Foam Concrete Research Articles

Study on the Coupled Heat Transfer of Conduction, Convection, and Radiation in Foam Concrete Based on a Microstructure Numerical Model

Foam concrete is a typical cement-based porous material; its special microstructure endows it with excellent properties, such as light weight, energy efficiency, thermal insulation, and fire resistance. Therefore, it is widely used as a thermal insulation material for buildings. The heat transfer modes of foam concrete include conduction, convection, and radiation. However, previous studies considered conduction to be the dominant mode, often neglecting the effects of convection and radiation. In this study, a stochastic numerical model of the foam concrete microstructure is established based on the statistical parameters of the pore structure. With this model, the heat transfer mechanism of foam concrete is analyzed at the mesoscopic level, and the equivalent thermal conductivity is calculated. By comparing four different working conditions, the influence of conduction, convection, and radiation on the heat transfer of foam concrete is analyzed, and the specific contribution rates of conduction, convection, and radiation are calculated. The results show that the convection effect is weak due to the pore size being smaller than 1 ; so, the influence of convection can be neglected in the heat transfer analysis of foam concrete. The contribution of radiation increases with the decrease in foam concrete density and the increase in temperature difference. When the temperature difference is 40 and the density is 300 , the contribution of radiation exceeds 20. Therefore, for low-density and high-temperature difference situations, the influence of radiation cannot be ignored. The heat transfer in foam concrete is mainly through conduction, but with the decrease in density and the increase in temperature difference, the contribution of conduction shows a downward trend. Nevertheless, the contribution of conduction is still much larger than that of radiation and convection.

Imaging of foam concrete air bubbles with an alternative method of combined digital holographic microscopy

Five different foam concretes were synthesized and examined. A new hybrid optical sensor, called combined digital holographic microscopy (CDHM), was proposed by combining microscopic fringe projection profilometry and lateral shearing digital holographic microscopy to detect the pore radii of produced foamed concretes. It was applied in addition to SEM and has not been applied to foam concretes before. Thanks to the proposed method, it was revealed that the measured CDHM radii contained a relative error of less than 6% compared to the SEM radii. The pore radii increased as the % of foaming agent used in the samples increased. Accordingly, the sample densities decreased and thermal insulation properties enhanced. Two-layer quantum chemical calculations performed at the ONIOM (M06-2X/6-31+G(d,p):UFF) theoretical level showed that thermodynamic stability of foam concretes increased as the % of foaming agent used, or more precisely, the pore radius, increased. The CDHM method provides results close to SEM and has superior features such as being more cost-effective, cleaner and faster. For this reason, it is thought that the proposed method will lead to future studies in terms of measuring pore radii as an alternative to SEM.Graphical The combined digital holographic microscopy (CDHM) method is proposed as an alternative to SEM with a relative error of less than 6% in determining the pore radius of foam concretes.

Synergistic effect of fly ash and polyvinyl alcohol fibers in improving stability, rheology, and mechanical properties of 3D printable foam concrete

Foam concrete, a lightweight cellular cementitious mixture has gained significant attention globally due to its multifunctional properties. Employing such multifunctional material to additive manufacturing helps in reducing the material wastage, time for construction and cost of production. However, there are various challenges encountered in employing such material with conflicting attributes in 3D concrete printing technology. Therefore, it is important to address these challenging requirements (i.e. stability along with printability). In this study, fly ash and polyvinyl alcohol fibers are employed as sand replacement and reinforcing material respectively to improve stability, rheology and mechanical characteristics of 3D printable foam concrete. Initially, printability of the mixture is achieved through moderation of slump and slump flow. Further, these mixtures are studied for fresh density, rheological properties and buildability. Essential hardened properties like oven dry density, compressive strength, flexural strength, bond strength, and thermal conductivity are studied. Later, microstructural studies are conducted to analyze the variations in hardened properties. Results show that replacement of sand with fly ash has significant influence (more than 100%) in improving the printability (for both 1300 and 1000 kg/m3 densities), however it has negative impact on the stability of foam. Stability of foam concrete could be counteracted by adding the fibers which forms networks with the foam bubbles and reduced the breakage and coalescence. Nonetheless, addition of fly ash increased the mechanical performance and thermal conductivity, but the dry density is increased due to bubble breakage. Addition of fibers reduced dry density with significant reduction in thermal conductivity and minimal compromise in mechanical performance.

Investigation of Effect of Proposed Two-Stage Foam Injection Method and Modified Additive on Workability of Foam Concrete.

