However, addressing the issue of cracking in structures using non-fired building materials remains a concern for investors, design consultants, and contractors. In reality, for projects using state budget funds, the use of non-fired building materials is mandatory, hence investors comply.
For projects not mandated to use non-fired building materials, investors often avoid using it, even willing to pay fines to avoid its use. Nevertheless, some investors and contractors have successfully used non-fired building materials. What is their approach? Why are they willing to use non-fired building materials while others hesitate?
Editor-in-Chief Nguyễn Thái Bình hopes that this seminar will answer these questions, helping stakeholders understand and correctly apply non-fired building materials, thereby avoiding future failures.
Sharing an overview of the application of non-fired building materials in our country, Dr. Phan Hữu Duy Quốc, Deputy Secretary-General of VCA, stated that limiting fired clay bricks will bring many benefits, such as reducing CO2 emissions, conserving agricultural land, and utilizing industrial waste in the production of non-fired building materials.
non-fired building materials has three basic characteristics: it is a type of building material produced without using heat for firing. In most cases, cement is used as a binder. Finally, non-fired building materials typically replaces fired clay bricks in construction.
Currently, non-fired building materials comes in four basic types. First is concrete bricks. Second is lightweight materials: bricks or panels from autoclaved aerated concrete, non-autoclaved aerated concrete, and foam concrete.
Third is gypsum wall panels, 3D panels, concrete panels, and lightweight panels. Fourth are various bricks made from construction waste and industrial waste.
Since 2010, the government and the Ministry of Construction have issued numerous policies to promote the development of non-fired building materials, notably Decision No. 2171/QD-TTg dated December 23, 2021, approving the program for the development of non-fired building materials in Vietnam until 2030.
The government aims for 100% of publicly funded construction projects and projects using state capital outside of public investment to use non-fired building materials by 2030. Construction projects with nine floors or more must use at least 90% non-fired building materials.
However, for various reasons, the production and consumption of construction materials have been continuously declining, and the non-fired building materials sector faces many difficulties, with slow consumption and high inventory, affecting business operations and the implementation progress of the government's program.
The production of non-fired building materials in 2023 is about 4.9 billion standard bricks, with consumption around 4.8 billion standard bricks, accounting for about 30% of the total construction material production.
Furthermore, some projects using non-fired building materials have experienced cracking and leaking, reducing trust in non-fired building materials. However, Dr. Phan Hữu Duy Quốc argues that the quality of non-fired building materials structures is influenced not only by the quality of non-fired building materials but also by the construction process and other supplementary materials.
Therefore, practitioners need to understand the issue correctly and follow the guidelines provided by experts. Local authorities need more technical support, and practitioners need training to understand and apply the correct techniques. Additionally, standards need to be reviewed and adjusted to meet the actual costs of using non-fired building materials.
Meanwhile, non-fired building materials (concrete aggregates, foam concrete, AAC panels, wall panels, etc.) had almost no large-scale production facilities, except for some small-scale production of concrete aggregate and foam concrete bricks by households in certain districts with available stone powder raw materials from nearby quarries.
By 2010, despite the city's directive to implement Decision No. 567/QD-TTg dated April 28, 2010, approving the program for developing non-fired building materials until 2020, only a few facilities produced concrete aggregate bricks with a capacity of 5-10 million bricks per year.
From 2011 to now, after the approval of the city's VLXD planning, Hanoi has completed the elimination of all traditional brick kilns, creating a premise for the development of non-fired building materials from 2016 to 2020, with 18 non-fired brick (GKN) factories planned. Each factory has a capacity of about 20-70 million bricks per year.
After reviewing the actual situation, most non-fired building materials products from the above-mentioned facilities are consumed in Hanoi. non-fired building materials has been used in many high-rise buildings, including those of households and businesses. State-funded projects use 100% GKN.
However, the non-fired building materials used are mainly heavy GKN (cement aggregate stone powder bricks). Other lightweight non-fired building materials types are not commonly used in some residential projects.
