Foam Concrete Research Articles

Carbon Fiber Effect on Compressive Strength of Lightweight Foamed Concrete

Carbon Fiber Effect on Compressive Strength of Lightweight Foamed Concrete

Research on flexural mechanical properties and mechanism of green ecological coir fiber foamed concrete (CFFC)

To explore the effect and mechanism of coir fiber on the performance of foamed concrete, the flexural performance test, pore characteristics and microstructure test of coir fiber foamed concrete with different content were carried out. First, Image-Pro Plus (image processing software) was used to study the pore morphology, porosity, average pore diameter, and pore roundness of CFFC with various fibers dosage (0, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%) by binarization processing method. Then, a total of eighteen specimens, divided into six groups, were used to investigate the effect of CF dosage on flexural strength, toughness, energy absorption, and failure patterns of FC through a three-point flexural test. Furthermore, the microscopic properties of coir fiber foamed concrete (CFFC) were observed by scanning electron microscope (SEM) and energy dispersive X-ray detector (XRD) to explain the influence mechanism of CF on FC flexural properties. According to the research, CF can affect the pore characteristics of CFFC and improve its flexural performance. When CF content is 1.5–2.0%, the porosity, diameter and roundness of CFFC have lower values of 68.6%, 1.96 mm and 1.29. After the fiber dosage reaches 1.5%, the CFFC failure mode changed to plastic damage, the flexural strength increased from 0.33 to 0.73 MPa, and the toughness energy absorption value was increased from 0.05 to 1.4 J. The optimum dosage of coir fiber is 2.0% for improving the flexural mechanical properties of FC. CF affects the process of hydration reaction of CFFC, but does not change the type of hydration product. However, the flexural performance of FC would decrease with excessive dosage of CF (> 2.0%) due to accelerating the formation of Ca(OH)2. CFFC can solve problems such as brittleness and easy cracking existing in traditional foamed concrete, and it can be used in the field of pavement engineering, foundation backfill and lightweight wall structure with CF dosage of 15–2.0%.

A study on sustainable foam concrete with waste polyester and ceramic powder: Properties and durability

The textile and apparel sectors currently produce millions of tons of textile waste annually on a global scale. Textile waste fibers are a viable option for sustainability as they can be utilized to reinforce cement-based composites internally by improving ductility and reducing the development of cracks. The issue of ceramic waste accumulation can be effectively resolved by using ceramic waste as supplementary cementitious materials (SCM), for sustainable construction, which also lowers energy use and CO2 emissions during the cement manufacturing process. This study evaluated the fresh, physico-mechanical, durability, and thermal characteristics of foam concrete (FC) reinforced with waste polyester (WP) incorporating waste ceramic powder (CP) as a replacement of cement in the rates of 0, 10 and 20 %. Twelve mixtures with a 0.3 water/binder (w/b) ratio were fabricated using a sodium lauryl sulfate foaming agent. The WP used in this study have four percentages of 0, 0.2, 0.4 and 0.6 % by volume. Durability performance of the mixtures for dry shrinkage, sulfate attack, high temperatures, alkali silica reaction and freeze-thaw cycles was also carried out. Microstructure of the mixtures was analyzed by SEM. Cost investigation and environmental impact of FC mixtures were also investigated. The findings indicated that the mixture with 10 % CP and 0.6 % WP had the largest 28-day compressive strength of 8.78 MPa, representing a 47 % decrease over the reference mixture (without CP and WP). The same mixture also exhibited the lowest dry shrinkage after the reference mixture. The mixture containing 0%CP and 0.2WP had the lowest thermal conductivity with a reduction of 74.0 % as per the reference mixture. The 0.4 % WP and 0%CP incorporated mixture exhibited the best thermal and F-T performance.

