Autoclaved Aerated Concrete Walls Research Articles

Experimental study on energy saving and thermal insulation of AAC walls and sandwich structures

Autoclaved aerated concrete (AAC) materials are increasingly being recognized as an effective method of improving the thermal efficiency of buildings. This paper uses a bolted AAC sandwich wall with rock wool to measure the indoor temperature enhancement and energy savings achieved by applying AAC and autoclaved aerated concrete sandwich (AACS) to building surfaces without ventilation. In addition, the energy efficiency and insulation of sintered brick (S) walls, AAC walls, and AACS walls in three test rooms are discussed in the fall and winter seasons. The study showed that the average daytime room temperatures of the AAC and AACS walls were reduced by 9.11 % and 14.31 %, and the heat load levelling was reduced by 28.41 % and 46.76 % compared to the S walls. The study concluded that compared to the S wall, AAC and AACS walls were reduced by 0.64 W and 0.8 W, respectively, and CO2 emissions were reduced by 11.78 g/m2day and 14.69 g/m2day.Under the premise that the building life cycle is 50 years, the energy consumption of the building electricity bill is saved by 157.14 RMB/m2 and 195.84 RMB/m2 for AAC wall and AACS wall, respectively, compared with S wall. Therefore, AAC shows a growing trend in the building material market due to its low-carbon insulation, green energy saving, and policy support, and it should be promoted in the construction industry.

TRM strengthening as effective prevention against premature failure of masonry walls

Masonry structures are very prone to cracking and premature failure in the presence of shear loading. Therefore, effective prevention of their premature damage is needed. This paper presents laboratory tests of small models made of autoclaved aerated concrete (AAC) blocks, which were externally reinforced using two different strengthening sets consisting of mortar and mesh, and subjected to diagonal compression. The experiments used a commercialised system designed for the strengthening of typical masonry substrates (brick, stone) and a low-cost and lowstrength mesh and mortar set used as part of a system for insulating buildings. The analyses presented are of a comparative nature and describe changes in the behaviour of the models depending on the strengthening set used. The application of full-surface strengthening clearly changed the behaviour of AAC walls from brittle one to the ‘pseudo-ductile’ one observed after the appearance of the first cracks. In all strengthened models, a significant increase in the load capacity (from 3% to 62%) and a post-peak phase were reported. An interesting finding was the high efficiency of nonstructural materials (plastering system), comparable to the effects of the use of commercialised system solutions. This strengthening can be successfully considered as an effective preventive action. Finally, a simplified method is provided to calculate the contribution of the strengthening to the load bearing capacity of the strengthened models. The method defines the effect of the mesh and the mortar independently, based only on the basic material properties of these two components.

Numerical simulation of autoclaved aerated concrete masonry wall subjected to close-in explosion and the structural damage assessment

In this study, we investigated the destructive effect of autoclaved aerated concrete (AAC) masonry walls subjected to close-in explosions. First, full-size refined finite-element models of the AAC masonry wall were established, and the accuracy of the models was verified by comparison with the test results. The destruction pattern and damage characteristics of the AAC wall were studied, and the effects of block size, wall thickness, mortar compressive strength, and explosion distance on the destruction degree of the AAC masonry walls were analyzed. The results showed that the destruction pattern of the AAC masonry wall subjected to close-in explosion manifested as punching damage in the middle of the wall. When the scaled distance remained unchanged, the punching damage area of the AAC masonry wall was positively correlated with the block size and negatively correlated with the wall thickness and mortar compressive strength. When the explosive equivalent remained unchanged and the explosion distance increased, the punching damage area first increased and then decreased. According to the damage mechanism of the AAC masonry wall, a calculation method for predicting the punching damage area of the AAC masonry wall was established, and the accuracy of this method was verified by comparing it with the numerical results. In addition, the damage criterion based on the punching damage area was established to determine the destruction levels of AAC masonry walls.

