Autoclaved Aerated Concrete Research Articles

Experimental Study on the Seismic Performance of New Energy Dissipation Connectors in an Autoclaved Aerated Concrete Panel with Assembled Steel Frame

This study proposes a new energy dissipation connector (NEDC) to connect an external autoclaved aerated concrete (AAC) wall panel with an assembled steel frame. To investigate the seismic performance and working mechanism of the NEDC under seismic action, horizontal low-cyclic loading tests were conducted on two sets of steel frames with different connectors using an MTS actuator. Similarly, the seismic performance and working mechanism of the AAC wall panels were elucidated using horizontal low-cyclic loading tests. Test results revealed that the NEDC increased ductility by 10.69–21.12% and energy consumption by 101.14% when compared to those obtained using hook bolt connectors. Overall, the NEDC provides good seismic performance, large deformability, and high energy consumption capacity, thereby rendering it ideal for assembled steel buildings. Furthermore, the NEDC can reduce wall panel damage during earthquake action and enhance the seismic performance of composite frames.

Mechanical and microstructural properties of lightweight CaO-activated fly ash composites in the presence of magnesium nitrate

The use of industrial by-products is required to replace cement to reduce carbon emission, and it is necessary to secure the strength of cementless binder to satisfy the required mechanical performance. The purpose of this study is to develop a new binder system composed of activated fly ash (FA) with CaO by adding magnesium nitrate ((Mg(NO3)2) as a new additive. To reveal the mechanism of strength enhancement, the influence of the dosage of Mg(NO3)2 on compressive strength, reaction products, and pore characteristics was observed. In addition, expanded perlite (EP) and expanded vermiculite (EV) were mixed in selected samples to develop a lightweight cementless composite. The results showed that adding Mg(NO3)2 significantly increased strength of CaO-activated FA system. In the reaction process, Mg(NO3)2 promoted the solubility of quicklime (CaO) to form more C-(A)-S-H and Ca–Mg–Al-(OH)-NO3-AFm phase and increased the initial concentration of silicon (Si) and aluminum (Al) from FA. The dense C-(A)-S-H formation enhanced mechanical strength by reducing porosity in binder matrix. When EP and EV were mixed in the selected binder, even if the strength decreased as the amount of EP and EV increased, the requirements for the strength and specific gravity of commercial autoclave aerated concrete (AAC) were satisfied.

Cyclic Behavior of Autoclaved Aerated Concrete External Panel with New Connector.

In this paper, a new slip-type crossing connector is proposed for autoclaved aerated concrete (ALC) panels with steel frames, and the proposed connector is also studied deeply in terms of seismic performance. The research included pseudo-static tests and finite element simulations. First, the seismic performance of slip-type crossing connectors and standard L-hooked bolts was studied comparatively, including the stability, bearing capacity, stiffness, energy dissipation, and hysteresis performance. ABAQUS 2020 software was used to establish finite element models, and the results of the experiments were verified with simulations on the basis. According to the simulations, a parameter analysis of connector optimization was carried out. The effects of connector thickness and connector plate length on the seismic performance were further investigated. From the experimental and simulation results, the slip-type crossing connector has excellent performance and good assembly efficiency, it can improve the deficiencies of the existing connectors. The comparison demonstrated that the slip-type crossing connector has a complete hysteresis curve, a high energy dissipation capacity, and a 9.7% increase in bearing capacity. The appropriate reduction in connector thickness and plate length can ensure superior seismic performance while saving resources. The finite analysis method can guide the design and implementation of new external ALC panel connectors.

Understanding the effect of sulfate ions on the hydrothermal curing of autoclaved aerated concrete

The addition of calcium sulfate in the preparation of autoclaved aerated concrete (AAC) leads to improved mechanical properties but the precise mechanism is not well constrained. To study this, the hydrothermal curing process was monitored quantitatively with and without sulfate addition using ex situ and in situ X-ray diffraction. Higher concentrations of sulfate ions delayed the formation of the intermediate C-(A)-S-H phase and the dissolution of quartz. Once the additional sulfate ions were depleted by hydroxylellestadite formation, C-(A)-S-H formation and quartz dissolution started simultaneously at higher rates. This delayed reaction is suggested to enhance the mechanical strength by i) improving the diffusion of silicate ions in hydrothermal solution, ii) improving the distribution of C-(A)-S-H and tobermorite crystallites, and iii) closing larger capillary pores in the range of 1–5 μm. This could explain some of the ambiguous results from previous studies and provide an opportunity to optimize the AAC production process.

