Mitigation of alkali-silica reaction in concrete using lithium-stabilized dispersion of silica

Abstract

Method and composition for mitigating alkali-silica reaction in concrete. According to one embodiment, the composition may comprise a lithium-stabilized colloidal silica or a powder that is obtained from a lithium-stabilized colloidal silica. The composition may be used as an admixture for a concrete mix that also comprises cement, one or more aggregates, water and, optionally, one or more supplementary cementitious materials.

Claims

1. A concrete mix, the concrete mix comprising: (a) a cement; (b) an aggregate; (c) an alkali-silica reaction mitigating agent, the alkali-silica reaction mitigating agent comprising at least one of (i) a lithium-stabilized dispersion of silica and (ii) a powder obtained by drying the lithium-stabilized dispersion of silica, wherein the lithium-stabilized dispersion of silica comprises a lithium-stabilized colloidal silica, wherein the lithium-stabilized colloidal silica comprises silica particles having a particle size of about 6 nm, and wherein the lithium-stabilized colloidal silica has a density of about 1.085 g/ml, a pH of about 9.8, a % Li.sub.2O of about 0.20, a viscosity of about 4 cps, a conductivity of about 4130 uS, a gravimetric solids percentage of about 13.7%, a surface area by Sears method of about 513 m.sup.2/g, and a calculated particle size of about 5.3 nm; and (d) water.

2. A concrete mix, the concrete mix comprising: (a) a cement; (b) an aggregate; (c) an alkali-silica reaction mitigating agent, wherein the alkali-silica reaction mitigating agent comprises a powder obtained by drying a lithium-stabilized dispersion of silica and wherein the lithium-stabilized dispersion of silica is a lithium-stabilized colloidal silica; and (d) water.

3. The concrete mix as claimed in claim 2, wherein the lithium-stabilized colloidal silica comprises silica particles having a particle size of about 3 nm to 125 nm.

4. The concrete mix as claimed in claim 2, wherein the lithium-stabilized colloidal silica comprises silica particles having a particle size of about 6 nm.

5. The concrete mix as claimed in claim 2, wherein the lithium-stabilized colloidal silica comprises silica particles having a particle size of about 3 nm.

6. The concrete mix as claimed in claim 2 wherein the powder has a bulk density of about 0.86 g/ml, a BET surface area of about 500 m.sup.2/g, a loss on drying at 105 C. of about 12.6%, a 10% slurry pH of about 10.5, a % SiO.sub.2 of about 83, a % Li.sub.2O of about 1.0, and a color of about 91/0.5/0.5.

7. The concrete mix as claimed in claim 2 wherein the powder has a bulk density of about 0.071 g/ml, a BET surface area of about 800 m.sup.2/g, a loss on drying at 105 C. of about 10-15%, a 20% slurry pH of about 9-10, a % SiO.sub.2 of about 86.5, a % Li.sub.2O of about 1.04, and a color of about 93/0.0/0.6.

8. The concrete mix as claimed in claim 2, further comprising one or more supplementary cementitious materials.

9. A concrete mix, the concrete mix comprising: (a) cement; (b) sand; (c) stone/aggregate; (d) water; and (e) a lithium-stabilized colloidal silica, wherein the lithium-stabilized colloidal silica has a density of about 1.085 g/ml, a pH of about 9.8, a % Li.sub.2O of about 0.20, a viscosity of about 4 cps, a conductivity of about 4130 uS, a gravimetric solids percentage of about 13.7%, a surface area by Sears method of about 513 m.sup.2/g, and a calculated particle size of about 5.3 nm.

10. The concrete mix as claimed in claim 9 wherein said concrete mix is a 3000 psi concrete mix for preparing a 1 cubic yard of concrete and wherein said cement is present in said concrete mix in an amount constituting 517 lbs, said sand is present in said concrete mix in an amount constituting 1560 lbs, said stone/aggregate is present in said concrete mix in an amount constituting 1600 lbs, said water is present in said concrete mix in an amount constituting 275 lbs, and said lithium-stabilized colloidal silica is present in said concrete mix in an amount ranging from 3 lbs to 240 lbs.

