Foam concrete

"The components of foamed concrete (type of cement... water... water/binder ratio... additives... and admixtures...) have a significant effect on its properties..."

"Even foamed concrete with a compressive strength of 70 MPa can be made by the addition of polypropylene fiber and fine and used in high-performance cement..."

"Foamed concrete (FC) is a high-quality building material with densities from 300 to 1850 kg/m3, which can have potential use in civil engineering, both as insulation from heat and sound, and for load-bearing structures. However, due to the nature of the cement material and its high porosity, FC is very weak in withstanding tensile loads; therefore, it often cracks in a plastic state, during shrinkage while drying, and also in a solid state."

"Several factors... affect the mechanical properties of FRFC, namely: fresh and hardened densities, particle size distribution, percentage of ic material... and volume of chemical foam agent. ...rheological properties ...are influenced by the properties of both fibres and foam; therefore, it is necessary to apply an additional dosage of a foam agent to enhance the adhesion and cohesion between the foam agent and the cementitious filler in comparison with materials without fibres."

"Various types of fibres allow the reduction of... autogenous shrinkage [by] a factor of 1.2–1.8 and drying shrinkage by a factor of 1.3–1.8."

"Incorporation of fibres leads to only a slight increase in the compressive strength of foamed concrete; however, it can significantly improve the (up to 4 times), tensile strength (up to 3 times) and impact strength (up to 6 times)."

"[T]he addition of fibres leads to practically no change in the heat and sound insulation characteristics of foamed concrete..."

"FRFC... has applications in various areas of construction, both in the construction of load-bearing and enclosing structures."

"Foamed concrete (FC) has recently become widespread building material for thermal insulation and structural purposes..."

"At its core, FC is made from a concrete mixture into which pre-prepared foam is introduced, creating a system of closed voids within the hardened composite..."

"FC, which is one of the varieties of cellular concrete[,] attracts... builders worldwide... has nice workability... can be used for thermal and sound isolation, flame protection as well as blast viscosity; nevertheless, low mechanical and physical characteristics... limit the scope of its application in concrete structures."

"[A]ttributable to a large amount of entrained air, the hardening mixture is subject to shrinkage to a large extent."

"The utilization of different fibres... reduce[s] shrinkage cracks and improve[s] mechanical properties, particularly tensile and flexural..."

"FC... reduces construction expenses and allows for sustainable designs with low weight..."

"To increase the target at least up to 25 MPa [3,626 psi], engineers have applied various modern approaches... In the making of high strength [cement], low water to binder ratio (w/b) and the inclusion of , , and ultrafine silica powder are recommended as a substitute to sand..."

"To increase FC’s mechanical characteristics, the water-binding ratio w/b is usually maximally reduced, as well as the use of finely dispersed ic raw materials as a replacement for fine aggregate..."

"Incorporation of randomly oriented fibres into foamed concrete can improve load transfer in different directions, and increases due to the creation of an elastoplastic composite... in load-bearing structures..."

"Considering that fibreglass also increases mechanical strength, this is an important factor in FC’s stability... High-strength foamed concrete is obtained by introducing (PP) fibre into the raw mix... Many of the currently used fibres have been investigated, including PP... blend of polypropylene with glass... ... ... steel... palm oil, coconut... and other fibres... introduced in an amount of 0.2–1.5% volume of the concrete mixture; however, in this article, the fibre content ranges upper limit has been extended to 5%. As an alternative to traditional reinforcement, one strategy with composite mesh and mesh combined with fibre has also been studied for lightweight foamed concrete (LWFC)..."

"Using synthetic and natural fibres (glass and carbon ones) in FRFC has shown excellent durability properties with reduced drying shrinkage, high modulus of elasticity and increased mechanical strength..."

"Except for some papers... the developed FRFC has a 28-day tensile and compressive strength not even more than 2.5 MPa and 50 MPa, respectively."

