The Effectiveness of Silicones as Water Repellents When Applied to Concrete Author(s): F. C. Lanning Source: Transactions of the Kansas Academy of Science (1903-), Vol. 61, No. 3 (Autumn, 1958), pp. 334-344 Published by: Kansas Academy of Science Stable URL: http://www.jstor.org/stable/3626454 . Accessed: 02/08/2014 12:06 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact
[email protected]. . Kansas Academy of Science is collaborating with JSTOR to digitize, preserve and extend access to Transactions of the Kansas Academy of Science (1903-). http://www.jstor.org This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/action/showPublisher?publisherCode=ksa http://www.jstor.org/stable/3626454?origin=JSTOR-pdf http://www.jstor.org/page/info/about/policies/terms.jsp http://www.jstor.org/page/info/about/policies/terms.jsp The Effectiveness of Silicones As Water Repellents When Applied to Concrete1 F. C. LANNING Kansas State College, Manhattan Concrete is one of the most important building materials and like other forms of masonry is subject to damage by weathering. Most of this type of damage is apparently due to freezing and thawing of wet concrete, which could be prevented largely by suitable water repellents such as silicones. These experiments were undertaken, as no thorough evaluation of the effectiveness of silicones on concrete has appeared in the literature. There are three types of silicone preparations on the market that give water repellency and stain resistance to masonry. All three types have been used in these tests. One type is represented by solutions of methyl, ethyl, or other silicone resins dissolved in volatile solvents such as toluene or mineral spirits. This type has been reported by Anderegg (1, 2) and the General Electric Company (3, 11) to give satisfactory water repellency to concrete. Lanning (6, 7) has reported this type of silicone to be effective on brick and sandstone. The second silicone preparation is a water solution of sodium methyl siliconate. This material was originally prepared by Krieble and Elliot (5). It has been reported by Kather and Torkelson (4), the General Electric Company (11, 12, 13) and by Lanning (6, 7, 8, 9) to produce satisfactory water repellency on various types of masonry. The third type of silicone has a type formula RSiY3 where R is a methyl group and Y is a water attracting group, alcoholic in nature. The alcoholic nature of Y is responsible for the solubility of these materials in water. When diluted with water, the silicone undergoes hydrolysis causing the replacement of the Y groups by OH groups to form Si-O-Si linkages with the result that a methyl silicone film is formed on the masonry. This type of silicone has been reported by Lanning (10) to be an effective water repellent on limestone. The silicones used were General Electric products known as SC-50, SR-53, Dri-Film 103, and GE.-81589 and a Linde Air Products Company solution known as C-25 and are thus designated in this paper. GE.-81589 belongs to the third class of silicones. Concrete presents problems not encountered with limestone and brick as it is a heterogenous mixture with widely differing porosities. Transactions of the Kansas Academy of Science, Vol. 61, No. 3, 1958. 1 Contribution from the Department of Chemistry, Kansas State College. [334] This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/page/info/about/policies/terms.jsp Silicones as Water Repellents When Applied to Concrete 335 This has made it necessary to study both highly porous materials, such as concrete block made with '"Haydite" aggregate, and dense concrete of low porosity. "Haydite" is made by firing shale. It has the composi- tion: SiO2, 53.98 per cent; A1203, 18.23 per cent; Fe203, 6.6 per cent; CaO, 9.06 per cent; MgO, 2.35 per cent; SO3, 1.40 per cent; K20,O, 3.31 per cent; Na20, 0.89 per cent; and ignition loss 4.03 per cent. Some of the aggregate is exposed on the surface of the concrete and the silicone must be effective on it as well as on the concrete paste. In order to get blocks in which a large aggregate surface was exposed, test blocks were cut by a diamond saw from large blocks of thoroughly cured concrete. Blocks made with ordinary portland cement and blocks made with air entrained cement were tested to determine whether or not the type of cement had any influence on the effectiveness of the silicones. In order to compare the effectiveness of silicones with other ma- terials used on concrete, tests were made with tar and asphalt preparations. Experimental The methods used to test the effectiveness of the silicones on concrete were as follows: 1. The samples of concrete were coated with silicone solutions containing the desired concentration of silicone solids by weight and thoroughly dried. The water absorbed was determined by soaking both treated and untreated samples in water for 72 hours. 