Rammed Earth (Earthbit) construction technology: a forgotten experience

 Today it is difficult to surprise specialists with new building materials. It must have impressive properties to stand out from dozens of other, new and traditional materials.

Nevertheless, there is one interesting, but safely forgotten construction technology that can attract the attention of, if not specialists, then enthusiasts of environmentally friendly housing. We are talking about the construction of walls of low-rise buildings from compressed earth.

In Russia, the emergence of earthbound architecture is associated with the name of the architect Nikolai Lvov, who, during his travels across Europe, drew attention to buildings made of an unusual material - earth. Returning home, he began to build earthen buildings on his estate, and then erected several houses near the then capital, near Gatchina.

Skeptics did not believe in the durability of such buildings, and even near slushy St. Petersburg. The most distrustful of broadswords tried to chop down the walls, but apart from the notches on the weapon, there were no signs of damage. As a result, Lvov received a contract for the construction of the Priory Palace in Gatchina, which has survived to this day. For more than 200 years, the building has stood in a humid climate as a symbol of the high skill and reliability of earthquake technology.

What are the advantages of a land dweller? First of all, in the cheapness of the main building material - earth. Most often, the earth removed from the foundation trenches is fully used in the construction of the walls. Earthen walls perfectly accumulate heat; with permanent residence in such a house in the hot summer months, air conditioning is practically not needed. The fine-pored structure of the walls smooths out the drops in humidity in the premises. Earthen buildings are fireproof, which is also important today.

An amazing feature of the soil biter is the significant increase in strength over time. If the initial value of the compressive strength lies in the range of 15-20 kg / cm2, then after about 20 years it increases to 120-150 kg / cm2, which is comparable to the strength of concrete and exceeds the strength of fired brick.

Construction of an earth house

The disadvantages include the need for a solid foundation and thorough waterproofing. After all, the main enemy of earth walls is soil moisture. The disadvantages include the high labor intensity of the construction of buildings from soil. Work must be carried out in the warm (summer) period of the year for good drying of the walls. But even these disadvantages can be circumvented.

Traditional wall technology is a sliding formwork that gradually rises as the wall is erected. An earth mass of natural moisture is laid in the formwork with a layer of up to 15 cm, rammed, and then poured with a layer of lime mortar. This is a way of erecting monolithic walls.

But, by analogy with adobe, it is possible to make earth blocks, which can be prepared during one season and laid in the next. Such blocks, made from earthen dough with the addition of Portland cement and dried in the open air, have a strength of about 45 kg / cm2.

The recipe for mortar mixes is varied and depends on the properties of local soils. "Oily" and "lean" soils cannot be used directly, but after adjusting with various additives, they are quite suitable for building walls. Knowing the type of soil in your region, the specific formulation of the mixtures and the features of the construction technology can be found on the net.

In the guides for earthen wall construction, dating from the 19th century, the compositions of the mixtures, the design of the formwork, the techniques and features of construction in different regions are described in detail. Therefore, taking into account the possibilities of using modern materials, such as cement, it is possible to build durable, relatively cheap and environmentally friendly housing.

The income level of the population in the CIS countries is noticeably inferior to the income in developed countries, and the need for housing is huge. Therefore, the possibility of building your own house at a low price is very important. A comparative assessment of the cost of a house built with the use of earth-bit technology shows that its price is about seven times lower than a wooden house, and an order of magnitude lower than a stone one.

The cost of brick and concrete houses, which are most often erected today, is about 5 times higher than those of earth-beaten ones. But you need to remember that we are talking about low-rise (1-2 floors) buildings. Multi-storey buildings made of earth bit are impossible due to its low initial strength.

Land house project

Information for those who consider the return to archaic technology to be an eccentricity of loners. In the USA and Europe, earth-pit and adobe wall technology close to it has become widespread. For example, using the Rammed Earth Tire technology, walls are created, the strength of which makes it possible to eliminate the foundation.

Of course, calls for a return to a forgotten technology raise certain doubts, fears, or even ridicule. Although in the times of Lvov there were enough of them. Practice is the only arbiter in such cases. Taking into account the modern possibilities of small-scale mechanization, it is possible to reduce the labor intensity of work, to use modern materials. It all depends on the desire of the developer and his capabilities, including financial ones.

The house that the robot built

 The construction of new buildings is a laborious and uneconomical human activity. An extensive UN study found that the construction sector accounts for nearly 40% of global energy consumption and CO2 emissions. The Swiss Higher Technical School of Zurich (ETH Zurich), in cooperation with more than 30 experts from the construction industry, has developed a new construction concept for 4 years that can solve this problem.

