hej...
det finns många bra greyer i USA for filling the "sprick"'s. This problem of logs spricking is a normal thing in cordwood, to be simply fixed after the first or second year by´putting a kind of wood-putty around the log ends...it is only done one time, and then the house should have no problems with air/water/bugs coming in.
Here is an answer from the biggest "expert" out there, Rob Roy, from this page:
http://www.greenhomebuilding.com/QandA/cordwoodQandA.htm"A: No building system, "natural" or otherwise, is completely without its problems. As a former polar bear, you can appreciate that an igloo eventually melts. Cordwood masonry will not melt in the hot Mexican climate, but you can expect that the logs will get very dry, and check and crack quite a bit. However, this would not deter me from building with cordwood masonry in Mexico. I would be inclined to stick with mortar (as opposed to cob), so that I could easily apply a flexible log chinking product (such as Log Jam by Sashco Industries or Perma Chink) to the mortar joints after the logs have done their shrinking. This should eliminate the "never-ending job" which you spoke of. Complete log-end shrinkage might not occur until a year or two after the home is built, though, so don't be in a big rush to apply the chinking. It is a time-consuming and expensive job that you will only want to do once. Do a Google search to get info on various log chinking products. Be sure to apply a thin coat to the entire mortar joint, not just the spaces around log-ends. Your wall will look great. Finally, during the masonry process, leave your log-ends sticking out a good quarter inch proud of the mortar matrix, so that there is room to apply the chinking. This also makes it easier to apply the material, as the log-ends will guide your brush. "