Use of untreated phosphogypsum as a raw material for autoclaved aerated concrete preparation

Phosphogypsum (PG) is a common industrial waste from the production of phosphoric acid by the wet process. Usually, it requires pretreatment before use due to the presence of impurities. Developing a method that can be directly used to reutilize untreated PG in building materials is thus of great significance. Autoclaved aerated concrete (AAC) has a load-bearing and filling structure, the use of solid wastes as substitutes for siliceous and calcareous materials in the production of AAC has been widely demonstrated. Herein, a new type of AAC was developed by using untreated PG, lime, Al powder, fly ash and cement. The influence of untreated PG content on the foaming process, mechanical properties and hydration products of the final AAC product was investigated through X-ray Diffraction (XRD), Thermogravimetric analysis (TG-DTA), Fourier Transform Infrared spectroscopy (FTIR), Mercury intrusion porosimetry (MIP) and Scanning Electron Microscope (SEM). The results show that the sample with 15% PG content (PG4) exhibited the best performance, with the values of the bulk density and compressive strength being 715 kg/m3 and 7.5 MPa, respectively. In addition, the density range meets the B07 level and the compressive strength exceeds the standard 2.5 MPa (GB/T11968-2020). This study described the effect of untreated PG on the performance of the AAC product, which provides a new approach to use of untreated PG and the production of AAC.

Seismic analysis of a G + 3 confined masonry building with AAC infill using SAP 2000

With increasing seismicity worldwide, there is a need for resilient structures that will withstand large earthquake forces. In this context, Autoclaved Aerated Concrete (AAC) blocks with Confined Masonry present an attractive option due to their light weightiness among other desirable qualities. Confined Masonry (CM) construction offers enhanced seismic resistance compared to unreinforced and non-engineered reinforced concrete frame construction and is preferred in high seismic zones. This study verifies the effectiveness of Confined Masonry construction with AAC blocks as infill material by modeling a 2D single-bay G + 3 frame in SAP2000. After the mesh convergence study and validation with existing results, the columns were checked as per IS 456 (2000) along with the stress and strain to ensure that they were within the linear limits of the AAC. The analysis is carried out for AAC infill thicknesses of 120 mm, 150 mm, and 200 mm for zones II, III, IV, and V as per IS 1893 (part 1) 2016. The result of the study is compared with 120 mm infill thickness in zone II as the base case.

Research on the methods for improving the compressive strength of solid waste-based high-strength autoclaved aerated concrete

Three methods were used to improve the compressive strength of autoclaved aerated concrete (AAC), namely, 1) raw material carbonation modification enhancement, 2) pressurized foam enhancement, and 3) immersion of product in alkali and then enhanced by carbonation curing enhancement. The experimental results showed that the optimal weight ratio of fly ash (FA):carbide slag (CS) was 7:3, that is, the calcium:silicon ratio was 4:5. When the CS amount was 2.5 %, after the raw material was modified by carbonation, the compressive strength of the test block reached the maximum of 4.7 MPa, which was 52 % higher than that of the ordinary test block, and the density increased by 10 %. When the foaming pressure was 1.0 × 103 Pa, the compressive strength of the test block reached 10.4 MPa, which was 236 % higher than that of the ordinary test block, and the density also increased by 34 %. When the carbonation curing time was 6 h after alkali immersing, the compressive strength of the test block was the best, reaching 4.4 MPa, which was 42 % higher than the ordinary test block, and the density increased by 4 %. The use of carbonation modification and alkali immersion carbonation together reduced the compressive strength of the test block. The test block prepared by carbonation modification and pressurized foam had the highest strength, which was 12.3 MPa, and the dry density was 857 kg/m3. The orders of the three methods to increase the compressive strength were pressurized foam > alkali immersion carbonation > carbonation modification. This study realized the coupling of AAC preparation and CO2 utilization.

Virtual modelling and analysis of manual material handling activities among warehouse workers in the construction industry.