11. A method of making a concrete structure, the method comprising the steps of: providing the concrete mix of claim 2, (b) then, casting the concrete mix to a desired form; and (c) allowing the cast concrete mix to cure.

12. The method as claimed in claim 11, wherein the lithium-stabilized colloidal silica comprises silica particles having a particle size of about 3 nm to 125 nm.

13. The method as claimed in claim 12, wherein the lithium-stabilized colloidal silica comprises silica particles having a particle size of about 6 nm.

14. The method as claimed in claim 13, wherein the lithium-stabilized colloidal silica has a density of about 1.085 g/ml, a pH of about 9.8, a % Li.sub.2O of about 0.20, a viscosity of about 4 cps, a conductivity of about 4130 uS, a gravimetric solids percentage of about 13.7%, a surface area by Sears method of about 513 m.sup.2/g, and a calculated particle size of about 5.3 nm.

15. The method as claimed in claim 12, wherein the lithium-stabilized colloidal silica comprises silica particles having a particle size of about 3 nm.

16. The method as claimed in claim 11 wherein the powder has a bulk density of about 0.86 g/ml, a BET surface area of about 500 m.sup.2/g, a loss on drying at 105 C. of about 12.6%, a 10% slurry pH of about 10.5, a % SiO.sub.2 of about 83, a % Li.sub.2O of about 1.0, and a color of about 91/0.5/0.5.

17. The method as claimed in claim 11 wherein the powder has a bulk density of about 0.071 g/ml, a BET surface area of about 800 m.sup.2/g, a loss on drying at 105 C. of about 10-15%, a 20% slurry pH of about 9-10, a % SiO.sub.2 of about 86.5, a % Li.sub.2O of about 1.04, and a color of about 93/0.0/0.6.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) As noted above, it is an object of the present invention to provide a novel technique for mitigating alkali-silica reaction in concrete. In this regard, according to one aspect of the invention, there is disclosed a novel concrete admixture for mitigating alkali-silica in concrete, the concrete admixture comprising (i) a lithium-stabilized dispersion of silica and/or (ii) a powder obtained by drying the aforementioned lithium-stabilized dispersion of silica.

(2) In addition, according to another aspect of the invention, there is provided a novel concrete mix. The concrete mix may comprise the following components: (i) a cement; (ii) an aggregate; (iii) water; and (iv) a lithium-stabilized dispersion of silica and/or a powder obtained by drying the lithium-stabilized dispersion of silica. The concrete mix may further comprise one or more supplementary cementitious materials, which may include, but are not limited to, conventional supplementary cementitious materials like Class F fly ash, silica fume, and metakaolin.

(3) The cement for the above-described concrete mix may be conventional and may consist of a single type of cement or may comprise two or more types of cement. For example, the cement may comprise a Type I/II Portland cement.

(4) The aggregate for the above-described concrete mix may be conventional and may consist of a single type of aggregate or may comprise two or more types of aggregate. For example, the aggregate may comprise at least one of the following types of aggregate: a mixed volcanic aggregate, a granite-based aggregate, a limestone-based aggregate, and a sand/gravel-based aggregate.

(5) The lithium-stabilized dispersion of silica for the above-described concrete mix may be conventional and may consist of a single type of lithium-stabilized dispersion of silica or may comprise two or more types of lithium-stabilized dispersions of silica. For example, the lithium-stabilized dispersion of silica may comprise one or more of a lithium-stabilized dispersion of fumed silica, a lithium-stabilized dispersion of silica gel, a lithium-stabilized dispersion of silica fume, and a lithium-stabilized dispersion of precipitated silica. A preferred lithium-stabilized dispersion of silica may be a lithium-stabilized colloidal silica, an example of which may be LiSol 6 lithium-stabilized colloidal silica, which is commercially available from the present applicant/assignee, Nyacol Nano Technologies, Inc. (Ashland, MA).

