The GT30: A Block Laying Robot by Shanghai Intelligent Masonry Technology

Words: Chai Qin

Why Develop the GT30?


China is the world's largest construction market and the largest producer and user of various types of building blocks (AAC blocks, hollow concrete blocks, porous clay sintered blocks, etc.). According to industry association statistics, the total production of AAC (autoclaved aerated concrete) products in China reached a record high of 210 million cubic meters in 2019. Despite the impact of COVID-19 and the declining growth rate of the construction industry, the total production of AAC products in 2023 is still close to 180 million cubic meters, of which AAC block production accounts for 160 million cubic meters, or 90%, and ALC panel production is 18 million cubic meters, or 10%. Despite the impact of the economic downturn cycle, combined with various statistical analysis data from construction industries, the total usage of all types of blocks and bricks in China will still exceed 500 million cubic meters in 2023.

Such a massive construction volume requires a large number of masonry craftsmen to support it. In the past decade, China's demand for masonry craftsmen has remained above 3 million (excluding material handlers and unskilled auxiliary workers). Engaging in masonry requires not only a strong body but also a clever mind and professional skills accumulated from years of work. This is not a job that can be quickly replaced. Therefore, the aging workforce in recent years has posed a severe challenge to the masonry industry. On one hand, a large number of excellent masonry craftsmen who have reached the age of 60 have withdrawn from the workforce under national regulations; on the other hand, young people are not willing to enter the construction industry and work from sunrise to sunset like their predecessors, engaging in arduous labor under strict schedules. The impact of the labor shortage on the masonry industry can be seen in the changes in construction costs: with employers providing accommodation and purchasing various types of insurance, the average post-tax daily wage of masonry craftsmen in 2018 was 280 RMB (about 40 USD), rising to 400 RMB (about 57 USD) in 2023, an increase of 42.5% in five years (compared to the average annual CPI index of about 2% during the same period).

The above situation is the background for our development of the block-laying robot GT30 (Figure 1). In 2019, we launched the GT30 project aiming to utilize the latest achievements in industrial robots and AI to develop efficient on-site construction equipment for block construction. This type of robot must significantly reduce labor intensity, reduce the dependence of operators on experience and skills, and guide young people who have received preliminary vocational education to enter the construction industry. At the same time, robots must significantly improve masonry efficiency to reduce construction costs and dependence on the number of workers.

Application Scenarios of the GT30

Due to the large population, the construction land available in China is relatively limited. Thus, the government has strict plot ratio requirements for real estate and other commercial development projects, public construction projects, etc. Under this limitation, most of China's new development projects are mainly in the form of multi-story structures with concrete/steel frame structures (Figure 2), concrete/steel frames plus shear walls, and high-rise structures with concrete/steel frames plus concrete core tubes (Figure 3).


 
                                                                    Figure 2                                                                                                                           Figure 3               

In these scenarios, blocks are mainly used to construct infill walls to meet the needs of external wall enclosure and internal space division. Due to strict seismic fortification requirements, unlike in the United States and Canada, the proportion of building load-bearing walls directly with blocks in China is very low and decreasing. This creates a unique requirement for robot applications: The GT30 needs to be able to enter indoor spaces for block construction operations after the completion of the main frame structure of the building (Figure 4). Meanwhile, it is necessary to easily access higher floors through construction elevators (Figure 5).


 
                                                                 Figure 4                                                                                                                                        Figure 5

Design Features and Main Performance Parameters of the GT30

The GT30 has undergone significant structural changes. The initial design (Figure 6) was to mount a six-axis industrial robotic arm and a specially designed block clamp on an autonomous mobile chassis with SLAM capability, capable of autonomously searching for and grasping blocks. However, we soon realized that this robotic arm's motion mode, based on the spherical coordinate system, posed a significant safety hazard to other workers in the cramped indoor construction environment. Therefore, we switched to the current configuration (Figure 7). We constructed the mechanical structure and motion mode of the robot based on the Cavendish coordinate system. After more than three years of construction verification with over twenty GT30s on nearly a hundred construction sites, it has been proven that the current structural design is safe and efficient.



 
                                                                         Figure 6                                                                                                                                             Figure 7

The table below shows the main performance parameters of the GT30. The GT30 is equipped with AI-based rapid wall design software (Figures 8 and 9), which can quickly calculate the arrangement of blocks based on construction requirements, such as the width and height of the wall, the type and size of blocks used, and the specific location of openings on the wall, to control robot operations.





 Figure 8 Figure 9

How Does the GT30 Work


The GT30 adopts a two-person team (Figure 10), with one operator responsible for robot positioning, AI software human-machine interaction settings, and placing blocks on the belt conveyor. An auxiliary worker is on the other side of the wall, responsible for applying mortar, securing steel bars, and correcting deviations. Because the blocks delivered to the construction site always have dimensional deviations, manual correction is still inevitable. The initial design of the GT30 included an automatic mortar application mechanism, but after repeated verification on the construction site, we ultimately canceled it. The reason is that the existence of mortar pumps increases the cleaning workload for workers, and it is impossible to discharge the sewage generated by cleaning during construction on high-rise buildings. The cancellation of automatic plastering reflects the compromise between technological advancement and practical feasibility. Our experience is that this compromise is necessary if robots want to enter the construction site. Due to the adoption of a two-person team, the safety of equipment and personnel during construction operations and robot transfers (Figure 11) can also be ensured.

 
                                                                      Figure 10                                                                                                                                                Figure 11

Efficiency and Return on Investment of the GT30

In China, the average price of building blocks is currently 300 RMB (about 43 USD) per cubic meter. The GT30 can complete 15 cubic meters or more of masonry per day, which means the daily output value can reach 4500 RMB (about 643 USD). After deducting personnel wages of about 1000 RMB and other miscellaneous expenses, the owner of the robot can receive at least 3000 RMB (about 420 USD). According to the current selling price of approximately 50,000 USD for the GT30, after purchasing the GT30, the investment in the robot can be recovered within a cumulative 120-150 days of construction, thereby earning considerable profits.

We have sold over twenty units of the GT30 in the past three years, with buyers including construction contractors, professional masonry teams, and equipment rental companies. At present, we are working hard to reduce the production cost of the GT30, further optimize and improve the performance of the equipment, enhance its applicability to various complex sites, and promote more GT30s to enter the construction site to reduce the labor intensity of workers.


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