Foam Concrete as a Thermal Insulation Building Material

Actuality. An analysis of accidents at nuclear power plants and power plants has shown that these incidents are accompanied by high temperatures and high-intensity radiation. In an emergency situation, the technological equipment of the protective shell must ensure the localisation of all radioactive materials released during the accident within its volume, protect the environment from ionising radiation, and counteract high temperature effects. Today, there are various forms and design solutions for protective shells, each of which has its own advantages and disadvantages. Therefore, when choosing protective shell designs, it is necessary to take into account the conditions of construction, operation, and possible emergency impacts. Modern construction encourages the use of new materials such as foam concrete (aerated concrete), which will reduce material consumption and construction costs, as well as improve thermal and ionising protection. Purpose. The main objective of the article is to study the fire protection effectiveness of foam concrete and its γ-absorbing capacity. Main results. Two methods were developed for the research: to determine the fire-retardant properties of foam concrete and to determine the effectiveness of foam concrete in absorbing γ-radiation. It has been established that the fire resistance of foam concrete for steel structures ranges from 130 to 150 minutes for slab thicknesses from 20 mm to 60 mm, accordingly. Studies of the absorption of γ-radiation by foam concrete have shown that foam concrete with a bulk weight of 1200 kg/m3 has a γ-radiation attenuation coefficient similar to that of fine-grained concrete with graphite (with a bulk weight of 1800 kg/m3), which indicates its significant effectiveness (1,5 times). Conclusions. A series of experimental studies has shown that foam concrete is an effective fire-retardant material and can be used for fire protection of steel building structures. It was found that with a foam concrete thickness of 20-60 mm, the fire resistance limit of a steel structure in terms of load-bearing capacity is 130-150 minutes, and in terms of thermal insulation capacity – 80-150 minutes. The effectiveness of using foam concrete to protect technological equipment and its ability to absorb γ-radiation has been substantiated.

An experimental investigation was conducted to study the strength characteristics of silica fume incorporated foam concrete. Light Weight Foamed concrete (LFC) has become most commercial material in construction industry for non-structural applications owing to its lesser density, stability and high thermal insulation properties. The aim of this study is to develop structural foamed concrete by using silica fume and fly ash. Constant cement: fly ash: sand ratio of 1:0.5:1.5 and W/C ratio of 0.65 was used for all mixes. The study presents the use of fly ash for partially replacing sand to produce foamed concrete. Fine silica fume is used to improve properties of foamed concrete. Four variations of foam (2, 3, 4 and 5%) were added and cement was partially replaced with silica fume of various percentages (0, 5, 10, 15 and 20%). The results indicate that foamed concrete with a density of 600–1450 kg/m3 and compressive strength of 6–13 N/mm2 can be made by using silica fume. The silica fume improved the compressive strength of foamed concrete.

As a typical cellular lightweight material, foam concrete is produced by mixing cement, water, aggregate and a suitable foaming agent and has a density usually below 1600 kg/m3. The large number of air spaces present in foam concrete ensures that the concrete has advantages such as lightweight, high fluidity during pouring, excellent thermal and sound insulation, superior fire resistance, and outstanding energy absorption capacity. Its high porosity and the connectivity of the pores, which can allow the entry of negative substances into the concrete environment, cause foam concrete to have a very low physico‐mechanical and durability performance. To eliminate or reduce these disadvantages, this study adopted the use of basalt fibers (BF) as eco‐friendly fiber type and calcium aluminate cement (CAC) as aluminous cement with waste marble powder (WMP) as aggregates in foam concrete. In that respect, 9 mixes with varying content of foaming agent (FC) and basalt fiber have been prepared. Assessment of mechanical performance was based on compressive and flexural strength after 6 h, 1, 7, and 28 days. Dry bulk density, thermal conductivity, porosity, water absorption, and sorptivity of the concretes were determined. Durability characteristics of the concretes were examined by dry shrinkage, high temperature, magnesium sulfate, sulfuric, and hydrochloric acids. The obtained results showed that the content of BF affected the compressive strength of the mixtures slightly negatively or positively depending on the FC. The lowest value in thermal conductivity was gained as 0.645 (W/m K) for the mixture incorporating 1% BF and 50 kg/m3 foam quantity. In addition, the foam concrete incorporating foam of 30 kg/m3 and 1% BF showed the best resistance against MgSO4. The mixture with 2% BF and 30 kg/m3 FC exhibited the lowest mass loss after HCI exposure.

Mechanical performance and reinforcing mechanisms of foamed concrete strengthened by carbon fibers

Foamed concrete has been used as a building material since early 1920. In the beginning, it was used as an insulation material with very low density. Since then there have been attempts to make this material more load-bearing and structural. In present-day foamed concrete is being used in soil reinforcement, building blocks and other sorts of building materials [1]. Geopolymer concrete has been around for more than 40 years. It is being used in all sorts of buildings such as railroads, reservoirs, and houses. As both of these materials, structural capacities and usage increases there still are questions regarding their long-term properties like creep and shrinkage. This article aims to determine the differences in the time-dependent long-term properties of these two different building materials. The size of all creep and shrinkage specimens was 46mm in the diameter and 190mm in height. The creep properties of the specimen were determined by loading them with 20% of the ultimate stress value. The compressive strength, creep and shrinkage of both materials were determined. Also, new information on geopolymer concrete and foam concrete specimen modulus of elasticity variation differences in-time were determined. Modulus of elasticity did reach 31.39 GPa on the 30th day, 36.79 GPa on the 62nd and 48.34 GPa on the 135th day since specimens were made for geopolymer concrete and 12.22 GPa on the 30th day, 12.49 GPa on the 62nd and 14.23 GPa on the 135th day since specimens were made for foam concrete. All the data regarding compressive strength, long-term properties, and modulus of elasticity of the specimens have been obtained by experimental investigation only.

