Aerated concrete blocks are white wall blocks that have been used for many decades for interior and exterior walls, but also for ceilings and roof systems, so that buildings can be built entirely from aerated concrete.
Aerated concrete is characterized by its low bulk density with a pore content of up to 90%, so it is very light. This results in very good thermal insulation values and easy processing. In contrast to bricks or sand-lime bricks, they are basically solid bricks, i.e. without perforations.
Additional insulation on exterior walls is not absolutely necessary, even when building particularly energy-saving houses. However, aerated concrete walls also meet high requirements for sound and fire protection, so they can be used universally. In addition to small-format flat blocks, entire wall and ceiling panels in element construction are also possible.
planning thermal insulation: Due to the excellent thermal insulation properties with a lambda value of up to 0.07 W/mK, passive houses can also be built monolithically without additional measures. Alternatively, an outer wall with 17.5 cm to 24 cm thick aerated concrete blocks can also be provided with a thermally insulating outer shell such as a thermal insulation composite system .
Summer thermal insulation: Aerated concrete has a specific heat capacity of c = 1000 J/kgK and, depending on the product selected, a heat storage capacity of S = 300 to 650 kJ/m³K for a 36.5 cm thick, monolithic outer wall. This means that there are good conditions for aerated concrete walls to protect buildings from overheating in summer.
Fire protection: Aerated concrete blocks are non-combustible and comply with building material class A1 according to DIN 4102-4. They therefore have excellent fire protection properties.
Statics: Aerated concrete has a relatively low permissible compressive stress σ according to DIN 1053-1. This varies from 0.28 to 1.6 MN/m². The higher the values for the permissible compressive stress, the worse the thermal insulation values. Aerated concrete masonry is therefore significantly less resilient than, for example, masonry made of sand-lime brick.
Sound insulation: Apartment buildings, for example, are subject to very high requirements for sound insulation. Aerated concrete can be used for this purpose if properly planned and executed. The specific sound insulation quality of the wall can be controlled, among other things, by the choice of raw densities. Due to the longitudinal sound conduction, most manufacturers recommend separating the outer walls made of aerated concrete in the area of the apartment partition walls and making the apartment partition walls double-skinned. In principle, it is advisable to have a noise protection report drawn up. But manufacturers also offer extensive services on this topic.
Masonry dimensions: Even though aerated concrete is very easy to work with on site and most craft businesses today have modern cutting equipment, it still makes sense to take the masonry dimensions into account as much as possible in the planning. These are regulated in DIN 4172 and are based on a grid of 12.5 cm (see ►Masonry dimensions in the lexicon).
Vapor diffusion: Aerated concrete walls have a water vapor diffusion resistance coefficient μ of approx. 5 to 15 and thus have a relatively high vapor permeability. Any type of outer skin should also be either rear-ventilated or diffusion-open.
Ecology: Aerated concrete is harmless from an ecological point of view. The starting materials are lime, cement, sand and water, without the addition of chemical additives. Only aluminium is added in very small quantities, about 0.05%, as a propellant. The energy required for the production of aerated concrete blocks is relatively low, and disposal is unproblematic. The low consumption of resources is evident in the comparison that 5 cubic metres of aerated concrete are produced from one cubic metre of raw material.
Special components: A large number of supplementary products are offered as a supplement to the wall blocks. These include compensating stones for height compensation, lintels, U-shells, etc. Compensating stones can also be installed as so-called chine stones with a significantly improved thermal insulation value. The chinestones achieve a thermal separation between the outer masonry and the floor slab or ceiling.
: Before the first row of stones is placed, a horizontal seal against rising damp and a levelling layer of normal mortar of mortar group III with a thickness of 1 to 3 cm are applied to the ceiling or floor slab. This serves to compensate for unevenness, so that the first row can be created absolutely perpendicular and aligned.
Bearing joints: Due to the manufacturing method, aerated concrete blocks of all kinds meet high requirements for dimensional accuracy, so that they are usually mixed with 2 mm thick thin-bed mortar of mortar group III. As a result, the thermal insulation properties are not weakened by mortar joints and the building moisture remains low. When moving, overflowing mortar must be removed with a filler after tightening.
Butt joints: Aerated concrete blocks are usually used in the butt joint technique. But there are also tongue and groove systems. The stones must always be bricked in a bond, i.e. with staggered butt joints. The offset (over-binding dimension) must be at least 0.4 x H or 40 mm for masonry blocks whose height is 250 mm or smaller. For stones that are higher than 250 mm, at least 0.2 x H or 100 mm. For the plan elements and wall panels, a relocation plan must be prepared by the manufacturer, depending on the approval.
