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In May 2024, this journal published the paper "Experimental and a dual-scale analysis of the influence of coating on humidity control ability of hygroscopic materials with different porosity", in which a series of hygrothermal properties of foamed concretes are primarily measured, and subsequently used in a interior-humidity-levels performance evaluation via hygrothermal simulation and buffering correlations. This post-publication discussion voices concerns on the sorption isotherm and vapour permeability measurements performed on the foamed concretes. Concerning the sorption isotherms, it is established that these differ from other results on the same materials, and their overly high 75 %RH moisture contents are doubtful. Regarding the vapour permeabilities, the execution and interpretation of the cup tests differ from the relevant standard, and plausibly an incorrect element of the set-up has been weighed. As these hygroscopic properties are the crucial factor in the hygrothermal performance simulations, the findings on that front are equally jeopardised. • This post-publication critique expresses concerns on a previously published paper. • The paper's sorption isotherm measurements deviate from other literature results. • They furthermore bring about an excessively high moisture content at 75 %RH. • The paper's vapour permeability measurements deviate from the relevant standard. • They moreover are based on weighing of the wrong element of the cup set-up. [ABSTRACT FROM AUTHOR]

Materials possessing sufficient strength, exceptional thermal insulation, and energy-efficient characteristics are in short supply within the construction industry. Foamed concrete, known for its cost-effectiveness, ultralight composition, and prominent thermal insulation characteristics, has displayed significant potential in applications geared towards enhancing energy efficiency. Nevertheless, its widespread adoption is hindered because, at present, the strength and thermal insulation properties of foamed concrete fail to meet engineering requirements due to inadequate foam stability. In response to this challenge, an ultra-stable foam with a multi-walled core-shell structure is successfully synthesized by modifying the gas-liquid interface through coupling the synergistic effects of surfactant, Janus-ZrO 2 nanoparticles, and hydrophilic homogeneous SiO 2. Utilizing the innovative approach, we incorporate the ultra-stable foam, containing 5 wt% Janus-ZrO 2 nanoparticles, in the fabrication of foamed concrete with a resultant density of 500 kg m−3. Notably, this foamed concrete exhibits remarkable mechanical properties (compressive strength of 5.1 MPa) and outstanding thermal insulation performance (thermal conductivity of 0.091 W/(m·K)). These enhancements can be attributed to the refining of the pore structure and an increased proportion of closed pores within the foamed concrete, both facilitated by the utilization of the ultra-stable foam. The introduction of this unique ultra-stable foam is poised to expand the applications of foamed concrete in the construction sector. [ABSTRACT FROM AUTHOR]

How to effectively reduce the damage of frequent accidental explosions and explosion attacks to existing walls is an important concern of the blast resistance field. In the present study, the influence of the foamed concrete (density 820 kg/m3, water-cement ratio 0.4) coating thickness on the blast resistance of a 120 mm RC (reinforced concrete) wall was studied through blast experiments, numerical simulations, and shock wave theory. Results show that the influences of foamed concrete on the blast resistance of RC walls are jointly decided by the stress drop caused by impedance effect and exponential attenuation and the stress rise caused by high-speed impact compression. The coating thickness mainly affects the foam concrete's fragmentation degree and stress attenuation. A lower critical coating thickness exists in foamed concrete-coated RC walls. The blast resistance of the RC wall will decrease when the coating thickness is less than that value. The lower critical coating thickness is related to the intensity of blast load and the energy absorption capacity of foamed concrete, and it can be predicted by monitoring the explosive stress and energy incident to the RC wall. [ABSTRACT FROM AUTHOR]

In this paper, the effects of dry density, w/c ratio, and municipal solid waste incineration (MSWI) powder on the multi-scale properties and internal pore structure of foamed concrete were studied by using a single-factor controlled experiment. It was found that an increase in the dry density of foamed concrete could effectively reduce the porosity, leading to the improvement of compressive strength and impermeability and to the reduction of water absorption. The compressive strength, water absorption, and impermeability were mainly affected by the porosity when the w/c ratio changed. With the increase in porosity, the water absorption rate increased, and the compressive strength and impermeability decreased. The addition of MSWI powder caused no obvious change in the overall pore size distribution of the foamed concrete, and there was no significant change in the water absorption and impermeability of the structure. However, because the hydration activity of MSWI powder was lower than that of ordinary Portland cement, the compressive strength of foamed concrete decreased with the increase in MSWI powder. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the foamed-concrete-backfilled-gas-pipeline project, the fluidity of foamed concrete has a great impact on the construction quality. This research studied the fluidity of foamed concrete through laboratory tests. By changing the water–cement ratio, admixtures, additives, foaming-agent content and other test parameters, foamed concrete with different fluidities was prepared, and the effects of the above parameters on the fluidity of foamed concrete were analyzed. At the same time, the construction equipment was improved in the three steps of transportation, production and pouring. The results show the factors affecting the fluidity of foamed concrete are, in order of importance, foaming-agent content > water–cement ratio > water-reducer content > admixture content. According to the orthogonal-test results, the control scheme meeting the fluidity requirements of the actual engineering project had gains as follows: the water–cement-ratio range from 0.5 to 0.6, the amount of admixture from 35% to 40%, the water-reducer content at 1% and the foaming-agent content from 3% to 3.5% so as to ensure the automatic leveling of foamed concrete under the best flow state. [ABSTRACT FROM AUTHOR]