This article presents the results of an investigation of the proposed method and the influence of a modified additive on foam concrete properties. X-ray diffraction analysis showed that the modified additive has a variable mineralogical composition, and the joint use of the components contributes to the synergistic effect, improving the processes of cement hydration. Microscopy of the foam concrete samples showed the presence of microcracks and micropores in samples both with and without the additive. However, the use of the additive significantly reduced their number and size, which indicates an improvement in the structure of the material. The strength values showed that the samples with the additive have high strength. In particular, the strength values of samples of type 3 at different stages of curing exceed those of samples of type 1 by 1.32-1.51 times and samples of type 2 by 1.07-1.10 times. The obtained strength values are 2.82-3.21 MPa for type 1, 3.64-4.04 MPa for type 2, and 4.39-4.84 MPa for type 3, which corresponds to grade D600. The evaluation of water absorption also confirmed the advantages of the proposed method and the additive, significantly reducing the water absorption of the samples and increasing their hydrophobicity. The obtained values of water absorption are 13.8-16.6% for type 1, 13.7-16.1% for type 2, and 9.5-11.2% for type 3.

Mn–Zn ferrite foam concrete: Enhanced electromagnetic wave absorption and pore structure by incorporating carbon fibers

In this study, an absorbent composite of carbon-fibre-reinforced Mn–Zn ferrite foam concrete was fabricated. The influence of carbon fibre (CF) concentration on the mechanical and electromagnetic wave (EMW) absorption characteristics of Mn–Zn ferrite foam concrete within the 0.2–5GHz were investigated. Key performance indicators, such as compressive and flexural strengths, electromagnetic parameters, reflection loss, and absorption bandwidth were thoroughly analysed. The pore size and distribution were examined by X-ray computed tomography (CT) to reveal the EMW absorption mechanism. The findings indicate that CF effectively mitigates agglomeration in Mn–Zn ferrites, enhancing dielectric and magnetic losses synergistically, which improves not only the mechanical properties but also the EMW absorption capacity of Mn–Zn ferrite foam concrete. The optimal wave absorption performance was observed at a CF content of 0.3 wt%, yielding an impressive absorption bandwidth of 1.46 GHz and a minimum reflection loss (RLmin) of −28.75 dB. A noteworthy observation was the inverse correlation between the CF doping level and resistivity. The attenuation constant peaked at 108.13. When the CF content reached 1.2 wt %, the composite attained its percolation threshold, manifesting a resistivity of 145.4 Ω·m.

ПЕРСПЕКТИВЫ ПРИМЕНЕНИЯ ПЕНОБЕТОНА В НОВЫХ МЕТОДАХ СТРОИТЕЛЬСТВА

The article presents modern effective methods of accelerated construction using foam concrete

3D-ПЕЧАТЬ ЗДАНИЙ С ПРИМЕНЕНИЕМ ПЕНОБЕТОНА

The article presents a method of building construction using 3D printing technology. 3D printing is the process of erecting a construction object through computer-controlled build-up of three-dimensional shapes. In this technology, the use of foam concrete of structural and thermal insulation grades is fully justified, since this material performs a bearing and enclosing function. This technology is most effective for the production of works on the construction of objects of geometrically complex struc-tures and shapes

КАРКАС ЛСТК И ПЕНОБЕТОН: ПОВЫШЕНИЕ КАЧЕСТВА СТРОИТЕЛЬ-СТВА ЖИЛЬЯ

The article presents a frame made of galvanized bent lightweight profiles, which is filled with non-autoclaved monolithic foam concrete of light density grades in a non-removable formwork made of waterproof plates

Utilization of waste foam concrete with MPCM as a substitution material for cement in mortars

Given the rising popularity of foam concrete (FC) for both structural and insulating purposes, evaluating the feasibility of recycling after its lifespan is crucial in the context of the growing emphasis on sustainable building practices. One approach to recycling FC incorporating microencapsulated phase change material (MPCM) involves utilizing recycled foam concrete powder (RFCP) as an additive in cement composites. This article aims to investigate the impact of RFCP without and with MPCM when employed as a partial replacement for cement in mortars. Furthermore, the study verifies various processing methods such as crushing, grinding, and heat treatment for RFCP. The results reveal that introducing RFCP, regardless of the MPCM presence and processing method, significantly affects the properties of both cement and mortar. The presence of MPCM in RFCP negatively influences the flowability of fresh mortars, delays the setting time, and reduces the hydration heat within the first 48 h. However, the presence of MPCM does not significantly affect mortars' strength and water absorption but simultaneously it increases shrinkage and decreases thermal conductivity. Grinding RFCP mitigates the adverse effects of MPCM, while thermal processing removes MPCM from RFCP, albeit with an associated increase in water demand. A noteworthy finding is that mortars having 20 % RFCP, with or without MPCM, exhibit compressive strengths exceeding 16 MPa and 42.5 MPa after 2 and 28 days, respectively. These results meet the requirements outlined in EN-196-1 for cement of class 42.5, highlighting the potential to produce CEM II/A-F 42.5 using RFCP with MPCM.

