Foam Concrete Research Articles

Investigation on the sustainable use of different sizes of sawdust aggregates in eco-friendly foam concretes: Physico-mechanical, thermal insulation and durability characteristics

The extensive mining of natural resources, such as sand, for the construction industry, poses a hazard to the environment. To preserve the environment, the researcher must thus take into account the use of industrial byproducts rather than natural materials. The use of sawdust (SD) produced by the wood industry in foam concretes (FC) has been investigated in this study. This study examined the physical, mechanical, thermal, microstructural and durability characteristics of FC containing SD as a replacement of silica sand (SS) in the rates of 0, 25, 50 and 100 %. Two different SD sizes of 0–4 mm (SD4) and 0–1 mm (SD1) were used in the fabrication of FC mixtures. Protein-based foam agent was used to create FC mixtures. Fourteen mixtures with a 0.6 water/binder (w/b) ratio were produced at two different cement contents of 400 kg/m3 and 500 kg/m3. The fresh, mechanical, physical, and sorptivity characteristics of the FC mixtures were investigated in relation to the impacts of cement dosage, SD size, and SD replacement levels of SS. Durability of FC against high temperature, sulfate attack and freeze-thaw cycles was assessed. Costs and CO2 emissions from the blends were also assessed. The outcomes revealed that a 25 %SD1 integrated FC mixture with a cement content of 500 kg/m3 generated the highest 28-day compressive strength of 3.56 MPa with a 20 % strength loss as per the Ref.500 mixture. 17 % lower thermal conductivity was gained with the inclusion of 100 %SD4 as per the Ref.400 mixture. The mixture with 50 %SD4 and 400 kg/m3 cement dosage exhibited the best resistance to high temperature. The mixture with 25 %SD1 and 400 kg/m3 cement dosage showed the best frost resistance. SD incorporated mixtures showed better durability performance than the reference mixtures.

Improving thermal conductivity and drying shrinkage of foamed concrete with artificial ceramsite from excavation soil and sewage sludge

Foamed concrete (FC) is susceptible to crack induced by shrinkage, which results in a degradation of the thermal insulation. This study proposes a solution by incorporating artificial ceramsite (AC) from excavation soil and sewage sludge in FC for improving thermal conductivity and drying shrinkage. The characteristics of AC and its effects with varying particle size distributions (PSDs) as well as volume contents on the fluidity, strength development, drying shrinkage, thermal conductivity, pore structure and morphology of FC were explored. Both the water absorption and porosity of AC increased whereas its apparent density reduced as the PSD rose. The fluidity tended to decrease as the replacement elevated, but the rate of fluidity loss decreased. Compared to FC, fine AC with high replacement was detrimental to strength, while coarse AC with low replacement had no marked adverse impact on strength. More importantly, the presence of AC performed better in mitigating drying shrinkage and thermal conductivity, especially for the higher replacement of coarse AC. Furthermore, the existence of AC with tailored porosity increased the porosity and average pore diameter but improved the pore circularity and pore connectivity.

Dynamic properties of alkali residue-based foamed concrete under cyclic load

Alkali residue-based foamed concrete (A-FC), consisting of cement, alkali residue, blast furnace slag, and foam, has great potential for application in subgrade engineering. A series of dynamic triaxial tests were conducted, and the influences of confining pressure, vibration frequency, and curing age on the dynamic properties of A-FC was revealed. Test results indicated that the backbone curves of A-FC exhibit a hyperbolic shape, effectively captured by the H-D model. After 7 days of curing, A-FC possessed robust dynamic bearing capacity. As the dynamic strain increases, the dynamic elastic modulus of A-FC exhibits an initial rise followed by a gradual decline. Concurrently, the damping ratio demonstrates an initial decrease and subsequent gradual increase. Elevated confining pressure, prolonged curing age, and higher vibration frequency were found to contribute to a progressive increase in the dynamic elastic modulus of A-FC. Throughout the damping ratio growth stage, the increasing curing age and confining pressure led to the decrease of damping ratio, with minimal influence from vibration frequency. A calculation model for the maximum dynamic elastic modulus of A-FC was proposed, considering confining pressure, vibration frequency, and curing age. This research underscores the capacity of A-FC to withstand cyclic loading, thereby offering valuable support for its engineering applications.