Waiting times: Experience has shown that the majority of the regular changes in the shape of a shell take place in the first weeks and months. Accordingly, a waiting period before plastering is recommended to avoid cracks. A waiting period of about 6 months is advisable.
Frost and heat: If the heat is too strong, the stones should be wetted to prevent the mortar from being absorbed too quickly into the absorbent stone. In the same way, the masonry must be protected from frost and heavy moisture penetration. The construction of masonry with frozen building materials is not permitted. Exposed window sills or masonry open at the top should be covered with plates or tarpaulins.
Note: The DIN 1053 series of masonry standards has been withdrawn with the exception of the revised DIN 1053-4 (prefabricated components). Its successors are the Eurocode standards of the DIN EN 1996 series. Although DIN 1053-1 (calculation and execution) has also been withdrawn by the Standards Institute, it is still valid until the end of 2015 via the building regulations in Germany. Their application is possible as an alternative to the regulations of Eurocode 6, but may not be mixed with them.
Note: DIN 4108-1 (Thermal insulation in building construction; Sizes and Units) has been withdrawn and replaced by DIN EN ISO 7345.
DIN 1053-1, Masonry - Part 1: Calculation and execution
DIN 4108 Supplement 2, Thermal insulation and energy saving in buildings - Thermal bridges - Planning and execution examples
DIN 4108-2, Thermal insulation and energy saving in buildings - Part 2: Minimum requirements for thermal insulation
DIN 4109, Sound insulation in building construction; Requirements and verifications
DIN 4109 Supplement 2, Sound insulation in building construction; Instructions for planning and execution; proposals for increased sound insulation; Recommendations for sound insulation in one's own living or working area
DIN 4109/A1, Sound insulation in building construction - requirements and verifications; Amendment A1
DIN 4172, Dimensions in Building Construction
DIN V 4165-100, Aerated Concrete Blocks, Part 100: Flat Blocks and Plan Elements with Special Properties
DIN 20000-404, Application of Construction Products in Buildings: Part 404: Rules for the Use of Aerated Concrete Blocks according to DIN EN 771-4
DIN EN 771-4, Specifications for Masonry Blocks – Part 4: Aerated Concrete Blocks
DIN EN 1996-1-1 , Eurocode 6: Design and construction of masonry structures - Part 1-1: General rules for reinforced and unreinforced masonry
DIN EN 1996-1-1/NA, National Annex - Nationally determined parameters - Eurocode 6: Design and construction of masonry structures - Part 1-1: General rules for reinforced and unreinforced masonry
DIN EN 1996-1-1/NA/A1, National Annex - Nationally Determined Parameters - Eurocode 6: Design and Construction of Masonry Structures - Part 1-1: General Rules for Reinforced and Unreinforced Masonry; Amendment A1
DIN EN 1996-1-2, Eurocode 6: Design and construction of masonry structures - Part 1-2: General rules - Structural design for fire
DIN EN 1996-1-2/NA, National Annex - Nationally defined parameters - Eurocode 6: Design and construction of masonry structures - Part 1-2: General rules - Structural design for fire
DIN EN 1996-2, Eurocode 6: Design and construction of masonry structures - Part 2: Planning, selection of building materials and execution of masonry
DIN EN 1996-2/NA, National Annex - Nationally defined parameters - Eurocode 6: Design and construction of masonry structures - Part 2: Planning, selection of building materials and execution of masonry
DIN EN 1996-3, Eurocode 6: Design and construction of masonry structures - Part 3: Simplified calculation methods for unreinforced masonry structures
DIN EN 1996-3/NA, National Annex - Nationally determined parameters - Eurocode 6: Design and construction of masonry structures - Part 3: Simplified calculation methods for unreinforced masonry structures
DIN EN 1996-3/NA/A1,National Annex - Nationally Determined Parameters - Eurocode 6: Design and Construction of Masonry Structures - Part 3: Simplified Calculation Methods for Unreinforced Masonry Structures; Amendment 1
DIN EN ISO 7345, Thermal insulation - Physical quantities and definitions
EnEV - Energy Saving Ordinance for Buildings, Ordinance on Energy-Saving Thermal Insulation and Energy-Saving System Technology for Buildings
Masonry Atlas, the Construction of Supporting Structure and Building Envelope, Günter Pfeifer, Rolf Ramcke, Joachim Achtziger, Konrad Zilch, 2001
► Thermal Bridge Catalogue Federal Association of the Aerated Concrete Industry e.V.
► Aerated Concrete Handbook Federal Association of the Aerated Concrete Industry e.V.
Source: bauwion
