Foam Concrete Mix Research Articles

Optimizing foaming agent concentration and recycled fine aggregate content to enhance mechanical and durable properties of foam concrete mixes

This research explores the impact of using recycled fine aggregates from construction and demolition wastes (CD-RFA) through the replacement of natural sand in proportion of 0 %, 10 %, 30 %, 50 %, 70 %, and 100 % for making foam concrete mixes. Protein based foaming agent was diluted with water in ratios of 1:20, 1:40 and 1:60. It was found that with the increase in the proportion of recycled fines, the porosity, sorptivity and water absorption of foam concrete mixes increases significantly. At the same time, a downward trend in the mechanical characteristics was noted. However, the obtained values of compressive strength, flexural strength, and split tensile strength of 22.35, 5.68 and 2.27 MPa were found to be well within the ACI 523 R 2014 recommended ranges of 8–22, 3–6.4 and 1–2.2 MPa, respectively. Hardened density, abrasion resistance, and resistance to sulphates and chlorides attack showed perceptible decline. The present study recommends the replacement of natural sand up to 50 % with CD-RFA. The foam concrete mix prepared using recycled fines will help clearance of a large quantities of CD wastes, thereby benefiting the environment and ecology.

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

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

Research on the Improving Performance of Foam Concrete Applied to the Filling of Natural Gas Pipeline Cross-River Tunnel.

The shield tunnel is a common solution for natural gas pipelines crossing rivers. Consequently, the development of natural gas tunnel filling materials with excellent performance is crucial to the safe operation and maintenance of pipelines. The foam concrete offers a reasonable solution. Nevertheless, since its inherent compressive strength decreases almost proportionally with the decrease in density, obstacles remain concerning obtaining the high density and relatively low strength required for natural gas tunnel filling. Here, a synergistic optimization strategy was proposed involving the orthogonal test, univariate control, and comprehensive balance method. It involves modifying the type and proportion of cementitious matrix, in particular by incorporating fly ash and PVA fibers in the mix design, and synergetic determining the best mix ratio from the aspects of compressive strength, stability, and dry density. The obtained foam concrete has a compressive strength of 4.29 MPa (FC4) and a dry density of 1060.59 kg/m3 (A11), which meets the requirements of pipeline pressure and pipeline anti-floating. This study is applied to the Yangtze River shield crossing project of the Sino-Russian Eastern Gas Pipeline, and ANSYS was used to simulate the stress and deformation of the foam concrete. This work provides an efficient foam concrete optimization mix scheme, and supports the application of foam concrete in the filling of the long-distance cross-river natural gas tunnels.

Study on the performance of GFRP strengthened, fiber reinforced lightweight foam concrete

Regular clay bricks and concrete blocks are replaced with light-weight fibre-reinforced foam concrete modules. For light weight foam concrete, various natural and synthetic fibes are employed as micro- and macro-fibre reinforcement. Three distinct fibres were used as fibre reinforcement in this study, and their strength qualities were investigated. As microfibre reinforcement, synthetic-polypropylene fibre, natural-Jute fibre, and banana micro fibres were used at volume fractions ranging from 0.22 to 0.55 percent in the foam concrete mix. The compression behaviour of stack bonded masonry prisms was investigated in the first phase of the experiment. The second phase of research focused on the microfibre-reinforced prism, which was reinforced with multiple layers of GFRP sheets. Both jute and banana fibres added as microfiber reinforcement to the matrix, impart ductility to the brittle masonry unit and reduce the sudden failure mode of the Fibre-Reinforced Lightweight Foam Concrete (FRLWC) prism. The insertion of GFRP sheets between the masonry layers provides additional stiffness and ductility to the FRLWC masonry prism, which greatly improves the post-cracking behaviour. When compared to a standard LWC prism, failure patterns show that both synthetic and natural fibre-reinforcement provide improved fracture bridging mechanisms, which is mostly owing to the arresting of cracks by micro polypropylene, jute, and banana fibres. The GFRP layers provided between the masonry units prevented the formation of major crack planes.