(6) Lithium-stabilized colloidal silica may be prepared by at least the following three types of methods: (1) Deionization of sodium silicate to prepare silicic acid, which is then condensation polymerized to form colloidal silica particles. The particle size may be controlled by process parameters such as temperature, concentration, addition rates, and any additives. The process can be operated in batch or column formats or hybrid processes. (2) Deionization of sodium- or potassium- or ammonia-stabilized colloidal silica in a column or batch mode, followed by replacing the alkali cation with lithium. This process does not produce as low of an impurity profile as the first method. (3) Condensation polymerization of high purity silicic acid prepared from tetramethyl orthosilicate (TMOS) or tetraethyl orthosilicate (TEOS) with lithium in the starting reaction mix.

(7) A more detailed protocol for preparing a lithium-stabilized colloidal silica for use in the present invention may be as follows: First, in a stirred tank reactor, 20,000 lbs. of deionized water is prepared, and 55 lbs. of lithium hydroxide powder is dissolved in the deionized water, thereby creating a 0.1% Li.sub.2O solution. Next, 6000 lbs. of sodium silicate with a SiO.sub.2/Na.sub.2O ratio of 3.22 is diluted to 4.5% SiO.sub.2 with deionized water. Next, the dilute silicate is passed through a column of IR120 ion exchange resin in the hydrogen form, creating a pseudo stable silicic acid solution. Next, the silicic acid is fed into the lithium hydroxide solution over 10 hours at 47 C., and the resulting lithium stabilized silica sol is concentrated to 15% SiO.sub.2. The foregoing concentrated colloidal sol is sold by the present applicant/assignee (Nyacol Nano Technologies, Inc., Ashland, MA) as LiSol 6 lithium-stabilized colloidal silica, which has the following properties: (1) density: 1.085 g/ml; (2) pH: 9.8; (3) % Li.sub.2O: 0.20; (4) viscosity: 4 cps; (5) conductivity: 4130 uS; (5) gravimetric solids: 13.7%; (6) surface area by Sears method: 513 m.sup.2/g; and (7) particle size (by calculation): 5.3 nm.

(8) It is to be noted that adjustment of the above-described process conditions may be used to produce lithium-stabilized colloidal silicas of other particle sizes. Particle size may be controlled by the time, temperature, and feed rates used in the process. Larger particle sizes may be prepared by a buildup method, in which silica is deposited on existing particles to grow the particles to a desired size.

(9) In general, particle sizes may range from 3 nm to 125 nm, with the preferred particle size depending on the goals of the formulation. The colloidal silica can only be concentrated to certain solids levels according to the particle size since the viscosity will increase rapidly, leading to gelation as the threshold is exceeded. For example, 6 nm can be made to 15% to 17% by weight, 8 nm can be made to 30%, and 20 nm and larger can be made to 40% or 50% solids by weight. It is advantageous for shipping costs and reduced handling costs to use higher solids; however, the reduced specific surface area may reduce the effectiveness of the product.

(10) An example of a lithium-stabilized colloidal silica having an average particle size of 3 nm is sold by the present applicant/assignee (Nyacol Nano Technologies, Inc., Ashland, MA) as LiSol 3 lithium-stabilized colloidal silica. The foregoing product was prepared using essentially the same process as described above for LiSol 6 lithium-stabilized colloidal silica, except that the process conditions were adjusted to increase the surface area to 800 m.sup.2/g.

(11) As noted above, in addition to using, or instead of using, a lithium-stabilized dispersion of silica, one may use a powder that may be obtained by drying the lithium-stabilized dispersion of silica. According to one embodiment, such drying may be spray-drying. In general terms, such spray-drying may comprise feeding the colloidal sol into a rotating high-speed atomizer to form a spray and then mixing the foregoing spray with high temperature air. The nano-structured powder that results may be conveyed from a drying chamber to a cyclone for separation of the powder from the drying air.