Foamed concrete is mostly used for backfilling of long-distance tunnels and compressive strength is an important technical index to control the quality of foamed concrete. The influence factors on compressive strength of low-density foamed concrete were obtained by the single factor test method based on the targeted dry density and compressive strength. The results show that the HT composed of pollution-free animal protein oil and vegetable oil is an efficient foaming agent and can produce stable foams. The cementation ability of cement can be fully expressed when a water to cement ratio of 0.45~0.5 is employed, making foamed concrete have a compressive strength higher than 2 MPa. The foam content is inversely proportional to the compressive strength and dry density of foamed concrete, and the volume ratio of slurry to foam should be 2:1~3:1. The content of fly ash is also inversely proportional to the compressive strength but positively proportional to the dry density. When the content of admixture is 40~55%, the compressive strength of foamed concrete with low density is not less than 2 MPa. The mixing proportion can be changed in the reasonable range to meet the requirements of different projects. [ABSTRACT FROM AUTHOR]

This is a study on how to reduce shrinkage and improve crack resistance of foamed concrete. By selecting different curing temperatures and humidity, six different curing conditions were analyzed. The shrinkage deformation and maximum crack width of foamed concrete blocks with water–cement ratios of 0.4 and 0.5, under six curing conditions, were measured by a comparator and optical microscope, and the cracking time was recorded. The effects of curing temperature, humidity and water–cement ratio on the shrinkage and crack resistance of the foamed concrete were analyzed by comparing the experimental results of each group. We studied the primary and secondary order of the three factors affecting the drying shrinkage of foamed concrete. The results show that: temperature is the primary factor that changes the drying shrinkage performance of foamed concrete, followed by the water–cement ratio, and finally humidity. The interaction of these three factors is not obvious. The shrinkage of foamed concrete increases with the increase in temperature; increasing the humidity of curing can control the water loss rate of foamed concrete and reduce shrinkage. Lower humidity and higher temperature will make cracks appear earlier; with an increase in the water–cement ratio, the initial cracking time is shortened and the cracking property of foamed concrete is improved. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lightweight foamed concrete (LFC) is extremely permeable, and its thermal properties reduce with rising in the number of voids. In turn, to improve its thermal properties, the solid matrix of LFC can be adjusted by incorporating several natural fibers. The influence of sisal fiber in LFC was not investigated before in the current body of knowledge. Hence, there is some ambiguity considering the mechanism by which and the extent to which the sisal fiber can influence LFC thermal properties. Hence, this study concentrates on distinguishing the potential use of sisal fiber in LFC. The purpose of this research is to determine LFC's thermal characteristics when sisal fiber is added. Casting and testing of densities of 800 kg/m3 and 1600 kg/m3 were done. Various weight fractions were employed pertaining to sisal fiber, i.e., 0.15%, 0.30%, 0.45% and 0.60%. The components of thermal properties, which consist of specific heat, thermal conductivity as well as thermal diffusivity were evaluated. To get comparable results, we fixed the water to cement ratio as 0.45 while keeping constant the cement to sand ratio at 1:1.5. It was seen that optimum results were achieved with the addition of 0.45% of sisal fiber with regard to all the thermal characteristics regarded in this exploration. At 0.45% weight fraction about sisal fiber, maximum compaction was achieved with fibers as well as the cementitious matrix, which ensued in good mix uniformity. Beyond the optimum level pertaining to the presence of sisal fiber, it could be seen that fibers would agglomerate and exhibit non-uniform dispersion, which resulted in a decline with regards to the entire thermal characteristics assessed. [ABSTRACT FROM AUTHOR]

In this investigation, the confinement effects of micro synthetic fibers on lightweight foamed concrete (LFC) were examined. The parameters evaluated were porosity, water absorption, shrinkage, compressive strength, flexural strength and tensile strength. Three densities were cast which were 600 kg/m3, 1100 kg/m3, and 1600 kg/m3. Besides, the number of layers (1 to 3 layers) of micro synthetic fibers was also being examined. Based on the result obtained, the porosity improved by 8.0% to 16.3%, 13.8% to 25.6%, and 9.3% to 24.5% for the LFC with densities of 600 kg/m3, 1100 kg/m3, and 1600 kg/m3 confined with 1 layer, 2 layers, and 3 layers of micro synthetic fibers, respectively. Besides, for the water absorption test, the enhancements were 6.9% to 15.6%, 20.0 to 27.1%, and 12.2 to 29.6% for the respective densities and number of layers of micro synthetic fibers employed, while the drying shrinkage improved by 48.5% to 76.8%, 57.4% to 72.1%, and 43.2 % to 68.2% for the respective densities and number of layers of micro synthetic fibers employed. For the strength properties, a confinement with 3 layers of micro synthetic fibers showed significant results, where enhancements of 153% (600 kg/m3), 97% (1100 kg/m3), and 102% (1600 kg/m3) were obtained for the compression strength; 372% (600 kg/m3), 258% (1100 kg/m3), and 332% (1600 kg/m3) for the bending strength; and 507% (600 kg/m3), 343% (1100 kg/m3), and 332% (1600 kg/m3) for the splitting tensile strength, respectively, compared to the control LFC. [ABSTRACT FROM AUTHOR]

