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The pressure method uses one of two devices: the A meter or the B meter. Both of these meters rely on the relationship between pressure and volume to determine the air content of a concrete mixture. The pressure methods are not suitable for testing the air content of lightweight aggregate concrete and other porous aggregate concretes, as they would measure the air void system of the aggregates and not just the air content of the paste in the mixture. The A meter is sensitive to altitude and must be calibrated to accommodate the altitude at which it will be used, while the B meter uses the change in pressure of a known volume of air and is not affected by altitude variations.
The volumetric method requires the removal of air from a known volume of concrete by agitating the concrete in an excess of water. This test is typically used for lightweight and porous aggregate concrete mixtures. Care must be taken to assure that the sample has been agitated sufficiently to remove all of the air from the sample.
The gravimetric method is a comparison of the actual unit weight of the concrete versus the theoretical weight of all of the concrete constituents. The actual specific gravity of all the materials in the mixture must be known to avoid errors with this method. It can be used as a convenient way to assure against variation in air contents as significant changes to the unit weight would identify a change in the air content of the mixture.
Table: Test Methods for Alkali-Silica Reactivity (Source: Farny and Kerkhoff, 2007)
|
Test Name |
Purpose |
Type of Test |
Duration of Test |
Comments |
| ASTM C 227, |
To test the susceptibility of cement-aggregate combinations to expansive reactions involving alkalies |
Mortar bars stored over water at 37.8°C (100°F) and high relative humidity |
Varies: first measurement at 14 days, then 1, 2, 3, 4, 6, 9, and 12 months; every 6 months afterthat as necessary |
Test may not produce significant expansion, especially for carbonate aggregate. Long test duration. Expansions may not be from AAR. |
| ASTM C 289, |
To determine potential reactivity of siliceous aggregates | Sample reacted with alkaline solution at 80°C (176°F). | 24 hours | Quick results. Some aggregates give low expansions even though they have high silica content. Not reliable. |
| ASTM C 294, |
To give descriptive nomenclature for themore common or important natural minerals—an aid in determining their performance | Visual identification |
Short duration—as long as it takes to visually examine the sample |
These descriptions are used to characterize naturally-occurring minerals that makeup common aggregate sources. |
|
ASTM C 295, |
To outline petrographic examination procedures for aggregates—an aid indetermining their performance | Visual and microscopic examination of prepared samples—sieve analysis, microscopy, scratch or acid tests | Short duration—visual examination does not involve long test periods | Usually includes opticalmicroscopy. Also may include XRD analysis, differential thermal analysis, or infrared spectroscopy—see ASTM C 294 for descriptive nomenclature. |
|
ASTM C 342, |
To determine the potential ASR expansion of cement-aggregate combinations | Mortar bars stored in water at 23°C (73.4°F) | 52 weeks | Primarily used for aggregates from Oklahoma, Kansas, Nebraska, and Iowa. |
ASTM C 441, |
To determine effectiveness of supplementary cementing materials in controlling expansion from ASR | Mortar bars—using Pyrex glass as aggregate—stored over water at 37.8°C (100°F) and high relative humidity | Varies: first measurement at 14 days, then 1, 2, 3, 4, 5, 9, and 12 months; every 6 months after that as necessary | Highly reactive artificial aggregate may not represent real aggregate conditions. Pyrex contains alkalies. |
ASTM C 856, |
To outline petrographic examination procedures for hardened concrete—useful in determining condition or performance | Visual (unmagnified) and microscopic examination of prepared samples | Short duration — includes preparation of samples and visual and microscope examination | Specimens can be examined with stereomicroscopes,polarizing microscopes, metallographic microscopes, and scanning electron microscope. |
ASTM C 856 (AASHTO T 299), |
To identify products of ASR in hardened concrete | Staining of a freshly-exposed concrete surface and viewing under UV light | Immediate results | Identifies small amounts of ASR gel whether they cause expansion or not.Opal, a natural aggregate, and carbonated paste can glow—interpret results accordingly.Tests must be supplemented by petrographic examination and physical tests for determining concrete expansion |
| Los Alamos staining method(Powers 1999) | To identify products of ASR in hardened concrete. | Staining of a freshly-exposedconcrete surface with two different reagents. | Immediate results | |
ASTM C 1260 (AASHTO T303), |
To test the potential for deleterious alkali-silica reaction of aggregate in mortar bars | Immersion of mortar bars in alkaline solution at 80°C (176°F) | 16 days | Very fast alternative to C 227. Useful for slowly reacting aggregates or those that produce expansion late in the reaction. |
ASTM C 1293, |
To determine the potential ASR expansion of cement-aggregate combinations. | Concrete prisms stored over water at 38°C (100.4°F) | Varies: first measurement at 7 days, then 28and 56 days, then 3,6,9,and 12 months; every 6 months as after that as necessary | Preferred method of assessment. Best represents the field. Requires long test duration for meaningful results. Use as a supplement to C 227,C 295, C 289, and C 1260. Similar to CSA A23.2-14A. |
| ASTM C 1567, Potential
alkali-silica reactivity of combinations of cementitious materials
and aggregate (accelerated mortar-bar method) |
To test the potential
for deleterious alkali-silica reaction of cementitious materials
and aggregate combinations in mortar bars |
Immersion of mortar
bars in alkaline solution at 80°C (176°F) |
16 days |
Very
fast alternative to C 1293. Allows for evaluation of effectiveness
of supplementary cementitious materials. |
Rebound hammers test the surface hardness of concrete, which cannot be converted directly to compressive strength. ASTM C 805-97, Standard Test Method for Rebound Number of Hardened Concrete, states that "because of the inherent uncertainty of estimating strength with a rebound number, the test is not intended as the basis for acceptance or rejection of concrete."
