Autoclaved Aerated Concrete Blocks Research Articles

Simplified Model Study of Autoclaved Aerated Concrete Masonry Flexible Connection Infilled Frames with Basalt Fiber Grating Strips

Infilled walls and frames typically employ closely spaced rigid connection, which, under seismic actions, can lead to adverse effects such as amplified seismic responses, overall torsion, and the formation of weak layers in the structure. Flexible connection isolating the infilled walls from the frames can effectively mitigate the adverse effects of rigid connections. In order to reduce the structural mass and seismic impacts, Autoclaved Aerated Concrete (AAC) masonry flexible connection infilled walls have been widely researched. However, most AAC masonry flexible connection infilled walls require complex process operations for AAC blocks, which is not conducive to practical applications in engineering. Therefore, an AAC flexible connection infilled wall with Basalt Fiber Grating (BFG) strips instead of steel bars, with simplified process operations, has been proposed. Existing finite element models for BFG strip-reinforced AAC masonry flexible connection infilled walls employ solid elements, which are difficult to apply to large-scale structural simulations; moreover, existing simplified models for flexible connection infilled walls cannot simulate out-of-plane loading. In this paper, based on homogenization methods, using simplified elements to simulate components, a simplified model for the BFG strip-reinforced AAC masonry flexible connection infilled frame is proposed. Utilizing this model, stress analyses under both in-plane and out-of-plane loading are conducted and compared with corresponding experimental results. The results indicate that the in-plane simplified model (ISM) fits well with the experimental results in terms of hysteresis curves, with similar relationships between stiffness degradation and strength attenuation. The displacement force curve of the out-of-plane simplified model (OSM) before reaching the peak load is in good agreement with the experimental results. The maximum plastic range of OSM is 5% smaller than the test results, and it can be considered that the plastic ranges of the two are comparable, manifesting the models’ capability to adequately manifest arching behavior. The simplified model enables simulation of out-of-plane loading and provides a new approach for modeling large-scale frame structures with flexible connection infilled wall.

Stress-strain characteristics of autoclaved aerated concrete masonry under varying displacement rates

Comprehending the impact of displacement rate on the mechanical properties of autoclaved aerated concrete (AAC) masonry is critical for predicting the response of structures to seismic and other natural dynamic loads. This study investigates the effect of varying displacement rates (0.1 mm/min, 1 mm/min, and 10 mm/min) on the mechanical properties of AAC masonry under uniaxial compression through systematic laboratory tests. Results indicate a substantial increase in elastic modulus (100 %) and compressive strength (200 %) as displacement rates rise from 0.1 mm/min to 10 mm/min. Finite element analysis using a micro-modelling strategy in Abaqus corroborates experimental findings, simulating crack propagation and identifying stress and strain distribution. The outcomes of this study would facilitate the accurate design and analysis of framed buildings infilled with AAC block masonry, especially under dynamic loading. These findings are expected to significantly contribute to the enhancement of structural engineering practices, enhancing the reliability and effectiveness of AAC block masonry for constructing resilient buildings.

Consciousness and Prospects of Autoclaved Aerated Concrete (AAC) Blocks for Wall Construction: Comparative Study Nigeria and South Africa

Autoclaved Aerated Concrete Block (AACB) is a viable, sustainable walling material for building projects but has not been given the attention it deserves in developing countries. To increase the usage of AACB on building projects, this study examines the consciousness and prospects for its use in Nigeria and South Africa. The objectives are (i) to evaluate the degree of knowledge about AACB, (ii) the variants in Nigeria and South Africa, and to assess the likelihood of adopting AACB in Nigeria—the study centres on Lagos and five provinces in South Africa. Lagos was chosen in Nigeria because the State is the only place in Nigeria where AAC blocks have been used. A total of 145 questionnaires were administered to professionals who had been involved in AAC projects. In contrast, 17 South African respondents familiar with AACB in construction projects were polled online using Google Forms. Convenience and snowball sampling procedures were used for construction professionals in both countries. Data were analysed using Statistical Package for the Social Sciences (SPSS) version 23.0. Statistics such as percentages and mean scores were explored using analysis of variance (ANOVA) and the Mann-Whitney U test. Findings indicate that construction professionals in Nigeria know very little about 19 of the 20 documented AACBs. However, the South African professionals are very knowledgeable about AACB grade 42.5 OPC and AACB of AP/RHA and fully aware of AACB with grade 52.5 OPC, though they know nothing about the Bamboo Leaf Ash (BLA) AACB. This means that Nigerian professionals have a moderate stance on using AACB. The study concludes that South African Builders are more aware of AACB and its variants than Nigeria. This implies that AACB manufacturing in Nigeria would not thrive in the construction market due to poor patronage since patronage is directly related to product awareness. The study, therefore, suggests that building construction professionals should increase their understanding of AACB through continuous development training, workshops, and seminars on environmentally friendly building materials. Another suggestion is for consultants, clients, developers, contractors, governments, and research institutions to continuously conduct research and embrace findings on the AACB and new building construction materials regarding usage, wear, tears and durability.