Seismic behavior of autoclaved aerated concrete masonry walls reinforced with glass-fiber geogrid

Reinforcing horizontal mortar joints with steel bars can improve the seismic performance of autoclaved aerated concrete (AAC) masonry walls. Nevertheless, the diameter of steel bars can require a large thickness of the mortar joints, which in turn results in the thermal bridging effect. Glass fiber geogrids (GFGs) can be employed to replace steel bars to reduce the thickness of mortar joints, and thus can mitigate the thermal bridging effect. Despite considerable advancements in understanding the mechanical performance of GFGs in masonry walls, their effect on the seismic performance of AAC walls remains unknown. Therefore, this study investigates the effect of different GFG configuration rates on the seismic performance of AAC masonry walls using reciprocating load tests. Furthermore, the effect of different vertical compressive stresses on the seismic performance of GFG-reinforced AAC masonry walls was studied via comprehensive finite element simulations. The test results show that the ultimate load-bearing capacity and ultimate displacements of the wall specimens were enhanced as the GFG configuration rate increased, approaching that of benchmark specimens reinforced with steel bars. On the other hand, the cracking and ultimate loads, along with ultimate displacements of GFG-reinforced AAC masonry walls were significantly improved compared to those of the unreinforced AAC masonry walls. It was also evidenced that the crack formation, failure mode, ductility and energy dissipation capacity of the specimens simulated through the finite element method were highly comparable to that of experimentally tested specimens. Accordingly, the vertical compressive stresses were in the range of 0.1 MPa ∼ 0.6 MPa, while the seismic performance of GFG masonry walls was improved with the increase in vertical pressure. The results of the current study confirm that embedding GFG in horizontal mortar joints can delay the cracking of AAC masonry walls and improve their seismic performance. Ultimately, an empirical equation was developed to calculate the seismic shear strength of GFG-reinforced AAC masonry walls.

Comprehensive studies of the influence of superficial strengthening with the FRCM system on the load‐bearing capacity and deformability of AAC walls

AbstractThis article presents the results of tests on walls made of AAC (autoclaved aerated concrete) strengthened with the FRCM system. The effect of the applied strengthening was determined based on the results of tests on masonry models subjected to compression, diagonal compression and shear. Models of walls without strengthening, strengthened on one and two sides were tested. The research models were built of masonry elements made of autoclaved aerated concrete (AAC) SOLBET OPTIMAL 4/600. The walls were erected on a system thin‐layer mortar, class M5, without filling the head joints. PBO fiber meshes embedded in a mineral matrix were used as superficial reinforcement. The walls were strengthened by applying the PBO‐MX GOLD MASONRY system mortar to the side surfaces of the models and the PBO‐MESH GOLD 22/22 mesh was embedded in it, and then the top layer of the PBO‐MX GOLD MASONRY system mortar was applied. The compressive strength test was performed on 18 models in accordance with the requirements of the PN‐EN 1052‐1: 2000 standard. In the case of compression, additional tests were performed on models weakened by a cut imitating cracking. The diagonal compression test was performed on 18 models in accordance with the requirements of ASTM E519‐81 standard. The shear load test was performed on 27 models in accordance with the requirements of the PN‐EN 1052–3: 2004 standard. A clear increase in load capacity in each type of test was noted in models strengthened on two sides. In models strengthened on one side, the positive effect of strengthening was observed only by increasing the deformability of the wall. Regardless of the test type, the use of surface reinforcement allowed for smoother behavior of the test models after the loss of load capacity in relation to models without strengthening.

Development of a Novel Low-Energy Building: Effects of Room Orientation and Wall Materials

The development of low energy buildings in hot subtropical and desert like climates such as Australia and Kuwait, requires strategies that are rather challenging. Five (5) experimental rooms are going to be built to assess these energy saving techniques for a research program jointly between Kuwait and Australia. Before the construction phase, these rooms are simulated in TRNSYS18 for the two sites based on available weather data collected from Kuwait International Airport and Rockhampton Airport. The objectives are to investigate room orientation and walling materials on energy performance of the rooms. It was found that all rooms return identical temperature profiles in each of the eight (8) dominant directions, i.e., N, NE, E, SE, S, SE, E, and NW. Five (5) different commercially available wall materials were employed for the five (5) simulated rooms in Kuwait and Australia. It was found that autoclaved aerated concrete (AAC) wall materials and north (N) building face orientation are the preferred construction material and orientation in both sites. The energy performance index (EPI) showed that AAC wall materials for the room faced towards north (N) provides the lowest cooling EPI of 646 and 448.4 kW/m2/year in Kuwait and Rockhampton, Australia, respectively.

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.

Experimental Investigation of Bond strength Autoclaved Aerated Concrete (AAC) Masonry

Masonry walls can be load-supporting as well as non-supporting in which AAC blocks are utilized. Binding tenacity of autoclaved aerated concrete block-mortar interfaces formed of standard cement-sand mortars of various formulas and polymer-modified mortars is investigated in this study.It is presented a method for increasingnormal sand-cement mortar's binding strength without modifying the block surface qualities. Following the application of a thin cement-slurry coating to the block surfaces, a thick sand and cement mortar is poured. A triplet test was used to establish the brickwork's shear bond persistence, while a cross-couplet test was used to determine the tensile bond strength. Bond strength test’s failure patterns were investigated. The costs of AAC walls with various types of interfaces were then calculated.