(12) An example of a powder as described above may be obtained by spray-drying LiSol 6 lithium-stabilized colloidal silica. Such a powder, which is designated herein as LiSol 6-SD powder, may be prepared using a GEA MOBILE MINOR Model 53 spray dryer (GEA North America, Columbia, MD), with a liquid feed rate of 40 ml/min and a discharge temperature of 200 F. The powder may have the following properties: (1) bulk density: 0.86 g/ml; (2) Brunauer-Emmett-Teller (BET) surface area: 500 m.sup.2/g; (3) loss on drying at 105 C.: 12.6%; (4) 10% slurry pH: 10.5; (5) % SiO.sub.2: 83; (6) % Li.sub.2O: 1.0; and (7) color: 91/0.5/0.5.

(13) Another example of a powder as described above may be obtained by spray-drying LiSol 3 lithium-stabilized colloidal silica under the same types of conditions described above to obtain LiSol 6-SD powder. The powder, which may be identified herein as LiSol 3-SD powder, may have the following properties: (1) bulk density: 0.071 g/ml; (2) BET surface area: 800 m.sup.2/g; (3) loss on drying at 105 C.: 10-15%; (4) 20% slurry pH: 9-10; (5) % SiO.sub.2: 86.5; (6) % Li.sub.2O: 1.04; and (7) color: 93/0.0/0.6.

(14) As can be appreciated, when including the lithium-stabilized colloidal silica or corresponding powder of the present invention in a concrete mix, one may wish to use an amount that mitigates alkali-silica reaction yet, at the same time, does not adversely affect the composition of the concrete mix in other respects. To this end, one may wish to consider whether the material is to be regarded merely as a lithium source and/or whether the material is to be regarded as a silica source to replace cement or supplementary cementitious materials like Class F fly ash or silica fume. In addition, one may also wish to consider whether the material may be effective in controlling alkali-silica reaction, without requiring fly ash or silica fume, for a range of aggregate materials.

(15) In this regard, the present inventor notes that the American Association of State Highway and Transportation Officials (AASHTO) makes the following recommendations regarding the mitigation of alkali-silica reaction: (1) for reactive aggregates, substitute 20% of the cement with Class F fly ash; and (2) for reactive aggregates, determine the amount of lithium to be added as Li/(Na+K)=0.74 as a mol ratio. (Na+K) is commonly expressed as Na.sub.2Oe.

(16) Using the first AASHTO recommendation above, where, for example, the cement that is used may be 440 grams of Type I/II Portland cement, a 20% substitution would be 440 grams0.2=88 grams of silica solids. For LiSol 6 lithium-stabilized colloidal silica, 88 grams of silica solids would equate to 642 grams of LiSol 6 lithium-stabilized colloidal silica, which seems to be a very high amount and would be impractical from a cost and formulating point of view.

(17) Using the second AASHTO recommendation above, where, for example, the cement is 440 grams of Type I/II Portland cement and has a Na.sub.2Oe of 0.46%, the mass of Na.sub.2Oe would be 2.024 grams, or 0.0653 gmol. The amount of Li to be added would be Li=0.740.0653=0.0483 gmol Li7 grams/gmol=0.338 grams of Li. LiSol 6 is 0.2% Li.sub.2O, which is equivalent to 0.09% Li. Accordingly, one would need to add 0.338/0.0009-375 grams of LiSol 6 if only serving as a lithium source, which again is a high result that is impractical from a cost and formulating point of view.

(18) An alternative approach to the above would be to consider that the lithium-stabilized colloidal silica may be regarded as a silica source in place of a portion of the cement or supplementary cementitious materials. Such an approach may be analogous to the approaches discussed above in Belkowitz and Zeidan in connection with sodium-stabilized colloidal silica. In the approaches of Belkowitz and Zeidan, cement is replaced with the sodium-stabilized colloidal silica. Based on the examples in Belkowitz and Zeidan, the silica addition would be in the range of 20 to 48 grams of SiO.sub.2 for Belkowitz and would be 26 grams of SiO.sub.2 for Zeidan; however, it should be noted that only the alkali-silica reaction performance of Belkowitz meets both the 14-day and 28-day requirement of 0.1% maximum expansion.

