Internal frost damage in concrete - experimental studies of destruction mechanisms Fridh, Katja 2005 Link to publication Citation for published version (APA): Fridh, K. (2005). Internal frost damage in concrete - experimental studies of destruction mechanisms. Division of Building Materials, LTH, Lund University. Total number of authors: 1 General rights Unless other specific re-use rights are stated the following general rights apply: Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Read more about Creative commons licenses: https://creativecommons.org/licenses/ Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. LUND UNIVERSITY PO Box 117 221 00 Lund +46 46-222 00 00 Download date: 09. Oct. 2021 LUND INSTITUTE OF TECHNOLOGY LUND UNIVERSITY Division of Building Materials INTERNAL FROST DAMAGE IN CONCRETE Experimental studies of destruction mechanisms Katja Fridh Report TVBM-1023 Doctoral thesis Lund 2005 ISRN LUTVDG/TVBM--05/1023--SE(1-276) ISSN 0348-7911 TVBM ISBN 91-628-6558-7 Lund Institute of Technology Telephone: 46-46-2227415 Division of Building Materials Telefax: 46-46-2224427 Box 118 www.byggnadsmaterial.lth.se SE-221 00 Lund, Sweden Preface The work presented here was carried out at the Division of Building Materials at the Lund Institute of Technology. It was financed by Cementa AB and the Swedish Agency for Innovation Systems (Vinnova) as a part of the research consortium Road /Bridge/Tunnel. The support received is gratefully acknowledged. Being part of this large research group, which provided opportunities to meet with representatives of the building industry and with PhD students from all parts of Sweden on regular basis, was highly stimulating. I would like to express my gratitude to my supervisor Professor Göran Fagerlund who initiated the project and introduced me to the fascinating topic of ice in con- crete and for his effort during finalisation of this thesis. I would also like to thank my assistant supervisor Dr. Björn Johannesson for in- troducing to me the world of thermodynamics and for valuable discussions we had concerning science and the evaluation of measurements. Dr. Lars Wadsö provided great inspiration through the passion he showed for calorimetry and applied science and sharing it with me. Many thanks to Dr. Sture Lindmark for his support and encouragement and the valuable discussions we had at the beginning of the project. I would also like to thank my friend and colleague Peter Utgenannt for his sup- port and encouragement and for the discussions we have had throughout the project. To the boys in the laboratory, Bosse, Ingemar, Bengt och Stefan - without you, this day would have been a reality only in some distant future. Thank you for your patience and your good spirits. My sincere gratitude to all my colleges at the Division of Building Materials for being able to share with you all the very enjoyable and the less enjoyable episodes of my life during my time at the Division, especially since you never had the choice not to….. I would like to thank my dad and granddad for introducing me to the world of buildings and I hope you forgive me for approaching it theoretically. To all the intelligent and strong women in my life, especially Mum, Rita, Cecilia, Eva-Lena, Vicky, Ullis, Gunilla, Ulrika, Åse and Kaisa, each for inspiring me in your own very special way. Finally, my deepest gratitude to my family, my parents for always encouraging me to be the best I could ever be and for never once doubting my ability, and the two loves of my life, Christian and Josefine, who give me more than they will ever under- stand. I At last, Malmö May 2005 Katja Fridh II Summary Summary Chapter 1 presents the background to the project. There are two different types of attack; surface scaling and internal damage. Only internal frost attack is dealt with in the report. This type of attack, is often very severe, since big reduction in strength and stiffness can occur. After wide introduction of air-entrainment internal frost damage has become less frequent. Much phenomenological research on internal frost damage has been performed, but little research aiming at understanding the destruc- tion mechanism. Understanding of frost destruction is stated to be important for many reasons; e.g. for safe use of new types of concrete, for development of realistic freeze/thaw test methods, for development of durable surface treatments and repair. Understanding internal frost damage might also contribute to understanding of the surface scaling mechanism. Surface scaling which is a phenomenon of big economical importance is still unsatisfactorily clarified. Chapter 2 briefly describes the