2. The repetition of number one above, by spraying water on one surface of the concrete for 8 hours. The other surfaces were covered with a paraffin wax coating to waterproof them. This test measured the water-repellency to rain. 3. Determination of the durability of the silicone films by study- ing the rate of water absorption before and after 10 cycles of freezing and thawing. The freezing was carried out in a room with a temperature at -100 F. 4. Precoating concrete samples with 3 per cent sodium silicate solution made by diluting a 400 Be commercial waterglass solution with water. After the concrete samples were dried, the silicone solutions were applied, and the samples were soaked in water as in numimber one. 5. The repetition of number four above using "Bondex", a cement paint, as the precoating material. 6. Determination of resistance to natural weathering by determin- This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/page/info/about/policies/terms.jsp 336 Transactions Kansas Academy of Science ing the amount of water absorbed by the concrete in 72 hours of soaking, before and after one year of natural weathering. 7. The resistance of silicone films to electrolytes was determined by soaking silicone-coated concrete samples in 0.1 N solutions of NaC1, CaCl2 and NaOH for nine days. The difference in water absorption before and after treatment was a measure of the durability of the film. 8. Repetition of number seven above, by soaking in wet soil, pH-8, for 40 days. 9. The determination of the durability of the silicone films to infrared radiation. This was done by determining the rate of water absorption before and after exposure to 164 hours of radiation from a 250 watt infrared heat lamp with built in filter. The surfaces of the samples were placed 9 inches from the lamp. The 164 hours of radiation corresponds to the radiation that an average wall would receive from 315 days of midsummer Kansas sunshine. 10. The effectiveness of silicones in preventing seepage of water through concrete was determined by use of hollow concrete blocks. Hollow concrete blocks with 1 inch thick walls were coated on the out- side with silicone films and then dried. The blocks were filled with 0.1 N NaCl solutions and allowed to stand 240 hours. Evidence of seepage was obtained by appearance of water or of salt crystals on the outside of the blocks. The silicones used in these experiments were diluted as follows: 1. SR-53 and C-25 were diluted with toluene to make solutions containing 3 per cent silicone solids by weight. 2. Dri-Film 103 was diluted with "Skellysolve F" to produce a solution which contained 5 per cent silicone solids by weight. 3. The SC-50 and GE-81589 solutions were prepared by diluting with water until the solutions contained 2 and 5 per cent silicone solids respectively by weight. In all cases, the silicone solutions were applied by brushing them freely on the concrete. A comparison of the effectiveness of asphalt and tar preparations to the effectiveness of silicones was obtained by coating concrete blocks with these preparations by brushing them on at a high enough temperature that preparation was in the liquid state. The samples were then soaked in water in the same manner as in number one under the tests for the silicones. The preparations used were: roofing tar, waterproofing tar, and a thin asphalt paint with turpentine as the thinner. This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/page/info/about/policies/terms.jsp Silicones as Water Repellents When Applied to Concrete 337 Results Water Absorption by Soaking (a) Cut concrete samples Blocks 4 X 4 X 2 inches were cut by a diamond saw from large blocks of thoroughly cured concrete. The concrete was prepared by mixing by weight 1 part of water with 5 parts of sand, 