Foamed concrete is a controlled low-density concrete, and due to its excellent thermal insulating and acoustic absorption properties, its application has been on a steady rise. Palm Oil Fuel Ash (POFA), an agricultural waste generated by the Palm Oil industry and Eggshells, causes many environmental problems. The pozzolanic nature of POFA and the high calcium oxide content in Eggshell Powder (ESP) are the components that contribute to their suitability as a partial cement replacement in concrete. This experimental work studied the flexural behavior, as well as the compressive strength of lightweight ternary binder foamed concrete incorporating 20% - 25% POFA and 5% - 10% ESP by weight of the total binder, as partial cement replacement. The test results were analyzed and compared with conventional foamed concrete without POFA and ESP. It was observed that POFA is a class C pozzolanic material. The combined utilization of POFA and ESP increased the compressive and flexural compared with control concrete. Furthermore, most of the cracks of the prisms were nearer to the middle of the samples and between two locations of loads applied due to the same load value applied at both locations. It was also observed the air voids were blocked due to increased pozzolanic activity and development of C-S-H gels and thus increase in strength. The utilization of POFA and ESP in concrete can be beneficial in reducing the overall cost. The cost to produce 1 m3 of concrete incorporating POFA and ESP was reduced ranging from was reduced by 12.59% (with 20% POFA and 5% ESP) to 17.53% (with 25% POFA and 10% ESP). It can be concluded that the M4 concrete mix is the optimum and cost-effective, as the maximum cement content is replaced (35%), as well as the compressive and flexural strengths are significantly higher than the control concrete M0. [ABSTRACT FROM AUTHOR]

Currently, the cost of construction rises along with the ongoing impact on the environment, and it has led the researchers to the acceptance of biomass natural fibers, such as biomass frond fiber (BFF), for the improvement of the mechanical properties of cement-based materials. BFF is abundantly accessible, making it relatively pertinent as a reinforcing material in foamed concrete (FC). In addition, natural fiber-reinforced concrete has been progressively employed in construction for several decades to reduce the crack growth under the static load. This paper intends to experimentally investigate the effectiveness of the addition of BFF to FC to improve its mechanical properties. The FC samples were strengthened with BFF at the weight fractions of 0.12%, 0.24%, 0.36%, 0.48%, and 0.60%. This study used three FC densities: 600 kg/m3, 800 kg/m3, and 1000 kg/m3, with fixed constitutions with 0.45 and 1:1.5 cement-to-water and cement-to-sand ratios, respectively. The evaluated strength characteristics included bending, splitting tensile, and compressive strengths. The experimental outcomes indicated that adding 0.36% BFF to FC facilitates optimal splitting tensile, compressive, and bending strength results. BFF enhances material strength by filling the spaces, microcracks, and gaps inside the FC structure. The BFF helped to reduce crack spreading when the plastic state of the FC cementitious matrix was loaded. Furthermore, the optimum level of BFF inclusion and the accumulation and the non-uniform distribution of BFF were detected, which caused the lowering of the strengths of the FC significantly. Beyond the optimum level of BFF, the agglomeration and the non-uniform dispersion of the BFF were seen, which resulted in a drop in mechanical properties. The output from this research will give a better insight into the potential utilization of plant fiber in FC. It is of profound significance to guide the sustainable development and application of FC material and infrastructures. [ABSTRACT FROM AUTHOR]

Processed spent bleaching earth (PSBE) is the end product derived from the processing of de-oiled spent bleaching earth (SBE) after the oil is recovered. Bleaching earth is very fine powder clay, and its main component is silicon dioxide used for refining process of palm oil and its by product is known as SBE is commonly disposed to landfill. The bleaching earth that is used for decolouring during the palm oils refining process form a solid sludge called the SBE. The SBE is generated in large quantities and it is becoming increasingly difficult to ignore the disposal of SBE when production of palm oil increases rapidly. Hence, the problem can be overcome by reusing solid waste as construction materials. In this study, the effect of using PSBE as a partial cement replacement in foamed concrete on durability resistance sulphate attack is investigated. Sulphate resistance in terms of expansion, loss in mass and loss in compressive strength after 52 weeks immersed in 5% sodium sulphate was evaluated. On the other hand, the microstructure changes in the specimens were analysed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetry analysis (TGA). Comparisons are made between two mixtures which main ly control foamed concrete (FC) and foamed concrete containing 30% PSBE (PFC). Major findings show that when 30% PSBE added in a concrete mixture, after 52 weeks samples being immersed in 5% sodium sulphate, it will be more durable compared to control specimen (FC). It was recorded that change in mass, in expansion and loss in strength was 1.32%, 0.98% and 7.5% respectively. The microstructure study has confirmed that inclusion of PSBE in foamed concrete is known to improve the internal structure of PFC to be denser than control FC specimen with the visible image of crowded tiny of cotton shaped (CSH) and few hexagonal plates (CH) contributing to enhanced strength and durability. Conclusively, the foamed concrete containing 30% PSBE as partial cement replacement which exhibits enhanced strength and durability than plain foamed concrete has the potential to be used in construction application. [ABSTRACT FROM AUTHOR]

