Walls can be quickly constructed without the use of mortar, thanks to research by a team at the University of Luxembourg, who have engineered new masonry elements that interlock with each other.
The building elements are slotted into one another in an interlocking system reminiscent of Lego bricks. Key to this development is Shariar Agaajani, managing director of the company Asars Construction, who worked half-time at the university conducting research for his thesis.
The new masonry modules are made of two C50/60 concrete side walls which are connected to each other by concrete cross-connections. They plug into each other, preventing relative movements in the horizontal plane, and also contain hollow sections that can be filled with insulation, steel bars, concrete, or other materials to provide thermal, acoustic and mechanical reinforcement.
According to Agaajani, masonry elements that can be laid without using mortar in the horizontal joint have enormous benefits.
“Using conventional methods you first have to build the wall up to half its full height, and then let it dry before you can continue. With the interlock system, you can build a whole storey in one day and the load of the superstructure can be applied immediately,” he explained.
Mortarless walls are also easier to handle and lay down, and result in faster construction. Furthermore, they are easier to demolished, and the elements can be reused easily.
Agaajani studied the characteristics of walls built with interlocking elements sans mortars, and developed a new numerical technique to determine the extent to which the bearing capacity and weight distribution change in mortarless walls.
The main issue is the lack of mortar between each layer of blocks, because mortar plays a part in evenly distributing the load throughout the walls’ structures.
The lack of a load-distributing layer in mortarless walls means even minor relative height differences between neighbouring blocks and geometrical imperfections will cause localised and almost unique internal stress distributions induced by external loads. The amount of stress at point-contacts causes the premature weakening of the wall structure.
“No matter how precisely the blocks are manufactured, in practice neighbouring elements will never have exactly the same height,” explained Agaajani.
Agaajani and the researchers at the university worked with building materials manufacturer Chaux de Contern to manufacture prototypes of their blocks, then built up 2.5 m high walls and subjected them to shear, centric and eccentric loads, in order to compare their performance against conventional masonry systems such as hollow and shuttering blocks.
They found that when the modular elements are grinding after production in order to get regular and even contact surfaces, mortar can be safely omitted.
The investigations showed overall relative high structural performances for the developed dry-stacked elements. In addition, Agaajani developed an algorithm in order to simulate the load distribution and intensity in the wall in various height-to-length ratios.
Using these "virtual walls", the researchers were able to identify potential weak points and then further optimise the construction parts.
The researchers will work further to develop the building blocks until they are ready to be brought to market, estimating that they will be ready for use on building sites from 2017.
[Image courtesy Asars Construction.]
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