Enhanced interface and thermal insulation in cement composites using polydopamine-modified hydrophobic silica aerogels

Silica aerogels (SA) have exceptional thermal insulation capabilities, however, their superhydrophobic nature hinders the formation of a uniform composite when combined with cement slurry. To address this issue, an aqueous solution was employed to disperse SA particles using sodium dodecyl sulfate (SDS). Subsequently, the dispersed micelles were coated with polydopamine (PDA) through in situ polymerization. This approach effectively enhanced the dispersion of SA in cement slurry and improved its connection force with the cement hydration products, thereby mitigating the adverse effects of aggregated SA on the mechanical properties of the cement composite. The successful PDA coating led to the formation of smaller aggregated micelles, resulting in a 30% improvement in compressive strength of cement composites containing modified SA compared to those using unmodified SA, while maintaining the desired thermal conductivity properties. With a strategic increase in the quantity of modified SA, a remarkable thermal conductivity of 0.1351 W/m·K was achieved without significantly compromising the compressive strength, which reached about 13.94 MPa. This enhanced compressive strength surpassed that of conventional thermal insulation materials like expanded polystyrene (EPS) and foam concrete. Consequently, this novel technique has the potential to markedly enhance the thermal insulation of cement composites without excessively impacting their compressive strength, thus contributing to the development of green insulation and energy-saving building materials.

High-performance lightweight foam concrete enabled by compositing ultra-stable hydrophobic aqueous foam

The major limitations of lightweight foam concrete are inferior mechanical properties and durability. This study designs a novel high-modulus hydrophobic foam to produce high-strength and durable foam concrete. Poly (methyl hydrogen)siloxane (PMHS) was employed to construct a hydrophobic boundary of hydroxypropyl methylcellulose (HPMC) foam. The produced hydrophobic foam bubbles exhibit a high modulus, fine bubble size, and exceptional thermodynamic stability. A dense foam wall of 8 μm in thickness functions as a structure for chemical loadings of inorganic-organic particles onto the viscoelastic bubble film. This facilitates their interaction effect of adsorption and chemical bonding, contributing to the hydrophobic nature of the foam wall. The resulting hydrophobic foam concrete shows low water adsorption and high mechanical strength. The hydrophobic foam concrete demonstrates superior chemical resistance and anti-chloride diffusion compared with normal concrete. This study might provide a practical strategy for designing high-performance lightweight foam concrete with significant potential as structural elements.

Solidification of heavy metal in municipal solid waste incineration fly ash and performance evolution of alkali-activated foam concrete

The heavy metals in municipal solid waste incineration fly ash (MSWIFA) limit its large-scale application. To improve the utilization ratio of MSWIFA, a slag-MSWIFA-fly ash alkali-activated foam concrete (ASFC) was prepared in this study. The influence of MSWIFA content on the performances of ASFC and the solidification effect of heavy metals in MSWIFA by alkali-activated materials were studied. The results show that the performance of ASFC was directly related to the pore structure, which was affected by the fluidity and setting time of the paste, as well as the quantity and type of hydration products. When the MSWIFA substitution rate was 25–50 %, the fluidity of the paste was better, the pore diameter decreased, and the number of closed pores increased. The compressive strength of ASFC at 28 d was 1.72–2.01 MPa, and the thermal conductivity was 0.1305–0.1340 W/(m∙k). The leaching concentrations of the six heavy metal elements in the 28 d hardened paste of ASFC were all lower than 0.04 mg/L, and the solidification efficiencies of Pb and Zn, the two heavy meta elements with higher concentrations in MSWIFA, were both greater than 90 %. This study provides a technical and theoretical reference for applying MSWIFA in alkali-activated foam concrete.