(19) In contrast with the SiO.sub.2 amounts described above for admixtures of sodium-stabilized colloidal silica, significantly smaller amounts of SiO.sub.2 may be used in connection with admixtures of lithium-stabilized colloidal silica in accordance with the present invention. More specifically, using LiSol 6 lithium-stabilized colloidal silica, amounts of SiO.sub.2 ranging from 1.95 grams SiO.sub.2 to 15.6 grams of SiO.sub.2 may be used. The lithium-stabilized colloidal silica need not be substituted for, and preferably is not substituted for, the cement, as this keeps the Na.sub.2Oe higher, and the constant cement amount may be helpful for compressive strength. Also, the water in the colloidal silica is preferably not subtracted from the water to be added. Instead, the colloidal silica may be diluted with the standard 0.47 water-to-cement ratio, and the aggregate and cement may be blended with this pre-diluted mixture. It is believed that this approach may give a better dispersion of the lithium-stabilized colloidal silica in the mixture.

(20) According to the present invention, an exemplary formulation of a 3000 psi mix for use in preparing a 1 cubic yard of concrete may be as follows: (i) cement: 517 lbs; (ii) sand: 1560 lbs; (iii) stone/aggregate: 1600 lbs; (iv) water: 275 lbs (i.e., approximately 33 gallons); and (v) LiSol 6 lithium-stabilized colloidal silica: 3 lbs to 240 lbs, depending on the alkali-silica reaction of the unmitigated formulation.

EXAMPLES

(21) The following examples are given for illustrative purposes only and are not meant to be a limitation on the invention described herein or on the claims appended hereto.

(22) Materials:

(23) The following materials were used as specified in the examples below: 1. Cement-Type I/II Portland cement from Continental Cement, Davenport Plant (Buffalo, IA), meeting ASTM C150 and TM standard specifications. The Na.sub.2Oe for the cement is 0.46%. 2. Mixed volcanic-origin aggregateaggregate of mixed volcanic-origin crushed and graded to the required sizes for ASTM C1260 standard specifications. 3. Granite-origin aggregatecrushed and graded to the required size for ASTM C1260 standard specifications. 4. Limestone-origin aggregatecrushed and graded to the required size for ASTM C1260 standard specifications. 5. Empire Sand (Empire Sand & Gravel Co., Inc., Billings, MT)graded to the required size for ASTM C1260 standard specifications 6. Class F fly ashBoral Prairie State55.2% SiO.sub.2+18.2% Al.sub.2O.sub.3+10.9% Fe.sub.2O.sub.3. Total 84.4%. 7. Waterregular tap water. 8. LiSol 6 lithium-stabilized colloidal silica, Nyacol Nano Technologies, Inc., Ashland, MA. 9. NexSil 5a 5 nm sodium-stabilized colloidal silica with 15% SiO.sub.2 content, Nyacol Nano Technologies, Inc., Ashland, MA 10. NexSil 20Aa 20 nm, low sodium colloidal silica produced at 30% SiO.sub.2 and pH 3, Nyacol Nano Technologies, Inc., Ashland, MA

(24) All alkali-silica reaction and other concrete testing was conducted by Element Materials Corp., St. Paul, MN, in its accredited concrete laboratory.

Example 1: Mixed Volcanic-Origin Aggregate Screening Test

(25) Mixed volcanic-origin aggregate is known to show high expansion in the ASTM C1260 test. The formulation of TABLE 1 below was prepared, cast into test bars, and cured and aged as specified, with periodic measurements of expansion made.

