One-dimensional compression behaviour of reconstituted clays with and without humic acid

It is often recognized that organic matter contained in natural clays and dredged clays is detriment to the engineering properties by increasing their compressibility. This study takes humic acid as an example to illustrate that organic matter may decrease the compressibility of reconstituted clays with a wide spectrum of predominant clay minerals: kaolinite, illite and smectite, based on experimental results from thirty types of one dimensional incremental load consolidation tests. It is found that the main factors of influencing the compression behaviour of reconstituted clays with humic acid are initial void ratio and void ratio at liquid limit. The difference in compression curves between reconstituted clays with and without humic acid can be attributed to humic acid effects on particle density and liquid limit of clays. The humic acid effect on the compressibility of smectite-dominant reconstituted clays is found to be much more sensitive than that for kaolinite- and illite-dominant reconstituted clays. A quantitative approach is also suggested to assess the compression behaviour of kaolinite- and illite-dominant reconstituted clays with humic acid using intrinsic compression concept.