Tex-400-A, Sampling Stone, Gravel, Sand, and Mineral Aggregates

Transcription

1 Mineral Aggregates Contents: Section 1 Overview...2 Section 2 Definitions...3 Section 3 Securing Representative Field Samples...4 Section 4 Record Form...5 Section 5 Sample Size...6 Section 6 Sampling Procedures...7 Texas Department of Transportation 1 08/99 12/09

2 Section 1 Overview Section 1 Overview Effective Dates: August 1999 December This method describes procedures for sampling stone, gravel, sand and synthetic aggregates including shell, slag, riprap, and/or mineral filler for preliminary investigations of material sources, for quality testing of materials from sources, and for testing of materials at the mixing plant or project site. Samples are to be selected by TxDOT personnel or by an authorized representative. Field sample size should be according to the 'Size of Field Samples' table. Units of Measurement The values given in parentheses (if provided) are not standard and may not be exact mathematical conversions. Use each system of units separately. Combining values from the two systems may result in nonconformance with the standard. Texas Department of Transportation 2 08/99 12/09

3 Section 2 Definitions Section 2 Definitions The following term and definition is referenced in this test method: Hot bins - Hot bins are aggregate bins that feed directly into the weight-box or the proportioning mechanism. Texas Department of Transportation 3 08/99 12/09

4 Section 3 Securing Representative Field Samples Section 3 Securing Representative Field Samples The sampler must obtain samples that show the true nature and condition of the materials that they represent. Do not combine materials that apparently differ in property or character to make a composite sample. Differences may be indicated by color or texture. Samples taken from a quarry or pit for a source investigation may be taken from various existing layers or strata, and the samples should be combined in proper proportion to represent the entire pit face that will be processed in the same operation. Use sampling tubes where experience has indicated representative samples can not be obtained otherwise. Sample fine aggregates (sands) with tubes of at least 31.5 mm (1-1/4 in.) diameter, and coarse aggregates, up to 19.0 mm ( 3/4 in.), with tubes of 100 mm (4 in.) diameter. The method of sampling will depend on the place, the quantity of the material, and the proposed treatment and tests to be performed in the laboratory. Where practical, take samples of the finished product from commercial plants. Preferably, obtain samples from cars or trucks during the loading of the materials. NOTE: Sampling must be done by an authorized TxDOT representative. Texas Department of Transportation 4 08/99 12/09

5 Section 4 Record Form Section 4 Record Form Identify samples on Form 202, "Identification of Material Samples." In addition to the general information accompanying all samples, show the: name of the producer name of the pit or quarry producer code number location of the stockpile sampled (pit, HMAC or concrete plant, project, etc.) approximate quantity of the material in the stockpile or unit sampled specification item number. Texas Department of Transportation 5 08/99 12/09

6 Section 5 Sample Size Section 5 Sample Size The required sample size depends upon the maximum aggregate size and the number and types of tests to be performed. The size of field samples should conform to the 'Size of Field Samples' table. The field sample is reduced to the laboratory test size by means of a sample splitter or quartering cloth. Texas Department of Transportation 6 08/99 12/09

7 Section 6 Sampling Procedures Section 6 Sampling Procedures Riprap Obtain 4 to 6 pieces of riprap representative of the proposed material. Reduce the entire sample to a maximum particle size of 150 mm (6 in.). Submit approximately 50 kg (110 lb.) of the material retained on the 4.75 mm (No. 4) sieve. From Bins or Belts For preliminary investigation work, sample aggregates in their natural condition prior to plant processing. If the materials are being fed to the plant from bins, the sample shall be obtained from the collector belt after materials have passed the scalping screen. The preferred method of sampling from the belt is a mechanical belt sampling device approved by the engineer. This method does not require the belt to be stopped, but simply diverts the flow of aggregate for a designated period of time where the sample is collected. When mechanical devices are not used, the belt must be stopped prior to sampling, and the sample should be taken from the entire width of the belt and at least one meter of the length, using a square-nosed scoop. After the aggregate is removed, all fines should be brushed from the exposed section of the belt using a stiff bristled brush, and added to the sample. From Stockpiles NOTE: Segregation often occurs when material is stockpiled. For mixed coarse and fine aggregate or coarse aggregate alone, make every effort to use power equipment to develop a separate small sampling pile. Compose the sampling pile of the materials drawn from the various levels and locations in the main stockpile. If power equipment is not available, compose the field sample of three or more increments taken from the top third, midpoint and bottom third of the volume of the sampling pile. Dig a small trench or hole into the pile and take the sample from the innermost part of the hole. Texas Department of Transportation 7 08/99 12/09

8 Section 6 Sampling Procedures A board shoved vertically into the stockpile just above the sampling hole aids in preventing segregation during sampling. Do not use the aggregate on the surface (3 to 4 particles deep) as part of the sample. If determination of the degree of variability of the main stockpile is desired, retain the increments as individual samples. From Railroad Cars and Trucks Excavate at least three trenches across the width, evenly spaced across the length of the bed. Each trench bottom should be approximately 0.3 m (1 ft.) in width and 0.3 m (1 ft.) in depth. Take samples from at least three locations equally spaced along the length of the trench and combine all samples to create a single field sample as directed in Test Method "Tex-100-E, Surveying and Sampling Soils for Highways." From the Plant Make a general inspection of the plant and a record of the screening facilities. For a weigh-batching type plant, take samples from the aggregate bins that feed into the weigh-box. For a continuous mix type plant, take samples from the aggregate bins that feed the proportioning mechanism. For a drum type plant, take samples from the collector belt feeding the aggregate into the drum. When an aggregate flow diversion chute is not available, stop the feed belt prior to obtaining the sample. Take samples from the entire cross-section of the flow of material from each individual bin as it is being discharged. Prior to sampling, permit the plant to produce a minimum of 4.5 Mg (5 tons) of mixture. Texas Department of Transportation 8 08/99 12/09

9 Section 6 Sampling Procedures The following table indicates the size of field samples. Size of Field Samples Nominal Maximum Size Of Particles* Approximate Minimum Mass Of Field Samples, kg (lb) 2.00 mm (No. 10) 10 (25) 4.75 mm (No. 4) 10 (25) 9.5 mm (3/8 in.) 10 (25) 12.5 mm (1/2 in.) 15 (35) 19.0 mm (3/4 in.) 25 (55) 25.0 mm (1 in.) 50 (110) 37.5 mm (1-1/2 in.) 75 (165) 50.0 mm (2 in.) 100 (220) 63.0 mm (2-1/2 in.) 125 (275) 75.0 mm (3 in.) 150 (330) * For processed aggregate, the nominal maximum size of particles is the largest sieve size listed in the applicable specification upon which any material is permitted to be retained. NOTE: The sample for test shall be obtained from the field sample by quartering or splitting. Texas Department of Transportation 9 08/99 12/09