Mechanical properties, workability and pore structures of foamed concrete (FC) reinforced with different fibres were investigated. In order to characterise the cementitious matrix with entrained bubbles and fibres, X-ray computed tomography (X-CT) technology and Digital image correlation (DIC) technique were employed to analyse the pore structure and the real-time strain field distributions under applied loads, respectively. The results demonstrated that the inherent properties of fibres, including density, modulus and wettability, and bond performance between the cement matrix and fibres are two main factors in determining the mechanical properties of the fibre reinforced FC. Meanwhile, the fibres also had an influence on the workability and rheological properties of fresh FC slurry through changing the bubble numbers and distributions in the slurry. According to the strain analysis during the bending tests using the DIC technique, it was found that carbon fibre and polyacrylonitrile fibre were conducive to distributing the strain field in the FC in a homogeneous fashion and delayed crack widening after the peak loads effectively.

Phase change materials (PCM) are widely known for their high thermal storage capabilities. They are generally utilized to increase the thermal mass of buildings’ lightweight materials, which improves their thermal performance and reduces the need for air-conditioning systems. PCM layers are commonly applied to the buildings’ interior parts, close to the indoor environment, which helps regulate the indoor temperature. However, few studies reported that PCM application on the exterior of the envelopes increases their thermal insulation, which can reduce the outdoor heat gain. Therefore, this study aims to develop PCM-based composites for the exterior finishes of building walls. To this end, microencapsulated PCM was integrated into the cement render and foamed concrete with different fractions. The developed composites were tested, evaluated, and compared to the composites without PCM integration. The results showed that PCM integration into foamed concrete reduced the density and thermal conductivity to 896 kg/m³ and 0.18 W/mK, respectively, i.e., lower by 50% and 86% compared to the conventional cement render. Besides, PCM integration added thermal energy storage of 38 J/g to the composite, which can improve its thermal mass. Although the compressive strength decreased by 53% with PCM integration into the cement render, it increased by 28–49.7% with PCM integration into foamed concrete due to PCM capsules substituting some of the air gaps. The findings of this study demonstrate a high potential of using PCM-based foamed concrete to produce lightweight cladding panels for building exteriors with improved thermal insulation and thermal mass to reduce external heat gain.

As a lightweight construction material, foamed concrete has garnered considerable attention due to a variety of advantages. However, the high-water absorption increases the burden on the structure and accelerates freeze-thaw damage, and thus reduce the durability of foamed concrete. Herein, two kinds of waterproofing materials based on isobutyl triethoxysilane (IBTS) emulsion and graphene oxide/silane (GO/IBTS) composite emulsion were synthesized and used for foamed concrete by facile coating and soaking method. The results show that the soaked specimens exhibit excellent waterproof performance and the water absorption is almost 0%. By contrast, an internal waterproof layer is occurred in the coated specimens, and the water absorption rates of foamed concrete coated with IBTS emulsion and GO/IBTS emulsion are reduced by 75% and 82%, respectively. The waterproofing mechanism of the silane emulsion were analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), flourier transform infrared (FT-IR), x-ray fluorescence analysis (XRF) and x-ray diffraction (XRD). The results demonstrate that the foamed concrete shows a rough surface topography and low surface energy after IBTS treatment, which resulted in a superhydrophobic surface. While the surface of foamed concrete became rougher with the admixture of GO, which further enhanced the waterproof performance of foamed concrete.

Foamed concrete consists of cement matrix and air-foam and has more complicated structure characteristics than normal concrete. However, current research on the elastic modulus of foamed concrete is still limited to empirical equations. In this work, a new theoretical prediction model was proposed for calculating the elastic modulus of foamed concrete. The elastic modulus calculation model for the spherical shell element of foamed concrete is constructed based on the Walsh formula and the assumption of spherical pores. Moreover, the theoretical prediction model is established by introducing the two-layer embedded model for the elastic modulus of foamed concrete. Then, the compressive test is employed to verify the accuracy of the model. The results show that the elastic modulus of foamed concrete decreases with the increase in porosity and matrix Poisson's ratio, and increases with the increase in the matrix elastic modulus. The research results can improve the mechanical theories of foamed concrete materials and have good engineering application values. [ABSTRACT FROM AUTHOR]

The entraining and distribution of air voids in the concrete matrix is a complex process that makes the mechanical properties of lightweight foamed concrete (LFC) highly unpredictable. To study the complex nature of aerated concrete, a reliable and robust prediction model is required, employing different machine learning (ML) techniques. This study aims to predict the compressive strength of LFC by using a support vector machine (SVM) as an individual learner along with bagging, boosting, and random forest (RF) as a modified ensemble learner. For that purpose, a database of 191 data points was collected from published literature, where the mix design ingredients, i.e., cement content, sand content, water to cement ratio, and foam volume, were chosen to predict the compressive strength of LFC. The 10-K fold cross-validation method and different statistical error and regression tools, i.e., mean absolute error (MAE), root means square error (RMSE), and coefficient of determinant (R2), were used to evaluate the performance of the developed ML models. The modified ensemble learner (RF) outperforms all models by yielding a strong correlation of R2 = 0.96 along with the lowest statistical error values of MAE = 1.84 MPa and RMSE = 2.52 MPa. Overall, the result suggests that the ensemble learners would significantly enhance the performance and robustness of ML models. [ABSTRACT FROM AUTHOR]