Study on the Performance Behaviour of Fibre Reinfored Foam Concrete

Study on the Performance Behaviour of Fibre Reinfored Foam Concrete

Physico-mechanical, thermal insulation properties, and microstructure of geopolymer foam concrete containing sawdust ash and egg shell

Recently, energy conservation through building thermal insulation has gained significant importance in solving sustainability-related issues. In this context, this study investigates the potential for manufacturing geopolymer foam concrete (GFC) containing eggshell powder (ESP) and sawdust ash (SDA) using aluminium (Al) powder as a foaming agent. The role of Al-powder percentages on the mechanical and thermal properties of GFC was thoroughly investigated. The effect of ESP and SDA incorporation as partial replacements of precursors (from 0 to 20 %) on the thermal properties, durability, and microstructure of GFCs were also discussed. The experimental findings demonstrate that the bulk density and compressive strength of GFC with different Al-powder contents ranged between 1928 and 1798 kg/m3 and 17.45 and 9.37 MPa, respectively. The SEM images and MIP tests show that foams with different numbers of micro- and macropores are formed in GFCs. The ESP-based GFC had an apparent porosity range of 13.09 %–10.29 % and a bulk density range of 1823 to 1713 kg/m3. The SDA-based GFC had an apparent porosity range of 14.21 %–12.96 % and a bulk density range of 1834 to 1807.8 kg/m3. It was found that the 10 % ESP and 5 %, SDA mixtures enhanced the strength by 16.54 % and 4.45 %, respectively, compared to the control mix. The thermal conductivity, thermal diffusivity, and specific heat of 10 % ESP-mixture and 5 % SDA-mixture were 1.237 and 1.167 W/(mK), 0.795 and 0.922 mm2/S, and 1.556 and 1.266 MJ/m3K, respectively. Finally, the residual strength and microstructure investigations demonstrate that ESP-based GFCs have more stability than SDA-based GFCs and the control mix when subjected to elevated temperatures.

Preparation and performance influencing factors of sludge-based non-sintering ceramsite foam concrete block

In this study, the preparation of ceramsite foam block using Sludge-based Non-sintering Ceramsite (SNSC) was investigated through orthogonal test and performance optimization test to investigate the effects of different coal fly ash addition, volume ratio of SNSC, water binder ratio and sodium silicate concentration on the performance of the concrete block, and the optimal material mixing ratios were obtained as follows: cement was 400 kg/m3, coal fly ash was 100 kg/m3, SNSC was 371 kg/m3, water binder ratio was 0.43, CaCl2 was 10 kg/m3, and Na2SO4 was 5 kg/m3. The performance of Sludge-based Non-sintering Ceramsite Foam Concrete Block under these conditions meets the specification requirements of GB/T 36534–2018 "Ceramsite Foam Concrete Block". Its compressive strength was 7.76 MPa, dry bulk density was 948.7 kg/m3, the water absorption was 20.75 %, and the softening coefficient was 0.861. XRD and SEM analyses revealed that the internal physical phase of the concrete blocks under the optimal conditions was tightly bonded, with fewer and uniformly distributed pores, and that the hydration generated C-S-H, C-A-H gel-like substances, calcium alumina (AFt), and hydrated calcium chloroaluminate generated by hydration could significantly improve the physical and mechanical properties of concrete blocks.

Mechanical testing and engineering applicability analysis of SAP concrete used in buffer layer design for tunnels in active fault zones

Abstract To tackle the challenge of dislocation damage when tunnels traverse active fault zones, this study introduces the concept of using brittle buffer materials for anti-dislocation. Building on this concept, we propose a novel concrete buffer material utilizing large-sized spherical super absorbent polymers (SAP) as a porogen, aimed at ensuring the safety of tunnel structures during active fault dislocations. To investigate the feasibility and superiority of SAP concrete as a buffer material compared to other similar materials, we prepared samples with three different SAP concrete proportions and conducted a series of physical and mechanical tests. The results show that SAP pre-hydrated with 0.2 mol·L−1 sodium carbonate solution exhibits a slower rate of moisture loss in the cement slurry, aiding the hydration reaction of concrete. The permeability coefficient of SAP concrete is approximately 10−7 cm·s−1, slightly lower than foam concrete of the same density level. SAP concrete buffer material demonstrates significant brittleness, in contrast to the mostly ductile nature of other buffers such as foam concrete and rubberized concrete. Utilizing the brittle nature of SAP concrete materials, when applied to tunnels affected by stick–slip active fault dislocations, its instantaneous loss of compressive capacity provides excellent yield performance, thus protecting the tunnel lining from damage. However, under certain circumferential pressure conditions, both the peak and residual strength of SAP concrete significantly increase. High peak and residual strengths do not favor the effective buffering effect of SAP concrete; therefore, an approach involving the intermittent arrangement of precast buffer blocks has been proposed for application.

The surface treatment of PVA fibres to enhance fibre distribution and mechanical properties of foam concrete

Fibres are often used to improve the mechanical properties of foam concrete. However, the poor dispersion of PVA fibres in foam concrete significantly restricts their reinforcement efficiency. Limited studies have been conducted on improving the distribution of PVA fibres in a cementitious matrix, particularly in relation to foam concrete. This is noteworthy because pore structure, which can be significantly influenced by the fibres and fibre treatment agents, is a critical parameter that affects the mechanical properties of foam concrete. Therefore, this study employed polar agents (non-ionic surfactants) to treat the fibre surface, aiming to enhance the distribution and reinforcement efficiency of PVA fibres in foam concrete. In view of safety and feasibility, two non-hazardous polar agents, namely PEG-PPG-PEG (designated as PA A) and Polyoxyethylene (20) cetyl ether (designated as PA B), were used to treat the PVA fibres. The impact of fibre treatments on fibre dispersion and pore structure was investigated, and the compressive strength and flexural behaviour of foam concrete were measured before and after the treatments. PA A was found to be unsuitable for fibre treatment due to its poor bonding with the fibre surface. On the other hand, PA B exhibited good bonding with PVA fibres, resulting in enhanced fibre dispersion and pore structure in the foam concrete. Compared to plain foam concrete, the fibres treated with PA B increased the compressive and flexural strength by 47.4 % and 190.3 %, respectively. Moreover, the treated fibres (by PA B) were observed to improve the 0.8 mm toughness of foam concrete by 27.2 %.

Facade Panels with Integrated Clinker Products

The paper covers current trends in the development of facade systems. Modern innovative hinged panels made of glass fiber reinforced concrete and polyurethane foam with integrated clinker products are considered. An analysis of the defects identified during the inspection of the panels was carried out. Possible mechanisms of their damage are described. The most likely cause of damage to clinker products integrated into panels are tensile and shear stresses resulting from differences in temperature deformations of clinker and glass fiber reinforced concrete. An analysis of the stress state of these materials at positive and negative temperatures was performed. The results of experimental studies are presented. Installing a damping layer of deformable material might be the way to compensate the stresses between clinker products and glass fiber reinforced concrete. An analysis of the stress state of the connection of ceramic tiles with polyurethane foam is given. It is shown that due to the significant difference in their temperature deformations, a concentration of shear stresses is observed in the contact zone, resulting in delamination of the tiles. The paper discusses the potential implication of the described panels and their possible further improvement.

Characterization and preparation of eco-friendly foamed concrete using a foaming agent: Optimizing the design by Taguchi analysis

Solid waste management has emerged as the primary global environmental challenge due to the constant production of increasing waste by-products and materials. Using waste materials makes concrete production economical and helps resolve disposal problems. The effects of lightweight foam concrete reinforced with corncob ash (CA) and basalt fibre (BF) on durability, thermal conductivity, and mechanical properties are investigated elaborately in this study. The foam concrete mix is prepared in three series with a foam (F) content of 25, 50, and 75 kg/m3 with and without the CA and BF reference mixes. The mix of corncob ash is chosen as a cement replacement in six different concentrations: 0%, 20%, 30%, 40%, 50%, and 60%. In addition, compositions of 0.5%, 1.5%, and 3% basalt fibre length variation were incorporated into the weight of the cement. Split tensile, compressive, and flexural strengths are determined at 7, 14, and 28 days. The workability, porosity, durability, and thermal characteristics are also examined. This study analyses the confirmation experiment to verify the optimum mix proportions of lightweight foam concrete by applying Taguchi’s experimental design for concrete mixes incorporating by-products as a partial cement replacement. Adding BF improved the mechanical properties of compressive, tensile, and flexural strength, whereas adding CA decreased porosity and thermal conductivity. The 50% CA with 1.5% BF blended concrete with 50 kg/m3 F exhibits high strength compared to 25 and 75 kg/m3 at all ages. The split tensile strength of the F50CA50BF1.5 mix varies from 2.19 MPa to 2.73 MPa, and the compressive strength of 29.13 MPa is higher than that of 14.36 MPa, 18.63 MPa, and 0.88 MPa for the R 25, R 50, and R 75 kg/m3 mixes. The highest mechanical strength and improved durable properties are achieved by replacing 50% of CA and 1.5% of BF with F 50 by-products at all curing periods.