3D-printed multi-functional foamed concrete building components: Material properties, component design, and 3D printing application

The use of multi-density foamed concretes (FCs) to produce multi-functional building components by 3D Concrete Printing (3DCP) is investigated. The use of medium-density 3D-printed foamed concrete (3DPFC_800), primarily serving a load-bearing role, and ultra-lightweight foamed concrete (ULFC_300), as thermal insulation material poured in the voids defined by the former, is proposed. This enables meeting diverse performance requirements within a single cementitious matrix, eliminating the need for multiple materials. The main properties of the proposed mixes are investigated. The compressive strength and thermal conductivity are equal to 7.04 MPa and 0.205 W/mK, and 1.43 MPa and 0.072 W/mK for 3DPFC_800 and ULFC_300, respectively. A successful 2D-printing test validates the suitability of 3DPFC_800 for 3DCP, and a robotic arm is employed for 3DCP tests. The proposed application allows for further knowledge on the use of FC in 3DCP and the identification of some issues and challenges that still need to be addressed.

Study on strength deterioration mechanism of foamed concrete under freeze-thaw cycles: Experiment and numerical simulation

In cold regions, freeze-thaw (F-T) cycles pose a severe challenge to the long-term durability and structural reliability of foamed concrete (FC). In response, this study proposes a comprehensive multi-level evaluation system integrating macro and micro scales, aiming to thoroughly investigate the decline mechanisms of compressive strength of FC under F-T cycles. Through macroscopic experiments, the extent of mass loss and strength degradation has been quantified. The evolution of internal damage, progression of surface displacements, and changes in pore structures have been effectively tracked and captured by using non-contact techniques. The findings reveal that after F-T cycles, the mass loss rate and strength loss rate of FC can be up to 6.62 % and 37.61 %, respectively. There is a marked acceleration in the expansion rate of non-stable internal cracks; peak displacements show significant growth, and the failure mode changed from brittle to brittle-ductile. Furthermore, the porosity and the proportion of irregular pore shapes have increased by 25.84 % and 18.39 %, respectively. Additionally, a discrete element model incorporating irregular pore characteristics has been established, elucidating the profound impact of F-T cycles from a microscopic physical perspective. Specifically, the weakening and the increased number of fracture events of the contact forces between cement particles lead to the deterioration of FC's strength.

UTILIZING FIBER MESH AND NYLON ROPE AS NON-STEEL REINFORCEMENT FOR SANDWICH CONCRETE PLATE PRECAST IN COASTAL AREA STRUCTURES

Reinforced concrete, a popular construction choice, is often selected due to the limited availability of materials like wood and increased familiarity with concrete. However, coastal structures using steel bars in reinforced concrete usually face corrosion issues. Corrosion can be mitigated by increasing concrete compressive strength and enlarging the concrete cover to protect the steel from saltwater. These measures are challenging for small structures due to the small dimensions of columns, beams, and plates, making thick concrete covers difficult. Additionally, small structures are often built manually or semi-manually, complicating the achievement of higher compressive strength and watertightness. However, there is hope. Researchers have developed reinforced concrete with non-metal reinforcement, such as fiber mesh and nylon rope, and combined regular and lightweight concrete to reduce dead loads, creating a sandwich concrete slab. Test results show that the slab has sufficient strength for light construction, with a strong bond between mortar and foam concrete. Although fiber mesh and nylon rope do not yet increase the slab's flexural strength, nylon rope prevents brittle failure. This promising research paves the way for further studies and potential improvements in the future.