(26) TABLE-US-00001 TABLE 1 Ingredient Weight (g) Type I/II Portland cement 440 Aggregate (ASTM C1260, Table 1 990 Grading) Water 207 LiSOL 6 lithium-stabilized colloidal 26 silica Total mass without LiSOL 6 1637 lithium-stabilized colloidal silica Total mass with LiSOL 6 lithium- 1663 stabilized colloidal silica Water/Cement Ratio 0.46

(27) The expansion test results are shown below in TABLE 2. As can be seen, it is clear that mixed volcanic-origin aggregate has high expansion after 14 days and requires mitigation. The addition of low levels of LiSol 6 lithium-stabilized colloidal silica is effective in reducing alkali-silica reaction and an addition of 0.46 wt % as SiO.sub.2 enables even the Federal Aviation Administration (FAA) specification to be met (i.e., no more than 0.1% expansion at 28 days using the accelerated mortar bar test). These results also show that lithium-stabilized colloidal silica is surprisingly effective and performs in an unexpected way as a lithium source for alkali-silica reaction control.

(28) TABLE-US-00002 TABLE 2 Mixed Volcanics Aggregate-% Length Change Average of 3 Measurements Wt % SiO2 from Day Day Day Day Day Day Specimen Lisol 6 0 2 7 11 14 28 Control, no LiSOL 6 0 0.000% 0.096% 0.184% 0.232% 0.290% 0.32% LiSOL 6 at 13 Grams 0.11 0.000% 0.023% 0.054% 0.096% 0.135% LiSOL 6 at 26 Grams 0.23 0.000% 0.012% 0.049% 0.077% 0.110% LiSOL 6 at 52 Grams 0.46 0.000% 0.000% 0.035% 0.039% 0.054% 0.080% LiSOL 6 at 104 Grams 0.9 0.000% 0.008% 0.028% 0.039% 0.054% 0.066%

Example 2: Empire Sand Screening Test

(29) Empire sand is a known poor performer for alkali-silica reaction. The standard mix design described in Example 1 was used, except that Empire sand was substituted for the mixed volcanic-origin material. The test was carried out to 56 days to demonstrate long-term effectiveness of the LiSol 6 lithium-stabilized colloidal silica. As can be seen below in TABLE 3, LiSol 6 lithium-stabilized colloidal silica is effective in controlling alkali-silica reaction up to 56 days.

(30) TABLE-US-00003 TABLE 3 Empire Sand-% Length Change Average of 3 Measurements Wt % SiO2 from Day Day Day Day Day Day Day Specimen Lisol 6 0 2 7 11 14 28 56 Control, no LiSOL 6 0 0.000% 0.012% 0.060% 0.160% 0.220% 0.350% 0.390% LiSOL 6 at 52 Grams 0.46 0.000% 0.000% 0.014% 0.021% 0.028% 0.030% 0.056% LiSOL 6 at 104 Grams 0.9 0.000% 0.000% 0.011% 0.014% 0.019% 0.028% 0.038%

Example 3: Granite-Based Aggregate

(31) Granite-based aggregate was substituted in the formulation of Example 1, and alkali-silica reaction aging tests were conducted for 28 days. The granite-based aggregate was already a good performer and required no mitigation. Nevertheless, as can be seen below in TABLE 4, the addition of LiSol 6TM lithium-stabilized colloidal silica further reduced alkali-silica reaction. Moreover, this example shows no negative effect in a known good system.

(32) TABLE-US-00004 TABLE 4 Granite based aggregate-% Length Change Average of 3 Measurements Wt % SiO2 from Day Day Day Day Day Day Specimen Lisol 6 0 2 7 11 14 28 Control, no LiSOL 6 0 0.000% 0.001% 0.015% 0.026% 0.040% 0.052% LiSOL 6 at 52 Grams 0.46 0.000% 0.000% 0.017% 0.027% 0.030% 0.034% LiSOL 6 at 104 Grams 0.9 0.000% 0.000% 0.008% 0.013% 0.018% 0.023%

Example 4: Limestone-Based Aggregate

(33) Limestone-based aggregate was substituted in the formulation of Example 1, and alkali-silica reaction aging tests were conducted for 28 days. The limestone-based aggregate was already a good performer and required no mitigation. Nevertheless, as can be seen below in TABLE 5, the addition of LiSol 6TM lithium-stabilized colloidal silica further reduced alkali-silica reaction. Moreover, this example shows no negative effect in a known good system.

