There can be different innovations in the use of materials in the buildings. One of the innovations that can be observed these days is the “RACC. The full name of this is “Reinforced Autoclaved Aerated Concrete”. This is considered to be a modification of the traditional concrete. This provides an option for sustainable construction. The origin of this form of concrete lies in the mid of the 20th century. In this form of concrete, concrete is made with reinforcement and is lightweight at the same time. The reinforcement provides strength to the concrete whereas aeration makes the concrete light in weight. The production of this type of concrete is done in an autoclave by the curing of the precast concrete. The result of this can be seen in the form of concretes having a good property of insulation. There are several reasons are there for which this concrete is widely used these days. Some of these reasons are less environmental impact, energy efficient, and more durable. Because of such advantages, there are different researches going on this concrete to find out the modifications that can be done on this concrete. This chapter presents a review of the literature of the different authors regarding this concrete.
Empirical Study
There are different researchers who have been working on the RACCs for a long time. Henecv, there are different papers available on this. For this reason, it is easy to obtain different valuable information regarding the RACCs. In this section, the different details of this concrete according to various authors are presented. The main things this concrete that was checked in This section were its “mechanical behavior”, “performance” and “practical applications” (Rudchenko & Serdyuk, 2022). It can be seen that different authors have presented different opinions regarding this material. In addition to this, different aspects of this material were highlighted in their papers by the different authors. The description of these are as follows.
Mechanical Properties of RACC
According to Liddell et al. 2023, the mechanical properties of a material are very important for the practical use of the material. It can be seen that depending on the mechanical property of a material the use of the material is decided. Moreover, it can be seen different behaviors of materials under changing conditions of loading. There are different forms of loadings are act on a material in actual practice. For this reason, it is important to check the behavior of a material under different conditions of loading (Liddell et al. 2023). The best way of doing this is to analyze the “mechanical properties” of the material. Some of these properties of the RACC were checked by the author.
The first thing that the author checked was the compressive strength of the RACC. It can be seen that in this form of concrete air is entered into the concrete. For this reason, there can be a small reduction in the compressive strength of the concrete than traditional concrete. However, there is no significant effect of this reduction can be seen in actual practice. This reduction is dependent on the amount of air entering into the concrete. This concrete takes into account the use of steel reinforcement (Stepien et al. 2022). Hence, the tensile strength of this concrete remains almost the same as that of the traditional concrete. There are different standard tests are there that are used for the determination of the mechanical properties of the concrete.
Structural Characteristics of RACC
According to Bernard et al. 2022, it is to be noted that the main use of concrete is to prepare different structural members. Also, concrete is a universal material that is used for different structural works. Because of the great potential of structural use of this material, the author identified several uses of this concrete (Bernard et al. 2022). The application of this concrete was checked both in terms of laboratory use and real-life applications as structures. The first thing that was checked in this literature was the capacity of bearing load by RACC. It is to be noted that structural members are subjected to different forms of loading. The weight of this concrete is less than that of traditional concrete. So, where required, more large sections can be used with concrete. Also, the deformation of material becomes an important criterion for the use of a material. In this case, also, it can also be seen that RACC retains its brittle nature. So, very less amount of deformation is seen in this concrete. Also, the “mode of failure” of a material plays an important role in defining the structural use of the material. For this reason, the author checked the failure mode of this material. It was observed that this concrete shows a brittle mode of failure in RACC.
Durability of RACC
According to Mollaei et al. 2022, the durability of a material is the most important for a material. It can be seen that for concrete also, the durability of it plays an important role in defining the characteristics of the concrete. There are different criteria are considered in checking the durability of the material. These are the resistance to chemical attacks, a reaction against “freezing & thawing” and the “carbonation effects”. It can be seen that this concrete is more resistant to chemicals than the usual concrete (Mollaei et al. 2022). Moreover, there is air present in RACC. Hence, it provides a good resistance against freezing. As a result of this, it becomes suitable for use in areas having cold weather. Also, the effect of carbonation is less in this concrete than the traditional concrete.
According to Khalil et al. 2020, bonding plays an important role in making the concrete durable and fit for structural use. The bond is defined as the attraction between the concrete and the reinforcement present in the concrete. It can be seen that increasing the “tensile strength” of concrete depends a lot on the “bond strength” of the concrete (Khalil et al. 2020). This strength depends on the adhesive force between the concrete & steel. In this form of concrete, there can be seen a good amount of bond strength in the concrete.
