Aerated concrete blocks and 3D printing: Technology perspectives



The urban population is growing.

Demand for housing increases. To meet that demand we need new homes. And a lot of them.

Based on the figures for demand, experts assert that by the year 2020 the global market for capital construction and construction materials is able to grow up to 9.6 trillion United States dollars. And that all because of the growing needs of mankind.

If we build 170 million capital houses in India, it will solve the housing problem of the local population. Although, we will have to wait for at least 15 years to do so.

Today, therefore, people speak not only of cheap and reliable, but also rapid construction. The problem is acute, but how is it solved?

Relatively inexpensive low-rise houses are often built of wood, aerated concrete or foam blocks. These are technologies and materials to which everyone are long accustomed, and so frame construction and construction using prefabricated materials are difficult to replace. Despite the fact that replacement is already taking place.



Using construction 3D printing people have learned to erect monolithic stone houses that are cheaper, faster and better in quality. 3D printing technology in construction has several significant advantages, which, unfortunately, are not always obvious to everyone.

To understand how the 3D printing overtakes traditional construction and why will companies that make a bet on new technology become winning, let us compare the two approaches — the classic and the new one. To do so, we will follow all technological processes and stages of construction of two houses — one made with aerated concrete and one printed using an Apis Cor 3D printer. Aerated concrete house is chosen for comparison for a purpose, since a «printed house» is still a «stone house».




Let’s start with blocks. More precisely, with their production.
Aerated concrete blocks are produced on factories: this process involves raw materials, employees, workers, industrial equipment and tools. On top of this, manual labor and depreciation expenses are added.



After the blocks are made, they should be stored and then sent to the construction site, which may be hundreds or thousands of kilometers away from the place of production. So it is quite logical if the calculation of blocks cost and production time will include handling, equipment work and transportation.

Before we start laying the blocks, they need to be unloaded. A long and difficult procedure: an average house with area of 120 square meters requires about 86 cubic meters of blocks, which corresponds to 60 cargo pallets. In addition to the vehicle used to transport blocks they also require a truck crane and workers who perform about 60 unloading operations in total.

It turns out that if we want to arrange for delivery and unloading we must also take into account transportation costs.



The blocks were delivered to site and unloaded. We are ready to start house construction. But in fact, it is easier said than done.

It all starts with future house markup. To this end, builders mark diagonals of the future house to ensure it’s of the correct geometry. Precision works and their verification can take up to two days. After making the building foundation, workers begin laying the first layer, which will form the basis of the building. In order to lay the first layer blocks are filed, polished and workers constantly monitor the level of masonry — by setting a thread to line up with horizon.

Then workers start the masonry works. They have to constantly use threads and level to perfectly align the horizontal line on each layer of blocks. This slows down the process, because all the work is carried out manually. Factory blocks often do not match the desired geometry, so each block is inspected and adjusted in size, with workers removing material in width, length and height. Each consecutive layer is leveled out with a special tool and then dust is removed with a brush. The last block is always sized to fit, without exceptions: It is impossible to calculate an integer number of blocks per the perimeter of the building.

In short, bricklaying requires constant adjustments.

In the process of laying the blocks they are stuck together with a special cement-based adhesive, which regularly gets mixed on site. Also, workers carry blocks manually, which requires time and effort.

Every two layers of blocks builders lay down horizontal reinforcement. To do this, around the entire perimeter of the house, on the top face of the blocks, using a manual or electric cutter, workers cut grooves. After dust is removed from cavities they are filled with a glue solution. Armatures are laid down into the solution and the excess is removed.

Masonry usually takes about 1-1.5 months. When construction is complete, you get a house with uneven walls due to the fact that between blocks there are seams and joints, sealing which requires additional work and time.



Aerated blocks cannot be left without finishing or insulation. In other words, we need an external facade — brick, ventilated facade, stucco. All the options are comparable in price and volume of works with the block laying itself. And approximately the same amount of time will be required to turn a box of blocks into the dream house. And don’t forget about the «bonus» — construction waste on the site which has to be loaded on a truck and taken away.