Graphite-enhanced foam cement-based materials: Mechanical properties, pore structure and electromagnetic wave absorption performance

To reduce the environmental pollution caused by electromagnetic waves (EMW), graphite-enhanced foam cement-based electromagnetic wave-absorbing materials were prepared. The effects of hydration products and pore structure on the mechanical strength and microstructure have been investigated. The results show that at a graphite content of 10 wt%, resulting in a reduction in pore size and concentration within 400μm. This led to improved material compactness, resulting in an increase in compressive strength of 32.01 % and 29.13 % for 3-day and 28-day foamed concrete, along with a 35.40 % and 29.27 % increase in flexural strength. For the 10 mm thick foamed concrete, the reflection loss is −24.08 dB with an effective absorption bandwidth of 0.466 GHz (3.762–4.228 GHz). The impedance matching increased by 129 %, moving from 8.3 to 10 mm up range to 6.1–10 mm, while the frequency range increased by 61.35 %, moving from 3.37 to 5 GHz up range to 2.37–5 GHz, compared to the control group.

Research on the interaction between trench material and pipeline under fault displacement

With the large-scale construction of oil and gas pipelines, the safety issues of long-distance buried pipelines in the service and construction have become increasingly prominent. The complex geological and topographical conditions of the special zone will put forwards extremely high requirements on pipe trench laying backfill materials and construction technology. For example, pipelines are inevitable to cross the active fault, while the trench backfilled with soil has limitations in protecting them from failure under the active fault displacement caused by the earthquake. Therefore, it is necessary to study the pipe–soil interaction mechanism, determine the stress state of the pipeline and propose a new backfilling material that can protect the pipeline from failure. Foam concrete (FC) provides a new choice to backfill the buried pipeline trench due to its high-homogeneity, lightweight, controllable-strength, and self-compacting. To further determine the applicability of the FC, the pipe-FC interaction mechanism is studied. Then, a FE model of the FC-pipeline-soil interaction system is established by Abaqus to quantitatively analyze the applicability of the FC based on the experimental data of the mechanical performance of the FC. It proves that using FC as trench backfill material has a noticeable protective effect on the pipeline under the earthquake-induced displacement of the normal fault. Furthermore, FC has a better protective effect on the pipeline subjected to compressive than tensile. Therefore, the reference for applying FC in trench backfilling of pipelines crossing normal fault is provided.

Effects of Mixing Techniques and Material Compositions on the Compressive Strength and Thermal Conductivity of Ultra-Lightweight Foam Concrete.

The research focuses on ultra-lightweight foam concrete with a dry density below 200 kg/m3, primarily used as insulation material. Factors that may affect material properties are categorized into mixing techniques and material composition, and experimental investigations were conducted on the impact of these factors on the rheological properties of cement slurry, density at different time intervals, compressive strength, and thermal conductivity of foam concrete samples. The experimental results indicate the influence of mixing speed and mixing duration on the instrument during the cement slurry production and mixing process with foam. Additionally, variations in foam concrete sample properties are observed due to the water-to-cement ratio, foam content, and foam density in the selected material compositions. By analyzing the material density at different time intervals, the relationship between the ambient air trapped during the mixing process and the viscosity of the material can be indirectly observed. This analysis can also reveal the correlation between the unplanned air content and the properties of the material.

A Thermal Study on Foam-Based Eco-friendly Cinder Tiles

This study focusses on usage of fly ash and metakaolin as industrial waste to aerate lightweight foam concrete (LFGC) using hydrogen peroxide. By designing and optimising the components of metakaolin, hydrogen peroxide, and fly ash, physical properties such as mechanical strength, thermal characteristics, and heat resistance are assessed. Lightweight foam concrete has a dry density between 1400 and 1800 kg/m3, a bending strength between 0.7 and 1 MPa, and thermal conductivity between 0.1 and 0.7 W/mK, all of which indicate that it is more lightweight than normal concrete. By dumping solid waste on land, the environment suffers, and it leads to the release of toxic gases into the atmosphere and get polluted. As a byproduct, swapping out the cement with concrete would be a practical and cost-effective way to use the refuse. Alkaline solutions such as NaOH and Na2Sio3 are used to prepare geopolymer concrete. Samples of geopolymer concrete made with fly ash and metakaolin are cured in the oven for 24 hours. Geopolymer concrete is a form of material-based construction in which industrial raw materials supplied by businesses are incorporated into it. This lowers carbon emissions and makes the concrete more environmentally friendly. Using MATLAB, we predict which is the best value of bending strength, thermal conductivity, heat resistance, and dry density of various ash concrete. Effective input variables for geopolymer concrete include the amounts of fly ash, metakaolin, NaOH, and Na2SiO3, Fine aggregate, and the ratio of NaOH and Na2SiO3 and the output variables are bending strength, dry density, thermal conductivity, heat resistance.