Fire Resistance of RACC
According to Okasha et al. 2022, structural concrete can be subjected to different forms of loading. Among these loadings, one of the major important loadings is fire loading. It is to be noted that this is one of the most undesirable instances. The fire resistance of a material is very much necessary for checking the durability of a structure against fire. The resistance of fire depends on the nature of the element present in a material (Okasha et al. 2022). The fire resistance of RACC is similar to that of the usual concrete. The thing that makes it different from traditional concrete is the level of insulation that it provides. Because of the presence of void spaces inside the RACC, it results in making a good insulating material. Hence, the heat of fire cannot penetrate easily inside.
Compression Strength Test
According to the author, the first step of doing the compressive strength test is to make a specimen either in cubical or cylindrical shape. It varies with the country standards. The specimen is then cured by putting in in a water bath. After this, the specimen is tested in a “compression testing machine” at regular intervals. The load at which the specimen breaks gives the failure load of te specimen. The load is divided with the “cross-sectional” area of the specimen. This gives the failure stress of the specimen. The average of tested specimen values are taken for identifying the compressive strength of RACC sample.
Tensile Strength Test
According to the author, the first step of doing the tensile strength test is to make a specimen either in cylindrical shape. It varies with the country standards. The specimen is then cured by putting in in a water bath. After this, the specimen is tested in a “tensile testing machine” at regular intervals. Here, tensile load is applied to the specimen from both the ends. The load at which the specimen fails is noted. After this, the load is divided by the “cross-sectional” area of the specimen. The average of tested specimen values are taken for identifying the tensile strength of RACC sample.
Effect of Carbonation Test on RACC
According to the author, the first thing that is done is to prepare the sample having a specified dimension. After this, the specimen is placed in a controlled “carbonation environment” where CO2 is introduced artificially. Next, the depth of carbonation depth with the time is checked. After exposing the sample to the carbon environment for a specified time the sample is removed from the environment. Then, compression test on the sample is carried out. The result of this is matched with the original compression test. Also, the change in the mass of the reinforcement is also checked. It can be seen that the effect of carbonation is less on RACC as compare4d to te traditional concrete.
Effect of Temperature Test on RACC
According to the author, the first thing that is done is to prepare the sample having a specified dimension. After this, the specimen is placed in a controlled “temperature environment”. After exposing the sample to the temperature environment for a specified time the sample is removed from the environment. After this, the corrosion in the material is checked. It can be seen that the effect of temperature is less on RACC as compared to the traditional concrete.
Theories and Models
The theories and models chapter of this project has thoroughly discussed the ways the theories and models have been used to describe the study of RAAC which have points such as the performance of the structure, behavior of the mechanics, and long-lasting durability of the concrete.
Different models of the composite material
In this section the study is discussed that is related to composite materials which helped in studying the nature of RAAC. It creates the codependency between the matrix of the concrete and the materials that are used for reinforcing where steel can be used as the reinforcement framework. The properties such as properties of the materials, fractional volume of the concrete, and mechanisms involved in the transfer of the loads that are applied (El, 2023). The theories help in understanding the materials that are used for making the structure and use of the concrete and the reinforcement strength development which helps in creating the support framework for the structure.
Figure 2: RACC Construction Process
Applicability of FEA in modeling the concrete
The analysis of the nature of the RAAC concrete can be studied by the implementation of FEA. The design of FEA can be involved with the development of some complicated models that have many numerical variations which can design and create the geometry of the structure, the conditions and regulations of the area of the structure, and the characteristics of the substances that are used as the main frame elements of the creation and analysis of the structure of the concrete (Liddell et al. 2023). The distribution of the stress and the system of the deformation process can be analyzed by the process of FEA which can be useful in understanding the structure.
Behaviors of the RAAC bonds
The difference in the appearance of the structure of the mixed concrete and the structure of the reinforced concrete can be studied and the behavior could be predicted for the concrete material. The bond models analyze the behavior and reaction of the concrete to the surface of the structure which includes various properties of the surface that could be used to conditions with curing properties of the agents that are used for the bonds (Goodier et al. 2022). The strength of the bond of the concrete can be predicted and analyzed which could be used to have the details of the bond of the concrete.
Literature Gap
In the section on the literature gap, the discussion of the journals lacked some crucial information that could be used for further discussion of the topic. The topic which is related to the structural analysis of the RAAC concrete is mostly discussed in this instance through the journals but it some gaps in the proper information that are crucial in this project for the discussion. The authors have lagged in informing about the proper uses of models that can be used for a better discussion of the project. The authors could have given the necessary models and theories for a better understanding of the analysis of the RAAC concrete.
Conceptual Framework
The conceptual framework helps in understanding the different dependent and independent variables that are associated with this project. The dependent variable in this project is the ‘strength of the RAAC’. The independent variables are ‘cutting time’, ‘moisture content’, ‘aeration process’, ‘temperature’, ‘concrete mix proportions’, ‘reinforcement type’, and ‘curing conditions. The dependent variable is working based on the independent variables (Khalil, 2020). The independent variables have the role of contributing many properties to the dependent variable which can be done for the structural study of the concrete. The proportion of the mixture and other factual analyses of the other properties create the development procedures that are relevant to the RAAC concrete project.
