China’s aerated concrete is one of the earliest developed and most widely produced new wall materials. With over 50 years of progress, it now boasts a complete industrial system encompassing raw material production, equipment manufacturing, supply of supporting materials, and design research.
Aerated concrete is a lightweight material composed of cement, lime (a calcium-based material), fly ash or fine sand (silicon-based materials), aluminum powder (a gas-generating agent), along with small amounts of additives and water. After precise mixing and gas expansion, the mixture forms a porous body that is hardened through cutting and steam curing.
In the realm of wall material innovation, aerated concrete blocks have largely replaced traditional small clay bricks. About 98% of aerated concrete production in China consists of block-shaped units used for both interior and exterior walls. These blocks have a bulk density ranging from 500 to 800 kilograms per cubic meter, which is roughly one-third to one-fifth the density of ordinary sand and gravel concrete, and about one-half to one-third that of solid clay bricks. Naturally, their compressive strength is relatively low, between 2.5 and 10 megapascals, making them suitable primarily for non-load-bearing infill walls. With special treatments and reinforcement using rust-resistant steel bars, they can also be adapted for load-bearing walls.
Key Characteristics of Aerated Concrete
Aerated concrete offers four major advantages:
1. Abundant Raw Materials: The primary raw materials—lime and sand or fly ash—are plentiful in China. In areas lacking natural sand, machine-made sand serves as a full substitute. Fly ash, an industrial byproduct, exemplifies waste-to-resource recycling. Compared to ordinary concrete, producing aerated concrete reduces natural resource consumption by up to 75%.
2. Low Energy Consumption in Production: Manufacturing aerated concrete products with a density of 600 kilograms per cubic meter requires only about 45% of the energy needed to produce sintered bricks of the same volume.
3. Superior Energy Conservation: When used for exterior walls, aerated concrete offers higher thermal resistance and insulation performance than other composite wall materials. Consequently, walls can be constructed with less weight and thickness.
4. Reduced Transportation Energy: Due to its low density, aerated concrete products allow vehicles to transport larger volumes per load. This reduces the number of trips, saves fuel, and helps alleviate urban traffic congestion.
Transitioning from Blocks to Panels
Currently, most aerated concrete products in China are blocks, which often compromise wall quality and increase labor costs. In contrast, abroad, the ratio of aerated concrete blocks to panels is nearly 60:40. Aerated concrete panels are commonly used in high-rise construction—not only for interior and exterior walls, but also as reinforced floor slabs and roof panels.
The author collaborated with a prefabrication research institute to analyze various residential building layouts. Aside from the reinforced concrete frame system, internal and external wall panels and floor slabs make up approximately 46% to 59% of the volume of structural components in prefabricated residential buildings. Adopting aerated concrete panels for these elements could reduce the total structural weight of a building by about 25%, resulting in significant material savings. Additionally, this switch can decrease the demand for steel-reinforced concrete in load-bearing structures.
This highlights the high level of standardization achievable with aerated concrete panels. Their sizes and specifications can be produced using existing aerated block manufacturing facilities. Each panel typically weighs less than one ton, making them far easier to handle than conventional concrete wall panels and floor slabs, which often weigh around five tons and require 10-ton cranes for installation.
Aerated concrete panels are cut from larger blocks, avoiding issues related to manufacturing molds, depreciation, or scrapping commonly associated with reinforced concrete components. This contributes significantly to energy savings and emission reductions. True industrialization and standardization can only be realized by replacing custom-made concrete components with standardized aerated concrete panels for walls and floors—this remains the greatest advantage of aerated concrete panels.
Article source: China Construction News
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