5 parts of gravel and 2.2 parts of portland cement. The gravel contained pieces of dense limestone as well as siliceous matter. The surfaces of the blocks consisted of cement paste and stone. A silicone must be effective on cement paste, on the limestone, and on silica in order to be effective on such a material. This concrete was rather dense and showed a total water absorption of only 1.7 per cent in 75 hours. Figs. (1) and (2) show that Dri-Film 103, SC-50, SR-53, and C-25 all gave some protection to the concrete. C-25 gave the best results. Better results were obtained with the SR-53 when two coats of the silicone were applied. No improvement was obtained by use of two coats of C-25. (b) Cast concrete samples These tests were made with 4 X 4 X 2 inch blocks of cast concrete. The blocks were made in the laboratory and had the same composition as the cut concrete except that there was no limestone in the concrete. Figs. (3) and (4) show that Dri-Film 103, SC-50 and C-25 are all effective. Figs. (7) and (10) show that GE.-81589 also gives satis- factory results. Dri-Film 103 gave the best results. (c) Sidewalk Concrete Fig. (5) shows the results obtained by using SC-50, SR-53, Dri- Film 103, and C-25 on samples of rough concrete sidewalk with large pores. None of the silicones were as effective as might be desired. SC-50 was almost ineffective while C-25 was the best. Water Absorption by Spraying The cast concrete samples were sprayed with water for eight hours. Fig. (6) shows that all silicones tested were effective. Dri-Film 103 was the least effective. The others allowed less than 0.5 per cent of water to penetrate into the concrete in eight hours. These results show that all the silicones would be effective in shedding rain water. Resistance of Silicone Films to Ten Cycles of Freezing and Thawing Fig. (7) shows the results obtained by exposing concrete samples This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/page/info/about/policies/terms.jsp 338 Transactions Kansas Academy of Science I__ 1 I I [ III I I I l I I I I I I I I I I I 1 Cut concrete Cut concrete 2 Uncoated 2 0- Coated once with SR-53 2 0 Coated with SC-50 0 Coated twice with SR-53 0 Coated with Dri-Film 103 -l Coated once with C-25 O Coated with C-25 Coated twice with C-25 10 20 30 40 50 60 70 10 20 30 40 50 60 70 Time In Hours Time In Hours 12C t 6 .4 CONCRETE 105 9o ,Uncoated 85FmCoated with De-Fim103M4 0 Coated wath C-25 0U C Q ConrtUcoa ted 6 Concrete coated -Wth 5 rDr- Film 105 5 042 2 0_1 1 1to 20 30 40 50 60 70 0so 10 20 30 40 50 60 70 TI ME IN HOURS Tme In Hours I? I I I I I" I I I I I I I I SConcrete '6 Spraying Tests With Concrete 6 Ito 9 O Uncoated 8 - Coated with SR-53 4 * Coated with Dri-Film 103 0 Coated with C-25 0 Unicoated 6- 0 3 Coated with SC-50 64 < El [] Coated wtC-25 5 - ) Coated with Dri-Film 103 2 X Coattd with SR-53 twice 2 4 2 3 4 5 6 7 I0 20 30 40 50 60 706 Time In Hours Time In Hours I - I I I I I" 2 Concrete After 10 Cycles of - 12 - Concrete made with SC-50 ,, 7 Freezing and Thawing- 8 S Btefote Air rentrained coated with SC- 50 A II II i 81589 t10 - Before I0 cycles of freezing and thawing 9 - . . . ; ' i m ! : 9 - 0 A ir e n tr a in e d w it h h ig h S C - 5 0 c o n t e n t al lI II 25Di-Film 103 9 OeAir entained with hioh SC-50 content At tee8xPortland coated with C-o Air entrained with low SC- 50 content After Air entrained coated with SC- 50 A r s h n50cn 0 7 -6 I1 81569 -Afttere10 cycles of freezing and thawing - c t i Dri Film 103 Air entrained with high SC-50 content SXPottland coated with C-25 6 Air enaied ithloSC-50 content A Portland with low SC-50 content "_5 - 5 _ 20 30 40 50 60 70 0 20 30 40 50 60 70 Time In Hours Time In Hours This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/page/info/about/policies/terms.jsp Silicones as Water Repellents When Applied to Concrete 339 to 10 cycles of freezing and thawing. The samples were frozen in a room at a temperature of -100 F. The SC-50 and GE.