Eco-friendly incorporation of sugarcane bagasse ash as partial replacement of sand in foam concrete

The sugarcane bagasse is locally utilized in sugar industries for power production that yields a huge amount of dumped waste sugarcane bagasse ash, which poses threats to human health by mutilating the atmosphere through particulate matter. Besides, river sand resources are depleting worldwide due to the uncontrolled extraction of sand for concrete production. Therefore, this research presents the microstructural, fresh, physicomechanical, and thermal properties of bagasse ash incorporated foam concrete and its comparison is made with control foam concrete. Microstructural characterization includes morphology, oxide composition, chemical reactivity, and its crystallographic characteristics. The characterization results revealed that it has flaky, tubular, and irregular-shaped particles containing amorphous silica and thus, possesses pozzolanic reactivity. The results of physicomechanical and thermal properties of 10% sugarcane bagasse ash incorporated foam concrete mix produced the maximum increase in compressive strength of 14.50% and a decrease in thermal conductivity of 10.76% compared to control-mix. The rise in compressive strength of sugarcane bagasse ash-based foam concrete was due to the formation of secondary calcium silicate hydrate gel due to the formation of pozzolanic hydrates. Whereas the decreased thermal conductivity was due to lightweight bagasse ash. Contrarily, the higher replacement of sugarcane bagasse ash changes the pore size and shape, which consequently damages the distribution of the pores by imploding foam bubbles due to the adsorptive nature of sugarcane bagasse ash. Conclusively, sugarcane bagasse ash provides eco-friendly sand replacement in foam concrete without degrading its mechanical properties. • Sugarcane bagasse ash poses threats to human health by mutilating the environment. • Densification of foam concrete microstructure occurred upon sugarcane bagasse ash incorporation. • Mechanical properties of foam concrete improved due to micro-pore refinement in cement paste matrix. • Thermal conductivity of concrete mixes reduced due to low specific gravity of incorporated ash.

An Investigation of Foam Concrete Usability as a Cavity Filler Material in Mining

Strength and deformability properties of different cavity filler materials of a phenolic foam, a polyurethane based foam and a foam concrete (FC) mix were investigated and compared in this study. Instead of using polymeric foam fillers, FC usage was found to supply better load bearing capacity and modulus of elasticity values. The fresh FC mixes consisting of cement, water and foaming agents are able to be filled into the mine cavities. In the cavity filling applications, typical polymer foams cause support reactions with low stiffnesses and let the rock mass at the roof to be loosened. A relatively stiff cavity filling material can help rock masses to bear itself by prevention of the loosening. To avoid excessive deformations of the rock masses, the deformation modulus is an important parameter as well as the strength property. The FC filler materials were found advantageous because of economical supply of improved load bearing capacities and stiffness values for controlling the rock mass convergences.

Effect of Water and Admixture on Foam Concrete Properties

The paper presents mathematical modeling of additives and water’s effect on foam concrete’s compressive and flexural strength at 28 days of normal hardening. The requirements of GOST 10180-2012 determined the compressive and flexural strength of foam concrete. The initial composition of the foam concrete mix was calculated using the absolute volume method.Results received first-order regression equations. The compressive strength and flexural strength of foam concrete depended on the relations from and the image surface expression and objective function for the regression equations. The optimal value obtained: compressive strength = 8.075 MPa and flexural strength 1.087 MPa.

Features of setting and strength gain of the foam concrete massif

The paper presents a study of the regularities of the processes occurring in the matrix and aerated concrete mass at the initial time after laying and later, during the strength gain. The colloidal properties that appear in the foam concrete mix begin at the stage of mixing the components containing binder and aggregate particles, and are activated by the mixer blades. In this case, the mixture is transformed by mass transfer of the matrix material onto the foam grid and a new spatial reorientation of the bubbles under conditions of physical and mechanical effects on the thin-film structure of the foam. In technology, it should be taken into account that the processes occurring in the foam concrete mixture can be attributed to two opposite actions occurring simultaneously. First, in a freshly laid foam concrete mixture, as in any thermodynamically unstable system, sedimentation and coalescence of air pores begins, which is especially manifested at forcedly high water-solid ratios. This can lead, if the technology is not followed, to complete stratification of the mixture. Secondly, in the cement slurry, the setting and further formation of the cement stone occurs. A necessary technological condition for product quality is compliance with the optimal water-solid ratio of the mixture and ensuring the beginning of the setting of the foam concrete mass before its stratification.It was also experimentally determined that an increase in the hardening duration of foamcement systems for more than 28 days is impractical, since it was revealed that an increase in the strength of foam concrete is similar to the same process in structural concrete. It is quite possible to achieve the strength required for foam concrete according to GOST 25485-89 within 28 days and even earlier due to the high technological discipline and the use of modern plasticizing additives.