Life cycle assessment and life cycle cost analysis of different walling materials with an environmental approach (comparison between earth-based vs. conventional construction techniques in Iran)

PurposeClimate change, environmental concerns, and economic problems pose challenges to the construction sector in Iran, which must provide affordable solutions while addressing environmental issues. Hence, natural earthen building materials are critically needed to reduce energy-intensive and costly construction practices dramatically. The purpose of this paper is to provide a framework for comparing life cycle assessments (LCA) and life cycle costs (LCC), for load-bearing walls of an single-family affordable housing unit in a desert part of Iran, Ardakan City.MethodsTo do so, both LCA and LCC for the unit were performed, considering a cradle-to-site perspective. For this purpose, 22 load bearing wall systems are assessed, including 18 stabilized and unstabilized earthen construction techniques, such as adobe, rammed earth (RE), and compressed earth block (CEB), in addition to four conventional wall assemblies of fired brick (FB), autoclaved aerated concrete block (AAC), ceramic block (CB), and concrete masonry unit (CMU). As well as assessing the environmental impact and life cycle costs associated with the life cycle of each wall, the optimal assembly of the wall is also examined.ResultsResults show that unstabilized earthen walling alternatives have significantly lower environmental impacts than conventional materials.ConclusionsSensitivity analysis indicates that by utilizing local materials to the maximum extent possible, impacts can be further minimized. Considering the results, transportation may even account for a greater proportion of EI than wall components.

PromotingSustainable Construction Practices in Developing Countries: Comparative Insights and Future Directions

Sustainable construction practices contribute significantly to the advancement trajectory in developing and developed nations. Emphasising environmental conservation, efficient resource utilisation, and the facilitation of healthier, more productive living and working environments, sustainable construction practices are fundamental to achieving a more prosperous and ecologically balanced future. However, the effective transition to and adoption of these practices in developing nations raises significant challenges. ‘Which way forward to addressing these issues as discussed in the last issue including the editorial (Windapo and Umeokafor 2023). These challenges, explored in depth in the diverse research articles featured in this issue, illuminate the ongoing difficulties developing nations face in embracing sustainable construction practices, along with potential solutions and future directions for research. They contribute to answering the question in the last issue, 'Which way forward?' (Ibid).
 This twelfth issue of the Journal of Construction Business and Management offers a thought-provoking and insightful collection of five seminal research articles by 11 authors from Nigeria, South Africa, Uganda, the United Kingdom and the United States of America. The key themes of the articles include promoting awareness of Autoclaved Aerated Concrete Blocks (AACB) for construction, enhancing government construction project success through effective leadership styles, fostering the adoption of Building Information Modelling (BIM) in Quantity Surveying, examining the link between Quantity Surveyors' conflict-handling styles and personality traits, and tracking technological and organisational change in the UK construction sector. As discussed below, each theme contributes to a nuanced and comprehensive understanding of the urgent need for, obstacles to, and promising strategies for sustainable construction in developing countries.