Block construction can be seen as a series of demanding and repetitive processes. Moreover, on the quality of each of these steps depends the quality and reliability of the whole structure. As you may have noticed, all stages of construction use manual labor, which increases the potential cost of human error. One wrong action of a worker may lead not only to an increase in cost and time, but also increase the number of structural defects that reduce the quality of the object as a whole.
Building a house using blocks cannot do without a large set of tools and consumables. To ensure that builders receive all the necessary items, logistics processes have to adjusted so that the lack of the required tools doesn’t disrupt construction time.

The quality and condition of the tools directly affects the quality of blocks processing, which creates an extra link in the chain of block process risks.
And most importantly, to build a house out of blocks, you need to gather a construction team and create all the conditions for effective and safe operation at the construction site.
If we carefully analyze all the stages of block construction again, we will note that this method is far from the principle of organic production.





Raw material for construction material is a dry mix that is supplied to the mixing system on site and immediately turns into a building material.



To begin construction, you need to bring the dry construction mix, 3D printer and the automatic mixing system to the site. A standard crane manipulator vehicle is enough for printer delivery.



Dry mixture, mixing system, and a 3D printer and installed directly on the construction site, and the operator starts printing. Site leveling is not required. All works are automated. The printer prints the walls and workers stack reinforcements on the finished layers every 30 − 40 cm. Complex construction works using manual labor are not required, therefore, the working team consists of two people. They control the printing process, monitor the equipment and perform simple construction works, such as laying fiberglass inserts and horizontal reinforcements.

After a 2-3 days print you get a stone house with smooth walls surfaces.



There is no construction waste. Nothing to recycle or dump. One just needs to wait a little.

One or two weeks — usually that much time is needed for the construction team to put the roof, install windows, floors, do the engineering and insulate the house. And that’s that. You can move in and do the inner finishing works.





For printing of 1 m³ of wall 0,267 m³ of construction mixture is required. That is to say that 1 m³ of blocks is replaced by 0,267 m³ of 3D construction mixture. The speed of vertical walls construction is increased up to 6 times.


Compared with the traditional construction using aerated blocks, Apis Cor construction method of 3D printing reduces the cost of transporting building materials by 3.7 times.



Masonry works speed estimate, without reinforcement, is 3.56 man-hours per 1 m³ concrete blocks. 3D printer produces 1 m³ of walls 333 mm thick per 0.85 man-hours.

At the same time, this value is constant and does not vary from machine to machine, and also does not depend on the complexity of the geometry of the building structure.

Material cost reduction — 2.8 times

Cost of an aerated concrete block wall structure, 400 mm thick, with wet facade and foam insulation, including the cost of blocks, glue, plaster, insulation and other materials, as well as the cost of masonry works, finishing, facade thermal insulation works is approximately 4445 Rubles.
The cost of a 3D-printed Apis Cor wall similar in thermal characteristics, appearance and bearing capacity is 1556 Rubles.




The new construction method has such characteristics as high speed of construction, relatively low cost compared to traditional construction, minimization of manual labor, stability of high quality of constructed homes.

In addition to these key parameters there are also several others: Construction 3D printing allows you to eliminate waste — after all, we only print what’s necessary for a project and nothing more.

One-story houses are built within a few days. This speed of construction allows people to settle in the new, fully finished house within a couple of weeks from the start of construction.

Construction 3D printing opens up a host of new design possibilities. The architect can design any form and shape, and the buyer is getting a dream house as a result. Walls printed using 3D technology have monolithic structure and surface immediately ready for finishing works.

Dozens of companies worldwide have already evaluated opportunities that construction 3D printing has to offer and became pioneers of innovative construction technologies. In the next two years we expect an offset of the dominant construction method towards mobile 3D technology.


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