For lightweight chemical foaming mixtures, it is a technical challenge to control the stability while reducing its density. In this study, cenospheres (CP, a lightweight component) was used to replace part of fly ash (FA) to prepare ultra-lightweight foamed geopolymer concrete (UFGC), and the relationship between the fresh properties of the paste and the stability of UFGC mixture were discussed. Results show that incorporating CP to the slag-FA system can effectively reduce the reaction rate and heat release of the geopolymer paste, thereby effectively slowing down the decomposition rate of H 2 O 2. Different from prefabricated foams, the initial size of the foams decomposed by H 2 O 2 is also affected by the fresh properties of the paste. Meanwhile, the float of bubble and the drainage of the paste are controlled by the yield stress of the paste in the stable stage. As the CP substitution ratio increases, the initial yield stress of the paste decreases, which is beneficial to generate smaller initial bubbles. However, for bubbles of the same size, the low yield stress of the paste is detrimental to its long-term stability. Finally, the UFGC mixture with 50% CP has better stability and the best hardened pore structure. In addition, the calculated critical yield stress that prevents the foamed mixture from collapsing is compared with the initial yield stress of the geopolymer paste. [ABSTRACT FROM AUTHOR]

Copyright of Multipurpose Utilization of Mineral Resources / Kuangchan Zonghe Liyong is the property of Multipurpose Utilization of Mineral Resources Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Foamed ceramic foam concrete composite wall was prepared by a direct casting method. Compressive and tensile tests were carried out on different densities of foamed ceramic boards. Changing rules of interface bonding properties of the composite wall under the influence of foamed concrete age, the surface treatment of foamed ceramic boards, and exposure to freeze–thaw cycles were studied; and the failure mechanism was analyzed and discussed. The results show that a foamed ceramic board with a density of 410 kg/m3 is suitable for a panel of composite wallboard; when the age of the foam concrete increases from 3 to 7 days, and the interface bond strength of the composite wallboard increases, then the bonding strength of the composite wallboard gradually decreases with the increase in age; with the increase in freeze–thaw cycles, the interface bond strength of the composite wallboard decreases gradually. The interface agent was pre-painted on the foamed ceramic board, which can improve the interface bonding strength of the composite wallboard. The drying, shrinkage, and freezing and thawing cycles of the foam concrete have a great influence on the interface bond strength of the composite wallboard. The perforated long hole and rubber sleeve can be used to improve the safety of the composite wallboard. [ABSTRACT FROM AUTHOR]

Construction materials contribute to about 75% of the CO2 emission of all the construction processes. Concrete is one of the most widely used construction materials and is thus primarily responsible for CO2 emission. In particular, 8 − 9% of global greenhouse gas (GHG) emission are produced by concrete. CO2 emissions can be considerably reduced in the construction phase through a careful selection of materials with low environmental impact or through specific admixtures. In this study, different concretes are taken into consideration, including foamed concrete, lightweight aggregate concrete, recycled concrete and ordinary concrete. A series of mix designs of these four classes of concrete, characterized by a comparable mechanical strength or a comparable density, are taken from the relevant literature and compared to one another in terms of CO2 emission. Some guidelines or possible research lines aimed at reducing CO2 emission are finally outlined in this contribution. [ABSTRACT FROM AUTHOR]

Microcrystalline self-leveling is an ideal leveling material for dry area (non kitchen and bathroom) of civil buildings because of its good volume stability and large adjustment range of construction thickness, especially for the dry area floor with wood floor as the final decorative layer. Although the cost of self-leveling without sand is cheap, the volume stability is not good due to high water addition, and the strength retention rate is low after meeting with water, so it is not suitable for large-scale promotion. The sand-containing microcrystalline self-leveling has good compatibility with the foamed concrete cushion, and the system surface has good crack resistance. When the microcrystalline self-leveling is constructed on the foamed concrete substrate, replace the interface agent with saturated water for interface treatment is more appropriate, G12 and G16 present better matching performance with these foamed concrete substrate. The minimum construction thickness of self-leveling should be 10 mm. [ABSTRACT FROM AUTHOR]

Hydroxypropyl methyl cellulose ether (HPMC), an organic thickener, was used as foam stabilizer to study its effect on foam properties, and HPMC modified foam was applied to foamed concrete. The results show that HPMC can improve the viscosity of foaming agent, inhibit the flow of foam liquid and the gas overflow in bubble, so as to improve the stability of foam, but HPMC can reduce the foaming multiple of foaming agent and affect the foaming ability of foaming agent. HPMC modified precast foam can improve the compressive strength and pore structure of foamed concrete. [ABSTRACT FROM AUTHOR]

The study aims to conduct a direct pull-out test on fifty-four cube specimens considering different variables, including the type of reinforcement (sand-coated glass fiber-reinforced polymer (GFRP) and ribbed steel bars); the type of concrete (normal weight concrete NWC and lightweight foamed concrete LWFC); the diameter of the reinforcing bars (10 mm; 12 mm; and 16 mm) and the bonded length (3∅, 4∅, and 5∅). The hybrid fiber hooked-end steel (0.4% by volume) and polypropylene (0.2% by volume), respectively were used to improve the properties of LWFC by converting the brittle failure to ductile. The results showed that in the case of strengthened foamed concrete (FC), the bond strength with steel bars was greater compared to that with the GFRP bars. The bond strength ratio between the GFRP and steel bars of the FC specimens was found to vary between 37.8–89.3%. Additionally, in all specimens of FC, pull-out failure was witnessed with narrower crack width compared to NWC. Furthermore, mathematical equations have been proposed for predicting the bond strength of FC with steel and GFRP bars and showed good correlation with the experimental results.