Effect of loading rate on mechanical properties of autoclaved aerated concrete having steel wool fibres, construction waste and alkaline solution by employing accelerated curing

This paper introduces a new method for developing Autoclaved Aerated Concrete (AAC) blocks, investigating the impact of different loading rates on compressive strength and failure behaviour. Alkaline solution and accelerated curing tank curing were explored as alternatives to conventional methods using aluminium powder and autoclave curing with fly ash. Construction and demolition waste was used as a substitute for fly ash, and chopped steel wool fibres were added to enhance block strength. The blocks were tested under various loading rates, and stress–strain graphs were generated to calculate Young’s modulus of elasticity values. ANSYS software was used for simulation and comparison, validating the accuracy of analytical models. The study shows a correlation between experimental and simulated values, confirming the successful incorporation of CDW and CSWF in AAC block development. Increasing the loading rate during testing leads to lower measured Young’s modulus, indicating strain rate dependency. However, including CSWF enhances Young’s modulus by redistributing stress and restraining crack propagation. The research contributes to understanding AAC's mechanical properties and performance, supporting its potential as a sustainable alternative for masonry materials in structural applications.

Autoclaved Aerated Concrete (AAC); An Eco Friendly Building Material: A Brief Study

Abstract: Autoclaved Aerated Concrete (AAC) is an eco-friendly building material. It is a product of fly ash which is mixed with lime, cement, aluminum powder and water in a certain proportion. The use of fly ash, a waste product collected from coal based thermal power plant can be consumed as a significant resource as building material. AAC is a best option for traditional red clay brick and cement brick. It is useful in residential, commercial and industrial construction projects. In this study, the review covers the study about AAC concrete blocks, advantages and its importance, AAC block manufacturing and its potential use as green construction material.

Characterization of mechanical behavior of different types of masonry with a detailed investigation of full-field strain using digital image correlation

This article presents an experimental study on the mechanical characterization of three different types of masonry: burnt clay bricks, fly ash bricks, and autoclaved aerated concrete (AAC) blocks, with a detailed focus on strain distribution and failure mechanism. The specimens were subjected to direct and diagonal compression loading, and the stress–strain curves and failure modes were studied. Digital image correlation (DIC) was used to obtain full-field strain data, allowing for detailed analysis of failure mechanisms, tracking of crack propagation, and examination of other intricate details. The DIC analysis showed that in burnt clay brick and fly ash brick masonry, failure under compression was initiated by the tensile splitting of the brick, while in AAC block masonry, it was initiated by the tensile splitting of the mortar. Additionally, the study identified that the failure modes under diagonal compression were different for each type of masonry, with bed joint sliding being the dominant failure mode in fly ash brick and AAC block masonry. In contrast, the failure mode in burnt clay brick masonry was due to vertical splitting along the loaded diagonal. In the diagonal compression test, the shear strain along both diagonals was negligible, and principal strain directions were observed to be aligned along the two diagonals.

Examining Carbon Emissions in Building Materials: A Case Study of Government Buildings in Pokhara Metropolitan City

Numerous studies placed particular emphasis on reducing carbon emissions from operations, often ignoring the importance of embodied carbon emissions. To evaluate the embodied carbon emissions associated with government buildings in Pokhara Metropolitan City, a systematic process-based approach was used to estimate the total embodied carbon over the lifetime of these structures. The research findings reveal that the cumulative embodied carbon emissions stemming from these buildings contributed a total of1281.56 metric tons (Mt) and 12504540.5 MJ of embodied energy. Furthermore, the study explored the potential for reducing these emissions by adopting alternative construction materials. In particular, the inclusion of AAC (Autoclaved Aerated Concrete) blocks, hollow cement concrete blocks, and stabilized soil blocks (8% cement)in the same building demonstrated reductions in total emissions by 5.56%, 4.38%, and 5.16%, respectively. It is crucial to acknowledge that this study primarily focuses on the construction stage of the building and exclusively considers civil construction materials. It did not encompass elements such as sanitary and electrical fixtures or other stages in the building's lifecycle, including operation and maintenance and eventual demolition. Consequently, it is recommended that future research endeavors undertake a more comprehensive analysis, encompassing electrical and sanitary fixtures, as well as all phases of a building's lifecycle, to gain a more holistic understanding of embodied carbon emissions in government buildings

A review on the effects of chemical admixtures on Autoclaved Aerated Concrete (AAC) blocks

