496 
Journal of Agricultural Research 
Vol. XXIV, No. 6 
(17) It is not necessary for the tile to be actually in the peat for dis¬ 
integration to take place, but merely that the peat waters shall have free 
access to it. 
(18) The violent alkalinity of the tile, continuing even to the time of 
complete disintegration. 
(19) The destruction of solid concrete if the acid waters lie against it 
continuously. 
PART V. DISCUSSION AND CONCLUSIONS . 
The mechanical adaptability of such a material as concrete to the 
manufacture of drain tile and the aid which it can give to drainage work 
is very great. Its permanence in ordinary soils seems to be all ^at can 
be desired. That, however, is not a part of the discussion of this paper. 
It is with the suitability of concrete for peat soils or soils high in organic 
matter with which this paper deals. 
From the facts brought out in the investigation it would seem that 
there are some things which should be remedied before concrete tile, as 
now made, can be said to be suitable for use in soils high in organic 
matter. The first of these difficulties is the presence of free alkali. The 
observations of the past year seem to indicate that this is a characteristic 
of all concrete tile, retained even to the time of complete collapse. If it is 
true that free alkalinity is an inseparable characteristic of concrete as 
now made, and if water is present as a conveying medium, then the 
ultimate destruction of the tile in the presence of organic acid seems 
inevitable. The free alkali and the free acid are incompatible and must 
react against one another. This might not be serious if the products 
of the reaction were insoluble in water. The investigation has shown 
that they are highly gelatinous and are very readily soluble in water 
carrying carbonic acid. 
That carbonic acid is absorbed in large quantities by the concrete is 
indicated by the tests with the cement patties. It may also have had 
considerable to do with the increase in weight and density of the tile 
which lay in the stock pile at Coon Creek. 
Destruction of the concrete by water carrying carbonic acid must 
eventually take place exactly as the lime is leached from the surface of 
any soil by the formation of the double carbonates of calcium, but this 
process probably would be extremely slow and would not be of economic 
interest to the engineer. It is the rate of decomposition that is the 
controlling factor. 
DISINTEGRATION IN LOW-LIME PEATS 
On this rate of decomposition, the character of the surrounding mineral 
soil, the porosity of the tile and the character of the ground water flow, 
seem to be the controlling factors. In strongly acid soils, with the peat 
wet throughout the season, ordinary tile appear to break down after one 
year. At Grand Rapids, Minn., the peat is highly acid but the tile were 
laid shallow and the ground water, except for short intervals, kept well 
below them through the greater part of the season. Some of the tile were 
in fair condition at the end of ii years. At Weyauwega, Wis., in acid 
soil in the presence of abundant moisture, the tile were not placed directly 
in peat but in the sand below it. The system began to give trouble after 
two years and was very bad in three. In Wood and Juneau Counties, 
Wis., in acid peat above acid subsoil poor tile break down in a year. 