Preparation of a novel foamed concrete modified with carbon fiber and graphite: Mechanical, electro-magnetic and microstructural characteristics based on X-CT

In this paper, foam concrete is modified using graphite and carbon fiber as absorbents. The mechanical properties are analyzed in conjunction with hydration products, pore size distribution based on XCT test. Additionally, the resistivity, complex permittivity and complex permeability are tested. The results demonstrate that carbon fiber enhances the proportion of pores with diameters less than 200 μm in foam concrete, thereby significantly enhancing its flexural strength. Furthermore, incorporating graphite helps offset the initial retardation of sulfoaluminate cement hydration induced by carbon fibers, leading to an increase in the average pore size and a reduction in compressive strength. The incorporation of carbon fibers at a concentration of 0.6 wt% achieves the percolation threshold, akin to scenarios with singular fiber incorporation. Exceeding 2 wt% graphite content results in negligible influence on the conductivity. The synergistic integration of graphite and carbon fibers significantly improves the electromagnetic wave absorption performance of the composite. At a thickness of 6 mm, the material exhibits an effective bandwidth where the reflection loss is less than −10 dB, extending up to 2.5 GHz, which constitutes 52.08 % of the tested frequency spectrum.

Sandy soil based foam concrete with ultra-small pore structure through in-situ mechanical frothing

During the manufacturing of foam concrete, conventional chemical and physical foaming methods are still inadequate for regulating and stabilizing the bubble properties. In this work, a one-pot method, denoted as in-situ mechanical frothing, was proposed preparing foam concrete by vigorously stirring the mixture of water, cement, sandy soil, and foaming agent. Sandy soil (SS) was used in the content range of 25–75 % as cement replacement to decrease the binder consumption and reduce costs. The influence of in-situ mechanical frothing technology and SS dosage on the properties of paste rheology, pore structure, compressive strength, and thermal properties was investigated. The results showed that the average pore size of foam concrete prepared by this method is between 45.73 and 74.58 μm. The compressive strength of the formed foam concrete at dry density of 600–1000 kg/cm3 was 2.78–16.37 MPa, which was 85%–231 % higher than that the standard values. The incorporation of SS resulted in smaller and homogeneous pore structure in foam concrete. Moreover, foam concrete with 25–75 % SS dosage showed 7–40 % decrease in thermal conductivity. The overall analysis showed that the 25–50 % SS-incorporated foam concrete enabled achieving higher standard properties through in-situ mechanical frothing.

Comparative Study on the Effect of Synthetic Foaming Agent and Natural Foaming Agent on the Engineering Properties of Foam Concrete

The abstract discusses the imperative for the construction industry to pursue sustainable practices, particularly in materials selection. It introduces the study examining how different foaming agents impact the properties of foam concrete, a lightweight material crucial for sustainable construction. The construction industry's contribution to global sustainability efforts necessitates exploring eco-friendly alternatives for building materials. This study investigates the impact of synthetic and natural foaming agents on the engineering properties of foam concrete, with a focus on environmental considerations aligned with global sustainability goals. Foam concrete, a lightweight material without coarse aggregate, relies on the type of foaming agent used. This paper presents a comparative study of the effects of natural and synthetic foaming agents on foam concrete's engineering properties, including compressive strength, water absorption, and density. Experimental results indicate that foam concrete produced with a natural foaming agent exhibits greater compressive strength and density while absorbing less water than foam concrete with a synthetic foaming agent. These findings reduce the dead load on structures and minimize labour costs during construction.