Cement based foam concrete with hardening accelerators

The results of studies of the effect of hardening accelerators on the properties of cement based foam concrete mix and foam concrete of natural hardening are given in this article. The study was conducted in the Laboratory of Tomsk State University of Architecture and Building which is accredited in accordance with the national standards requirements. It has been proposed to decrease the shrinkage deformations of the concrete mix and increase compressive strength of hardened foam concrete by affecting the cement matrix with the calcium chloride and calcium oxalate in the amount of 2 and 0.5% of the cement mass, respectively. This increases the aggregative stability and reduces the plastic shrinkage of the foam concrete mix by 47-65%. In foam concrete with the hardening accelerators the compressive strength rises from 0.31 to 0.47 MPa and from 0.96 to 1.44 MPa at the age of 28 days while maintaining the average density of D400 and D600 respectively. The developed composition of cement based foam concrete is recommended for constructing monolithic walls at a construction site or wall blocks in factory conditions for individual housing construction.

Improving the behaviors of foam concrete through the use of composite binder

The most important task in the production of foam concrete is the selection of silica-containing components from both natural and technogenic raw materials, the use of which can not only reduce the consumption of the most energy-intensive and expensive component of foam concrete/Portland cement, but also allows to control the process of structure formation. The novelty of the paper is to identify the scientific patterns of the process control to foam concrete microstructure formation by using the system “Portland cement - opoka marl-fly ash” as a composite binder. The composite binders obtained by mechanochemical activation of Portland cement, opoka marl and fly ash were prepared as the novel compositions, based on which the concretes with improved behaviors are created. The physico mechanical characteristics of the concretes were researched by a series of tests including heat intensity of hydration, shrinkage, average density, and compressive strength, in addition to the durability characteristics (freeze-thaw resistance, vapor permeability) and thermal conductivity. The morphology and microstructure of the obtained cement pastes and concretes was studied by a complex of methods, including SEM images, XRD analysis and DTA analysis. For the first time, the scientific data on the properties of the composite binders and the foam concrete based on it were obtained. The nature of the influence of fly ash on the microstructure formation processes of the foam concrete mix for wall materials is revealed. The composite binders obtained by milling components have a compressive strength of up to 60 MPa with cement savings of up to 40%. Based on the composite binder, the foam concrete with a density of 500–700 kg/m3 with a compressive strength of up to 4.26 MPa were obtained.

Dependence of foam concrete properties on technological factors

The dependences of foam concrete properties on various factors, which are divided into 4 groups, are considered. The dependence of physical and mechanical properties on the properties of materials, conditions for maintaining foam concrete, on the brand and mineralogical composition of cement was revealed. Joint and separate methods of preparing a foam concrete mixture using pressure-chamber turbulence-cavitation mixers and modernized standard forced-action mortar mixers are considered. The importance of technological influence of temperature in foam concrete technology is determined. Methods of transportation of foam concrete mix, which also affect the properties of the material, are considered.

Assessment of the potential of a naturally available foaming agent for use in the production of foam concrete

This paper evaluates the performance of naturally available saponin based hingot fruit (Balanites aegyptiaca) as an alternative to synthetic foaming agent for use in foam concrete. Two methods of hingot surfactant preparation viz (i) water soaking for 24 h without heating and (ii) with the heating of hingot pericarp over a range of temperature (i.e., 25–100 °C) are evaluated in this study. Assessment on the essential properties of foam such as initial foam density (IFD), foam stability and bubble microstructure for different parameters viz., hingot concentration, the rotational speed of stirrer, temperature and duration of heating process of surfactant extraction are carried out. Comparative studies on two different methods of hingot extraction indicate that the heating process adopted in hingot surfactant extraction is efficient method as it facilitates maximum extraction of saponin. Hence the resulting foam is of better quality with relatively greater amount of air, lesser drainage and smaller size bubble microstructure when compared to surfactant extracted without heating process. For instance, a maximum reduction of 50% in IFD is achieved when the temperature of heating of hingot surfactant extraction process is increased from 25 °C to 75 °C for duration of 5 h. Based on the studies on influence of surfactant production parameters on foam properties, the optimum surfactant production parameters (5% hingot concentration, 5 h of heating of surfactant preparation solution at 75 °C, stirrer speed of 3600 rpm) are derived. Further, the chosen value of surfactant production parameters is verified to be satisfactory for the production of stable foam concrete mix according to the guidelines of ASTM C796 and ASTM C896.

