Glimmermineralens påverkan på obundna bärlager: Glimmerhaltens inverkan på kornfördelning och tjällyftning
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Mica is a common mineral in the Swedish bedrock and the proportion differs between different places. It is commonly known that mica has a negative effect on desirable properties of construction aggregate, whether if it regard bituminous mixes, unbound aggregates or concrete.There are several investigations of mica’s effect on an unbound construction aggregate. Something most of them have in common is that they are based on a small amount of data which makes it difficult to make correct conclusions from the results since the results often are unclear. Since these investigations partly determines which aggregate that is appropriate for construction use there are a great economical interest to map at which mica content an aggregate is to be considered appropriate for construction use. Another very important aspect is that the knowledge about mica’s effect should be known in order to avoid substandard aggregate in a construction which may cause significantly shorter lifetime for the construction.The purpose with this investigation is to increase the knowledge base in order to achieve better assessments whether an aggregate is suitable or not depending on the proportion of mica in the material.The project was divided into two parts where the first part consisted of a literature study which purpose was to examine investigations that have already been done and provide ideas to new investigation methods. The second part consisted of laboratory work which’s purpose was to examine how the particle size distribution changes due to mechanical processing and repeated freeze-thawing. Furthermore, the mica’s effect on the frost heave has been investigated. The literature study showed that there are several investigations that treat micas effect on construction aggregates. However, many of them present opposing results when it comes to the materials’ mechanical properties. The research of literature has nevertheless given important information about different laboratory methods and their deficiencies as well as measures for the deficiencies.The laboratory work was done with three different unbound aggregates with a mica content of 32% to 59%. The laboratory work included freezing attempts combined with mechanical processing and some complementary standard investigations. The results showed that the proportion of fines increased in all materials due to mechanical processing and freezing attempts. The materials with higher mica content were more resistant against mechanical processing than the materials with lower mica content. On the other hand, the materials with lower mica content were more resistant against the freezing attempts than the materials with higher mica content. Any clear connection between how much a material expands with freezing and the mica content of the material could not be found. Furthermore, it is not possible from this investigation to determine whether the limits for what is considered to be an appropriate aggregate are correct, regarding the mica content. The amount of attempts is too small and the results too vague. The mica content definitely seems to have an effect but it is difficult to determine the importance of it.The method that is used for determining mica content with The Swedish Transport Administration as developer is the method VVMB 613. The investigations showed that this method is not reliable since there was a large spreading of the analysis result of the mica content.
Place, publisher, year, edition, pages
2013. , 59 p.
Life Earth Science
Bio- och geovetenskaper, Glimmer, Obundna Bärlager
IdentifiersURN: urn:nbn:se:ltu:diva-50912Local ID: 81f4e64e-1181-401c-991d-fc7132d26731OAI: oai:DiVA.org:ltu-50912DiVA: diva2:1024275
Subject / course
Student thesis, at least 30 credits
Civil Engineering, master's level
Validerat; 20130614 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved