Section III, 1918 lii5] Trans. R.S.C. 



On The Penetration of Frost in Coficrete Structures 



By Louis V. King, M.A.; D.Sc, Associate Professor of Physics, 



McGiLL University 



(Read May Meeting, 1918) 



A problem of considerable interest and importance in marine 

 construction was suggested to the writer in 1911 by Sir John Kennedy, 

 Consulting Engineer to the Montreal Harbour Commission. It is 

 found that concrete piers built in tidal waters and exposed' to temper- 

 atures considerably below freezing suffer gradual disintegration 

 between low and high tide level, due to alternate freezing and thawing 

 as the surface is alternately exposed and covered by the rise and fall 

 of the sea. Meteorological observations taken in the neighbourhood 

 of Halifax show that early in the winter extreme cold may suddenly 

 set in while the temperature of the sea is considerably above freezing. 

 Alternate freezing and thawing takes place in the concrete face of the 

 pier throughout a shallow layer between high and low tide, the rest 

 of the structure remaining in an approximately constant state during 

 the whole winter. The expansion of the wet structure on freezing 

 and the change of volume on thawing gradually disintegrates 

 the concrete which flakes off and exposes a fresh surface 

 for the repetition of the process. The annual freezing and 

 thawing out of the structure and other slow changes which take 

 place owing to changes of weather are of very minor importance. 

 In the interior of the solid at a considerable distance from the surface 

 these fluctuations are very much reduced in amplitude and no actual 

 disintegration takes place which exposes a new region of action as in 

 the case of tidal effect. 



A method of protection proposed by Sir John Kennedy is to face 

 the concrete structure over the range of maximum tidal range with 

 thick water-soaked wooden planks. Alternate freezing and thawing 

 would then be confined to the wood while the concrete behind would 

 remain in a more or less constant state throughout the winter. The 

 question is then to determine what thickness is necessary to confine 

 the maximum depth of penetration of the freezing and thawing region 

 within the wooden facing. 



Section 2. 



Consider a thick water-soaked slab initially just at the freezing 

 point 0°C exposed to air temperature —^'' at the instant / = 0. The 