USABILITY OF PCF-ASH AS LIGHTWEIGHT AGGREGATE IN FOAM CONCRETE

Foam concretes can be produced with aggregate or without aggregate. In this study, the possibility of using PC ash as lightweight aggregate in the production of foam concrete was investigated. Waste- PC ash is emerging from the pulverized coal furnace about 10 tons/day in a textile factory located in the vicinity of Dinar (Afyonkarahisar). The chemical properties, particle size distribution and grain densities of PC-ash were determined. Foam concrete with a dry density of 450 kg/m3 at a cement dosage of 250 kg/m3 and w/c:0.65 was produced after the aggregate analysis. The PC-ash which is used in foam concrete mix is between 0 and 200 kg/m3. 100 mm cube and 300x300x50 mm prism samples were prepared with this foam concrete. The compressive strengths of the cube samples and the thermal conductivity coefficient of the prism samples were tested at the 28th day. The average compressive strength of foam concrete samples with a density of 452 kg/m3 was determined as 1.07 MPa and the thermal conductivity coefficient was determined as 0.097 W/mK. As a result, it has been determined that PC-ash as lightweight aggregate can be successfully used in production of precast element and light floor-screed.

Modification of Foam Concrete with Organo-Mineral Admixtures

A multi-level optimization of size-consist of foam concrete is considered with the aim of significantly increasing its construction and mechanical properties. The results of theoretical and experimental studies confirming the expediency of using this process technology are given. In the course of the studies, theoretical and experimental conditions for creating balanced size-consist of non-autoclaved modified foam concrete with an increased solids concentration per volume unit and performance properties with complex organo-mineral admixture of sustained action on the basis of balanced ratio of chemical and finely-dispersed mineral ingredients optimizing its size-consist and structure were developed. The use of microsilicasuspension in foam composition is theoretically justified, and in the composition of foam-concrete mix of finely-dispersed slag and complex chemical modifier with an accelerating agent, that provide an increase in the strength of non-autoclaved foam concrete by more than 2 times, a decrease in thermal conductivity by 25%, shrinkage – by more than 4 times.

ETHOD FOR MANAGING THE STRUCTURAL-MECHANICAL PROPERTIES OF FOAM CONCRETE MIXTURES

Objectives At present, the urgency of scientific research aimed at reducing the material consumption of building structures is growing. Since foam concrete proved to be an effective material for wall structures, the aim of the present work was to develop scientific ideas about features of their macrostructural formation at the “viscous to solid” phase transition.Methods The evaluation of plastic strength was carried out according to the patent for invention No. 2316750 (“Method for determining the plastic strength of foam concrete mix” registered in the State Register of Inventions of the Russian Federation on February 10, 2008). Synthetic PO-3NP (TU 38-00-058079999-20-93) and "Arecom-4" galipot glue analogue (TU 31-10) were used as foam generation agents. Control over the kinetics of the plastic strength of the test mixtures of equal density was carried out in five-litre vessels at an interval of 15 minutes for three hours.Results The paper considers the most important features of mass transfer, which control the formation of defectiveness for interporal partitions in foam concrete. From the analysis of theoretical and experimental data, it follows that the ratio between water and surfactant consumption is an important tool for managing the quality of foam concrete mixes. Definingthe optimal relationship between water consumption and the amount of foaming agent allows the maximum amount of surfactants to be located at the gas-liquid interface ensuring minimal defect in the structure of the interporal partitions in the cured concrete.Conclusion The theoretical and experimental studies carried out make it possible to consider the relationship between the consumption of water and surfactant as an important tool for controlling the structural and mechanical properties in foam concrete mixes.