AbstractAutoclaved Aerated Concrete (AAC) is a special composite and widely accepted construction material owing to good durability, raw material availability, and environmentally friendly nature. Nevertheless, the continuing focus of the industry remains in cost optimization and maximizing the performance of blocks. The investigations related to the effects of admixtures in AAC are continuing globally with the objective of improving the productivity and strength improvement of AAC blocks. It is now well documented that the behavior of admixtures in conventional concrete and AAC is different, partly due to the low quantities of cement in a mix design and production systems. Hence it is essential to conduct a detailed investigation for finding the suitability of chemical admixtures. This review paper shows the trend of admixtures used in AAC and describes how they affect the rheological characteristics, setting time, and mechanical properties. From the review, it is clear that the performance of admixtures mainly depends on the type of binder, type, and dosage of admixtures. PCE‐based superplasticizers and performance enhancers are generally recommended to provide incremental improvement in flow behavior and mechanical strength. However, it is important to note the mix design and complex interplay of various materials have a large impact on the performance of any admixture employed. The investigations thus far indicate that chemical admixtures also impact the initial curing times without sacrificing the mechanical properties of AAC. In general, the usage of admixtures can enhance the strength of blocks between 5% and 15% depending on the type and quantity of admixture.

Out-of-plane flexural behavior of autoclaved aerated concrete block masonry walls strengthened with high-ductility concrete

Masonry walls are susceptible to out-of-plane failures during seismic events. Therefore, this study investigated the out-of-plane flexural behavior of autoclaved aerated concrete (AAC) blocks masonry walls, strengthened with high-ductility concrete (HDC) and HDC with built-in textile grid (TR-HDC), to improve the flexural behavior of AAC block masonry walls. Nine groups of specimens, one group of reference walls, four groups of HDC-based strengthened walls, three groups of TR-HDC-based retrofitted walls, and one group of mortar-based retrofitted walls were built and tested using four-point loadings. The experimental parameters included the thickness of the strengthening layer, retrofitting configuration, shear-to-span ratio, and reinforcing textile ratio. The effects of these parameters on the failure mode, bearing capacity, deformability, and strength index were discussed based on four-point bending test results. The results demonstrated that the HDC and TR-HDC overlays improved the failure mode of the specimens from brittle to ductile fracture and increased their bearing capacity, ductility, and absorbed energy. The loading capacity of the strengthened walls further improved with an increase in the strengthening layer thickness and reinforcing textile ratio. Finally, based on the failure mode of the strengthened specimens, equations for estimating their out-of-plane bending and shear capacities were proposed.

Comparison of life cycle cost and embodied energy for buildings with alternative walling materials

Life cycle cost analysis (LCCA) is a process for determining the overall economic cost of an asset by examining original costs and discounted future expenditures, such as maintenance, repair, and renewal costs. The analysis of the Life Cycle Cost (LCC) of a project in the early stage of design helps in the decision-making process because this provides options for refinement and improvement to reduce the overall project cost. This study focuses on the Life Cycle cost analysis of Glass Fibre Reinforced Gypsum (GFRG) panelled and Autoclaved Aerated Concrete (AAC) block walling construction methods with conventional clay brick walling. The GFRG panel as a roofing component is also compared with traditional RCC roofing. Along with LCC, the embodied energy of materials adopted for the construction in each case has been compared.The initial, operational, and maintenance costs data are collected from various literature, data book, and industry. The Net Present Value (NPV) concept is used to analyse the cost-efficiency of alternatives using Life-Cycle Cost Analysis (LCCA). Buildings with GFRG and AAC consume less operational energy when compared to conventional construction with clay brick walling and RCC roofing systems. The comparative study indicates that constructions with GFRG panels and AAC blocks have lesser LCC and are economical. Also, for a structure with the same floor area, the embodied energy of materials for a building with GFRG panelled wall and roof is less compared to constructions with AAC block and brick.

