Frost susceptibility

Turnips are generally lower in dry matter content than swedes and are divided into two main groups white-fleshed varieties (8% dry matter), often called stubble turnips, which are frost susceptible and prone to bruising, but grow very fast and make valuable catch crops which can be grazed in situ and yellow-fleshed varieties (8-10% dry matter) which are whole season crops and produce higher yields. 

Thermal property is another critical property for furnace slag. Because of their more porous structure, blast furnace slag aggregates have lower thermal conductivities than conventional aggregates. Their insulating value is of particular advantage in applications such as frost tapers (transition treatments in pavement subgrades between frost-susceptible and nonfrost-susceptible soils) or pavement base courses over frost-susceptible soils. 

Oulfur foam can be used to protect the permafrost by using a combina- tion of sulfur foam and local embankment materials for road, airfield, and other construction to reduce both the overall cost and the amount of embankment material that needs to be quarried in the arctic wilderness. The use of sulfur foam as subbase insulation prevents thawing of permafrost, which can cause subsidence during the warmer months. Another application uses sulfur foam with conventional pavement construction material for subbase insulation in frost-susceptible areas to prevent frost heave which is caused by freezing of the underlying soil. 

Mechanical analysis Sieve Hydrometer Soil classification, estimate frost susceptibility, compaction characteristics, shear strength, permeability... 

Absorption limits are specified in BS 882 [8.2]. BS 8007 [8.5] recommends that absorption should not generally exceed 3 %. A maximum value of 2.5 % is sometimes specified. In general, if the absorption is less than 1 %, the aggregate can be regarded as non-frost susceptible [8.1], although values of 2 % and above may be acceptable. 

The durability of concrete depends on both the long-term stability of the aggregate and on the quality of the cement paste system. The main aspects of aggregate durability are soundness, alkali reactivity and frost susceptibility. 

The other requirements consist of additional aggregate requirements such as frost susceptibility, permeability, leaching or mechanical behaviour of unbound mixtures. These requirements must be considered and stated when conditions arise. 

The site investigation mainly concerns resilient modulus determination, evaluation of the shrink-swell potential of high-plasticity soils, frost heave-thaw weakening potential of frost-susceptible soils and soils drainage potential. 

Additionally, in case the subgrade material is frost susceptible, the total pavement thickness (slab and sub-base) is recommended to be greater than 450 mm, unless the estimated mean annual frost index is less than 50 (see Section 13.5.10). 

Upheaval is caused by swelling of the subgrade owing to the moisture effect on expansive soils. Sub-zero temperatures and frost-susceptible subgrade material will also cause pavement upheaval owing to expansion of ice formation. 

Unlike silt, loess does not appear to be frost susceptible, this being due to its more permeable character, but it can exhibit quick conditions as with silt and it is difficult, if not impossible, to compact. Because of its porous structure, a shrinkage factor must be taken into account when estimating earthwork. 

Slope When air cools it becomes heavier and will move down a slope and force warmer air upwards. This is why frost often occirrs on the lowest ground on clear still nights whereas the upper slopes may remain free of frost. Frost pockets occur where cold air collects in hollows or alongside obstracting banks, walls, hedges, etc. (Fig. 2.1). Frost-susceptible crops such as early potatoes, maize and fruit should not be grown in such places. 

Trench backfill Some backfill materials are corrosive or frost susceptible... 

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