Mechanical and durability properties of polymer fiber reinforced one-part foam geopolymer concrete: A sustainable strategy for the recycling of waste steel slag aggregate and fly ash

This paper assesses the feasibility of geopolymers (GPs) for use as lightweight foamed concrete, a crucial step towards reducing the carbon footprint and conserving natural resources. A powder activator (i.e., sodium metasilicate) less harmful to the environment was used to activate the fly ash-based GPs, while the limestone aggregates were gradually replaced by up to 100 % waste slag materials to conserve natural resources. Polypropylene fibers were incorporated at high dosage rates of 1 % or 2 %, by volume, to reduce the concrete density and improve its durability properties. Tested properties include flow, density, water absorption, porosity, thermal conductivity, mechanical strengths, drying shrinkage, and resistance to sulfate attack, freeze/thaw cycles, and elevated temperature. Results showed that the concrete mechanical properties improved when the limestone aggregate was replaced by slag materials, but the density and thermal conductivity were slightly curtailed at higher addition rates. The use of polypropylene fibers proved efficient to improve the resistance to freeze/thaw cycles, drying shrinkage, and expansion due to sulphate attack. Such data can help sustain the green building industry development by reducing the carbon footprint and conserving natural resources in foamed concrete applications.

Enhancing the engineering performance of lightweight limestone calcined clay cement concrete using used engine oil as a foam stabilizer

Lightweight foam concrete is an appealing thermal insulation material with great potential for decarbonizing the building sector, given that its superior thermal insulation and reduced material usage promote energy-efficient and low-carbon constructions. However, traditional foam concrete largely depends on carbon-intensive ordinary Portland cement (OPC) and costly foam stabilizers, e.g., nanomaterials. To address these issues, this study developed an eco-friendly foam concrete formula incorporating limestone calcined clay cement as a low-carbon cement substitute and used engine oil (UEO) as a foam stabilizer. The viability of this formula was confirmed by assessing foam stability performance of UEO-enhanced foam and crucial engineering performance – thermal conductivity and compressive strength – of foam concrete. Experiments demonstrate that 1 % UEO notably boosts foam stability, with prolonged stable time by 75 % and enhanced remaining foam fraction by 43 %. Additionally, 1 % UEO-containing foam concrete exhibits superior compressive strength of 3.2 MPa and reduced thermal conductivity of 0.162 W⋅m-1K-1, outperforming foam concrete without UEO. The mechanisms of macroscopic performance changes were revealed through scanning electron microscopy (SEM), which disclosed a uniformly established UEO-enhanced pore system and UEO-driven hydration process as the microscale origins. These findings provide waste-enhanced foam stabilizers and present an environmentally appealing alternative to traditional foam concrete, with implications for clean waste management and building decarbonization.

Dynamic mechanical behaviors of foamed concrete using modified viscoelastic SHPB

This study aims to investigate the dynamic mechanical behaviors of foamed concrete (FC) utilizing a modified viscoelastic split Hopkinson Pressure Bar (VE-SHPB). The VE-SHPB proposed in this study enables impedance matching between bars and FC, enhancing measurement precision. Dynamic mechanical behaviors of FC with different densities (400, 700, 1000, 1300 kg/m3) under various incident pressure (0.2, 0.5, 0.8, 1.1 MPa) are examined using the VE-SHPB. The failure modes of FC are categorized into Spalling (Mode I), Disintegration (Mode II), and Comminution (Mode III) based on fracture states of post-impact. The mechanism of strain rate and density on failure mode, dynamic strength, dynamic increase factor (DIF), and energy consumption density are discussed. The results show that FC's dynamic mechanical properties increase with increasing strain rate, but present different strain rate sensitivities at different densities. The dynamic mechanical properties of FC are determined by both the pore structure and matrix properties. Notably, Mode II shows better ability of energy consumption, specifically FC with a density around 700 kg/m³ demonstrates higher energy absorption density.

Quantitative characterization of bubble stability of foam concrete throughout extrusion process: From yield stress, viscosity and surface tension point of view