Properties of Autoclaved Aerated Concrete in Different Curing Conditions: A Review

Abstract: Autoclaved aerated concrete (AAC) has many benefits for structures, such as heat insulation, sound insulation, fire resistance, reduced dead weight, and many more. AAC products include blocks, wall panels, floor and roof panels, and lintels. Besides its insulating capability, one of AAC's advantage in construction is its quick and easy installation since the material can be routed, sanded, and cut to size on-site using standard carbon steel band saws, hand saws, and drills. Although AAC has been produced for many years, there are still some points that need to be clarified. One of these points is the effect of humidity intrusion on AAC members in areas with high relative humidity levels, like Mediterranean climates. Therefore, various tests associated with the mechanical and physical properties of AAC concrete should be carried out, particularly Compressive Strength test in order to assess the strength of AAC blocks. The current project intends to analyse the physical and mechanical properties of autoclaved aerated concrete blocks at three different curing conditions using an accelerated curing tank to compare the effects of curing on the properties of AAC

Out-of-plane seismic performance of bed-joint reinforced Autoclaved Aerated Concrete (AAC) infill walls damaged under cyclic in-plane displacement reversals

The infill walls made of Autoclaved Aerated Concrete (AAC), which is a lightweight, fire resistant and energy efficient material, provide effective insulation solutions for building types of structures and becoming more and more popular in earthquake prone regions. Although the number of experimental tests examining the seismic response of clay brick infills is extensive, the amount of prior research on infill walls built of AAC blocks is rather limited. Past research revealed that the use of bed-joint reinforcement is one of the promising solutions to improve the global seismic response of masonry walls by enhancing strength and displacement capacity. In this study, the out-of-plane (OOP) seismic performance of AAC infill walls with flat-truss and innovative cord-type bed-joint reinforcement is experimentally evaluated. Also, consideration is given to the prior in-plane (IP) damage, which was found to degrade the seismic performance of infills in OOP direction. For this purpose, three IP and four OOP, in total, seven experimental tests were performed on four full-scale AAC infill wall specimens. The test parameters were selected in such a way as to make it possible to parametrically compare the OOP performance of AAC infills with flat-truss and cord-type bed-joint reinforcements with unreinforced AAC infill walls, together with the effect of prior IP damage on the OOP response of unreinforced AAC infill walls. It was found that the use of innovative cord-type bed-joint reinforcement improved the OOP strength to a similar extent to what was obtained from the truss-type reinforced specimen. In terms of ultimate displacement and energy dissipation capacity enhancement, the specimen with cord-type reinforcement performed better. In addition, the damages formed due to IP cyclic displacement reversals up to 0.005 drift ratio, which is defined as the drift limit for buildings with brittle infill walls in certain design codes, resulted in a significant reduction in the OOP strength and stiffness properties of AAC infills. The theoretical OOP strength calculations were found to provide unconservative strength values for the IP-damaged specimens.

Thermal and sound performance of new PVC prefabricated wall panel with log home style

This prefabricated wall panel is utilized and assembled from PVC pipe 3” for facilitating transportation and assembling into a log home style building. This paper aims to evaluate and compare the thermal and acoustic performance of 4 types of wall composite materials as follows: 1) 3” PVC pipes panel, 2) Autoclaved Aerated Concrete (AAC) block 3) Single fiber cement panel 4) Double fiber cement panel with air cavitation core. Physical property testing is by means of measurements, weighing, observations from operations. Evaluation is done of the heat transfer (hot box) and sound acoustic performance (sound box) inside the manufactured test boxes. The test results show that the PVC pipes panel has great potential being lightweight and having long service life. It is easy and fast to work with, install and decorate. This wall panel has a heat insulating performance as good as an AAC block. It can insulate more sound than test materials except for AAC block.
 Therefore, the use of PVC pipe as a prefabricated wall panel is an extremely attractive option in the building industry.

Utilization of steel wool fibers in AAC blocks containing a mix of flyash, CDW, and glass powder

The present article discusses the mechanical performance of autoclaved aerated concrete (AAC) blocks prepared by different constituents i.e., OPC-53, hydrated lime, flyash, and gypsum powder. These constituents are added in specific percentages obtained for AAC with a target density of 800 kg/m3 and their mechanical properties are found. Initially, flyash is used and then subsequently substituted by construction and demolition waste (CDW) and glass powder in 50% and 100% proportions along with the other constituents kept constant to make AAC blocks more sustainable. For this AAC block, the heat curing is done using an accelerated curing tank (ACT) instead of autoclaving and a mixture of alkaline solution in a ratio of (Na2SiO3/NaOH = 1.5) is used instead of aluminium powder for keeping the homogeneity constant throughout all the batches. Further, mechanical performance is enhanced when chopped steel wool fibers (CSWF) are added to the AAC blocks as reinforcement by a 5% weight percentage. For getting more improved mechanical performance heat curing is performed using an ACT at 65 °C ± 5 °C for 10 ± 2 h, which shows block density of the AAC blocks in the range of 1000–1600 kg/m3 with and without steel wool fibers. It is observed that the batches with the inclusion of steel wool fibers has 9–20% gain in compressive strength and a more than 18% increase in flexural strength of the blocks compared to those batches without CSWF. Hence, it is noted that the AAC blocks prepared with 5% CSWF have better mechanical properties. Moreover, a relationship between compressive and flexural strength is established as no Indian standard codebooks provide specific guidelines for determining the flexural strength of AAC blocks. The three different models gave three different relationships and Ellipse curve fitting showing a coefficient of determination (R2) = 0.998.

