News & Markets
Promising approach for a trend reversal – part 1
Prospects for the development of modular panels made of AAC in Poland
Autoclaved aerated concrete (AAC) blocks are the most popular material for wall construction in Poland [1], with a market share of approximately 42% [1, 2] in wall materials and 50% in masonry materials.
The production technology of standard AAC blocks has not significantly changed over the past 10 years. Technologies for producing lighter AACs have been developed, which can be used as monolithic partitions even with current thermal requirements [3]. AAC materials used as typical insulation materials have also gained popularity [4]. Larger sized blocks have appeared on the market, but they have not gained the same popularity.
In 2023, the production of a new type of product, modular wall panels, began in Poland. These panels are floor-height and are intended for both partition and structural walls. Reinforced AAC elements have been produced and used in Poland since the 1950s, although their market share has never exceeded 2-5% of total AAC production [5, 6]. Production included both vertical and horizontal elements. Reinforced AAC products were used in single-family and multi-family housing. Polish scientists have made significant contributions to the development of this product, including the development of manufacturing standards and installation guides for these elements. Many innovative methods of corrosion protection for reinforcement have also been developed. In the early 1990s, there was a decline in construction in Poland, especially in industrialized methods, which somewhat halted the production of reinforced elements. Producers at the time withdrew from the production of reinforced AAC elements, mainly due to the increase in the number of self-built houses and low labor costs in the early transformation period. Currently, we are dealing with different social and economic conditions that create new opportunities for the development of these elements.
Partition walls made of modular AAC panels, produced according to modern assumptions and recipes, have been used in Poland since 2012. However, due to imports from Germany and the Netherlands and transport costs, they have only gained popularity in a few regions of Poland. Production in Poland has the potential to significantly increase the popularity of these elements. The prospects for the development of the AAC industry have been discussed in [7]. The aim of this publication is to describe the technical possibilities of using modular AAC wall panels and to present market and demographic analyses that affect the prospects for the development of technology in the current market realities.
Market shares and application possibilities in various market segments
Approximately 50% of masonry materials in Poland are used in the single-family housing market segment, where the market share of AAC is estimated at around 55% (Fig. 1). In this market segment, AAC has gained popularity mainly due to its ease of installation and excellent thermal properties. In non-residential construction market segment (about 25% of masonry materials) and renovations (about 5% of masonry materials), the market share of AAC is estimated at around 50%. In these segments, AAC has gained popularity due to its ease of installation and good fire properties. In the multi-family housing market segment (about 20% of the masonry materials market), autoclaved aerated concrete has a smaller market share (about 15%) and is mainly used for partition walls and external cladding walls.
Modular wall panels in their available form can be used as structural elements in the single-family housing segment and in non-residential construction. In single-family houses, optimal conditions for the use of modular AAC panels are provided by flat roof and hipped roof house designs. They are particularly useful in repetitive developer projects, where shorter construction time and lower labor intensity have a greater impact on the fixed costs of the investment.
In multi-family buildings, modular AAC panels are mainly used for the construction of internal partition walls. A certain limitation in the application is the height of the panels (up to 3.0 m) and the required acoustic insulation of partitions [8], which requires the use of heavy, thin partitions. However, acoustic requirements in multi-family buildings allow the use of 10 cm thick panels for the construction of partition walls. The advantage of the panels is the possibility of thin-layer finishing, which significantly reduces the actual thickness of the partitions. Walls made of modular elements can also be used for inter-apartment partitions as double partitions with mineral wool between the layers [9]. This variant, due to the double installation cost, is more expensive to implement but is used in the adaptation of existing buildings for residential purposes, where the floors were not designed to carry the loads of massive partitions.