Foam concrete (FC) is suitable to be used as printing ink for drones in extreme environment because of its light weight, it can reduce the load of drones and improve printing efficiency. Furthermore, since the FC density and thermal insulation performance can be flexibly changed by changing the bubble content, it can be used to print functional gradient components and special-shaped insulation walls. The stability of bubbles is crucial as it directly impacts the performance of 3D printed FC (3DPFC). Here, we examined the bubble destabilization and deformation of FC throughout the mixing process, resting period prior to extrusion, and extrusion process based on three parameters, i.e., yield stress, viscosity, and surface tension. The results indicate that increasing the yield stress from 1406 Pa to 13379 Pa of the precursor leads to a decrease in bubble volume fraction after mixing from 38.26 % to 27.24 %, while increasing viscosity from 2.16 Pa s to 6.65 Pa s and decreasing surface tension from 72.4 mN/m to 33.5 mN/m are favorable for improving the sphericity of bubbles with the diameter between 300 and 800 μm in FC. In the resting stage, the yield stress of the interstitial paste is the primary factor controlling bubble stability. When the initial yield stress of the equivalent interstitial paste is 5212 Pa, the bubble volume fraction decreases by only 0.8 % within 60 min. During extrusion, high yield stress leading to bubble deformation and instability, whereas viscosity and pore solution surface tension act as sources of bubble compression resistance. There exists a suitable diameter interval for bubble pressure-bearing limit under different paste environment during extrusion.

Study on properties of re-dispersible latex powder and polypropylene fiber-reinforced lightweight foam concrete

Foam concrete has a broad application prospect due to its lightweight, convenient construction and other characteristics. However, the low strength and tensile toughness limit the application range of foam concrete. In this study, re-dispersible latex powder and polypropylene fiber were used to improve the mechanical properties of foam concrete. The effects of re-dispersible latex powder and polypropylene fiber on the compressive and tensile properties of foam concrete were studied. The results showed that compared with ordinary foam concrete, the combination of re-dispersible latex powder and polypropylene fiber increased the energy absorption capacity, ductility index and tension compression ratio of foam concrete by 13.4 %, 5024.6 % and 190.7 %, respectively. The bio-membrane formed by the hydration of re-dispersible latex powder improves the internal pore structure, which can cooperate with polypropylene fiber to optimize the crack growth behavior and ductility of foam concrete, thereby improving the compression and tensile properties of foam concrete.

Effect of Waste Rubber Inclusion on the Microstructure and Mechanical Performance of Low-Density Foam Concrete

Effect of Waste Rubber Inclusion on the Microstructure and Mechanical Performance of Low-Density Foam Concrete

Influence of combined substitution of slag and fly ash in improving the pore structure and corrosion resistance of foam concrete mixtures used for reinforced concrete applications

Foam concretes (FCs) have been used for several light-weight applications demanding low strength; however, their use for reinforced concrete (RC) applications is limited since high macrovoid amounts result in weaker matrices. The high w/c and overlapping of macrovoids have been identified as critical factors constituting a permeable microstructure in FC systems. Since corrosion performance is a critical aspect in the design of RC members and that the durability parameters of concrete, such as its porosity, pore size distribution, and permeability, also play a vital role in restricting the diffusion of chloride ions, particularly in the cover region of members, it is imperative to determine these properties and thoroughly understand the material behaviour or characteristics. In the current study, five FC mixtures (GF0 to GF4) were produced using ground granulated blast furnace slag (GGBS) and fly ash (FA) as a replacements for cement and sand, respectively, at different dosages, considering both economic and environmental aspects. The principal objective of the study is to determine the pore and permeability related properties of produced FCs, assess their corrosion performance, and ascertain their suitability for RC applications by comparing their performance with that of conventional M25-grade concrete. Also, the influence of the combined effect of GGBS and FA addition and the individual effect of FA addition were assessed. The research findings showed that FCs had a higher water absorption capacity and porosity compared to M25 concrete. In addition, the inclusion of GGBS and FA resulted in a decrease in water absorption by 8%–19% and a decrease in porosity by 23%–36% compared to the control FC mixture. The Mercury Intrusion Porosimetry (MIP) results indicated a substantial enhancement in gel pores, threshold, and critical pore diameter, while the size of the larger capillary pore decreased by 90%–95% when GGBS and FA were added compared to the control FC mixture. The scanning electron microscopy (SEM) analysis and binary images from the image analysis revealed the presence of uniformly distributed and distinct macrovoids formed by foam. These macrovoids were predominantly found within the size range of 7.1μm – 100 µm. The addition of GGBS and FA particles to FC mixes resulted in a significant improvement in the chloride ion permeation (CIP) class, reducing it from 'High' to 'Very Low' compared to M25 concrete. The Accelerated Corrosion Test (ACT) results obtained from FCs demonstrated a significant increase in cracking time ranging from 30% to 323%, as well as a notable decrease in mass loss ranging from 56% to 85% when compared to M25 concrete. The Fourier transform infrared (FTIR) and energy dispersive spectroscopy (EDS) analysis results revealed the presence of corrosion products, including feroxyhyte, akageneite, and Friedel's salt crystal, in both FCs and M25 concrete, indicating the occurrence of corrosion by the chloride ions present in the NaCl solution outside the specimen. Overall, the porosity, CIP, and corrosion resistance of FC with GGBS and FA are superior to those of the M25 concrete, making it suitable for use in RC applications.