Musculoskeletal risks (MSRs) are a major concern among construction warehouse workers due to the lifting, carrying and lowering of heavy loads. The objective of this study was to reduce MSRs among warehouse workers in the construction industry using virtual modelling and analysis of activities. A preliminary study was carried out using the Standard Nordic Questionnaire. Biomechanical analysis, Ovako Working posture Assessment System (OWAS) and Rapid Upper Limb Assessment (RULA) were used to analyse the material handling activities. Virtual modelling was used develop the manikins with autoclaved aerated concrete (AAC) blocks at different carriage modes and stacking heights for the analysis. The preliminary study results revealed a higher prevalence of risk at their lower back (73.24%) among the construction warehouse workers. Biomechanical analysis showed a higher risk at L4-L5 joint of lumbar spine during overhead and bending postures for stacking the blocks. Posture analysis results of OWAS indicated a lower risk in overhead carriage mode. Detailed analysis with RULA confirms this result. Mean compressive force values at stacking heights were showed a significant difference (p < 0.05) in 8, 13, 18 and 21 kg AAC blocks. However, stacking height with a range of 120-140 cm was found as safer to the workers by considering all block sizes. An ergonomic intervention based on safer stacking heights was developed to reduce MSRs to an acceptable range. It improves productivity of handling the AAC blocks by reducing the cycle time. The intervention can be adapted for handling of similar materials in the construction industry.

Life cycle assessment of post-demolition autoclaved aerated concrete (AAC) recycling options

Autoclaved aerated concrete (AAC) is a widely used building material for masonry units, prefabricated reinforced components, and lightweight mineral insulation boards. Its low thermal conductivity and good fire resistance increase its popularity in residential buildings. Thus, post-demolition wastes are expected to increase in the future. However, post-demolition AAC (pd-AAC) is mainly disposed in landfills while landfill capacities decrease and legal framework conditions in Europe are tightening. This study performed life cycle assessments (LCA) of different pd-AAC recycling options and compared them to each other and to current landfilling to identify the best end-of-life handling of pd-AAC from an ecological perspective. The functional unit was 1 kg pd-AAC, and the system boundaries included pd-AAC at the demolition site, transports, pd-AAC treatment, and secondary production processes. Final products of the recycling process gained environmental credits/rewards for avoiding primary production using system expansion. Providing primary resources, primary production, and use phase were not in the scope of this study. Results show that especially closed-loop recycling of pd-AAC in AAC production has a high potential of improving environmental impacts. In the best recycling option (high substitution in AAC-0.35), potential savings per kg pd-AAC compared to landfilling reach up to 0.5 kg CO2-Eq, 7 MJ fossil resources, 0.005 mol H+-Eq (acidification), 0.17 CTU (freshwater ecotoxicity), 0.2 g P-Eq (freshwater eutrophication), 5.2 × 10-9 CTUh (carcinogenic effects), 4.4 × 10-8 CTUh (non-carcinogenic effects), 2.5 × 10-5 g CFC-11-Eq (ozone layer depletion), and 1.6 g NMVOC-Eq (photochemical ozone creation). Despite data uncertainties, recycling of pd-AAC is advantageous for several recycling options, including the production of AAC, light mortar, lightweight aggregate concrete, and shuttering blocks made from concrete without fine fractions (no-fines concrete). In Germany, up to 280,000 t CO2-Eq could have been saved in 2022 by pd-AAC recycling using different recycling options instead of landfilling.

Size distribution of pores and their geometric analysis in red mud-based autoclaved aerated concrete (AAC) using regression neural network and elastic mechanics

A large amount of red mud needs to be disposed of in China, which causes environmental pollution. The feasibility of using red mud in autoclaved aerated concrete (AAC) has been confirmed, and its strength and thermal properties are highly related to its pore structures. To further clarify the relationship between the pore diameter (shape) and performances of red mud-based AAC, this study aims to establish a quantitative relationship between the compressive strength and the pore structure of AAC with red mud as well as its average shape factor of pores with a diameter above 0.5 mm, which was relied on the principle of elasticity. The experimental results show the strength formula of red mud-based AAC considering its porosity and its pore shape is R=R00.031-1.21Vp23+0.95SHπ2-4π+8+SH2π4+16SHπ2-8SHπ316+SHπ2-4π+8+SH2π4+16SHπ2-8SHπ3. At the same time, to explore the constitutive relationship between the pore structure and thermal properties of red mud-based AAC, the series–parallel model of thermal conductivity is analyzed and modified, indicating that the series model has greater contribution to the effective thermal conductivity of AAC, where the expression is λeff=0.91v1/λ1+v2/λ2+0.19(v1λ1+v2λ2). Finally, through the neural network regression analysis, it is proved that the established model reveals good accuracy.

