Check this article published in the Journal of construction and building materials:
Miccoli, L., Müller, U., and Fontana, P. 2014. “Mechanical behaviour of earthen materials: A comparison between earth block masonry, rammed earth and cob.” Journal of Construction and Building Materials, Vol. 61, 30 June 2014, pp. 327–339.
This article highlights the following:
• Compression and diagonal compression tests of earthen wallettes were performed.
• Manufacturing practice is one of the key factors affecting performances of earth block masonry.
• Earth block masonry and rammed earth show a brittle mechanical behaviour under compression.
• Cob shows relatively ductile post peak behaviour under compression due to fibres content.
• Cob presents a relatively good performance as far as shear behaviour is concerned.
Good luck!
Check this article published in the Journal of construction and building materials:
Miccoli, L., Müller, U., and Fontana, P. 2014. “Mechanical behaviour of earthen materials: A comparison between earth block masonry, rammed earth and cob.” Journal of Construction and Building Materials, Vol. 61, 30 June 2014, pp. 327–339.
This article highlights the following:
• Compression and diagonal compression tests of earthen wallettes were performed.
• Manufacturing practice is one of the key factors affecting performances of earth block masonry.
• Earth block masonry and rammed earth show a brittle mechanical behaviour under compression.
• Cob shows relatively ductile post peak behaviour under compression due to fibres content.
• Cob presents a relatively good performance as far as shear behaviour is concerned.
Good luck!
Yes, that is a good article!
This was a question that was highly debated at the International Conference on Rammed Earth Construction - it's a pity you weren't able to be there! The key point was to treat rammed earth's material and structural behaviour separately. The general consensus was that CEMENT STABILISED rammed earth can be designed as a masonry structure, given its similar material behaviour to masonry. However, UNSTABILISED or LIME STABILISED rammed earth requires a few more considerations due to its strong material strength dependency on atmospheric conditions. Curing conditions also strongly affect the strengths of these materials, as well as compaction conditions (water content at compaction affecting both density and stabiliser hydration, and density affecting stabilisation product propagation). There are other issues, for example regarding the use of reinforcement, that also require additional research.
Dear Christopher, yes it is indeed unfortunate that I was unable to attend the conference due to some unavoidable circumstances. I agree with your answer and suggestion, however, will difference in materials properties not affect the structural behavior of the structure? If yes than how could masonry standard be used for designing cement stabilized rammed earth structures? Is the difference very minimal and to what scale?
Depending on the level of cement, the material properties vary either a lot or a little with the atmosphere. A VERY rough rule of thumb might be to say that for 10% cement and above, the material strength effectively becomes constant. What that strength is, though, depends on the construction process, as I briefly discussed above. Differences in the material properties will undoubtedly affect the structural performance, so limiting the use of the masonry code to only high (>10%) cement contents (which is the upper limit for the New Zealand code, as it happens) might be prudent for now.
Bricks, cooked or not, are integrated each other by any kind of mortar whereas give to the structure a different behaviour by using different kind of materials and various composition of mortar. Rammed earth are made 'in situ' using the same specific material which contribute for the structure in same performance based behaviour.
I am very much thankful to all of you for your valuable answers to my query. Indeed yours answers have really helped me a lot.
Yoy may kindly have a look at this book:
Shao, Y 2012, Advanced Building Materials and Sustainable Architecture : Selected, Peer Reviewed Papers From the 2nd International Conference on Civil Engineering, Architecture and Building Materials (CEABM 2012), May 25-27, 2012, Yantai, China, Applied Mechanics and Materials, Trans Tech Publications, Durnten-Zurich.
This book is really good in terms of obtaining information not only about rammed earth and masonry but about other materials currently used in the Architecture, Engineering and Construction industry. This book is like a bible of materials.
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