Foam concrete for lightweight construction applications: A comprehensive review of the research development and material characteristics

Abstract Foam concrete or foamcrete is a lightweight, porous material with a wide range of applications in the construction domain. This article focused on reviewing porosity, thermal conductivity, acoustic properties, compressive strength (f c′), elastic modulus (E), flexural strength (f y), stability, resistance to hostile environments, density, and fire resistance of foam concrete. A systematic literature analysis was conducted to identify relevant research trends on foam concrete. The challenges and limitations of foam concrete research were highlighted, including the lack of standardized testing methods and the need for more research on the long-term durability and structural performance of foam concrete. The analysis of the literature data revealed that there had been a growing interest in foamcrete research over the past decade. Foam concrete may be utilized in several construction applications due to its adaptability and wide range of uses. Its potential uses can be increased by developing new manufacturing methods and the inclusion of certain admixtures. The present research has the potential to be advantageous for scholars interested in collaborative advancement and the exchange of novel tactics and concepts, owing to the visual and statistical representation of the regions/countries and researchers that have contributed.

Strength Properties of Lightweight Foamed Concrete with Steel Fiber

The advancement in lightweight cementitious composite strength enhancement has promoting the usage of lightweight material across modern construction industry. Likewise, Lightweight foamed concrete (LFC) was introduced as an alternative material in the construction industry due to its properties including good thermal and sound insulation, lighter in weight and cost-effectiveness. In corresponded to LFC strength issue which often found to be diminished due to its lower density and porous structures. Studies have shown that the incorporation of steel fiber into concrete can recover the diminished strength of lightweight foamed concrete. Hence, this research focusses on the strength properties of LFC incorporate with 30 kg/m3 of steel fiber. Three types of LFC were prepared in this study including a trial mix of LFC (LFC-TM), a control mix of LFC (LFC-CTR), and LFC with 30 kg/m3 steel fiber (LFC-30SF). The LFC-CTR and LFC-30SF were casted based on the obtained optimum water-to-cement ratio from the plotted performance index graph, which was 0.56 for both mixes. The fresh properties of LFC-CTR and LFC-30SF were determined based on the result obtained from fresh density, flow table and inverted slump tests. Besides, the strength properties studied for LFC-CTR and LFC-30SF were compressive strength, splitting tensile strength and flexural strength at 7, 28 and 56 days after curing. From the test results obtained, the compressive, splitting tensile and flexural strength of LFC was found to be improved by adding the steel fiber into the mix. As for the fresh properties of LFC, the stability was found to decreased after the steel fiber was added into the mix, while the flowability and consistency was observed with an improvement subject to fibre addition. In short, incorporating steel fiber can improve the strength properties of LFC, which driving their usability and encouraging wider adoption across modern industries.

Experimental studies on the mechanical behaviors of cold-formed thin-walled steel-foam concrete composite walls

This paper presents experimental studies to investigate the compressive and shear behaviors of cold-formed thin-walled steel-foam concrete composite walls. Three compressive walls and three shear walls were tested. The failure mode and load-displacement curve of the specimen were obtained from the compressive experiment. The compressive wall infilled with foam concrete mainly experienced distortion buckling of the end stud and local crushing failure of the concrete. The stud openings had a limited effect on the compressive bearing capacity of the composite wall. The failure mode and load-deformation curve were obtained in shear tests. The ductility index, shear stiffness, yield load, peak load, energy dissipation, and stiffness degradation were analyzed. The shear composite wall filled with foam concrete mainly occurred concrete crushing failure, local or distortional buckling failure of the end stud, and cracking failure of the calcium silicate board. The shear stiffness, shear capacity, ductility, and energy dissipation of the composite wall could be significantly improved after filling with foam concrete.

Preparation and properties of carbon dioxide foamed concrete using nanoparticles as foam stabilizer and pre–carbonated cement slurry