The effect of pumice as aggregate on the mechanical and thermal properties of foam concrete

Pumice is a porous rock, which is formed as a result of volcanic activity and does not include any crystal water. Its porous structure makes it lightweight and provides advantage for heat and sound isolation. Foam concrete is a type of lightweight concrete. Foam concrete is obtained by adding the foam obtained from the agent to the mixture of cement, water, and aggregate. Foam concrete is an environmentally friendly structure and insulation material which provides light, heat, and impact sound insulation that can be used in place of the building elements used in the interior-exterior walls and floors of all buildings. Because of the lack of coarse aggregate in the foam concrete mix, it has some structural problems and this limits its usage area. In this study, four different types of pumice aggregates and stone powder were used to overcome the structural problems of foam. The cement dosages (250 kg/m3), aggregate amounts (250 kg/m3), fresh concrete densities and w/c ratio (0.45) were kept constant in all foamed concrete mixtures. Then, physical, mechanical, and thermal conductivity properties of the resulting foam concretes were investigated. When the findings were evaluated, the most suitable type of lightweight aggregates for use in foam concrete have been determined in terms of compressive strength and thermal conductivity properties. In all aggregate groups, Nevsehir Pumice has the highest compressive strength while Karaman Pumice has the lowest thermal conductivity. However, when both properties were evaluated together, it was determined that the most favorable lightweight aggregate was Nevsehir Pumice.

Experimental investigation on the compressive strength of foamed concrete: Effect of curing conditions, cement type, foaming agent and dry density

This paper presents the first results of an ongoing experimental campaign focused on foamed concrete. The dependence of the compressive strength upon dry density, water content, curing conditions, cement type and, most importantly, foaming agents employed in the cement paste is here investigated. In particular, this experimental study comprises more than 100 foamed concrete specimens with a fixed water/cement ratio and dry densities ranging from around 350 up to 850 kg/m3, two cement types, three foaming agents with either protein or synthetic nature, and curing conditions in water at 30 °C, in air as well as within a cellophane sheet at environmental temperature. Unlike most of the research studies in which the water/cement ratio is adjusted on the basis of the stability and the consistence of the foam concrete mix, in this experimental investigation this ratio is fixed constant for all the analyzed design densities. This specimen preparation has made it possible to highlight different behaviors of the employed foaming agents having different nature, which is not fully described in other similar studies of the relevant literature, especially for the range of low densities analyzed in this work. The variability of the compressive strength measured is ascribed to a different stability behavior of the foams generated by foaming agents having different nature during the mixing phase with the cement paste. It is found that the increase of the compressive strength with the density is more or less described by a linear trend and is more pronounced when protein foaming agents are employed in the mix design.

Utilization of fly ash and ultrafine GGBS for higher strength foam concrete

Foam concrete is a widely accepted construction material, which is popular for diverse construction applications such as, thermal insulation in buildings, lightweight concrete blocks, ground stabilization, void filling etc. Currently, foam concrete is being used for structural applications with a density above 1800kg/m3. This study focuses on evolving mix proportions for foam concrete with a material density in the range of 1200 kg/m3 to 1600 kg/m3, so as to obtain strength ranges that will be sufficient to adopt it as a structural material. Foam concrete is made lighter by adding pre-formed foam of a particular density to the mortar mix. The foaming agent used in this study is Sodium Lauryl Sulphate and in order to densify the foam generated, Sodium hydroxide solution at a normality of one is also added. In this study efforts are made to make it a sustainable construction material by incorporating industrial waste products such as ultrafine GGBS as partial replacement of cement and fly ash for replacement of fine aggregate. The fresh state and hardened state properties of foam concrete at varying proportions of cement, sand, water and additives are evaluated. The proportion of ultrafine GGBS and fly ash in the foam concrete mix are varied aiming at higher compressive strength. Studies on air void-strength relationship of foam concrete are also included in this paper.

Disperse Reinforcing Role in Producing Non-autoclaved Cellular Foam Concrete

Cellular concretes have become promising materials for the construction. The increase in the cost of energy resources, the thermo technical requirements for enclosing structures, a simple enough technology, the ability to obtaining single-layer protecting designs, technical and economic indicators confirm the high efficiency of cellular concrete as a wall material. Producing non-autoclaved curing foam concrete, reinforced with low modulus synthetic fibers is possible due to considering the technological role of dispersed reinforcement. Dispersed reinforcement influences the increase in the bearing capacity of the freshly prepared foam concrete mix, resulting in the elimination of destructive processes, increasing the dimensionally stability and raising its stability right after pouring it into the mould. The rate of plastic strength increase during the infusion of synthetic fibers by 1% by increases 2-4 times compared with the initial matrix.

Early structure formation of foam concrete mix containing modifying admixture

Early structure formation of foam concrete mix containing modifying admixture