U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
REPORT |
This report is an archived publication and may contain dated technical, contact, and link information |
|
Publication Number: FHWA-HRT-13-085 Date: October 2013 |
Publication Number: FHWA-HRT-13-085 Date: October 2013 |
For this study, the researchers chose aggregate sources that would provide a range of alkali reactivity for assessment using the NIRAS technique. The aggregate sources were selected after discussion with the teams at Clemson University and University of Texas at Austin, as well as with input from members of Federal Highway Administration’s Technical Working Group on ASR. Some of the same aggregate sources were examined by while maintaining a range of alkali reactivity.
The reactivity of the aggregates, shown in their “as received” condition in figure 8, figure 9, figure 10 through figure 13, was initially assessed by AMBT. Each of the aggregates was crushed, when necessary, to fit the grading requirements prescribed in ASTM C1260. The dimensions of mortar bars created were 1 by 1 by 11.25 inch(es) (25 by 25 by 285 mm). For each mix design, three samples were created. The samples were cured at about 100-percent relative humidity and 73.4 °F (23 °C) for 24 hours. After demolding, the samples were cured for an additional 24 hours while immersed in tap water at 176 °F (80 °C). The initial length measurements were performed after this curing period. ASR was then induced in the mortar bars by immersing them in a 1N sodium hydroxide (NaOH) solution at 176 °F (80 °C). The samples were removed from the NaOH solution at regular intervals for expansion measurements as prescribed by ASTM C1260.
Table 1 presents the average expansion of the three samples at 14 days. Again, these results were used as an initial means for assessing the reactivity of the individual aggregates used in the concrete prisms. According to ASTM C1260, expansion at the end of the test that is less than 0.10 percent indicates innocuous behavior, expansion greater than 0.20 percent indicates potentially deleterious expansion, and expansion between 0.10 and 0.20 percent may be innocuous or deleterious in field behavior.
In this research, all specimens for evaluation by NIRAS and CPT were cast according to the ASTM C1293 standard. The mix design matrix, described in table 2, was developed to examine a range of ASR behavior, including the combination of two non-reactive aggregates (Mix 1), and the use of aggregates termed here as “moderately to highly reactive” (HR) and “potentially (or may be) reactive” (MR) aggregates, each in combination with the same non-reactive aggregate (NR). (The nonreactive aggregate used in all the mix designs is a limestone from Adairsville, GA.) Considering the ASTM C1260 results, along with historical aggregate standard test results and field performance history of these aggregates, each of the aggregates was preliminarily classified as NR, MR, or HR. Table 2 gives these classifications, along with other details about the concrete prism mixtures, including the sample naming scheme.
In addition, an ASTM C150 Type I cement with alkali equivalent of 0.88 percent, meeting the ASTM C1293 requirements, was used in the casting of CPT samples; the alkali content of the concrete was “boosted” to 1.25 percent by mass cementitious materials, in accordance with the standard.
Table 3 summarizes the physical and chemical properties of this cement.
Figure 8. Photo. Las Placitas gravel aggregate as received
Figure 9. Photo. Spratt limestone aggregate as received
Figure 10. Photo. Adairsville limestone (coarse) aggregate as received
Figure 11. Photo. Adairsville limestone (fine) aggregate as received
Figure 12. Photo. Alabama sand aggregate as received
Figure 13. Photo. Illinois gravel aggregate as received
Table 1. ASTM C1260 results for the aggregates examined
Aggregate Source |
14-day AMBT Expansion (percent) |
AMBT Classification |
---|---|---|
Limestone, GA |
0.0787 |
Innocuous |
Las Placitas, NM gravel |
0.8533 |
Potentially deleterious |
Spratt limestone, Canada (crushed) |
0.2661 |
Potentially deleterious |
Alabama sand, AL |
0.1555 |
Innocuous or potentially deleterious |
Central Illinois sand, IL |
0.2088 |
Potentially deleterious |
Table 2. Mix design matrix for NIRAS and ASTM C1293 concrete prisms
Mix ID |
Coarse Aggregate |
Fine Aggregate |
Supplementary Cementing Materials |
---|---|---|---|
Mix 1 NR/NR |
Limestone, GA |
Limestone, GA |
— |
Mix 2 HR/NR |
Las Placitas, NM gravel |
Limestone, GA |
— |
Mix 3 NR/HR |
Limestone, GA |
Las Placitas, NM gravel (crushed) |
— |
Mix 4 HR/NR |
Spratt limestone, Canada |
Limestone, GA |
— |
Mix 5 NR/HR |
Limestone, GA |
Spratt limestone, Canada (crushed) |
— |
Mix 6 NR/MR |
Limestone, GA |
Alabama sand, AL |
— |
Mix 7 NR/MR |
Limestone, GA |
Central Illinois Sand, IL |
— |
Mix 8 HR/NR—25% FA |
Spratt limestone, Canada |
Limestone, GA |
25% Class F FA |
Mix 9 NR/HR—25% FA |
Limestone, GA |
Spratt limestone, Canada(crushed) |
25% Class F FA |
Mix 10 NR/HR—25% FA |
Las Placitas, NM gravel |
Limestone, GA |
25% Class F FA |
NR = nonreactive
MR = potentially or “may be” reactive
HR = moderately to highly reactive
FA = fly ash
— = no supplementary cementing materials
Table 3. Chemical analysis data for Type I cement
Chemical Requirements ASTM C114 |
Test Result, |
Specification Limits |
---|---|---|
Silicon Dioxide (SiO2) |
19.11 |
— |
Aluminum Oxide (Al2O3) |
4.99 |
— |
Ferric Oxide (Fe2O3) |
3.55 |
— |
Calcium Oxide (CaO) |
60.66 |
— |
Magnesium Oxide (MgO) |
3.24 |
— |
Sulfur Trioxide (SO3) |
3.96 |
3.0 maximum |
Ignition Loss |
2.71 |
3.0 maximum |
Insoluble Residue |
0.24 |
0.75 maximum |
Carbon Dioxide—CO2 Percentage |
1.71 |
— |
Limestone Percentage |
4.1 |
5 maximum |
CaCO3 Percentage in Limestone |
94.5 |
70 minimum |
Tricalcium Silicate (C3S) |
42.9 |
— |
Tricalcium Aluminate (C3A) |
7.0 |
< 8 |
C3S + 4.75C3A |
76 |
100 maximum |
Equivalent Alkalis (Na2O+.658K2O) |
0.88 |
— |
Chloride (Cl) |
0.01 |
— |
— No specification
All CPT samples were prepared using the ASTM C1293 testing procedure. Each sample, with a water-to-cement ratio of 0.45, is 3 inches long with a 3-inch square cross section (76 by 76 by 285 mm). The gradation for coarse aggregate was as specified in ASTM C1293. For fine aggregates, the gradation was adjusted through sieving or crushing to achieve a fineness modulus of 2.71. This was done to minimize any variability in NIRAS and expansion measurements that may have arisen owing to differences in fine aggregate gradation. For each mix design, eight specimens were cast, six with studs for expansion measurements and two without studs for petrographic examination. The samples were initially cured for 24 hours in a moist environment for 23.5 ±0.5 hours. After demolding, the initial lengths of three samples were recorded. Subsequently, those samples, along with one sample for petrography, were transferred to a container that is kept at 100.4 °F (38 °C) in an environmental chamber. The container also allows the elevation of the specimens above water, providing high relative humidity, which is necessary for inducing ASR. The remaining specimens were kept for reference at room temperature; when examined, these samples of the same composition as mixes 1 through 10 (table 2) but stored at ambient conditions are hereafter referred to as “reference” samples.