Figure 3: Conceptual Framework
The conceptual framework is designed for a better understanding of the properties that should be worked on depending on the variable which is dependent on the independent variables of this project. The project is done for the analysis of the structural bond and the stress distributions which are the main focus of this project (Stel’makh et al. 2022). The conceptual framework gives the outline of the basic structure of the methodology and theories that could be used for the description of the concrete.
Conclusion
There are many modifications in the construction sector that can be observed these days. Among these one of the major ones is the use of advanced materials. There are different forms of materials that are used these days. There are different modifications can be observed in the concrete. One such modification is RACC. The meaning of this is “Reinforce Autoclave Aerated Concrete”. The structural behavior of RAAC is studied in this paper for a better understanding of the bond and other complex models of the concrete. The materials are justifified in this paper which are used for the development of the concrete. The behavioral factors are used vastly for the implementations of the materials that are used for a completed work of development of the concrete. The journals that are discussed in this paper have helped to understand the behavior and the structure of bonds of the concrete. The authors have discussed the topic in a simple way so that it is easy to comprehend the structural behavior of the concrete. Proper use of theories and models has helped in understanding the working principle of the concrete. The literature gap has discussed the lack of crucial information that should be mentioned in the journals for a better understanding of the topic. This paper has surely helped in understanding and analysis of the RAAC concrete which also described the properties of the concrete.
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References
Journals
Bernard, V.A.R., Renuka, S.M., Avudaiappan, S., Umarani, C., Amran, M., Guindos, P., Fediuk, R. and Ivanovich Vatin, N., 2022. Performance investigation of the incorporation of ground granulated blast furnace slag with fly ash in autoclaved aerated concrete. Crystals, 12(8), p.1024.
El-Esnawi, H., 2023. Comparative Study between Structure Elements utilizing Reinforced Concrete and Autoclaved Aerated Concrete (Doctoral dissertation, Al-Azhar University Cairo).
Goodier, C., Cavalaro, S., Lee, K. and Casselden, R., 2022. Durability variations in reinforced autoclaved aerated concrete (RAAC)–extended abstract. In MATEC Web of Conferences (Vol. 361, p. 06005). EDP Sciences.
Khalil, E.A. and AbouZeid, M.N., 2020. Environmental Impact of Autoclaved Aerated Concrete in Modern Construction: A Case Study from the New Egyptian Administrative Capital. International Journal of Civil and Environmental Engineering, 14(1), pp.1-6.
Khalil, E.A., 2020. Impact of autoclaved aerated concrete (AAC) on modern constructions: A case study in the new Egyptian administrative capital.
Liddell, M., Palmer, M., Rolf, A., Atkins, C., Brown, R. and Goodier, C., Reinforced Autoclaved Aerated Concrete (RAAC) investigation and assessment–further guidance.
Liddell, M., Read, R., Palmer, M., Robertson, D. and Goodier, C., Reinforced Autoclaved Aerated Concrete (RAAC) panels: investigation and assessment.
Mollaei, S., Babaei Ghazijahani, R., Noroozinejad Farsangi, E. and Jahani, D., 2022. Investigation of behavior of masonry walls constructed with autoclaved aerated concrete blocks under blast loading. Applied Sciences, 12(17), p.8725.
Okasha, M.A.T.A., Abdel Razek, M. and El-Esnawi, H., 2022. EFFECTIVENESS AND STRENGTH OF AUTOCLAVED AERATED CONCRETE (AAC) IN THE COMPOSITE SECTION RC BEAMS AND SLABS. Journal of Al-Azhar University Engineering Sector, 17(64), pp.932-945.
Rudchenko, D. and Serdyuk, V., 2022. Environmental aspects of the production and use of autoclaved aerated concrete with low density. Budownictwo i Architektura, 21(1).
Stel’makh, S.A., Shcherban’, E.M., Beskopylny, A.N., Mailyan, L.R., Meskhi, B., Beskopylny, N., Dotsenko, N.Y. and Kotenko, M., 2022. Influence of recipe factors on the structure and properties of non-autoclaved aerated concrete of increased strength. Applied Sciences, 12(14), p.6984.
Stepien, A., Dachowski, R. and Piotrowski, J.Z., 2022. Insulated Autoclaved Cellular Concretes and Improvement of Their Mechanical and Hydrothermal Properties. In Thermal Insulation and Radiation Control Technologies for Buildings (pp. 393-419). Cham: Springer International Publishing.