The stability of carbon dioxide (CO2) foam is critical for preparation and performance of CO2 foamed concrete (CFC). This study evaluated the effectiveness of nanoparticles for stabilizing CO2 foam and pre–carbonation of cement slurry for mitigating CO2 foam loss during CFC preparation, and conducted a comparative study of CO2 foam, pre-carbonized slurry and CFC, aiming at preparing CFC with excellent performance. The results demonstrated that the incorporation of nano–silica can significantly enhance the stability of CO2 foam, with an improved half–life and diameter distribution. The pre–carbonation process optimized consistency and alkalinity of cement slurry and increased the retention rate of CO2 foam after its introduction into cement slurry, thereby facilitating the production of low–density CFC. CFC exhibits high compressive strength and early internal temperature, and has a low water absorption. The presence of CO2 within pores and their subsequent formation of potential negative pressure via carbonation reaction contributed to a much lower thermal conductivity of CFC compared to air foamed concrete. Moreover, a thin layer of calcium carbonate was formed on the inner wall, which can densify the microstructure and modify the pores. Although the carbonation degree of CFC may be lower compared to that of conventional carbonation–cured foamed concrete, the internal and uniform carbonation within CFC greatly enhanced material strength. The non–destructive nuclear magnetic resonance results show that CFC has a more concentrated pore size distribution with fewer fine pores and a smaller pore throat radius.

Development of an environmentally foamed concrete incorporating red mud.

In this work, an efficient utilization method for red mud (RM) is provided through recycling RM as a mineral admixture for the preparation of foamed concrete (FC). Specifically, FC with different RM contents was prepared and investigated in terms of workability, mechanical properties, and hydration products. Results show that adding RM can significantly shorten the setting time, while it inevitably weakens the mechanical properties and fluidity of FC. However, the compressive strength of FC can still meet the strength predicted by the specification requirements when the RM replaces cement with 60% content (3d > 1.6MPa). Most importantly, the heavy metals leaching from RM-based FC under the action of rain is still unclear, so a device for simulating stormwater runoff was designed to test the heavy metal leaching risk of RM-based FC. The findings indicate that the solidification of cement and the high basicity of the matrix can effectively reduce the leaching risk of heavy metals from RM in FC. Although the pore structure analysis demonstrates that the porosity and connected pores of FC will be deteriorated as RM concentration increases. The results are of great significance for the recycling of waste and the sustainable development of building materials.

Investigation of foam concrete's mechanical properties and multi-scale damage evolution characteristics under uniaxial loading

The macroscopic mechanical behavior of foam concrete damages its mesoscopic pore structure. To study the macroscopic mechanical properties of foam concrete, a series of uniaxial compression tests were carried out. AE-DIC and SEM characterization were used to reveal the multi-dimensional damage evolution characteristics of foam concrete under load. Furthermore, the porosity response law of the foam concrete damage characteristics was analyzed using the finite element method. The results show a significant linear relationship between the residual and peak stress of foam concrete under uniaxial load (σr = kσp), and the coefficient k decreases with an increase in porosity. During uniaxial compression, tensile and shear damages were dominant on both sides of the yield point of foam concrete. The macroscopic load retention characteristics in the failure stage typically result from microscopic fracture structure reorganization and stress path optimization. The damage-dissipation energy during this period accounts for approximately 100% of absorbed energy. An increase in the porosity led to frequent adjustments in the stress path of the foam concrete, and the tensile damage tended to be significant and diffuse.

Ultra-stable foam enabled by nano silica engineering for foam concrete improvement

Foam concrete is increasingly applied in construction due to its lightweight, good thermal insulation and fire resistance, and environmental sustainability, while its low strength limits its further popularization and applications. To enhance the stability and performance of foam concrete, amphiphilic nano silica (ANS) was employed in this study to modify the sodium dodecyl sulphate (SDS) based foaming agent. Then, the designed foam was utilized to fabricate foam concrete, of which the micro/macro performance was analysed in detail. The results showed that ANS-modified foam exhibited superior stability with a thicker foam wall thickness, contributing to the enhancement of foam stability within the cement matrix. The foam concrete with ANS exhibited higher strength compared to the control groups. The analysis of pore structures revealed that the ANS modification led to a more rounded and homogeneous pore configuration, characterized by an increased proportion of small and medium-sized pores and a decreased average pore size. The increase in pore roundness was accompanied by a reduction in the number of sharp edges of the pores and therefore a reduction in the stress concentration factor, while the moderately sized pore also was more conducive to increasing strength due to its lower stress concentration. As a result, the strength of the concrete is significantly increased. These findings demonstrate the potential of ANS as an effective foam stabilizer for foam concrete production, leading to enhanced foam stability and improved mechanical properties of concrete.