Improvement on manufacturing processing time of AAC Block
Authors:   Faculty of Mechanical Engineering, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam, Nguyen Cam Minh , Lưu Thanh Tùng ,   Faculty of Mechanical Engineering, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam
Published: October 2023

Autoclaved aerated concrete (AAC) was invented in 1920s. AAC is composed of lime, cement, sand, fly ash and aluminum powder, which is the component that plays an important role in creating air voids, an essential factor of the AAC. The production process of the AAC block comprises of stages such as: mixing, casting, cutting, autoclaving, etc. All of the stages are conducted in an eco-friendly manner. The AAC is also called the future of construction materials because of its light weight feature when compared to red bricks along with excellent sound/heat insulation. AAC Blocks will help to reduce the use of cement, sand together with steel and other materials in the construction work. AAC Blocks can be used for both interior and exterior construction. In many construction projects, the AAC block is a more expensive choice than the red brick but the AAC blocks are more often used due to its cheap total construction value. Application of AAC block is very wide such as in industrial constructions, commercial buildings, offices, schools in rural areas, especially in fast construction of houses. The AAC blocks use cement mortar to bond and require a thinner layer than red bricks. Although the bond layer is very thin at only a few millimeters, the strength of the bond is very strong in both cases of load bearing and non-load bearing walls. The AAC Block has many more advantages when compared to other brick types in the construction market, however, the manufacturing process still needs improving to compete with itself in the future. AAC is a kind of cast concrete. The manufacturing process consists of: First, the sand, cement, lime, water, aluminum powder with a reasonable ratio is mixed well until the mixture is slurry. Secondly, the mixture is poured into the mold and left in the mold for a few hours. Thirdly, a transportation device helps to unmold and move the products to the cutting area. At the cutting area, the mixture is cut into blocks and proceeds to the autoclave under heat and pressure for 10 hours. There are many approaches to decrease the manufacturing time of AAC blocks. The main focus of the previous approaches is the forming of air voids when casting. In the traditional method, the aluminum powder will react with calcium hydroxide and water to create hydrogen gas which results in the creation of foam within the concrete. This method takes a long period of time for the reaction to complete. To reduce the time needed, some researchers use air or different reaction methods to create the foam. In this paper, a new approach will be introduced. The reduction of time will be focused on the waiting time before the cutting by measuring the time needed for the material to reach the suitable hardness. Among the 4 stages in producing AAC blocks, the paper will focus on improvement the process of molding and unmolding to reduce the amount of time and also keeping the quality suitable. The paper also presents the method to measure the hardness of the mixture of lime, sand, etc. before cutting.