This standard is issued under the fixed designation C ; the number immediately 1 This test method is under the jurisdiction of ASTM Committee C09 on. All the Controls products ASTM C standard. Enter now!. Originally approved in Last previous edition approved in as C – 05a. 2 For referenced ASTM standards, visit the ASTM website,
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It is important to understand the benefits and deficiencies offered by various testing procedures. ASR can be avoided with a proper concrete mix design.
That is, if you have questions about the durability of your concrete, save some samples and leave them exposed to the elements. The alkali content of cement is not a significant factor in affecting the expansion.
Filling in the Blanks on Alkali-Silica Reaction
Petrography may be used to classify an aggregate as potentially reactive, but expansion testing is required to determine the extent of the reactivity and appropriate levels of prevention. Your email address will not be published. Metal atoms lose the electron, or electrons, in their highest energy level and become positively charged ions. For ASR to occur, four things must be present: Petrographic examination can conclusively identify ASR.
Highly reactive aggregate tended to be more sensitive to cement fineness and alkalinity. This new ASTM standard and related AASHTO provisional standard provides detailed protocols and guidelines using previous ASR testing data, petrography and historical performance to provide a prescriptive decision-making process for mitigation.
Development of a more economical and more abundant admixture may be the future for ASR mitigation. Comments Frank, Great article that gives a simplified overview of ASR, expansion testing, and mitigation techniques. C is used to test the reactivity potential of aggregates, while C includes the use of secondary cementitious materials within the mortar bar samples to determine the effective reduction of ASR.
Alkali metals, for example, which are found in the far left column of the periodic table, have a single electron in their outermost band. The same goes for calcium, but since it is in the second column of the periodic table, it must lose two electrons for this to happen. As stated earlier, many precasters will not have issues with ASR. Overall, ASR is characterized primarily by four main features: Non-metal atoms gain an electron, or electrons, from another atom to become negatively charged ions.
Consequently, the two tests are often run together.
Skip to main content. Search Enter search terms: If you can read like a chemist, it looks like this: What we do know, however, is important for precasters to understand. Atoms are comfortable with themselves when they are fully loaded on that outer band.
Although cement fineness and clinker alkali content did not affect the classification astn terms of potential reactivity of the aggregates used in this study, they might change the classification for the aggregates near the boundary between reactive and nonreactive aggregates. Cracking usually appears in areas with a frequent supply of moisture.
Ask your aggregate provider first for test results before asmt a laboratory.
APPLICATION OF MODIFIED ASTM C1260 TEST FOR FLY ASH-CEMENT MIXTURES
While the fundamental physical and chemical reactions remain poorly understood, it is well known that ASR destroys the durability of concrete and can cause serious maintenance and reconstruction costs. This test is similar to C with a testing period of 14 days. However, C takes one year to perform when evaluating aggregate reactivity, or two years when evaluating c12660 efficacy of SCMs to mitigate deleterious expansion.
This test exposes specimens to a solution of sodium hydroxide NaOH. Frank Bowen, a Master Precaster graduate, received his M. Federal Highway Administration, fhwa.
Great article that gives a simplified overview of ASR, expansion testing, and mitigation techniques. This is all critical to ASR to show where the reactivity is taking place. Lithium compounds have also been used, but they may be cost-prohibitive and limited in availability. When dealing with ASR, a process that takes place over decades, accelerated tests should be conducted with bias.
Keep in mind that some cements contain a higher proportion of potassium sulfate K 2 SO 4 than sodium sulfate Na 2 SO 4. These empty voids, when created, allow the gel to migrate into the cracks. A petrographic examination of aggregate will give a comprehensive description of the aggregate source and quantify the various rock and mineral constituents present.
If ASR has been identified by the specifying authority within the region, it is recommended that precast producers perform long-term testing on concrete samples.
This method aastm one of the best ways to see ASR happen if you intentionally use aggregates with a high silica content like glass in concrete. The results show that mortar-bar expansion was promoted with increased cement fineness regardless of clinker alkali, aggregate reactivity, or soak solution normality. This makes them highly reactive.
Photo provided by Frank Bowen.
ASTM C Standard
Signs of ASR are typically random map-cracking and spalled concrete. Specification of fineness and alkali content of cement, or both, might be beneficial to further improve the reliability and reproducibility of ASTM C However, this chemical approach, which alters the reaction gel to a less expansive nature, has us in what I feel to be the right direction.
In addition to the standard 1 N NaOH solution, a 0. If you compare this with the composition of your aggregates, you should give yourself a pat on the back.