The relationships between the mechanical properties of foam concrete and its pore structure and cement slurry properties have been confirmed, but these relationships cannot be directly reflected just through experimental research. Thus, experiments and the discrete element method (DEM) were used to reveal the relationship between pore structure, cement slurry characteristics, and mechanical properties in foam concrete in this paper. In order to ensure the authenticity and accuracy of numerical simulation, tests of foam concrete were carried out first, such as X-ray computed tomography (CT), the uniaxial compression test, and the three-point flexural test. On this basis, the failure process of foamed concrete was reflected by numerical simulation. The results show that the bearing capacity of foam concrete increases significantly with its increased density. In 750 kg/m3 foam concrete, the stress is mainly borne by the cement matrix. The ability of the cement matrix around the pores to resist tensile failure is weak, and the failure of foamed concrete is mainly caused by tensile failure. Moreover, when the loading rate is low, it takes a long time for the foamed concrete to break, and the cracks generated by the force expand along the weakest area around the pores to form a rough failure section. At higher loading rates, cracks tend to develop directly through the cement matrix along a straight line. The crack development process inside foam concrete is accurately presented by DEM. The density of foam concrete increases, the number of internal cracks decreases, and the cracks are dispersed. The crack development of foam concrete can be divided into the following stages: First, the microcracks are generated near the supports. Following that, the cracks are caused by tensile stress and gradually extend with increasing loading until the foamed concrete fails. Under full calibration, the engineering design of foam concrete can be completed by DEM.

The production of concrete emits greenhouse gases which aggravate global warming. Meanwhile, ceramic tile wastes generated from manufacturing factories, construction sites, and building demolition projects disposed of by landfills create land and water pollution. Therefore, in this study, the suitability of ceramic tile wastes (CTW) in powder form to partially replace cement in lightweight foamed concrete was investigated with the aim to discover a greener construction material. Once the research outputs show that the ceramic tile dust can appropriately serve as a replacement, environmental impact on air, land, and water pollution can all be reduced. Three types of lightweight foamed concrete with 0%, 25%, and 50% ceramic tile wastes as partial cement replacement material were prepared with a target density of 1,200 kg/m3, namely, LFC-CTW0, LFC-CTW25, and LFC-CTW50, respectively. The effects of ceramic tile wastes on the engineering properties of lightweight foamed concrete were investigated. Concrete specimens were water-cured and tested for various mechanical properties at the concrete ages of 7, 28, and 56 days. Results from the lab experiments showed that the incorporation of 25% ceramic tile wastes into lightweight foamed concrete was more feasible than that of 50%. LFC-CTW25, which performed better than LFC-CTW0 for the splitting tensile strength test at day 56. The results for the compressive strength test, modulus of elasticity, and compressive toughness test showed a minor reduction after the incorporation of ceramic tile wastes. Based on the results, it can be concluded that it is feasible to use ceramic tile wastes up to 25% as partial cement replacement material to produce foamed concrete.

A study was conducted to explore the effect of palm oil boiler ash (POBA) on foamed concrete by varying the percentage of POBA over sand quantities (0, 4, 8 and 12%). This paper primarily discusses the water absorption test, uniaxial compressive strength, and dry density findings. It indicates that substituting sand with POBA greatly enhances the strength of foamed concrete. When the quantity of POBA was raised up to 12% throughout all curing times, the compressive strength steadily increased in the range of 4.34–13.50 N·mm–2. Furthermore, the dry density of foamed concrete was shown to be directly related to the fraction of POBA in the mixture. The dry density of foamed concrete increases as the amount of POBA increases. Despite this, water absorption shown that increasing POBA increases water absorption percentage in foamed concrete from 7.4 to 10.4%. This is due to the fact that a composition with a high POBA percentage will generate more pores than a mixture with a low POBA percentage.

Copyright of Plastics Science & Technology / Suliao Ke-Ji is the property of Plastics Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Foamed concrete (FC) shows advantageous applications in civil engineering, such as reduction in dead loads, contribution to energy conservation, or decrease the construction phase labor cost. Compressive Strength is considered the most important factor in terms of FC mechanical properties. In recent years, Artificial Neural Network (ANN) is one of popular and effective machine learning models, which can be used to accurately predict the FCCS. However, ANN's structure and parameters are normally chosen by experience. In this study, therefore, the objective is to use particle swarm optimization (PSO) metaheuristic optimization (one of the effective soft computing techniques) to optimize the parameters and structure of a Levenberg–Marquardt-based Artificial Neural Network (LMA-ANN) for accurate and quick prediction of the FCCS. A total of 375 data of experiments on FC gathered from the available literature were used to generate the training and testing datasets. Various validation criteria such as mean absolute error, root mean square error, and correlation coefficient (R) were used for the validation of the models. The results showed that the PSO-LMA-ANN algorithm is a highly efficient predictor of the FCCS, achieving the highest value of R up to 0.959 with the optimized [5-7-6-1] structure. An interpretation of the mixture components and the FCCS using Partial Dependence Plots was also performed to understand the effect of each input on the FCCS. The dry density was the most important parameter for the prediction of FCCS, followed by the water/cement ratio, foam volume, sand/cement ratio, and the testing age. The results of the present work might help in accurate and quick prediction of the FCCS and the design optimization process of the FC. [ABSTRACT FROM AUTHOR]