Labor costs and forecasted availability of physical workers in Poland
In 2010, labor costs accounted for 28% of the costs of wall construction. Ten years later, labor costs already accounted for 48% of the costs of building walls with calcium silicate blocks. This is not solely related to the general increase in labor costs. Between 2017 and 2022, the labor rate increased by 80%, while the average wage increased by 55% (Fig. 2). At the end of 2023, due to the increase in the minimum wage, the difference decreased but still favored labor costs. The dynamics of the increase in construction labor prices are therefore greater than the dynamics of the increase in material prices and wage growth. Employment costs are currently indicated as the biggest barrier to business activity in the construction sector [13]. Unemployment among those seeking physical work in construction has fallen below 1%, and 93% of companies report a desire to hire workers in the masonry and reinforcement sectors [14]. Wall construction involves significant physical effort. Assuming that such work can be effectively performed by men aged 20-60, the number of people potentially able to work will decrease from the current 11.3 million to 8.0 million by 2050 [15]. Considering that the number of people with higher education increased by 30% between 2011 and 2021 (from 17.1% to 23.1%) [16], the prospect of improving the availability of workers willing to work in the masonry sector is unlikely.
The population decline is not associated with a proportional decrease in housing needs. In 2021, Poland ranked third from the bottom in terms of the number of dwellings per 1,000 inhabitants in European countries, with a number of 400 compared to 495 dwellings in the EU [17]. The new EPBD directive on the energy performance of buildings [18] aims to reduce energy consumption in residential buildings by 16% by 2030 and by 26% by 2033. After the introduction of renovation passports, it is likely that adapting many buildings to the zero-emission standard in Poland will be too expensive. In 2021, buildings over 50 years old accounted for 38% of the housing stock in Poland, and over a million dwellings in Poland were built over 100 years ago [19]. Adapting such buildings to the modern emission standard involves significantly higher costs, especially since the insulation of such buildings often cannot be carried out in the traditional way [20].
Given the above, many factors indicate that the number of people willing to do physical work will decrease, the need for energy-efficient residential buildings will increase, which will undoubtedly significantly affect the currently popular masonry technologies. Without mechanization, these works will become too expensive and may be replaced by other technologies. Even today, many contractors report that the only people willing to perform constant heavy physical work are those over 40 years age.
Concept of modular AAC panels production
In 2023, the production of AAC panels began in two plants in Poland – Ostrołęka (Ytong production plant, part of the Xella Group) and Śniadowo (Prefbet Śniadowo production plant) [21]. Although these elements were historically produced in Poland, the equipment of the plant and the product range concept were redesigned, allowing the products to be adapted to current material and construction requirements. The reinforcement at the Ostrołęka plant consists of ribbed bars supplied in coils. The reinforcement is automatically cut and delivered to the reinforcement station, where it is suspended on steel needles. A transport anchor is also placed at the reinforcement station. The reinforcement skeleton is then dipped in anti-corrosion paint and transported to the parking station. After the paint dries, the form with the mounted and anti-corrosion protected reinforcement is transported to the curing chamber. The needles suspending the reinforcement are removed from the mixture, which gains initial strength after a few hours in the curing chamber, ensuring the bars do not change position. The reinforced panels are then autoclaved, and further differences compared to small-sized blocks only occur during packaging. The produced assortment in terms of density is analogous to standard blocks. The range of elements intended for use in structural walls is presented in Table 1 [22]. The weight of a single element, depending on dimensions, type, and moisture content, ranges from 56 to 291 kg.
Table 1: Types of modular AAC panels for structural walls
Thickness | Compressive strength | Mean dry density | Intended use |
36.5 cm | 2.2 | 300 | External monolithic walls (U = 0.20 W/(m2K) |
20 cm | 4.0 | 475 | Internal structural walls or external walls intended to be insulated |
24 cm |
Table 2: Dimensions of available AAC panels for the construction of structural walls
Height / length [mm] | 299 | 374 | 449 | 599 |
800 |
|
|
| + |
1800 | +1) | |||
2000 | + | |||
2200 | + | |||
2400 | + | +1) | +1) | +1) |
2600 | + | + | + | + |
2800 | + | + | + | + |
3000 | +1) | +1) | +1) | +1) |
1) Elements on special demand
Each of the above elements are available in the dimensions specified in Table 2. The four available lengths of the elements allow for the easy adaptation of existing projects, and the adaptation does not affect the position of partitions and openings by more than 3.75 cm. The concept requires the availability of 11 types of panels of each width at the storage site. Elements with a height of 800 mm are used for walls in the under-window zone, elements with a height of 1800-2400 mm are used as elements supporting lintels, and elements with a height of 2600-3000 mm are used for full-height walls fragment. The wall height is increased by the height of the starting layer (100 or 200 mm), which is recommended to level the surface of the slab or foundation wall. In the system, it is possible to construct walls in a height module of 100 mm. This concept is a continuation of the “Efficient Construction” program, under which two innovative mini-cranes for building walls with calcium silicate blocks were developed in recent years, and the “Construction Services” service was introduced, allowing walls to be ordered directly from the manufacturer along with installation. The manufacturer provides installation plans developed in the BIM environment along with the product.