"[T]he use of fibres (e.g., synthetic, metallic and natural fibres) as reinforcement is reported as an effcient material added into the fibre-reinforced FC (FRFC) matrix... to bridge the cracks... [reduce] shrinkage crack[s], to enhance load transfer and to improve the hardened properties by altering the characteristic brittle behavior [in]to elastic–plastic behavior, particularly, the flexural and tensile properties."

"The fibre matrix interface and matrix densification can deliver a greater load carrying capacity of FC reliant on the toughness of the fibres. The FRFC prolongs post-crack ductility even... [with] repeating loading cycles."

"This paper reviews the production of FC, type of foam agents, method of foaming generation, type of fibres used and factors affecting the mechanical properties of FRFC. [It also provides] a critical review on the properties and behaviors of FRFC as well as... research development trends to generate... insights into the potential applications of FRFC as suitable concrete materials... robust FRFC composites, for modern buildings and civil engineering applications... to draw a more complete picture of the current state-of-the-art."

"Axel Erikson was the first to patent -based FC technology in the year 1923... The characteristics, behaviour and structural applications of FC have been widely investigated..."

"FC is reportedly proved to be superior to conventional concrete mainly due to its lower density, which helps in reducing the static construction loads, foundation volume, labour, transportation, and exploitation expenses..."

"Many countries like the United Kingdom, Germany, Philippines, Turkey, and Thailand have made the use of FC in many construction applications..."

"The bubbles’ volume varies from 6% to 35% of the total final mixture in most of FC applications..."

"Foam agents are inorganic and organic compounds... in pellet or powder foam. Organic agents are , hydrazocarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylene tetramine, toluenesulfonyl hydrazide, benzene sulfonyl , and barium azodicarboxylate. While inorganic agents are NaHCO3, NH4HCO3, (NH4)2CO3, and Ca(N3)2... foams are used as insulation spray for air-sealing buildings. stabilizer is added to enhance its slurry viscosity which consists of 20% of 40% of and 40% of hydroxypropyl methyl cellulose... [T]he various foam agents are available in E-markets worldwide."

"The chemical foamer is ordinarily protein-based, hydrolysed protein, detergents, synthetic, , soaps of resin, and glue resins... The protein foamers form in a more grounded and enclosed cell of air-void structure, which allows the incorporation of a more prominent volume of bubble and gives a higher steady bubble network. In contrast, the synthetic ones abdicate more prominent extension and hence lower density... [T]he extreme use of chemical foam volume causes a decrease in flow, density and mechanical properties of FC... However, FC’s flow is considerably influenced by the time of mixing, showing that the lengthy mixing can result in the damage of the enclosed cell of air-voids by plummeting the air content..."

"Reportedly, FC’s mechanical properties are commonly dependent on the volume of foam content instead of its dependence over the proportion of water and cement..."

"Fibre-reinforced concrete (FRC) is one containing fibrous material that improves its structural solidity..."

"Basalt fibre is cut from a continuous basalt fibre with a diameter of 17 μm, 2.5 times superior in tensile strength to superior steel. Average fibre length: 6 to 24 mm. Recommendations for the dosage of basalt fibre: 1 kilogram per 1 cubic meter of mortar or concrete. It is necessary to introduce it into the mix with water, after stirring the fibre until it is evenly distributed in the water, it is necessary to slightly increase the mixing time (up to 5–10 min) for uniform distribution in volume."

"For fibreglass concrete, an alkali-resistant (AR) fibre should be used."

"PVA fibres have a higher tensile strength [1300 MPa] than [other] synthetic[s] and are relatively economical... Due to its low density... the fibre is ideal for foamed concrete... the is 25 GPa..."

"[P]olypropylene fibre, despite the low modulus of elasticity (1.5–10 GPa), has relatively high durability... an even lower density than PVA... [and is] ideal for foam concrete. The... tensile strength is 240–760 MPa and the ultimate elongation is 15–80%..."

"[F]ibres content should be controlled within 5% to achieve optimum concrete behaviour where excessive fibres may reduce the concrete strength."