The foam concrete or aerated concrete is most widely used for construction applications where, lightweight, thermal insulation and fire resistance are crucial. While the application of foam concrete is successful in the construction industry, the emerging technology of concrete 3D printing possesses many challenges when using foam concrete. This is primarily due to the high flowability of foam concrete, since it contains a large proportion of air bubbles, resulting in poor shape retention and buildability characteristics. This study investigates the utilization of lightweight aggregate to reduce the foam content to achieve a lightweight 3D printable mix. The expanded perlite (EP) aggregate was used as a volumetric replacement to fine sand that substantially reduced the foam content in the mix. The effect of EP on the physical and mechanical properties was studied and compared with the control 3D printable foam concrete containing sand. The results showed that the replacement of sand with EP aggregate reduces the flow properties that is suitable for 3D printing. Besides, the compressive strength of 3D printed samples was also enhanced with the addition of EP aggregates. The compressive strength of EP based 3D printed specimens at 28 days was determined as 12.95 MPa, 15.5 MPa and 10.6 MPa in the perpendicular, longitudinal, and lateral directions respectively. On the other hand, control 3D printed samples displayed the compressive strength of 5.5 MPa, 8.4 MPa and 4.2 MPa at a slightly lower density range.KeywordsLightweight concrete3D printingPorous aggregateFlowStrength properties

Influence of expanded vermiculite powder and silica fume on properties of foam concretes

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

Chemical foaming concrete is a kind of new building material. In this paper, the quasi-static conditions of foam concrete and dynamic mechanical properties under impact dynamic conditions are studied. This paper also analyzes in detail the damage mechanism, deformation characteristics and energy absorption characteristics of the foam concrete under compression and stretch conditions. The results indicate that, the lower the density is, the less the cells on the surface and the inside of the concrete material is, and the larger the diameter of the pores is. When the density increases, the number of cells increases as well, and the diameter of the pores decrease gradually. The whole process of uniaxial compression of foam concrete is divided into three stages, that is, the material's elasticity and plasticity stage, platform stage and material densification stage. In the initial stage of stretch and compression, the stress-strain curve of foam concrete increases linearly basically. In platform stage, the foam concrete is mainly absorbing the energy, and there are both strain- softening and strain-hardening behaviors in this stage at the same time. The greater the density of the concrete, the earlier the densification stage occurs. The research on the impact dynamic properties of foam concrete shows that the dynamic strain rate is obviously positively correlated with the impact velocity, i.e., the greater the impact velocity, the greater the strain rate. The dynamic stress-strain curve of foam concrete is almost the same as that of static curve. It is also divided into three stages: linear elastic stage, material yield stage and material failure stage.

Evaluation of thermal insulation capacity and mechanical performance of a novel low-carbon thermal insulating foam concrete

Heat transfer simulation across a building insulated with foam concrete wall cladding

Effect of silane emulsion on waterproofing and Anti-icing performance of foamed concrete

As a new green building material, foam concrete not only has low deadweight and good thermal insulation performance, but also can add solid waste to reflect the principle of green environmental protection and resource reuse. However, the differences in the types and amounts of solid waste will significantly affect the performance of materials. Based on the systematic analysis of literature from around the world in the past five years, this paper introduces some kinds of fine aggregate substitutes in solid waste foam concrete, and summarizes the effects of expanded vermiculite powder, recycled concrete aggregate, and palm oil fuel ash on the performance of foam concrete. The research shows that the incorporation of these three kinds of solid wastes can improve the internal pore structure of foam concrete, thereby improving its mechanical properties and microscopic performance. Finally, the application of solid waste foam concrete in construction engineering is further discussed, and the development direction of future research is prospected.

Foam concrete is fire resistant and durable and has broad applicability as a building insulation material. However, cement has high energy consumption and causes pollution, necessitating an environment-friendly cementitious material to replace the cement used to prepare foam concrete. In this study, foam concrete was prepared through chemical foaming. The influence of the foaming agent material, foam stabiliser, and fly ash on the basic properties of the foam concrete, including the dry bulk density, compressive strength, and thermal conductivity, was studied, and the pore structure was characterised. The results show that with an increase in the hydrogen peroxide (H2O2) content, the dry bulk density, compressive strength, and thermal conductivity of foam concrete decreases, whereas the pore diameter increases (0.495 to 0.746 mm). When the calcium stearate content is within 1.8%, the pore size tends to increase (0.547 to 0.631 mm). With increase in the fly ash content, the strength of foam concrete gradually decreases, and the dry bulk density first decreases and then increases. When the blending ratio of fly ash is 10–40%, the thermal conductivity gradually decreases; an extreme thermal conductivity of 0.0824 W/(m·K) appears at the blending ratio of 40%, and the dry bulk density is 336 kg/m3.

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