Additionally, non-fired building materials has some drawbacks such as high water absorption and heavy weight. This requires businesses to closely cooperate with state management agencies to create more favorable conditions for the development of non-fired building materials in Hanoi in the future.
Acotec wall panels have five outstanding advantages. First, they are lightweight, soundproof, fireproof, and moisture-proof. Second, Acotec wall panels facilitate fast construction with less labor. Third, they are non-fired building materials, environmentally friendly, and easily recyclable. Fourth, these panels have a flat surface, do not require plastering, and allow easy installation of MEP (mechanical, electrical, and plumbing) systems. Fifth, Acotec wall panels are economically efficient, increasing usable space and offering a suitable price.
Engineer Nguyễn Đức Hiệp noted that some factors affect the production process, including ensuring consistent material sources, regularly maintaining production lines, adjusting screw extrusion speed to match production conditions, and frequently checking material quality.
Regarding the experience of installing Acotec wall panels, engineer Nguyễn Đức Hiệp highlighted the layout of the panels, construction techniques, installation of lintels, MEP works, and finishing.
At the seminar, Mr. Trần Trung Nghĩa, Chairman of the Board of Directors of Trung Hậu Green Technology Co., Ltd., introduced the technology of producing perforated bricks from 100% fly ash aggregate, reducing costs and protecting the environment.
This product consists mainly of cement, fly ash, and additives with mortar absorption similar to fired clay bricks, enhancing adhesion.
Fly ash aggregate bricks have many advantages such as lower cost than fired clay bricks, lighter weight than non-fired bricks of the same size, meeting TCVN 6477:2016 standards for concrete bricks, high production capacity (10-20 million bricks per production line), and easy automation in construction due to precise brick dimensions.
Therefore, Dr. Trần Bá Việt emphasized that the construction of non-fired building materials structures must strictly follow TCVN and technical guidelines, with detailed construction design. Workers must be trained in concrete bricklaying techniques, and supervision must ensure construction quality, particularly in connections and wall bracing.
Assoc. Prof. Dr. Trần Văn Miền from the Polytechnic University - National University of Ho Chi Minh City noted that many studies worldwide have identified causes of cracking in aggregate cement brick structures.
First, uneven expansion and contraction between wall materials and surrounding underground structures (columns, beams) due to changes in environmental temperature and humidity.
Creep and drying shrinkage of aggregate cement brick structures create shear stress on the mortar joints. When shear stress exceeds the adhesion stress between mortar and bricks, cracks form in the mortar joints. Another cause is the improper placement of connection details or expansion joints.
Cracks in aggregate cement brick structures due to shrinkage and heat usually appear vertically or diagonally. These cracks often start at window corners or openings. These types of cracks are common and do not affect the load-bearing structure. Cracks caused by improper placement of connection details and expansion joints usually occur along the wall length and depth. These cracks significantly impact the structure's load-bearing capacity.
Assoc. Prof. Dr. Trần Văn Miền suggests some solutions: Firstly, adding expansion joints in long wall sections to prevent shrinkage cracks. Secondly, closely monitoring aggregate brick construction techniques (ensuring brick soaking and proper layer placement). Thirdly, using highly adhesive mortar and properly curing mortar joints during construction. Fourthly, using aggregate bricks of suitable strength and dimensions.
Additionally, cracks in aggregate cement brick structures can be repaired by applying a thin layer of high-strength mortar on the wall surface. Finally, to improve construction quality and ensure non-fired building materials structures' durability, quality control must be enhanced, from raw material selection, and production processes, to construction techniques.
The construction sector should be proactive in learning and applying new technologies and techniques, with a focus on improving quality, reducing costs, and protecting the environment. The development and use of non-fired building materials will contribute to achieving sustainable construction goals and environmental protection.
Source: Báo Xây dựng - Dịch Phong