The silt-based foamed concrete, in which the cement is partially replaced with silt, has become a novel material in road construction projects. However, at the present time, only a few studies have been completed in which attention was paid the shear strength of the aforementioned type of material in subgrade applications. Therefore, in order to address those issues, this research investigation conducted triaxial shear tests. During the experimental testing processes, the mechanical behaviors of silt-based foamed concrete specimens were examined. Such influencing factors as wet density, silt content and confining pressure levels were considered in the experiments. As indicated by the stress-strain curves of the silt-based foamed concrete, the material had performed well in the elastoplastic model results. The stress-strain curves of the silt-based foamed concrete had displayed both hardening and softening phenomena. In addition, the peak strength and residual strength were observed to both increase to average levels of 0.82 MPa and 0.62 MPa, respectively, as the density increased to 100 kg/m3. Meanwhile, the peak and residual strength levels decreased the mean levels of 16.8% and 12.3%, respectively, when the silt content was increased by 10%. It has been found that the addition of silt will transform pore structures from uniformly distributed sphericity into irregular combined broken bubbles. In addition, increases in silt content could potentially increase the size of pores. The values of the cohesion and friction angles have been observed to greatly increase with higher density levels. The increases in silt content will decrease cohesion. However, the impacts of silt content on friction angles have been found to be complex. In the present research, the shear strength levels corresponding to different normal stress levels were determined.

Recent industrial developments have focused more and more on the applications of lightweight foamed concrete (LFC) in the construction industry, having advantages over normal-strength concrete. LFC, however, has several drawbacks including brittleness, high porosity, excessive drying shrinkage, rapid cracking, and low deformation resistance. Practical engineering typically chooses steel fiber or polymer fiber to increase the tensile and fracture resistance of LFC. The polypropylene twisted bundle fiber (PTBF) was added to the LFC with varying weight fractions of 0.0%, 0.5%, 1.0%, 1.5%, 2.0% and 2.5%. Three low densities of LFC were prepared, specifically 500 kg/m3, 700 kg/m3 and 900 kg/m3. The mechanical and durability properties of PTBF-reinforced LFC were determined through compression, flexural, splitting tensile, flow table, porosity, and water absorption tests. The results show that the addition of PTBF in LFC significantly improves the strength properties (compressive, flexural, and splitting tensile strengths) and reduces the water absorption capacity and porosity. The optimal weight fraction of PTBF was between 1.5 and 2.0% for mechanical properties enhancement. The inclusion of PTBF increased the ductility of LFC, and the specimens remain intact from loading to failure. The PTBF reduces the original cracks of the LFC and inhibits the development of further cracks in the LFC.

Concrete is the most commonly used building material. Even then, it has a drawback that it hasheavy density. Hence, researches are progressing everywhere to develop a new building material, which has low density, less water absorption as well as economical. And here lies the importance of foamed concrete. Foamed concrete is a type of lightweight concrete in which stable foam is used as the main ingredient. Stable foam is produced from standard foaming agent using a foam generator. The peculiarity of foamed concrete is that no coarse aggregate is used in it. An attempt is made in this research to use palm oil fuel ash as a partial replacement for cement and red gypsum as a partial replacement for manufactured sand. Both of these materials are waste materials and are abundantly available. The concrete made up of this will be more sustainable as well as economical. By adjusting the addition of stable foam, foamed concrete of various densities can be developed. Foamed concrete blocks made up of these materials can be used for load bearing as well as non-load bearing masonry works. It has been observed that the addition of Palm Oil Fuel Ash and Red Earth has improved the properties of foamed concrete.

This work’s goal is to investigate the influence of the type and size of fine aggregate on the characteristics of foamed concrete. Foamed concrete was produced, and its fresh and mechanical characteristics were investigated. It was found that the spread diameter decreased when the foam was added to mixes. With regards to sand grading, when the grading of sand decreased, the diameter of the flow decreased also. Strength improved for fineness sand and enabled the production of uniform and pore distribution, which enhanced the foamed concrete's strength. The increase in compressive strength reflects the other properties of concrete, like tensile strength, that also improved.