Research on the Behavior of Stiffening Walls in Single-Storey Buildings Made of Autoclaved Aerated Concrete (AAC) Masonry Units.

Experimental identification of stiffening walls is often limited to studying single-wall models. However, these samples do not reflect many additional effects—torsion of the building and redistribution of internal forces. This paper presents the results of two full-scale buildings made of autoclaved aerated concrete (AAC) masonry elements. The primary purpose of the work was to determine the changes in the stiffness of the shear walls and to attempt the empirical distribution of loads on the stiffening walls. The intermediate goals were: a description of the crack morphology and the mechanism of failure, the designation of the stiffening walls’ behavior. It was shown that the first crack formed in the tensile corner of the door opening, and the subsequent cracks formed in the wall without a hole. Based on the changes in the value of the shear deformation angles, the phases of work of the stiffening walls were determined. The presented research results are only a part of an extensive study of stiffening walls in masonry buildings conducted at the Silesian University of Technology.

The Use of Metakaolin in the Production of Autoclaved Aerated Concrete

The article provides an analytical literature review on the production of cements and cement materials with active mineral additives. The tendency exists to reduce a clinker component in cement and cement materials via use of blast-furnace granulated slag or other additives; it reduces expenses for cement production and improves performance of autoclaved aerated concrete (AAC). Inexpensive and affordable local effective pozzolanic additives can improve the economic and environmental attractiveness of autoclaved aerated concrete production. The performed studies have shown improved physical and mechanical properties of autoclaved aerated concrete with metakaolin, which is a product of low-temperature firing of kaolin.

Innovative recycling approaches to enable new material loops for AAC

AbstractThis paper shows different approaches to save mineral resources or energy for the production of autoclaved aerated concrete (AAC) using secondary materials. The goal is to implement new recycling routes in the building industry and to establish new material loops. It could be shown, that AAC can act as a sink for fine fractions from building rubble consisting of waste concrete and calcium silicate masonry units (CSU) by replacing the primary quartz sand. By choosing secondary raw materials like rice husk ash with a higher solubility than quartz, it is even possible to achieve AAC with the desired properties at lower autoclaving temperatures. After the end of life, AAC can be treated with the patented approach “ENSUBA,” a wet‐chemical washing procedure, which enables the complete removal of sulfate ions, which usually cause problems in the recycling of AAC. After this treatment waste AAC can easily be brought back to the material cycle and for example be used as a raw material for cement production. Most importantly, this ENSUBA approach can be combined sensibly with a carbon capture technique like the chilled ammonia process. This process captures CO2 from the cement production in an ammonia solution, leading to the precipitation of ammonium carbonate, which is needed for the ENSUBA process.

Circular economy's potential to reduce AAC carbon emissions

AbstractEstablishing a circular economy for Xella's building materials – among them Autoclaved Aerated Concrete (AAC) – is and will be one of Xella's key ESG projects for the coming years. In Germany, Xella has made it its goal to duplicate the powder‐input in the main AAC‐products from annually 60,000 t to 120,000 t by 2030.AAC‐powder used today emerges from the processing of AAC production leftovers, cutting residues and leftovers returned from job sites. In order to achieve the 2030 goal, Xella Germany will (1) generate new sinks, and (2) leverage new sources for AAC‐powder. Current production recipes are designed to take up emerging powder‐quantities, but nothing beyond. The present study describes the inspection and evaluation of current powder input shares per product type and options for their full exploitation by recipe amendments. In 2021, prototypes for Ytong PP2‐0,35 and PP4‐0,50 containing 20 m.‐% powder, and Ytong PP4‐0,55 containing 30 m.‐% powder were developed by the Xella Technologie‐ und Forschungsgesellschaft mbH. In order to prospectively supply sufficient quantities of AAC‐powder, Xella Germany aims at leveraging waste‐AAC from building demolition, so called “post‐demolition AAC” or “pd‐AAC”.We combined the “zero burden” and the “avoided burden methodology” to expand the life cycle assessment for the investigated circularity scenarios over the edge of waste generation. Our assessment revealed substitution credits of 0.55 kg CO2e/kg pd‐AAC for Ytong PP2‐0,35, and 0.43 respectively 0.33 kg CO2e/kg pd‐AAC for Ytong PP4‐050 and PP4‐0,55. The present study illustrates that our ambition to duplicate Xella Germany's powder consumption is achievable, when the new formulations are fully and consequently implemented. The recipe amendments have the potential to reduce expenditures for sand, quicklime, cement and gypsum/anhydrite, thereby reducing Xella Germany's annual (Scope 3) AAC carbon emissions up to 36 kt CO2e.