There are many factors other than concrete strength that influence rebound hammer test results, including surface smoothness and finish, moisture content, coarse aggregate type, and the presence of carbonation. Although rebound hammers can be used to estimate concrete strength, the rebound numbers must be correlated with the compressive strength of molded specimens or cores taken from the structure. The procedure used to develop this relationship is described in ACI 228.1R-03, In-Place Methods to Estimate Concrete Strength, American Concrete Institute.
While UL is a good
source of information for fire safety of products, there is no code
requirement for UL numbers regarding concrete and masonry construction
assemblies. Fire ratings for non-proprietary concrete and masonry
construction assemblies are determined based on the end point criteria
established in ASTM E 119. This standard specifies the intensity
of the fire, the size of the specimen, and the criteria for determining
the end point of the test.
These criteria require that:
(1) the structure support its design load
throughout the test without passage of flame or hot gases, and
(2) the temperature of the unexposed surface (i.e., the surface
not exposed to the fire) not rise more than 139°C (250°F) as an
average nor 181°C (325°F) at any one point.
Extensive testing over many years led to the development of procedures
to calculate the fire ratings of walls, slabs, beams, and columns
constructed of concrete or masonry. The variables required for these
calculations are unit density of the concrete (unit weight), aggregate
type, and the section thickness for nonflexural
elements. For flexural members the variables are unit density, aggregate
type, section thickness, restraint conditions, and provisions for
clear cover requirements for steel reinforcement.
In addition there are methods for calculating the fire resistance of flanged, ribbed and undulating sections, hollow concrete and masonry sections, slabs and walls of multiple layers of distinctly different concrete materials, multi-wythe masonry walls, concrete and masonry fire protection assemblies for steel columns, and the effect of finish materials applied to the fire exposed side of these assemblies.
See the table below for details. For example, a 4
in. masonry wall at 18 lb/ft2 would be rated at 40, while
the same thickness of wall with a weight of 27 lb/ft2
would have a rating of 45. An example of a painted wall (both sides)
weighing 22 lb/ft2 is rated at 43.
Source: IS159
- United States Bureau of Reclamation, “Method of Test for Determining the Quantity of Water-Soluble Sulfate in Solid (Soil and Rock) and Water Samples.”
- Canadian Standards Association (CSA) Test Method A23.2-3B, “Determination of Total or Water-Soluble Sulphate Ion Content of Soil.”
- California Department of Transportation (Caltrans) Test Method 417, “Testing Soils and Waters for Sulfate Content.”
- ASTM International (ASTM) C1580, “Test Method for Water-Soluble Sulfate in Soil.”
The methods differ in extraction ratio, extraction duration, and
sample preparation. Key characteristics of the four test methods
are summarized in Table 1.
| Table 1. Characteristics of Test Methods for Water-Soluble Sulfate in Soils | ||||
Test Method |
Sample Drying Method |
Measurement Technique |
Extraction Ratio Water:Soil (mL:g) |
Precision and Bias |
| USBR (May 1, 1973) |
Air dry | Electrical resistivity (total sulfate screen) andGravimetric |
10:1 (or higher if gypsum is present) agitated for at least 6 hr. | N/A |
| CSA A23.2-3B (2000) | Air dry at room temperature and humidity | Gravimetric (total SO4 screen and soluble sulfate) | [9 x (%SO4 by acid-soluble method)]:1 agitated for 6 hr. | N/A |
| Caltrans 417 (2006) | Not stated in test method | Ion chromatography or Gravimetric (soluble SO4) |
3:1 agitated for 15 min. | N/A |
| ASTM C1580 (April 2005) |
18 to 24 h @ 110°C | Turbidimetric or ASTM C 114 (soluble SO4) | ~8:1 and ~80:1 agitated for one hr. | 4.4% COV-S 21.2% COV-M |
- The USBR test method is not well suited to specifications for concrete structures. Critical provisions are not defined in “specification language” that would be enforceable in contracts or clear in dispute resolution cases. Also, the method does not have a limit on the permitted extraction ratio, nor does it require that the extraction ratio used is reported.
- The Caltrans method (California Test 417) is an internal method developed by the California Department of Transportation. The 3:1 extraction ratio is the lowest of the four methods and consistently gave the lowest results for water-soluble SO4.
- The CSA method (A23.2-3B) is a consensus method used in Canadian standards for concrete structures. It includes a “built in” screening mechanism whereby total acid-soluble sulfate is first measured. If the total sulfate value is 0.2% or less, no further testing is required. This screening method is efficient and useful. The extraction ratio is variable, defined as a function of the total sulfate level.
- The ASTM method (C1580) is also a consensus method. The method uses two extraction ratios with limiting ranges for values determined at the different extraction and aliquot levels based on sulfate solubility calculations. An advantage of the ASTM method is that sample preparation, especially the drying temperature, which can have a significant impact on the sulfate content of a soil, is clearly defined. The ASTM method gave consistently higher water-soluble SO4 results than the USBR method. The method is written in mandatory language suitable for specifications and is the only method that contains a precision statement.