three most frequently stated frost destruction mecha- nisms; (i) the hydraulic pressure mechanism, (ii) the closed container mechanism, (iii) the ice lens growth mechanism. A fourth mechanism, based on different thermal ex- pansion coefficient of ice and concrete, acting during thawing, is presented, but shown to be of no importance. Each destruction mechanism depends both on inter- nal factors, like degree of saturation, water-cement ratio, permeability, air content, air-pore size distribution, and on external factors like freezing temperature, rate of cooling, duration of cooling, wetness. Possible effects of each factor are discussed for each mechanism. A literature review concentrated upon research at which the effect of the different factors mentioned above is performed. Results obtained in different studies are not unambiguous. For example, some studies show that increased cooling rate is negative for frost resistance, other that it is positive. The reason is that, at changing one pa- rameter -like cooling rate-, also other parameters are changed, most often the degree of saturation. The latter often overshadows the other variations. A literature review is also made of previous low temperature calorimeter studies of ice formation and melting in cement paste and concrete. Work in which combined measurements of ice formation and length changes have been made are presented. Chapter 3 presents the aim and general layout of the work. The aim was to try to identify the destruction mechanism behind internal frost damage. This should be done by selected experimental work in which one parameter at a time was varied. A main characteristic of the work is that the moisture content is held constant when III Summary variation is made by some other factor, like rate of cooling. Investigated internal vari- ables are; (i) water-cement ratio, (ii) air content, (iii) degree of saturation, (iv) mois- ture /drying history, (v) salt concentration of pore water. Investigated external vari- ables are; (i) rate of cooling and warming, (ii) duration of constant low temperature, (iii) lowest temperature level. The experimental work was divided in three different types of study: Study 1: Length change measurements during moisture-isolated freeze/thaw. Study 2: Calorimeter investigations of ice formation and ice melting. Study 3: Simultaneous measurements of ice formation/melting and length changes. In APPENDIX to Chapter 3 experimental variables and characteristics of the con- cretes are presented. Chapter 4 describes the experimental procedure for length change measurements pre- sented in Chapters 5-8. Definition of different ‘damage parameters’ is made. Tech- nique for moisture pre-conditioning of samples before length change measurements are presented. Chapter 5 presents an investigation of the effect of cooling and warming rate on length changes during single cycle freeze/thaw. Two cooling/warming rates were studied; ‘normal rate’ 3.6ºC/h, and ‘rapid rate’ 7.8ºC/h. Tests were made with concrete pre- conditioned in different ways; (i) natural water content after 4 years water storage, (ii) vacuum-saturated, (iii) a number of adjusted degrees of saturation, between natural and complete saturation. The main result is that that the rate of cooling has no, or marginal, effect on the observed length change at each given temperature. Another result, that was also confirmed in the studies in Chapter 6-7, is that non-air-entrained concrete expands during freezing at all degrees of saturation investigated, while air- entrained concrete with natural water content contracts more than the normal ther- mal contraction, except concrete with w/c-ratio 0.40 for which a small expansion was observed. At high degrees of saturation air-entrained concrete behaves like nonair- entrained. No destruction was seen during the thawing phase in any concrete at any warming rate. In APPENDIX to Chapter 5 results for all samples are presented. Chapter 6 presents the results of an investigation of the level of the lowest temperature on length changes during single cycle freeze/thaw. Two temperature levels were in- vestigated; -15°C and -30°C. For non-air-entrained concrete, and for air-entrained concrete with high degree of saturation, damage (expansion) was found to be directly IV Summary proportional to the minimum temperature; i.e. –30°C gave twice as big expansion as –15°C. Air-entrained concrete with natural water content contracted more than normal thermal contraction over the entire temperature range. Contraction was not depen- dent of the minimum temperature. Temperature was held constant for 3 hours at the two levels -15°C and -30°C.