A method keeping total alkali content and maximizing water supply for concrete prism test of potential expansion by ASR

Late expansions due to alkali-silica reaction were observed in field samples for some aggregates and supplementary cementing materials (SCM) combinations despite meeting the 2-year expansion criterion of the concrete prism test. This fosters a research into the effect of sample geometry and aggregate reactivity on alkali leaching and expansion of lab samples. Larger samples showed less leaching compared to standard prisms. Cylinders of 100 mm-diameter showed higher expansion than 75 mm-standard prisms; however, both sample shapes showed similar expansions for one tested aggregate when used with SCM. Alkali leaching from concrete samples and alkali release from some aggregates could lead to cylindrical samples having higher expansion and better correlation to field samples compared to standard concrete prisms.

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Teaching Practice of Analytical Chemistry Laboratory Based on Heuristic Teaching Method: Taking the Determination of Total Alkali Content in Soda Ash as an Example

Daxue Huaxue ◽

10.3866/pku.dxhx201709003 ◽

2018 ◽

Vol 33 (1) ◽

pp. 21-23

Author(s):

Xia LIU ◽

Keyword(s):

Analytical Chemistry ◽

Teaching Practice ◽

Teaching Method ◽

Chemistry Laboratory ◽

Alkali Content ◽

Total Alkali ◽

Soda Ash

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Reliability of Miniature Concrete Prism Test in Assessing Alkali-Silica Reactivity of Moderately Reactive Aggregates

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120912247 ◽

2020 ◽

Vol 2674 (4) ◽

pp. 23-29

Author(s):

Harish Konduru ◽

Prasad Rangaraju ◽

Omar Amer

Keyword(s):

False Positive ◽

Standardized Test ◽

False Negative ◽

Test Method ◽

Test Procedures ◽

Concrete Prism ◽

Coarse Aggregates ◽

Fine Aggregates ◽

Mortar Bar ◽

Concrete Prism Test

Alkali-silica reaction (ASR) is one of the most significant durability issues in concrete structures. Although there are a number of standardized test procedures to evaluate the aggregate reactivity, each method has its own drawbacks. Two of the most common tests that are employed widely are the accelerated mortar bar test (AMBT) (ASTM C1260) and the concrete prism test (CPT) (ASTM C1293). The major issue with the AMBT test is the number of false-positive results from this test associated with high test temperature, rendering the test method unreliable. CPT is one of the most reliable tests for assessing the potential for ASR, but its major disadvantage is the duration of the test involved, which takes one to two years. In this research, a novel test method called the miniature concrete prism test (MCPT) was developed and the effectiveness and reliability of the results assessed when compared with CPT and AMBT. Samples of 26 coarse aggregates and 16 fine aggregates with various reactivity levels were employed for the testing. The test results were compared for MCPT versus CPT, in which 23 out of 26 coarse aggregates and eight out of 16 fine aggregates either passed or failed in both MCPT and CPT. For MCPT versus AMBT, 16 out of 26 coarse aggregates and 13 out of 16 fine aggregates either passed or failed in both MCPT and AMBT. The sensitivity of false-negative and false-positive aggregate sources is discussed and explained briefly.

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