Experimental and numerical investigation of polymer-reinforced and normal autoclaved aerated concrete masonry walls under large TNT explosive loads

With features such as a low mass ratio and good heat insulation and energy absorption properties, autoclaved aerated concrete (AAC) is extensively used as a filling material for building structures. To study the failure behaviour of AAC masonry walls under explosive loads, four full-size wall specimens divided into two groups were established in a field test field: two normal masonry walls (as references), a masonry wall coated with polymer only on the back, and a masonry wall coated with polymer on both sides, where all the polymer coatings were 4 mm in thickness. The two groups of walls were each subjected to explosion tests comprising 3,000 kg and 10,000 kg of TNT. The test results demonstrated the ultimate failure patterns of the masonry walls. In addition, overpressure sensors equipped with an independently developed remote data acquisition system were used to plot the incident and reflected overpressure curves at distances of 70 m and 100 m from the two high-charge TNT explosions. The differences between the arrival times, peaks and impulses (both incident and reflected) of the tested shock waves and the CONWEP predictions were compared. Then, based on the failure patterns of the specimens, post-explosion damage assessment criteria of AAC walls were preliminarily established. The assessment results indicated that the polymer coating on the wall surface remarkably improved the blast resistance performance of the masonry walls. Finally, the cohesive zone method (CZM) was introduced to simulate the blast resistance of building structures. According to the results of a comparative analysis and simulation, the CZM model can effectively reflect the explosion responses and ultimate failure patterns of masonry walls.

Analysis of confined AAC walls under monotonic compression

Confined walls are structures frequently encountered in seismic zones. They have been put to numerous tests over time, including entire buildings being tested under cyclic loading. However, the observed trend is that confined masonry structures are also built in areas of little or no seismic activity. The draft 2nd edition of Eurocode 6 even brings about calculation procedures for confined walls erected outside active seismic regions. That said, an insufficient number of tests have still been performed on confined masonry structures under monotonic load, a situation which has a considerable negative impact on the verification process regarding standard recommendations. This paper presents results obtained from tests carried out on 20 walls, both non-confined and with reinforced concrete confinement. The full-scale walls put to tests were built of autoclaved aerated concrete (AAC). They were subjected to one loading cycle until failure. The testing procedure involved numerical simulations and calculations based on data obtained from the strut-and-tie models, as well as calculations carried out in accordance with the procedures laid down in the draft 2nd edition of Eurocode 6. It was demonstrated during the tests that wall confinement has a significant impact on the masonry resistance under monotonic load. The numerical models were used to determine the distribution of stresses in the test walls and to select the effective strut-and-tie model. The authors of the paper also verified the standard recommendations.

Influence of the climatic conditions on the hygrothermal performance of autoclaved aerated concrete masonry walls

The energy performance of buildings has undergone major developments over the last few years. Due to increasingly demanding regulations, new technologies and constructive solutions have been sought to make buildings more energy efficient. Autoclaved aerated concrete (AAC) is a sustainable building material that provides a suitable solution to this problem. However, the hygrothermal behavior of AAC masonry walls is the subject of little discussion throughout the scientific community. The paper focuses on identifying the influence of climatic conditions, as well as the effect of surface layers or insulation systems on the hygrothermal performance of exterior walls made of AAC. For the purpose of this study, several constructive solutions were analyzed in different climatic settings, namely Munich, Germany; Stockholm, Sweden; and San Francisco, U. S. A. The effects of applying different types of render/plaster layers or external thermal insulation system on AAC walls was also determined using hygrothermal software. In addition, the damage potential of frost and rainwater were assessed to better comprehend how these walls behave. The results showed that the overall performance of AAC wall systems and frost damage potential was found to be greatly influenced by the hygric properties of the exterior render. Additionally, it was shown that calculating the thermal transmittance in steady-state conditions can lead to gross underestimations compared to transient models. The results indicate that the EPS and XPS insulated walls were susceptible to moisture increase, due to rainwater leakage, unlike the MW insulated wall, which dried significantly faster.