The assortment for partition wall construction (Table 3) results from acoustic requirements in multi-family buildings [8]. Since partitions are used in buildings with walls made of different materials and different height modules, production with a height graded every 2 cm, from 2600 mm to 3000 mm, is necessary.
Table 3: Available types of AAC panels for partition walls
Thickness | Compressive strength | Mean dry density | Intended use |
7.5 cm | 5.0 | 625 | Walls between rooms in multi-family buildings |
10 cm | 5.0 | 625 | Walls between rooms and bathrooms in multi-family buildings (RA1 ≥ 40 dB) [8] |
Panel production is waste-free, meaning the unused volume of the mold goes to the slurry tanks and is then re-added to production. Unlike the assembly of small-sized blocks, the system requires an installation plan that includes the arrangement of the panels. Depending on the phase of the investment in which the adaptation is carried out, the project requires slight dimensional changes or is modified for optimal technology application. In the case of adaptation, any changes resulting from the width module of the plates can be mitigated by reinforced concrete columns.
Assembly of AAC modular panels
Structural AAC modular panels are installed using lifting equipment. It is possible to install them using a typical construction crane, a telescopic rotating loader, a mini-crane, or lifting equipment on HDS-type transport. Renting a mini-crane is not expensive but requires the delivery of the equipment. This is why it is not optimal equipment unless contractors owns such equipment. Installation from wheels using HDS lifting equipment is possible at a short distance from the production plant, as such a vehicle has a smaller load capacity, which significantly affects the price of the material delivered to construction sites located more than 50-100 km from the production site. The most efficient installation method is a crane on a wheeled chassis, which is usually able to install the walls of a single-family house from one or at most two workstations.
AAC modular panels intended for use as structural walls are equipped with transport anchors to which ring couplings are attached. The construction of the walls begins with the laying of the first layer of small-sized blocks, which serves to level the surface for the installation of panel elements. The panels are installed by a brigade consisting of two installers and a crane operator, whose employment cost is included in the equipment rental price. When erecting the panels, vertical joints are filled, and the mortar is usually applied before lifting the element. After installation, the panels are stabilized by nailing two steel clips, and every fourth panel is secured with an oblique plumbing strut. Dedicated mortar is used for installation, the thickness of which should not exceed 3 mm. The elements are not equipped with vertical junctions. The connection using only mortar means that mutual load transmission between the elements is not considered in the design. The plumbing strut are released after the ceiling is completed [34]. Fig. 3 shows an example photo of the installation of panels used for the construction of structural walls.
To lift the panels for partition walls from the pallet, a manual trolley is most commonly used. This trolley is used for transport to the target location and serves as a workbench in case the panel needs to be cut. Before lifting the panel, rubber blocks are installed, which serve as expansion joints from the ceiling or structural walls. The panels are installed by rotation. During installation, the panel is lifted with a special lifter, and wooden wedges are placed under the bottom edge. After installation, the bottom cavity is filled with general-purpose mortar, and the ceiling cavity and expansion joints from the structural walls are filled with polyurethane foam [23]. Fig. 4 shows an example of the installation of panels used for partition walls.
Summary and outlook
In 2023, Poland began producing modular wall panels made of AAC, combining the benefits of AAC with faster installation times. These panels are designed for both structural and partition walls, aiming to address labor shortages, rising construction costs, and increasing demand for energy-efficient housing. While AAC blocks dominate the Polish market, modular panels could gain popularity due to reduced labor intensity and compatibility with modern construction standards. Challenges include limited acoustic insulation for certain uses and high transportation costs for non-local production. Innovations in panel production and installation techniques, such as automated reinforcement and mechanized assembly, support their market potential.
The second part of this article focuses on construction time and labor intensity of panel installation, safety during AAC modular panel assembly, environmental impact and sustainability and finally the market potential of modular reinforced panels.
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