Coupling effect of freezing-thawing cycles and dynamic loading on the accumulative deformation and microstructure of foam concrete

Coupling effect of freezing-thawing cycles and dynamic loading on the accumulative deformation and microstructure of foam concrete

Research on the performance of foamed concrete based on superhydrophobic bulk modification

Foamed concrete is a kind of lightweight insulation material formed by the uniform mixture of foam and cement slurry. The superhydrophobic bulk modification of foamed concrete can reduce its high water absorption and prolong its service life. In this paper, the compatibility of three hydrophobic agents named polydimethylsiloxane (PDMS), isoctyltriethoxysilane (ICTS) and SBT®-TIA with foams was studied, and the reasons of incompatibility were revealed. Then, the superhydrophobic bulk foamed concrete system was constructed by physical foaming method, adding polydimethylsiloxane (PDMS), calcium stearate (CS), nano-silica (NS) and covering the surface of the specimen with 200-mesh wire mesh. The results show that the maximum contact angles of the meshed surface and the internal polished surface of superhydrophobic foamed concrete were 162.7° and 153.5°, respectively. At the same time, the water absorption rate of the modified specimen was significantly reduced, and the reduction rate was up to 90 %. In addition, the deterioration degree of thermal insulation performance after soaking and the dry shrinkage rate were significantly reduced compared with ordinary foamed concrete. Scanning electron microscopy (SEM) revealed that increasing the multi-scale roughness could improve the hydrophobic properties of foamed concrete. Fourier infrared spectroscopy (FT-IR) also confirmed that low surface energy groups such as -CH2 and -CH3 in PDMS bonded to the cement hydration products, indicating the successful preparation of superhydrophobic bulk foamed concrete.

Electromagnetic wave absorption value of iron-rich steel slag for application in foam concrete

In this study, iron-rich steel slag (IRSS) and carbon fiber (CF) were incorporated into foam concrete to maximize the economic benefits of composites and multifunctional integration while improving the overall performance of foam concrete. The study found that the optimal IRSS content for maximizing foam concrete’s compressive strength was 15 %, which increased by 18.59 % compared to the control. Additionally, S15 specimens showed a 37.87 % increase in electrical conductivity compared to the control. In addition, the average value of the fundamental part of the dielectric constant of the S15 specimen was 7.409, the average value of the imaginary part was 3.057, and the angular tangent of the electrical loss (tanδε) value and the reflection loss were both improved, which indicated that the S15 specimen material had a better ability to absorb electromagnetic waves and had an excellent performance of electromagnetic loss.