-81589 coatings underwent considerable breakdown in effectiveness. Dri-Film 103 was the most effective and was slightly more effective after the freezing and thawing tests. C-25 was not affected by the freezing and thawing, but to star.t with, was not as effective as the others. Concrete Made with SC-50 Concrete made with SC-50 does not absorb much water but there is difficulty in preventing the formation of large pores in it. Several hollow blocks leaked water like a sieve even though the surface repelled water. Fig. (8) shows that samples of such concrete absorbed less than 2 per cent of water even after 72 hours of soaking. The same Fig. shows that a considerable increase in effectiveness occurred when the samples were exposed to 10 cycles of freezing and thawing. Effectiveness of Precoating with Waterglass When the results obtained by precoating concrete with Na2SiO, (Fig. 9) are compared with the results in Figs. (3) and (4), it is evident that the precoating of Na2SiO3 improves the effectiveness of SC-50, Dri-Film 103, C-25, and SR-53. Fig. (10) shows the same thing is true for GE.-81589. Resistance of Silicone Films to Electrolytes It is important that the silicones be resistant to electrolytes in the soil. Concrete samples coated with GE.-81589, SR-53, C-25, and Dri- Film 103 were soaked in 0.1 N solutions of CaCl2,, NaCl and NaOH for nine days. The results of these tests are shown in Figs. (11) through (16). None of the silicones tested were resistant to the NaOH and the samples absorbed water at about the same rate as uncoated samples. GE.-81589 and SR-53 coatings were almost completely broken down in the CaC12 and NaCl solutions. These solutions had no harmful effects on coatings of Dri-Film 103 and C-25. Similar tests made with SC-50 coated samples show them to be resistant to CaCl2 and NaCI solutions, but destroyed by the NaOH solution. Soaking in mud, pH-8, for 40 days had no harmful effect on concrete samples coated with SC-50, Dri-Film 103 and GE.-81589. SR- 53 coatings on concrete were completely destroyed by the same test. Resistance of Silicone Films to Weathering Concrete samples coated with C-25 and Dri-Film 103 were exposed This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/page/info/about/policies/terms.jsp 340 Transactions Kansas Academy of Science - L i 1 -I-7 1 1 1 1 1 1 1 1 2 Concrete Coated with No2Si036 10CONCRETE 0 0 Uncoated 0 Coated with SC-50 - Coated with Dri-Film 103 8 A Coated with 4% SR-53 H ooo40.,0oUeafe 00 26 --c Co, with GE- < , Concrete, Cootie with 3% NatSI(> + 1 iM GE r589 200 054 0 o o o0 N H0 60 70 00 03 20 30 40 50 60 70 TIME IN HOURS Timee InHours 6- 661 001 COORET COTE 010 G-tIRO12 CONCRETE COATED WITH GME-81389 CONCRETE COATED WITH GCE-815895 caRT TDWIHG 18 I ( Uncoated13.0 300ter oa in n CoGI0 solo. SAter Sooakng in 300H olin. 2 tefoel 320king W_ ao io 20 30 40 50 60 70 so . to 20 30 40 50 so 70 so TIME IN HOURS TIME IN HOURS 1 C3GRETE COATED WITH GE-81589 0 Before soaking in electrolytes 2-- ? After soaking in Cl2 - O After soaking inCo ? Aftr sokig inNaOH o NI soln. 0 20 40 0 TIME IN HOURS I 20 30 40 50 60 70 Time In Hours U5 Concrete Coated With C-25 2 0 efore soaking in electrolytes - 6 R E After soaking n CaCI 1 W I 103 n AftOer soaking i NoCI --ASB Aftero soaking in NOHci S3 0 20 30 40 50 60 70 0 10 20 O30 40 so 60 70 so T TImE In Hours TIME IN HOURS This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/page/info/about/policies/terms.jsp Silicones as Water Repellents When Applied to Concrete 341 to natural weathering for one year. Figs. (17) and (18) show that both silicones were quite resistant to the weathering. Resistance of GE.-81589 and Dri-Film 103 Films to Infrared Radiation One hundred sixty-four hours of infrared radiation caused some breakdown of C-25 and Dri-Film 103 films but the coatings were still fairly effective against water absorption. Results for Dri-Film 103 are shown in Fig. (19). SC-50, SR-53, and GE.-81589 films were seriously damaged by the radiation. The results for GE.-81589 are shown in Fig. (20). These results are in sharp contrast to experimental evidence obtained by Lanning (9) that SC-50 on limestone is very durable to infrared radiation. Effect of Bondex Cement Paint on Water Absorption Fig. (21) shows that cut concrete coated with Bondex absorbed water about as fast as uncoated samples, Fig. (1). Comparisons of Fig. (21) with Fig. (1) show that Bondex did not improve the effectiveness of SC-50 or C-25 coatings. A cement paint that does not have water repellency of its own can slow down seepage of water but can not lower the total percentage of water absorbed. Effectiveness of Silicones on a Very Porous Material Such as Concrete Made with "Haydite" The blocks coated with SC-50, SR-53, and Dri-Film 103 still absorbed water at a rapid rate. Best results were obtained with Dri-Film 103. In this case, the coated sample absorbed 6.46 per cent by weight of water in 3 hours as compared to a 11.36 per cent absorption by uncoated samples. A coating of Bondex before the application of the silicone had almost no effect on percentage of water absorbed. Effectiveness of Silicones in Slowing Down Seepage of Water Through Concrete Hollow concrete blocks with 1 inch thick walls were coated on the outside with SC-50, Dri-Film 103, SR-53, C-25, and GE.