(34) TABLE-US-00005 TABLE 5 Limestone based Aggreagte-% Length Change Average of 3 Measurements Wt % SiO2 from Day Day Day Day Day Day Specimen Lisol 6 0 2 7 11 14 28 Control, no LiSOL 6 0 0.000% 0.004% 0.004% 0.009% 0.010% 0.033% LiSOL 6 at 52 Grams 0.46 0.000% 0.004% 0.004% 0.000% 0.004% 0.022% LiSOL 6 at 104 Grams 0.9 0.000% 0.000% 0.001% 0.003% 0.003% 0.018%

Example 5

(35) This example was run to determine if low sodium colloidal silica can successfully mitigate alkali-silica reaction or if a lithium colloidal silica is required to mitigate alkali-silica reaction. NexSil 20A colloidal silica is an acidic colloidal silica produced by Nyacol Nano Technologies, Inc. (Ashland, MA). NexSil 20A colloidal silica is 30% SiO.sub.2, with a sodium content of 250 ppm (as Na) and a pH of 2.7. This amorphous silica is expected to mitigate alkali-silica reaction based on the same type of mechanism as fly ash, silica fume or metakaolin. The active silica and alumina contents react with the excess alkali in the pore space and, in so doing, suppress alkali-silica reaction. However, large amounts of the supplementary cementitious materials are used to achieve low alkali-silica reaction. These tests were run at the same SiO.sub.2 levels as the Lisol 6 lithium-stabilized colloidal silica tests above.

(36) NexSil 20A colloidal silica was tested with both the Empire sand and mixed volcanic aggregates. As can be seen below in TABLE 6, the results were promising at 14 days, but failed at 28 days. It is believed that this is due to the amorphous silica reacting with excess pore alkali, and, once it is used up, there is nothing to prevent alkali-silica reaction from proceeding. These results further confirm the surprising performance of lithium-stabilized colloidal silica.

(37) TABLE-US-00006 TABLE 6 Wt % SiO2 from Specimen 20A 0 2 7 11 14 28 Control Lab Test Data-Empire Sand-% Length Change Average of 3 Measurements Control, no NexSil 20A 0 0.000% 0.012% 0.060% 0.160% 0.220% 0.350% NexSil 20A at 52 Grams 0.92 0.000% 0.008% 0.016% 0.024% 0.037% 0.155% Nexsil 20A at 104 grams 1.8 0.000% 0.001% 0.005% 0.019% 0.024% 0.135% Control Lab Test Data-Mixed Volcanics-% Length Change Average of 3 Measurements Control, no NexSil 20A 0 0.000% 0.096% 0.184% 0.232% 0.290% 0.320% NexSil 20A at 52 Grams 0.92 0.000% 0.007% 0.018% 0.055% 0.087% 0.245% NexSil 20A at 104 Grams 1.8 0.000% 0.009% 0.017% 0.031% 0.052% 0.141%

Example 6

(38) This example compares NexSil 5 sodium-stabilized colloidal silica to LiSol 6 lithium-stabilized colloidal silica with Empire sand and mixed volcanic aggregates. The sodium of NexSil 5 sodium-stabilized colloidal silica would be expected to be detrimental to alkali-silica reaction performance.

(39) As can be seen below in TABLE 7, while there was some difference between the aggregate types, they all fail at 28 days-similar to what was found in Example 5 with NexSil 20A colloidal silica.