Foamed concrete produced from CO2/N2 foam stabilized by CaCO3 nanoparticles and CTAB

Foamed concrete (FC) has garnered popularity, especially with the growing demand for energy-efficient and sustainable construction materials. The stability of the FC slurry as it sets is crucial to the uniformity of the pore structure and, subsequently, FC performance. This study investigates the stability of a novel FC produced using aqueous CaCO3 nanoparticle (NP)/hexadecyltrimethylammonium bromide (CTAB) foam. The effect of NPs and gas type (pure N2, pure CO2, and a 2:1 gas mixture of CO2/N2) on the FC dry density, compressive strength, water absorption, macro- and microstructure, hydration products, and thermal insulation is explored. The results show that the dry density of FC increases with the inclusion of CO2 owing to gas liberation during mixing with the paste leading to less voids. Using the gas mixture, CaCO3/CTAB foam increases the compressive strength of the FC by 38% compared with CTAB alone owing to enhanced uniformity of the pore structure and a denser hydrated paste skeleton. Such structure leads to less connected pores, which reduces atmospheric carbonation, and improves thermal insulation performance. A 2-fold decrease in the largest pore size and a 25% decrease in surface temperature when exposed to an open flame are also achieved in the presence of CaCO3 NPs.

Durability against dry–wet and freeze–thaw cycles of alkali residue-based foamed concrete

Durability against dry–wet and freeze–thaw cycles of alkali residue-based foamed concrete

Mechanical properties and discrete element simulation of KH-560 modified polystyrene concrete

Polystyrene foam (EPS) concrete is a composite concrete material commonly used in construction, which has excellent thermal insulation and thermal insulation properties, but also has defects of weak bonding interface.KH-560 can significantly improve the characteristics of EPS particles and concrete matrix, which have different physical and chemical properties and are difficult to combine. In this study, the effects of different levels of KH-560 on the enhanced mechanical properties of EPS concrete were studied from the aspects of macroscopic mechanical properties, microstructure characteristics, chemical composition and discrete element simulation, and the mechanism of action was discussed. The results of mechanical experiments show that the compressive strength and flexural strength of EPS concrete mixed with KH-560 are higher than those of ordinary EPS concrete, and its mechanical properties gradually increase with the increase of KH-560 content. XRD, FT-IR and SEM observations showed that more C-S-H gels would be produced under the action of KH-560, which made the structure of the weak interface transition zone of EPS concrete more compact. The results of discrete element simulation show that the peak strength of EPS concrete increases with the increase of friction coefficient, but has little effect on its elastic modulus.

Research of foam concrete quality by two-stage foam injection method in comparison with classical foam concrete

The article presents a method of production of foam concrete, which involves two-stage injection of foam. The proposed method involves improving the pore structure of foam concrete, due to a more uniform distribution of pores throughout the volume of the material. Laboratory tests were carried out for two types of samples, represented by the proposed method of foam concrete production by two-stage foam injection with the use of modified additive in comparison with the classical foam concrete. The density of Type 1 samples varies from 410 to 793 kg/m3 (coefficient of variation from 5.12 to 7.31%), while the density of fiberboard samples lies within the range from 539 to 655 kg/m3 (coefficient of variation from 2.66 to 3.14%). The results of greater variation of densities by height in the Type 1 sample relative to the Type 2 sample indicate the influence of the technological process of foam concrete production on the quality of the pore structure of the material. The results of strength evaluation showed a large scatter of Type 1 samples in relation to Type 2 samples. The highest values of CM strengths are logically observed in the lower part of the sample and the lowest in the upper location: 44.04 and 32.33 kg/cm2 (coefficient of variation from 5.15 to 9.54%). For Type 2 samples, the same values are 55.18 and 44.44 kg/cm2, for the lower and upper locations, respectively (coefficient of variation from 2.79 to 5.35%). The results of thermal conductivity measurements of Type 1 samples range from 0.098 to 0.203 W/m0C (coefficient of variation from 4.59 to 11.88%), while the densities of Type 2 samples lie between 128 and 162 W/m0C (coefficient of variation from 3.38 to 3.55%).