Effect of variation in temperature and time in drying of soil samples

[defg]

Iwould like to know the effect of drying soil samples on an electric hot plate.Samples are placed on a container filled with sand at a certain level to ensure evenly distribution of the heat during drying.Compared to ordinary method of drying samples into ovens.Does it have detrimental effect compared to the test results carried out by drying in ovens?Please assist

 

[msucog]

i personally do not see a difference as long as caution is used with the hotplate. if the tech leaves the thing sitting there scorching part of the soil for long time, then there might be some slight variances. even then, i would find it hard to believe that a non-organic, sandy silt/silty sand soil would experience dramatic changes due to the lack of care during the drying process on a hotplate. i would say that the precision of the tests would probably be just slightly better with oven drying but the difference would likely fall within the variability of the test itself. if you ran say a proctor test 100 times with 50 times using oven dry and 50 times with hotplate, i'm willing to bet you would not see a discernable difference in the results due to the inherent scatter of points. you definitely would not see say a density test change from 96% to 86% (in other words, i'd say you're going to be in the realm of round-off error with what you describe). that's my opinion...

i'd be interested to see if someone has a bank of test trials with the two methods on the "same" material.

 

[civilperson]

The moisture turns to steam with explosive energy and scatters the particles outside the pan when heated on a hot plate, that is why the standard is oven dried below the temperature of steam.

 

[dirtsqueezer]

I've used a hot plate for drying extensively in the field (for sand cones), but I would always opt for an oven given the choice. I agree with civilperson and msucog. It eliminates dangers of loss of mass due to overheating organics or explosive loss.

Also, if you think about it, that pan will not heat evenly over the whole area. It's hotter in the middle and cooler on the edges. You might actually get a lower m% if you don't see the sample heated through.