ПОВЫШЕНИЕ НЕСУЩЕЙ СПОСОБНОСТИ ЦЕНТРАЛЬНО СЖАТОЙ СТОЙКИ ЗАМКНУТОГО СЕЧЕНИЯ В СРЕДЕ ПЕНОБЕТОНА

The paper considers a technology that combines the well-known method of frame-panel construction with the use of light metal structures and the production of heat-insulating, sound-insulating monolith-ic non-autoclaved foam concrete. The principle of the construction of monolithic frame structures us-ing foam concrete consists in the formation of a metal structure consisting of columns resting on the foundation and horizontal girder cells of ceilings lined with foam concrete, connecting all the elements of the frame into a single solid skeleton of the building

ОЦЕНКА НЕСУЩЕЙ СПОСОБНОСТИ ВНЕЦЕНТРЕННО СЖАТОЙ СТОЙКИ ЗАМКНУТОГО СЕЧЕНИЯ В СРЕДЕ ПЕНОБЕТОНА

A technical solution for frame racks is proposed for the construction of monolithic frame structures using foam concrete. The principle of the construction of monolithic frame structures using foam concrete consists in the formation of a metal structure, reinforced with foam concrete, which binds all the elements of the frame into a single solid skeleton of the building

Optimization of Mechanical Properties of Raw Agave Fibre-Reinforced Lightweight Foamed Concrete

The utilization of readily accessible natural fibres in lightweight foamed concrete (LWFC), which is already a widely used building material, can have a substantial positive impact on the environment. Therefore, the mechanical characteristics might be increased by using a correct mix proportion of fibre-reinforced LWFC. Innovative LWFC-agave fibre (AF) composites were created in this experiment. In order to get the best mechanical qualities, this investigation set out to establish the correct weight fraction of AF to be added to LWFC. Two LWFC densities of 750 and 1500 kg/m3 were produced with the addition of several weight fractions of AF, precisely 0.0%, 1.5%, 3.0%, 4.5%, 6.0%, and 7.5%, were used. To establish the mechanical characteristics of LWFCAF composites, flexural tests, tensile strength tests, axial compression tests, and ultrasonic pulse velocity tests were carried out. Test results revealed that the combination of LWFC together with a weight fraction of 4.5% of AF exhibited superior mechanical properties. Beyond 4.5% of AF’s weight fraction, the mechanical properties started to deteriorate. This study gives insight and crucial data on the mechanical characteristics of LWFC-AF composites therefore it will enable future researchers to explore other properties of LWFC reinforced with AF.

Sustainable use of waste glass sand and waste glass powder in alkali-activated slag foam concretes: Physico-mechanical, thermal insulation and durability characteristics

In many countries, the safe removal of the massive volume of waste glass has emerged as a major environmental priority. However, the manufacture of concrete pollutes the environment with greenhouse gasses and consumes vast amounts of natural resources. As a result, the construction industry has recently been paying more and more attention to reusing glass waste to produce environmentally friendly building materials. This work aims to manufacture environmentally friendly alkali-activated foam concrete (AAFC) by examining the combined effects of waste glass powder (GP) and waste glass sand (GS) as partial substitutes for granulated blast-furnace slag (GBFS) and river sand (RS) respectively. The present study involved the experimentation of AAFC mixtures with GP contents of 0 and 10 % as a replacement for GBFS and GS contents of 0, 25, 50 and 100 % as a replacement for RS. Eight AAFC mixtures with fixed alkaline solution-to-binder (A/B) ratio of 0.5 were fabricated and cured at 80 °C for 24 h. The effects of different GS and GP contents on the oven dry density, flowability, water absorption, porosity, sorptivity, thermal conductivity, compressive strength, flexural strength, high temperature resistance and hydrochloric acid (HCI) resistance of AAFC mixtures were evaluated. Microstructure of the mixtures was analyzed by SEM and EDS. The findings indicated that the AAFC mixture with 50 % GS exhibited the best mechanical properties with a compressive strength of 3.48 MPa, representing a 71.4 % increase over the reference mixture. The mixture with 50 %GS also exhibited the lowest sorptivity regardless of GP content. Thermal conductivity enhanced by 4.6 and 7.0 % by replacing RS with 50 % GS at 0 and 10 % GP content. Replacing RS with GS and GBFS with GP increased the high temperature and acid resistance of the AAFC mixtures and the best high temperature and acid resistance were obtained for the mixtures containing 100 %GS and 10 %GP.