Suppliers of materials shall be required to furnish certified test reports for cement, aggregates, admixtures, curing materials, reinforcing and prestressing steel, and hardware mat erials, indicating that these materials comply with the applicable ASTM standards, project specifications, and plant standards.
C6.2.2 Acceptance Testing of Materials
In some instances, materials may not conform to nationally recognized specifications but may have a long history of satisfactory performance. Such nonconforming materials are permitted when acceptable evidence of satisfactory performance is provided and approved by the architect/engineer.
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Standard Commentary
Page 6.4 MNL-116 4th Edition
1. Cement.
If mill certificates are not supplied, representative testing of each shipment of cement is required before use. The mill certificate shall contain the alkali content in percent expressed as Na2O equivalent. Mill certificates or test reports of cement shall be kept on file in the plant for at least five years after use. Characteristics of special cements not conforming to ASTM C150 shall be investigated prior to use to be certain that they do not exhibit undesirable attributes of high slump loss, strength retrogression, plateau strength, or other aberrations under typical casting and curing conditions.
1. Cement.
Mill test reports should be reviewed for changes from previous reports. Lower concrete strength should be expected from: lower cube strength;
lower C3S; lower fineness; higher percent retained on No. 325 sieve (45 mm); and higher loss on ignition. Increase in total alkali may reduce concrete strength gain after seven days and impair the strength-producing efficiency of water-reducing admixtures. Variation in the color of gray cement may in part be traced to a variable Fe2O3 content (a 2% variation in Fe2O3 being significant).
An additional report is available from cement producers which allows the concrete producer to evaluate cement strength uniformity (ASTM C917).
The data will show 7- and 28-day cube strengths with a five day moving average and standard deviation. It is suggested that precasters routinely obtain these reports for the previous 6 to 12 months to monitor consistency of cube strengths.
If the tricalcium silicate (C3S) content varies by more than 4% from the mean values used in mix design confirmation tests, the ignition loss varies by more than 0.5%, or the fineness by more than 375 cm2/g, Blaine (ASTM C204), then problems in maintaining a uniform high strength may result.
Sulfate (SO3) variations should be limited to
± 0.20%.
Until project acceptance, it is good practice to keep a 10- to 15-lb sample of each cement shipment (composite from 2 or 3 subsamples) in an airtight and moisture-proof container with a minimum air space over the sample to check color and strength development, if necessary.
2. Aggregates.
Fine and coarse aggregates shall be regarded as separate ingredients. Aggregates shall conform to ASTM C33 or C330 required design specifications. The grading requirements (only) of ASTM C33 or C330 shall be waived or modified to meet the required design specifications. Sieve analysis, in accordance with ASTM C136, shall be conducted on samples taken from the initial shipment received at the plant. Specific gravity, absorption, and petrographic analysis performed within the past five years shall be obtained from the supplier prior to the time of
2. Aggregates.
Sampling of stockpiles or conveyor belts for aggregates should be in accordance with ASTM D75. Once a sample has been taken, the sample should be mixed and then quartered in accordance with ASTM C702. Once the sample has been reduced to a test size, testing should follow ASTM C136. Sieve analysis tests are required to ensure uniformity of materials received and to check consistency of gradation with the aggregate supplier’s reported sieve analysis, taking into account expected changes in gradation that may be caused by rough handling in shipment.
first usage, when a new lift or horizon in a quarry is utilized, or there appears to be a change in quality of the aggregate.
Specific gravity and absorption of normal weight coarse aggregate should be determined according to ASTM C127 and for fine aggregate according to ASTM C128.
The specific gravity and absorption of an aggregate are used in certain computations for mixture proportioning and control, such as the absolute volume occupied by the aggregate. These values are not generally used as a measure of aggregate quality, though some porous aggregates that exhibit accelerated freeze-thaw deterioration do have low specific gravities.
Petrographic analysis should be made in accordance with ASTM C295 to ensure that selected aggregates are durable, inert, and free from iron sulfide (pyrite) and other deleterious materials. Favorable results of petrographic examination may eliminate the need for alkali reactivity tests. The frequency of testing will vary depending on the nature of the source of the aggregate.
The specific gravity of lightweight aggregate shall be determined in accordance with procedures described in ACI 211.2, Appendix A - Pycnometer Method. The oven-dry loose unit weight (ASTM C29) of the lightweight aggregate shall be determined. A maximum 10% change in unit weight of successive shipments from a sample submitted for acceptance tests is allowed.
For some relatively smooth-surface, lightweight coarse aggregates, regular specific gravity and absorption procedures by ASTM C127 can be used;
however, a lid is needed on the basket used in the test to confine floating pieces.
Lightweight aggregates should be ordered with specification restrictions. Uniformity of specific gravity and dry loose unit weight is an important concern for lightweight concrete. However, some sources do not consistently provide this material within a reasonable set of limits; therefore, adjustments in mix proportions may be required as properties change. Suppliers should forward gradation analyses and specific weight tests of the material with all initial shipments. The specific weight test or weight of specific volume should be performed on each shipment so adjustments in batching can be made as the material changes in specific gravity from that assumed in the mix design.
Evaluation of aggregates for potential alkali-silica or alkali-carbonate reactions (excessive expansion, cracking, or popouts in concrete) shall be based on at least 15 years of exposure to moist conditions of structures made with the aggregate in question, if available, or petrographic examination (ASTM C295) to characterize aggregates and determine the
When possible, aggregates should be evaluated from past performance in concrete, taking into account the alkali content of the cements used, whether the aggregate was used alone or in combination with another aggregate, and the exposure conditions and age of the concrete.
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Standard Commentary
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presence of potentially reactive components. If an aggregate is found to be susceptible to alkali-silica reaction using ASTM C295, it shall be evaluated further using ASTM C1260 and CSA A23.2-14A. Aggregates which exhibit ASTM C1260 mean mortar bar expansion at 14 days greater than 0.10% shall be considered potentially reactive. Aggregates further evaluated by CSA A23.2-14A that exhibit mean concrete prism expansion greater than 0.04% at one year shall be considered potentially reactive. Aggregate sources exhibiting expansions no more than 0.04% and demonstrating no prior evidence of reactivity in the field shall be considered nonreactive.
Reliance shall not be placed on results of only one kind of test in any evaluation.
If an aggregate is judged to be susceptible to alkali-carbonate reaction using ASTM C295, it shall be evaluated further for alkali-carbonate reaction in accordance with ASTM C586 or ASTM C1105.
Tests for deleterious substances and organic impurities shall be done at the start of a new aggregate supply and annually thereafter, unless problems are encountered requiring more frequent testing.
Staining due to iron sulfide generally becomes noticeable after a period of time in service due to moisture and oxidation from exposure to the atmosphere.
3. Water.
Water shall be potable, or chemically analyzed when a private well or nonpotable water is used in the concrete mix. Except for water from a municipal supply, an analysis of the water shall be on file at the plant, updated annually, and clearly related to the water in use.
Seawater or other sources of water that contain concentrations of substances known to be deleterious to concrete shall not be used.
Mortar cubes made in accordance with ASTM C109 using nonpotable or questionable mixing water shall have 7-day strengths equal to at least 90% of the strengths of companion specimens made with potable or distilled water.
Time of set (ASTM C191) for mortar made with questionable water may vary from one hour earlier to 1-1/2 hours later than the control sample made with potable or distilled water.
Water resulting in greater variations shall not be used.