Belite cement clinker from autoclaved aerated concrete waste – A contribution towards CO2‐reduced circular building materials

AbstractThe processing of belite cement clinker in a rotary kiln at about 1000oC is a new recycling option for autoclaved aerated concrete (AAC) waste that otherwise must be landfilled. The clinker produced can partially substitute ordinary portland cement (OPC) in AAC production. Waste quantities and landfill costs are minimized, while at the same time CO2 emissions and the primary resource consumption of AAC production are reduced. The technology is currently under development. New analytical possibilities and modeling have made it possible to optimize the process conditions to such an extent that the use of belite cement clinker in aerated concrete production has already been technically tested. Particularly large effects on CO2 emissions can be achieved through the electrical heating of the rotary kiln and the coupled sequestration of the released CO2 in other secondary products such as recycled aggregate for concrete production from waste concrete. Comparable concepts for the AAC cycle are currently being worked on together with the industry partner Xella. Although decentralized plant concepts would be useful in order to minimize transportation, small plants are currently not economical according to initial estimates. In the long term, emission‐free product cycles are aimed at.

Mechanical properties and interface improvement of bamboo cellulose nanofibers reinforced autoclaved aerated concrete

Autoclaved aerated concrete (AAC) has low density, suitable compressive strength, and excellent thermal and sound insulation capacity for building non-bearing walls. However, porous AAC blocks usually have low flexural strength and thus are prone to cracking during service life. Herein, bamboo cellulose nanofibers (BCNF) were incorporated into AAC matrix to enhance mechanical strengths. The BCNF was further modified by 3-mercaptopropyl-trimethoxysilane (KH590) to improve the interfacial bonding between BCNF and AAC matrix. Results showed that the AAC with the addition of 0.3 wt% KH590-modified BCNF had 49.2% and 20.7% higher flexural strength and compressive strength than those without BCNF, respectively. AAC slurry belongs to a pseudoplastic fluid with a yield value, which can be described by Bingham rheological model. With the increase of shear rate, the stress of AAC slurry increased and the viscosity decreased exponentially. The interfacial bonding of BCNF/AAC-matrix was characterized by FTIR, XPS, NMR, and SEM analyses. It was confirmed that the siloxane groups of KH590 react with the hydroxyl groups of BCNF, thus grafting the BCNF with hydrophobic moieties and improving their interfacial adhesion with AAC matrix. In addition, granite powders collected from stone processing mill were utilized as a main component of AAC matrix. This study provides a feasible way of utilizing renewable materials and solid waste in preparing high-performance AAC as green building materials.

Effects of red mud on workability and mechanical properties of autoclaved aerated concrete (AAC)

Red mud poses a severe threat to the local environment that needs to be disposed of properly. This study investigated the feasibility of using red mud in autoclave aerated concrete (AAC), whose performances were systematically assessed, and the performances were further interpreted by microstructural analyses. The initial results reveal the negative impacts of using red mud in AAC concerning workability and strength, which could be assigned to the low activity of red mud as well as its small particle size, and the process of gas generation inside AAC was inhibited. In addition, the worse pore structure and the excessive content of tobermorite in AAC with a higher amount of red mud could also account for its reduced strength. Further, 22.5% of red mud to replace fly ash in AAC could be the optimal ratio considering several indexes of AAC involving red mud, and the use of polycarboxylic acid in AAC or adjusting the water-solid ratio of AAC can greatly improve the overall performance of AAC with red mud, which satisfies the requirements stipulated by the standard.

Interfacial properties between autoclaved aerated concrete and concrete after high temperature