-81589. These blocks were filled with 0.1 N NaCLsolution. The salt solution was used since the appearance of moisture or salt crystals on the surface would detect seepage. Blocks coated with Dri-Film 103 and C-25 showed no evidence of moisture or salt crystals on the surface after 240 hours. SC-50, SR-53, and GE.-81589 showed some salt crystals after 240 hours. In the case This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/page/info/about/policies/terms.jsp 342 Transactions Kansas Academy of Science 6 17 oCETE COATED WITH DRI- FILM 103 18 CONCRETE COATED WITH C-25 0 u0 uncoated C After I yeearI oe weatweerhnri3 S eAfter I year of weathering 20 30 40 50 70 o0010 2069040 50 o0 0 so SS T IN HOURS ME IN HOURS 19 EFFECT OF INFRARED ON DRI FILM 103 20 EFFECT OF INFRARED ConctCOATINGS 4421 2 o CodCncrete,dUncoatedeaUntreated --3 Coated C o bod itdeh 3%nS SC-50iO in < 2U d Cotd odeCnatedon +G-1 1589,Befoe Radatio Unotdij Sm After Radiation 0 00 0 10 00 0T 010 20 30 40 50 60 70s Te I HosTIME IN HOURS TIME IN HOURS Concrete -21 0 Coated with bondex V Coated with bondex ana SC-50 O Coated With bondex and C-25 10 20 30 40 50 60 70 Tkme In Hours of SC-50 and SR-53, some blocks became damp on the outside after about four hours. Effectiveness of Asphalt and Tar Preparations on Concrete A thin asphalt paint made with turpentine as a thinner gave excellent results. Concrete that absorbed 4.5 per cent of water in 72 hours absorbed only 0.88 per cent in the same time period when coated with this material. Roofing tar on the same material was not quite as good since 1.54 per cent of water was absorbed in 72 hours. A thick waterproofing tar that had to be applied hot gave unsatis- This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/page/info/about/policies/terms.jsp Silicones as Water Repellents When Applied to Concrete 343 factory results as the concrete absorbed 5.5 per cent of H20 in three hours. It is practically impossible to get an unbroken coating of this material. Summary 1. Water absorption tests, including spraying tests, made on several types of concrete show that concrete can be made water repellent by several different silicone preparations providing it is not too porous. Dri-Film 103 and C-25 gave the best results. 2. Evidence has been obtained that some silicone films on concrete are more resistant to cycles of freezing and thawing than others. Dri- Film 103 and C-25 were not affected appreciably by 10 cycles of freez- ing and thawing; whereas, SC-50 and GE.-81589 coatings were seriously damaged. 3. Concrete can be made by adding SC-50 to the original mix. Such concrete is water repellent but there is difficulty in preventing formation of large pores. Such pores cause the concrete to leak water like a sieve. 4. Precoating of the concrete by other materials may or may not improve the effectiveness of a silicone on concrete. Waterglass improves the effectiveness of a silicone on concrete but some cement paints do not. 5. Silicones vary somewhat in their resistance to electrolytes. C-25, Dri-Film 103 and SC-50 are all very resistant to 0.1 N solutions of CaC12 and NaC1. SR-53 and GE.-81589 were almost completely broken down by the treatment. No silicones were found that were resistant to a 0.1 N NaOH solution. All the silicones tested, except SR-53, were resistant to a 40 day soaking in wet soil, pH. 8. 6. Natural weathering for one year had no effect on concrete samples coated with Dri-Film 103 and C-25. 7. Intense infrared radiation for 140 hours causes some breakdown of silicone films on concrete; SR-53 and SC-50 films were seriously damaged by such treatment. 8. Silicone films are not effective on a very porous material such as "Haydite." 