Seismic out-of-plane behaviour of unreinforced AAC walls

Autoclaved aerated concrete (AAC) is a building material widely used in many countries around the world. In earthquake prone areas, unreinforced masonry walls also need to be designed for earthquake scenarios. In this load case, the out-of-plane loads often have a significant impact on the load-bearing capacity. In most practical applications, simplified analytical methods are used to determine the out-of-plane capacity. The estimations of these models are often inaccurate as essential parameters like the vertical stiffness of the support and dynamic effects are neglected. To investigate the influence of these parameters, experimental tests have been performed on a shaking table. Numerical analyses have been carried out to determine the deformation response of the wall using non-linear single-degree-of-freedom systems. The results obtained from analytical models have been compared with experimentally determined maximum acceptable earthquake accelerations. Based on the results, the out-of-plane capacity is significantly higher than predicted by analytical models.

Effect of Openings on the Seismic Response of AAC Infilled Frames and an Innovative Method to Improve Performance

Autoclaved aerated concrete (AAC) is an attractive building material with lightweight, good insulation, fireproofing, and durability characteristics. The seismic response of AAC requires an in-depth understanding as its use as infill walls is gaining popularity in seismically active regions of many countries in Europe, Middle East, and Asia. Recent studies on the seismic response of AAC infill walls were mostly conducted on solid AAC walls without considering openings and simulated earthquake loading was applied in the plane of the frame. In this study, recent tests on the out-of-plane and in-plane seismic response of AAC infill walls with openings were investigated experimentally. The door opening was considered for the purposes of the study. The limited deformation capacity of the AAC infill walls was observed. An innovative system to improve the performance of AAC infill walls was briefly discussed.

Effect of openings on the seismic response of AAC infilled frames and an innovative method to improve performance

Autoclaved aerated concrete (AAC) is an attractive building material with lightweight, good insulation, fireproofing, and durability characteristics. The seismic response of AAC requires an in-depth understanding as its use as infill walls is gaining popularity in seismically active regions of many countries in Europe, Middle East, and Asia. Recent studies on the seismic response of AAC infill walls were mostly conducted on solid AAC walls without considering openings and simulated earthquake loading was applied in the plane of the frame. In this study, recent tests on the out-of-plane and in-plane seismic response of AAC infill walls with openings were investigated experimentally. The door opening was considered for the purposes of the study. The limited deformation capacity of the AAC infill walls was observed. An innovative system to improve the performance of AAC infill walls was briefly discussed.

Seismic out-of-plane behaviour of unreinforced AAC walls

Autoclaved aerated concrete (AAC) is a building material widely used in many countries around the world. In earthquake prone areas, unreinforced masonry walls also need to be designed for earthquake scenarios. In this load case, the out-of-plane loads often have a significant impact on the load-bearing capacity. In most practical applications, simplified analytical methods are used to determine the out-of-plane capacity. The estimations of these models are often inaccurate as essential parameters like the vertical stiffness of the support and dynamic effects are neglected. To investigate the influence of these parameters, experimental tests have been performed on a shaking table. Numerical analyses have been carried out to determine the deformation response of the wall using non-linear single-degree-of-freedom systems. The results obtained from analytical models have been compared with experimentally determined maximum acceptable earthquake accelerations. Based on the results, the out-of-plane capacity is significantly higher than predicted by analytical models.

Bond strength of Autoclaved Aerated Concrete (AAC) masonry using various joint materials

Autoclaved Aerated Concrete (AAC) blocks are used for both load bearing and non-load bearing masonry walls. The tensile and shear strengths of such walls are greatly affected by the bond strength of block-mortar interface. This article investigates the bond strength of AAC block-mortar interface made of ordinary sand-cement mortar of different compositions and polymer modified mortars. A method of improving the bond strength (both tensile and shear) of ordinary sand-cement mortar without altering the block surface characteristics is proposed. In this method, the block surfaces are coated with a thin cement-slurry coating before applying a thick sand-cement mortar. For all types of interfaces, the shear bond strength of the masonry was studied using a triplet test, while the tensile bond strength was determined based on a cross-couplet test. The failure patterns during the bond strength tests were studied. Subsequently, costs were estimated for AAC walls of different types of interfaces. Considering the bond strength as well as cost, using a weak mortar along with cement-slurry coating was found superior to the ordinary sand-cement mortar and polymer modified mortar.