"As claimed by Lim et al... finer... aggregate size may increase the strength of FC... As the particle size grading decreased, from passing through 2.36 mm sieve to 0.60 mm and 0.10 mm sieve, the strength has an increasing trend... With finer aggregate, the workability also increases and reduces the use of compaction that potentially bursts the bubble inside concrete paste."

"Silica fume has been found to benefit concrete properties [145], especially compressive strength and durability. It was added to FRFC and was found to have a 25% increment, at most, in compressive strength..."

"With the same quantity of addition, and specimens have higher compressive strength than silica fume... [N]ano-silica also have been investigated... The 4% nano-silica was found to have more excellent mechanical properties, durability and microstructure than plain FC and 15% silica fume... Silica fume was eFFectively enhanced the flexural, compressive and tensile strength and durability with a combination of waste marble material... [T]o enhance LWFC properties, apart from traditional materials, such as FA or SF... the recycled components like the slag of various types... or glass... have also been included in the LWFC concrete matrix... [T]he pozzolans may increase the concrete strength and its durability..."

"FC is obtained from mixing base mix (normally mortar) with preformed foam (diluted foam agent with high pressure). ...FC consists of cement as binders, sand as aggregates, water, and foams. As a consideration of economic and performance enhancements, many researchers... [introduced] additives or replacements to the FC, such as fly ash... silica fume... superplasticizer... fibres, and others. There is no specific method to determine the mixing proportions. However, Kearley... proposed the calculation of mixing the proportions by the target density method, and other researchers have practiced this."

"Fibre-reinforced foam concrete mixture is poured into molds without mechanical compaction, so it must have self-sealing ."

"For optimization various performances such as consistency, rheology and workability, segregation and bleeding should be considered... These parameters mainly depend on the water/cement ratio, supplementary cementitious materials, aggregates, s, foam agents, and the type and concentration of fibre."

"[T]he mixture’s components must be precisely calculated to improve the rheology and consistency of FRFCC, attain self-sealing behaviors, and enhance the adhesion and cohesion between the foaming agent and the cementitious filler. One of the main features influencing the rheology and texture of fresh FRFCC is the mixture’s water content. Another main factor is the fibre density... the adding of light fibre negatively influences the constancy of the mixture. Besides, the rheology of FRFC worsens with excess foam due to the higher air volume, while the incorporation of SP improved the flow rate. ...[T]he "Portland cement—silica-containing additive-complex modifiers" system can significantly reduce and create easily compacted fibre-reinforced foamed concrete mixtures."

"The introduction of fibre somewhat reduces workability. The fibres large specific surface absorbs more of the cementitious mortar around the fibres and, consequently, increases the viscosity of concrete, which contributes to a slight reduction in... spreadability. However, with proper FRFC mix... improvement in workability can be achieved by introducing the optimum fibre amount."

"The principle of the segregation and bleeding (water separation) test is that after sampling, the concrete mixture is left for 15 min... After that, the upper part of the sample is poured onto a sieve with a mesh size of 5 mm. After two minutes... [t]he stratification coefficient is calculated as the mixture ratio above the sieve to [that below it]."

"[[w:Superplasticizer|[S]uperplasticizers]], if used to reduce w/c, do not cause separation or water separation. The use of a clogging micro filler (for example, finely ground limestone or quartz sand) helps to reduce... water separation... [T]he micro filler [may create] an additional "stability framework," which increases... resistance to segregation..."

"[I]nclusion of fibres [having] more than one type or more than one size... [has been] recognized as hybrid fibres."

"[C]ompressive strength decreases exponentially when concrete’s density decreases... FC’s compressive strength commonly decreases gradually as the entrapped bubbles increased; however, its strength may be enhanced by adding fibres... [F]ibres can enhance its hardened [physical] properties (including... toughness and elasticity)..."

"[O]verall strengths were mainly influenced by the factor of combined water/cement and air/cement ratio..."

"The objective of this study is to develop structural fibered foamed concrete by the addition of polypropylene fiber, , and . Foamed concrete was obtained by replacing sand with fly ash. The properties of the foamed concrete were enhanced with polypropylene fiber and fine silica fume."