Multi-ribbed Composite Wall (MRCW) structure is composed of densely distributed ribbed frames, including ribbed beams and columns, and autoclaved aerated concrete (AAC) filled inside ribbed frames. This paper investigates the interfacial properties between concrete and AAC after high temperature, based on a combined experimental and Finite Element (FE) study. To this end, 70 prismatic bonding specimens (150 × 150 × 450 mm3) composing of the two materials were fabricated and subjected to seven high temperatures ranging from 100 °C to 700 °C. It was observed that, after being subjected to 300 °C or higher and then cooled down, a large number of transverse cracks appeared on the surface of the block. When the temperature was over 600 °C, cracks appeared at the interface of AAC and concrete.Next, slant shear tests were carried out. The failure mode was mainly interfacial shear failure. The maximum shear stress τmax, interfacial shear stiffness K, and fracture energy GC changed with shear angle and temperature, where τmax and K followed similar pattern. τmax and K were maximum at 200 °C. τmax of 30°, 38° and 45° at 200 °C were 146%, 137%, 110% of those at 100 °C, respectively. When exposed to temperatures above 200 °C, τmax gradually decreased. At 700 °C, τmax of 30°, 38° and 45° were 40%, 50%, 57% of those at 100 °C, respectively. As the shear angle increased, τmax increased. GC increased with the increase of test temperature and shear angle. At 700 °C, GC was more than three times of that at 100 °C. Further, Finite Element (FE) analysis using cohesive element to simulate the interface between AAC and normal concrete is conducted. There is a good correlation between the experimental and FE results, verifying the relationship between the interfacial parameters, temperature and bond angle used in the FE model.

Comparison of different post-demolition autoclaved aerated concrete (AAC) recycling options

Autoclaved aerated concrete (AAC) is used as masonry blocks and prefabricated reinforced elements preferably in residential buildings. Due to its porous structure and mineral composition, it combines low thermal conductivity and fire resistance properties. Consequently, the popularity of AAC increases. However, due to significant AAC production volumes in many European countries since the 1960s and 1970s and given building lifetimes, strongly increasing post-demolition AAC waste volumes can be expected in the following decades. Recycling these post-demolition AAC wastes could protect primary resources and landfill capacities and reduce greenhouse gas emissions. But, recycling of post-demolition AAC is not yet established. The majority of the waste is landfilled even though landfill capacities have decreased and the legal framework conditions in Europe regarding a circular economy are becoming stricter. Therefore, new recycling options are needed. Current research approaches propose different open-loop recycling routes for post-demolition AAC, e.g. lightweight aggregate concrete, lightweight mortar, no-fines concrete, floor screed, animal bedding, oil- and chemical binders, and insulating fills for voids and interstitial spaces. Additionally, closed-loop recycling is possible and under research. Finely ground post-demolition AAC powder can be directly used in AAC production or can be chemically converted to belite (C2S) clinker to substitute primary cement in AAC production. These promising recycling options are compared regarding environmental and economic aspects. We find that the resource consumption is lower in all recycling options since post-demolition AAC helps to save primary resources. Furthermore, greenhouse gas emissions associated with the substituted primary resources are saved - especially when substituting primary cement in closed-loop recycling. In economic terms, increasing landfill costs could be avoided, which leaves a considerable margin for the cost of pre-processing, transport and recycling. The results can help decision-makers to implement circular management for AAC by fostering post-demolition AAC recycling and reducing its landfilling.

Preparation and performance of autoclaved aerated concrete reinforced by dopamine-modified polyethylene terephthalate waste fibers

• Waste granite powder and polyethylene terephthalate (PET) fiber were used to prepare autoclaved aerated concrete (AAC). • A simple and efficient process was used to improve the interface bonding of the composites. • The flexural and compressive strengths of the AAC with the modified waste PET fiber increased by 37.2% and 12.7%, respectively. The low tensile and flexural strengths make autoclaved aerated concrete (AAC) susceptible to cracking and damage during transportation and service. This study investigated the use of waste polyethylene terephthalate (PET) fiber as AAC reinforcement, which is a byproduct from the textile industry. Meanwhile, waste granite powder from stone plate processing byproducts was used as a siliceous material in the preparation of fiber-reinforced AAC composites. The waste PET fibers were modified by dopamine hydrochloride to improve the interfacial adhesion between the fibers and the AAC matrix. Results showed that the AAC blocks with 0.1 wt% PET fiber (1 mm in length and 18 μm in diameter) increased the compressive and flexural strengths by 6.0 % and 28.4 %, respectively. By adding 2 g/L dopamine-modified waste PET fiber, the compressive and flexural strengths of the blocks were further increased by 12.7 % and 37.2 %, respectively. The PET fibers were characterized using water contact angle test, SEM, FTIR, XPS, and TG analyses. It was confirmed that the amino and hydroxyl groups were grafted onto the modified fiber surface, leading to improved hydrophilicity and reactivity of the fibers and thus enhanced interfacial bonding between the fibers and the AAC matrix.