (grams) = W_s ¤ (1 + w/100)

2.5 Determine the weight of the dried sample (W_ad), with the moisture content (w₁), required to obtain W_s, including an additional amount W_as of at least 500 grams (1.1 lbs) to provide material for the determination of moisture content at the time of compaction.

• W_ad (grams) = (W_s + W_as) ¤ (1 + w₁/100)

2.6 Determine the weight of water (W_aw) required to increase the weight from the existing dried weight of water (W₁) to the weight of water (W_w) corresponding to the desired compaction moisture content (w).

• W₁ (grams) = (W_s + W_as) ¤ (w₁/100)
• W₂ (grams) = (W_s + W_as) ¤ (w/100)
• W_aw (grams) = W₂ - W₁

2.7 Place the sample (W_ad) determined in 7.3.7 into a mixing pan.

2.8 Add the water (W_aw) to the sample in small amounts and mix thoroughly after each addition.

2.9 Place the mixture in a plastic bag. Seal the bag and place it in a second bag and seal it.

2.10 After mixing and storage at a minimum of overnight and a maximum of two days, weigh the wet soil and container to the nearest gram and record this value on the appropriate form (see Worksheet T46).

2.11 The material is now ready for compaction.