Utilization of waste materials in non-autoclaved aerated concrete blocks: State of art review

In the modern construction industry, there are many advanced materials used as a replacement for conventional bricks considering their advantages. Lightweight concrete blocks, Autoclaved Aerated Concrete Blocks (AAC), gypsum panels, etc. are some of the popular materials used for wall construction. They are preferred because of their easy workability and low density. Lightweight concrete blocks have high water absorption which reduces their durability. AAC blocks are extensively used but they are very costly and require a large quantity of water for autoclaving, thus the embodied energy increases significantly. NAAC is a lightweight concrete in which efforts are regularly made by researchers to incorporate waste material as a partial replacement of fine aggregate; this completes the definition of sustainable development to “meet the requirements of the present generation without risking future generations' ability to meet their own needs.” Waste materials such as fly ash, geopolymer, phosphogypsum, and rice husk have been used but waste marble dust, granite dust, and rubber which cause damage to the environment haven’t been yet incorporated as waste material in NAAC blocks. This review paper will focus on the advantages of using NAAC blocks and all the waste materials used in NAAC blocks to improve their mechanical properties. The characteristics which form the basis of comparison are Density, Water Absorption, Compressive Strength and Thermal Conductivity. A case study is mentioned for a single-storied bungalow in which the cost and time parameters of using NAAC block as a wall material were compared against AAC blocks and conventional red clay bricks using Primavera Software.

Effects of using autoclaved aerated concrete block debris as lightweight aggregate on internal curing of concrete

This investigation was carried out to evaluate the effects of using autoclaved aerated concrete (AAC) block debris as lightweight aggregate (LWA) on internal curing of concrete. The volumetric changes during the early period of curing leads to early shrinkage before to the concrete hardening. The formation of internal cracks due to the shrinkage had evidenced the strength and durability problems in concrete during later stage. The higher absorption capacity of LWA has been acted as internal water stored reservoir in concrete and facilitate the supply of water for internal curing to promote the additional hydration. The internal curing effect of pre-wetted AAC debris as LWA on mechanical properties and absorption behaviour of concrete was deliberated as novelty and the investigation was carried out using three different cement contents such as 340 kg/m3, 380 kg/m3 and 420 kg/m3. The granite coarse aggregate was replaced by 10%, 20% and 40% using AAC block debris of the same size by volume. The density reduction of concrete was determined after the addition of LWC. It was found that the AAC block debris can help in increasing the slump value of concrete and enhancing the mechanical properties and the absorption behaviour of concrete on par with control concrete.

Improvement on manufacturing processing time of AAC Block

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.

Experimental investigation on compressive strength and acid resistance of autoclaved aerated concrete using GGBS

The objective of this paper is to produce Autoclaved aerated Concrete (AAC) by using Ground Granulated Blast Furnace Slag (GGBS) as the partial replacement of the fly ash. AAC has emerged as one of the most prominent sustainable material because of its benefits such as fire resistance, light weight and high workability etc. Proportioning the mix components for AAC is a most important step in generating high-strength AAC block. The GGBS have been replaced at 24%, 30% and 36% of the total weight and have been tested for compressive strength, water absorption and acid resistance. The experimental results have shown that there has been an increase in compressive strength by 28–44% when compared to conventional AAC block and in acid resistance tests, the ratio of weight reduction and compressive strength declined as GGBS increased. It is been found that the block is eco-friendly as it contains non-toxic materials and the waste generated from industries. It can be used for constructing low load bearing structures and as the block is light weight material, it decreases the dead load of the structure.