The result of their activities was the three-story building DFAB House (stands for Digital Fabrication and Living), which became the first residential building completely digitally manufactured. That is, with the help of three-dimensional modeling, robots and a 3D printer. Building with an area of ??220 sq.m. required 60% less cement and meets stringent Swiss construction safety standards. More about the house, the technologies used and similar projects - in the next article from the provider Cloud4Y.

DFAB House was erected on the upper platform of the NEST complex ("Nest") in Dubendorf, Switzerland. More precisely, this is not just a complex, it is a full-fledged research laboratory, which consists of a central core with attached module houses. The first residents of DFAB House were employees of the research laboratories Empa and Eawag.

The space will not only be used as housing. It will also become a testing ground where new products from the energy and construction industries will be tested. This work is necessary in order not only to achieve increased efficiency in the construction of buildings, but also to ensure their high stability.

Building innovations

During the construction of the DFAB House, several of the research team's own developments were involved.

In situ Fabricator. Autonomous construction robot wagon. Able to create building elements using various tools with an error of less than 5 mm, and can operate semi-autonomously in changing conditions: work at the height of standard walls and pass through doorways. It is waterproof and dustproof, and is powered by mains power and battery. Among the disadvantages is too heavy weight (1.5 tons), but work is already underway to lighten the design of the robot.

Mesh Mold. An industrial robot with a height of two meters, on the manipulator of which a nozzle is installed for laying reinforcement rods and their welding. The robot, mounted on a tracked chassis, lays down and welds the reinforcement, preparing the foundation for the solid concrete walls. It automatically assembles the frame, after which a concrete solution is poured inside, which does not creep to the sides due to the dense structure of the frame and the composition of the solution itself. The main advantage of the system is the ability to create arbitrary shapes.

Smart Dynamic Casting. The technology of the automated process of concrete molding. Monolithic vertical structures are literally "grown" using a robotic arm equipped with various forming nozzles. The structure can get the desired shape due to the rotational motion of the die.

Smart Slab. A technology that allows you to create amazingly shaped concrete slabs using printed sand molds.

How it looks

The first floor of the DFAB House is dedicated to the common space. It has floor-to-ceiling windows supported by 15 specially designed concrete mullions. The central element of the room is an S-shaped wall that divides the ground floor area, creating open and hidden spaces. The thin concrete ceiling is cast in 3D printed formwork.

The second and third floors are living quarters. Climbing upstairs, visitors seem to find themselves in a modern alpine chalet. The four robot-created rooms are designed to create a sense of harmony and home warmth. They turned out to be light and rather spacious. These floors are supported by wooden frames, the layout of which has been simulated on a computer. Two construction robots participated in the installation. Digital design, according to the engineers, has resulted in significant material optimization and savings.

The house turned out to be modern in terms of technical equipment. In it, on command, the blinds rise and water in the kettle begins to boil, a multi-stage security and lighting control system functions. The equipment of the digitalSTROM company is responsible for the work of the "smart" home.

Technology is not only responsible for comfort, but also helps control energy consumption. Photocells on the roof provide energy (about 1.5 times more than is needed to maintain the house), and the control system monitors energy consumption and smooths out load peaks. The heat from the waste water is not wasted, but is transferred further through heat exchangers installed in the shower trays. Unused hot water is piped back to the boiler, which not only saves energy and water, but also prevents the growth of bacteria in the pipes.

The project is calculated using local or cloud capacities, the creation of the necessary templates for robots is done quite quickly. So the architectural potential of digital technology is huge, but almost never used on construction sites, the ETH team laments. Pilot projects like DFAB should accelerate the transition from theory to practice, says ETH Zurich professor Matthias Kohler. And to popularize this idea, the project team published their open source datasets and organized a traveling exhibit called How to Build a Home: Architectural Research in the Digital Age.

DFAB House is not the first building project to use digital technology. In 2014, the Chinese company WinSun demonstrated the architectural potential of 3D printing by releasing 10 one-story houses in one day. A year later, the Shanghai-based company also printed a neoclassical-style apartment building and mansion, but these projects remain under development.

Matthias Kohler explains that his team had no goal of breaking construction speed records. “Of course, we are interested in achieving a breakthrough in the speed and economy of construction, but we tried to stick to the idea of ??quality first of all,” he says. "You can do something very, very quickly, but that doesn't mean it's really sustainable."

Indeed, no one is particularly chasing speed so far. So, in Holland (sorry, the Netherlands) robots printed a full-fledged steel bridge - it took four machines six months of continuous work. The result is a one-piece design that will now be tested for strength and positioned over one of the ducts in case of successful tests.