For the purpose of reducing the energy consumption and construction cost of buildings, the preparation process of geopolymer based foamed concrete, which is a novel material of the wall and roof of building, had been studied in detail. Water glass and sodium hydroxide were used as the alkali activator to excite the mixture consists of slag, fly ash and Kaolin to form the geopolymer matrix, and finally the foams generated using the physical foaming method were filled into the geopolymer matrix to produce geopolymer-based foamed concrete blocks. In the preparation process, firstly one of the four parameters of foam content, water-binder ratio, water glass content, and water glass modulus had been changed separately to study the influence of a single factor on the compressive strength, dry density, thermal conductivity and specific strength of foamed concrete blocks. The experimental results show that the above four factors have different degrees of influence on the concerned performances. Next, some representative combinations of these factors were constructed by orthogonal experiment method, and the influence degree of each combination on the concerned performances was determined by means of range analysis. According to the results of analysis, the most important influencing factor in terms of thermal conductivity was the water-binder ratio, followed by foam content, water glass modulus and water glass content. When the foam content is 1.58%, the water-binder ratio is 0.45, the water glass content is 30%, and the water glass modulus is 1.2, the thermal conductivity of the prepared geopolymer foam concrete reaches 0.044 W/(m·K), which satisfies the expected requirements for heating in severe cold areas.

Much attention has recently been paid to investigating the internal mechanisms between the void structures of foamed concrete and its mechanical behavior. This study adopted the X-ray computed tomography (X-CT) technique to build three-dimensional (3D) internal void structures of foamed concrete before conducting the unconfined compression test. A sensitivity analysis was conducted to evaluate the influence of the void structure on the mechanical properties. The results showed that the contacts between voids had a primary influence on the residual strength, and the void size was the major influence factor on the modulus. A micromechanical model was developed to simulate the mechanical behavior of the foamed concrete under compression, and good agreements were found with the test results. A simple equation was proposed to predict the mechanical properties of the foamed concretes considering the effects and variations of the void structures on the mechanical properties. Combining the equation with the micromechanical damage model, the variations of the mechanical behavior due to the difference in void structures can be well predicted. [ABSTRACT FROM AUTHOR]

Worldwide, the construction industry has acknowledged the future demand for lightweight construction materials, with high workability, self-compacting, and environmentally friendly. Given this demand, recent innovative material namely foamed concrete (FC), has been found to reduce normal concrete’s weight potentially. However, while FC made with Ordinary Portland Cement has good compressive strength, other characteristics such as tension are relatively weak given the number of micro-cracks. Therefore, the study focused on the potential use of oil palm fibres in FC regarding their durability and mechanical properties. Notably, one of the major issues faced in the construction of reinforced FC is the corrosion of reinforcing steel which affects the behaviour and durability of concrete structures. Hence, in this study, oil palm fibres were added to improve strength and effectively reduce corrosion. Five types of fibre generated from oil palm waste were considered: oil palm trunk, oil palm frond, oil palm mesocarp and empty fruit bunch consisting of the stalk and spikelets. Specimens with a density of 1800 kg/m³ were prepared in which the weight fraction of the fibre content was kept constant at 0.45% for each mixture. Testing ages differed in testing and evaluating the parameters such as compressive strength, flexural strength, tensile strength, porosity, water absorption, drying shrinkage and ultrasonic pulse velocity. The results showed that the incorporation of oil palm fibre in FC helped reduce water absorption, porosity and shrinkage while enhancing the compressive, flexural and tensile strength of FC. [ABSTRACT FROM AUTHOR]

Lightweight foamed concrete (LFC) is recognised for its high flowability, minimal utilization of aggregates and superior heat insulation properties. LFC is excellent under compression but poor in tensile stress, as it produces multiple microcracks. LFC cannot withstand the tensile stress induced by applied forces without additional reinforcing elements. Hence, this study was conducted to examine the potential utilisation of oil palm pressed fibre (OPPF) reinforced LFC in terms of its mechanical properties. Two densities, 600kg/m3 and 1200kg/m3, were cast and tested with six different percentages of OPPF, which were 0.15%, 0.30%, 0.45% and 0.60%. The parameters evaluated were compressive strength, flexural strength and tensile strength. The results revealed that the inclusion of 0.45% of OPPF in LFC helps to give the best results for the compressive strength, flexural strength and splitting tensile strength. The OPPF facilitated to evade the promulgation of cracks in the plastic state in the cement matrix when the load was applied. [ABSTRACT FROM AUTHOR]

Increased usage of concrete contributes to urban thermal discomfort due to the Urban Heat Island effect. At the same time, the corresponding increased consumption of cement also causes a significant rise in carbon dioxide (CO2) gas emissions. This experimental work aims at evaluating the thermal and mechanical performance of 1800 kg/m3 dry density green sustainable foamed concrete (GFC) incorporating agroindustrial waste such as Palm Oil Fuel Ash (POFA) and Eggshell Powder (ESP) as supplementary cementitious materials (SCMs). The POFA content varied from 15 to 35%, with increments of 5%, while being supplemented with 5% ESP. To evaluate the performance of the developed GFC, the flowability, mechanical strengths (compressive and splitting tensile strengths), and thermal performances (thermal conductivity and surface temperature) were investigated. Incorporation of 15-25% of POFA supplemented with 5% ESP as partial cement replacement materials resulted in enhanced mechanical strengths. Although usage of POFA can reduce the thermal conductivity, the POFA content must be limited to 15–25% to prevent excessive heat absorption by the exterior surface of the concrete. Overall, the optimum use of 15% POFA in a combination of 5% ESP is desirable to produce an eco-friendly sustainable foamed concrete. [ABSTRACT FROM AUTHOR]