9. Some silicones are very effective in slowing down the seepage of water through concrete. Hollow concrete blocks coated with Dri-Film 103 and ,idocks coated with C-25, when filled with a salt water solution, showed no evidence of the solution seeping through the concrete after 240 hours in contact with the solution. 10. Some types of asphalt and tar preparations are effective water This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/page/info/about/policies/terms.jsp 344 Transactions Kansas Academy of Science repellents on concrete whereas others are almost ineffective. It is very hard to cover concrete completely and thoroughly with thick materials that have to be applied hot. Best results were obtained with a thin asphalt turpentine solution. Acknowledgment Thanks are due to the General Electric Company for the financial support it has given to the project and for the silicones it has furnished. Thanks are also due the Linde Air Products Company for supplying the C-25. Literature Cited 1. ANDEREGG, F. O. 1951. Surface waterproofing with silicone resins. Progressive Architecture, May. 2. . 1951. Results on testing surface waterproofers. A. S. T. M. Bulletin, May. 3. Dri-Film 103 water repellent silicone resin, Silicones Product Data, General Electric Co., June 23, 1954. 4. KATHER, W. S., and A. TORKELSON. 1954. Ind. Eng. Chem., 46:381. 5. KRIEBLE, R. H. and J. R. ELLIOT. 1948. U. S. Patents 2,441,442, and 2,441,423, May 11. 6. LANNING, F. C. 1955. The effectiveness of silicones as water repellents when applied to various types of brick. Trans. Kans. Acad. Sci., 58(3) :439-445. 7. . 1956. The effectiveness of silicones as water repellents when applied to sandstone. Trans. Kans. Acad. Sci., 59(4):427-431. 8. . 1954. The effectiveness of silicones as water repellents when applied to various types of limestone. Trans. Kansas Acad. Sci., 57(3): 374-385. 9.. 1955. Further studies on the effectiveness of sodium methyl siliconate as a water repellent when applied to limestone. Trans. Kans. Acad. Sci., 58(1):115-120. 10. . 1955. The effectiveness of a silicone of type RSiY3 as a water repellent on limestone. Trans. Kans. Acad. Sci., 58(4):545-548. 11. Silicones application data, AD-19A. G. E. silicones for rendering structural materials water repellent, Jan. 1, 1953. 12. Sodium methyl siliconate, silicone products data, General Electric Co., June 1, 1953. 13. Sodium methyl siliconate powder, silicone products data, General Electric Co., June 2, 1953. This content downloaded from 62.43.195.66 on Sat, 2 Aug 2014 12:06:45 PM All use subject to JSTOR Terms and Conditions http://www.jstor.org/page/info/about/policies/terms.jsp Article Contents p. 334 p. 335 p. 336 p. 337 p. 338 p. 339 p. 340 p. 341 p. 342 p. 343 p. 344 Issue Table of Contents Transactions of the Kansas Academy of Science (1903-), Vol. 61, No. 3 (Autumn, 1958), pp. 237-357 Front Matter Pollen as a Limiting Factor in Brood Rearing and Honey Production during Three Drought Years, 1954, 1955, and 1956 [pp. 237-248] Scientific News and Notes of Academy Interest [pp. 249-252] Junior Academy of Science Gas Chromatography [pp. 253-255] The Effects of Hypoxia on the Embryos of Pregnant Mice [pp. 255-258] Kansas Phytopathological Notes: 1956 [pp. 259-261] Kansas Mycological Notes: 1957 [pp. 262-272] Preliminary Studies of the Physiology of Growth and Pigmentation of Helminthosporium gramineum [pp. 273-279] Yield and Carbohydrate Content of Blue Grama Grass as Affected by Clipping [pp. 280-287] Effects of Five Diets on the Growth and Mortality of Fry to Fingerling Channel Catfish (Ictalurus punctatus) [pp. 288-298] Selected Records of Amphibians and Reptiles from Arizona [pp. 299-301] Additional Records of Mammals of Kansas [pp. 302-312] Pleistocene Lagomorpha and Rodentia from the San Josecito Cave, Nuevo Leon, Mexico [pp. 313-327] A Saber-Tooth Cat from South-Central Kansas [pp. 328-329] Stratigraphic Relations between the Ellsworth and Castine Formations, Castine, Maine [pp. 330-333] The Effectiveness of Silicones as Water Repellents When Applied to Concrete [pp. 334-344] Ninetieth Annual Meeting of the Kansas Academy of Science Ottawa University, Ottawa, Kansas, May 1, 2 and 3, 1958 [pp. 345-351] Minutes and Reports of the 90th Annual Meeting of the Kansas Academy of Science Ottawa University, Ottawa, Kansas, May 1, 2, and 3, 1958 [pp. 352-357] Back Matter