The Effects of Strengthening the AAC Walls Using Glass Mesh Arranged in Different Configurations

The usage of AAC (Autoclaved Aerated Concrete) blocks for the construction of new masonry structures, particularly low-rise residential buildings, has become very popular in Poland. It provides an uncomplicated erecting method, which is characterized by thin bed joints and unfilled head joins, but at the same time, makes these walls very sensitive to any internal tensile stresses, causing damage with varying intensity. To avoid premature cracking, leading to a brittle failure of existing walls, an external strengthening can be an acceptable and effective solution. Taking into account that AAC units are a natural material, the application of a FRCM system (instead of FRP) is more suitable here. This system uses a mineral-based matrix that provides congenial compatibility with a masonry substrate.This study presents an analysis of the influence of superficial strengthening on the behaviour and deformability of masonry walls made of AAC blocks. A typical glass mesh (most often used in thin external plastering) and mineral mortar dedicated to renovation works are used as strengthening materials. The specimens are strengthened unilaterally (two types) or bilaterally and are subjected to diagonal compression according to the RILEM 76-LUM standard. The consecutive work stages, shear strains and modes of failure are described and discussed.

Seismic Performance of the Pre-Fabricated Steel Frame Infilled with AAC Wall Panels and their Joint Connection: Full-Scale Shaking Table Test

A series of shaking table tests were performed to investigate the seismic behavior of the pre-fabricated steel frame structure infilled with autoclaved aerated concrete (AAC) external wall panels. The reliability of a new type of joint connections adopted in the structure between the steel frame and the wall panels was particularly validated during the test. Dynamic tests were carried out on a two-story full-scaled steel frame, considering seismic loading of three earthquake waves with different imposed peak accelerations in the range of 70[Formula: see text]cm/s2 to 400[Formula: see text]cm/s2. The experimental analyses encompassed cracking patterns, failure mechanisms, dynamic property and seismic response of the structure. The results show that the structural components, including the joint connections between the steel frame and the walls, behaved well even under the rare earthquake at 8∘. The structural stiffness of the steel frame infilled with wall panels was increased by 56%, compared with the steel frame infilled without wall panels. The damping ratio of the undamaged steel frame installed with wall panels was 7.25%.

Seismic behavior of autoclaved aerated concrete low rise buildings with reinforced wall panels

Reinforced Autoclaved Aerated Concrete (AAC) wall panels are more commonly used to construct load-bearing walls in low-rise prefabricated buildings located in seismic zones. In the scope of this study, the seismic response of buildings constructed with reinforced AAC wall panels was investigated. To this end, an in situ test was conducted on a two-story test building under reversed cyclic displacement excursions. It was determined that the test building could carry a lateral load of 60% more than its weight and has a global displacement ductility of about 3.5. The first story of the building was observed to be critical and the failure of the building was due to overturning response of the whole system. In addition, the proposed numerical models for simulating the behavior of the AAC wall panels were validated. These calibrated numerical models were utilized to conduct nonlinear static analysis of the test building and a reasonably good agreement was observed between the test results and simulations. The results of the incremental dynamic analyses demonstrated that i) the two-story test building could resist strong ground motions with PGA values up to 0.6 g without undergoing significant plastic deformations and ii) a reserve of ductility and over strength is available for the AAC panel building to survive earthquakes with PGAs reaching nearly 0.6 g. Based on these numerical results, reinforced AAC wall panel buildings appear to be good alternatives for low-rise construction in seismic regions.

Seismic behavior of reinforced autoclaved aerated concrete wall panels

AbstractVertical reinforced autoclaved aerated concrete (AAC) panel systems are among attractive alternatives for low‐rise buildings. The popularity of AAC panels in building construction is increasing due to their unique material properties, such as being light weight, good insulator, fire resistant combined with having high speed of erection and ease of quality control. However, past experimental evidence on the seismic response of reinforced vertical panels is rather limited with few tests on multi‐panel specimens. To overcome this issue, an experimental program was initiated to test six full‐scale AAC wall panel specimens. In the scope of this study, the in‐plane seismic behavior of AAC vertical load‐bearing wall panels was examined under constant axial load and two‐way cyclic lateral displacement excursions. First, the effect of axial loads on lateral behavior of reinforced AAC walls was investigated. For this purpose, four specimens composed of two and four AAC panels with and without axial loads were tested. Then, the effect of window opening was examined by conducting two more tests. The results of the experiments clearly indicated that the axial loads had a positive effect on the load carrying capacity. The window openings reduced the lateral strength and caused localization of the damage. The ultimate drift of the tested panels was found to be around 1%. The ability of estimating the measured moment versus curvature response of the tested specimens were examined for different adjacent panel assemblages. Finally, the code‐proposed equations to determine the lateral load capacity of AAC walls were critically reviewed in light of the experimental results.