(40) TABLE-US-00007 TABLE 7 Wt % SiO2 from Specimen Nexsil 5 0 2 7 11 14 28 Control Lab Test Data-Mixed Volcanics-% Length Change Average of 3 Measurements Control, noNexSil 5 0 0.000% 0.096% 0.184% 0.232% 0.290% 0.320% NexSil 5 at 52 Grams 0.46 0.000% 0.012% 0.020% 0.130% 0.260% 0.306% Nexsil 5 at 104 grams 0.92 0.000% 0.016% 0.023% 0.120% 0.240% 0.265% Control Lab Test Data-Empire Sand-% Length Change Average of 3 Measurements Control, no NexSil 5 0 0.000% 0.012% 0.060% 0.160% 0.220% 0.350% NexSil 5 at 52 Grams 0.46 0.000% 0.006% 0.014% 0.052% 0.074% 0.192% Nexsil 5 at 104 grams 0.92 0.000% 0.004% 0.014% 0.034% 0.048% 0.173%

Example 7: LiSol 6-SD Powder

(41) LiSol 6-SD powder was prepared as described above. This example was run to evaluate the use of a nano-structured powder in the ASTM C1260 procedure. A powder would offer advantages in terms of ease of use and transportation cost and would avoid the handling of bulk liquids and the related issues of water-to-cement ratio and slump control.

(42) The LiSol 6-SD powder was blended with the fine aggregate as part of the ASTM C1260 procedure and then the bars were cast and aged according to the procedure.

(43) As can be seen below in TABLES 8 and 9, the LiSol 6-SD powder was surprisingly good at very low addition levels. In fact, the results show that as little as 0.1% by weight is effective in controlling alkali-silica reaction in the Empire sand aggregate at 14 days.

(44) TABLE-US-00008 TABLE 8 ASTM C1260 Standard Mix Design Wt, Grams Wt % Cement Type I/II Continental Davenport 440 26.7% Aggregate (C1260 Table 1 Grading) 990 60.2% Water-Cement Ratio 207 12.6% Lisol 6-SD 8.18 0.5% 1645.18 Water/cement ratio 0.47

(45) TABLE-US-00009 TABLE 9 Empire Sand-% Length Change Average of 3 Measurements Wt % SiO2 from Lisol Day Day Day Day Day Specimen 6-SD 0 2 7 11 14 Control, no LiSOL 6-SD 0 0.000% 0.012% 0.060% 0.160% 0.210% Lisol 6-SD at 1.64 grams 0.1 0.000% 0.004% 0.008% 0.019% 0.031% Lisol 6-SD at 3.27 grams 0.2 0.000% 0.007% 0.014% 0.021% 0.032% Lisol 6-SD at 8.18 grams 0.5 0.000% 0.006% 0.014% 0.021% 0.034%

Example 8: LiSol 3-SD Powder

(46) LiSol 3-SD powder was prepared as described above and tested in the ASTM C1260 protocol using the Empire sand aggregate. As seen below in TABLE 10, LiSol 3-SD powder was also very good at low addition levels. In fact, the results show that as little as 0.1% by weight is effective in controlling alkali-silica reaction at 14 days.

(47) TABLE-US-00010 TABLE 10 Empire Sand-% Length Change Average of 3 Measurements Wt % SiO2 from Lisol Day Day Day Day Day Specimen 3-SD 0 2 7 11 14 Control, no LiSOL 3-SD 0 0.000% 0.008% 0.055% 0.150% 0.190% Lisol 3-SD at 1.64 grams 0.1 0.000% 0.001% 0.023% 0.045% 0.066% Lisol 3-SD at 3.27 grams 0.2 0.000% 0.001% 0.015% 0.038% 0.059% Lisol 3-SD at 8.18 grams 0.5 0.000% 0.002% 0.024% 0.045% 0.064%

(48) In summary, the above examples show that lithium-stabilized colloidal silicas and powders prepared from lithium-stabilized colloidal silicas are highly effective in controlling alkali-silica reaction in concrete. The LiSol lithium-stabilized colloidal silicas and LiSol-SD powder materials are effective at much lower levels of use than calculated or predicted by existing studies involving lithium nitrate. The lithium-stabilized colloidal silicas and related powders are also highly effective additives, performing at much lower levels than existing supplementary cementitious materials used to mitigate alkali-silica reaction.

(49) The embodiments of the present invention described above are intended to be merely exemplary and those skilled in the art shall be able to make numerous variations and modifications to it without departing from the spirit of the present invention. All such variations and modifications are intended to be within the scope of the present invention as defined in the appended claims.