Architecture

"The booming development of this new constituent material in buildings and constructions was enhanced in the late 1970s... A government-oriented assessment on FC could be seen as a milestone event to further widening FC applications."

"Lightweight concrete can be produced in three ways: 1. By omitting the fine aggregate. This is called a 'no-fines' concrete. 2. By using lightweight aggragate. 3. By using lightweight aggregate and producing what is generall known variously as 'aerated concrete', 'cellular concrete', 'gas concrete', 'porous concrete', and 'foamed concrete'. This should not be confused with air entrained concrete which has a weight nearly equal to that of ordinary concrete and in which the proportion of air is limited to about 9 per cent."

"FC was initially envisaged as a void filling, stabilization, and insulation material..."

"[A]dmixtures used in conjunction with air entraining agents will... significantly affect the amount of air entrained. The use of in concrete will reduce the amount of air entrained. Similarly, the use of calcium chloride also has the tendency to reduce and limit air entrainment."

"Air content is... reduced by the process of compaction, on account of the movement of air bubbles to the surface... [A]s much as 50 per cent of the entrained air may be lost after vibration for 2 1/2 minutes and as much as 80 per cent may be lost by vibration for 9 minutes."

"The constituents of the cement especially the alkali content plays an important part in the entrainment of air in concrete. Similarly, the fineness of cement is also a factor."

"The temperature of concrete at the time of mixing was found to have a significant effect on the amount of air entrainment. The amount of air entrainment decreases as the temperature of concrete increases."

"The amount of air entrainment is found to increase with the mixing time up to a certain time and thereafter with prolonged mixing the air entrainment gets reduced."

"The grading of aggregate has shown good influence on the quantity of air entrainment. It was established that the quantity of air increased from the lowest of sand to a peak at about F.M. of 2.5, and, thereafter, decreased sharply. The sand fraction of 300 and 150 microns showed a significant effect on the quantity of air entrainment. The higher quantity of these fractions resulted in more air entrainment."

"Water/cement ratio is one of the important factors affecting the quantity of air. At very low water/cement ratio, water films on the cement will be insufficient to produce adequate foaming action. At intermediate water/cement ratio (viz. 0.4 to 0.6) abundant air bubbles will be produced. But at a higher water/cement ratio although to start with, a large amount of air entrainment is produced, a large proportion of the bubbles will be lost progressively with time."

"Different air entraining agents produce different amounts of air entrainment, depending upon the elasticity of the film of the bubble produced, and the extent to which the surface tension is reduced. Similarly, different quantities of air entraining agents will result in different amounts of air entrainment."

"The effects of the incorporation of each of nine different air-entraining admixtures in concrete were investigated by the making of a large number of batches of concrete under carefully controlled laboratory conditions. The results of tests on the plastic and hardened concrete specimens from batches made in parallel with and without each admixture are presented and discussed."

"The Use of Preformed Foam... [A]lmost any desired density of concrete can be produced... dependent almost entirely on the amount of foam added. About two per cent by volume of a foaming agent is added to the water and mixed with compressed air in a mixing tube. ...The foam is delivered ... direct into the mixer in which the cement or cement sand mortar has previously been prepared. The product can be cast in situ or used for making precast blocks."

"The Use of Air Entraining Agents... The normal density produced from this system ranges from 60 to 100 lb per cu ft and the proportion of air entraining agent may be about 0.25 per cent of the mix. The quantity of air entraining agent, the cement/sand ratio, the speed of the mixer and the time of mixing are the chief factors..."

"Lightweight concrete is normally accepted as that having a density range between 25 and 110 lb per cu ft, but even lower densities can be used when it is required solely for insulating purposes."

"If the lightest concretes (25 lb per cu ft and under) are required a neat cement mortar is used, but for heavier weights (40 lb per cu ft and above) sand, preferably very fine, may be added up to a cement/sand ratio... of 1 to 4. A higher strength/weight ratio can be obtained if cement only is used, but the addition of sand cheapens the product."

"Very careful mixing of the mortar with the air entraining or other agent is essential in all cases if a uniform result is to be obtained."

"Aerated, cellular or gas concrete can be made in weights ranging from about 25 lb per cu ft or even less, to 110 lb per cu ft. Its most useful range is perhaps between 40 and 60 lb per cu ft. It can produced in the following ways: 1. By mixing air entraining agents with cement or cement and sand in special high speed or whisking mixers. If an ordinary mixer is used it is doubtful if sufficient air would be entrained to obtain a density as low as 90 lb per cu ft. The Cheecol process belongs to this class. 2. By making foam and and adding a given quantity of this to a cement or cement and sand mortar in the mixer. An ordinary mixer is suitable for this method. The Pyrene process belongs to this class. 3. By adding hydrogen peroxide (H2O2) to the concrete. 4. By the use of calcium carbide (Ca2C2). 5. By adding aluminum powder or powder to a cement mortar."

"Owing to its high drying shrinkage... [lightweight concretes] use for cast in situ should be restricted to cases where shrinkage cracks are not of much importance."

"FC has been quickly promoted as construction materials for tunnels and underground works. Its excellent self-flowing capacity can be used to fill voids, sink holes, disused sewage pipes, abandoned subways, and so on. The low and controlled self-weight makes it capable for load reduction or liner elements in tunnel and metro systems..."

"This study aims to assess the properties of foamed concrete with a density of around 500, 700, 800 and 1000 kg/m³ formed by using a synthetic polymer-based foaming agent. The distribution of pores, wet and dry density and compressive strengths were evaluated. In addition, the creep deformations... were measured."

"Foamed concrete with higher densities (700 and 800 kg/m³) showed similar characteristics of pores, which were different from those of samples with a density of 500 kg/m³."

"equal to 5.9... 5.1... 3.8... and 1.4... MPa was obtained for foamed concrete with a density of [1000, 800, 700 and 500] kg/m3, respectively. The obtained compressive strengths were higher than those found in the literature..."

"Due to sustainable development and the related reduction in energy consumption and CO2 emission... lightweight concrete, aerated concrete and foamed concrete are increasingly used..."

"Foamed concrete (FC) is classified as lightweight concrete with a density ranging from 280 to 1800 kg/m³... and with a minimum of 20% of air pore volume in the cementitious mix..."

"Foamed concrete was made using the pre-foaming method with physical foaming or mixing and the foaming method with chemical foaming..."

"Foamed concrete is characterized by its ability to flow, self-compact and self-level as well excellent thermal and acoustic insulation..."

"The compressive strength ranges from 0.21 to 10.34 MPa for a density of 300 to 1600 kg/m³ ...[in] typical application."

"Amran et al... Fadila et al... Kang... Fernando et al... and Portal et al... produced foamed concrete for use in wall panels. Rum et al... used foamed concrete as a component in a profiled composite slab. Kadela et al.., Drusa et al.., Tian et al... and Lee at al... used foamed concrete in a pavement or floor structure to transmit a load on a subsoil, including weak soil. Moreover, foamed concrete has been used in building foundations..."

"[F]oamed concrete has the potential to become a mainstream material that uses waste material successfully as a replacement for cement or fine aggregate..."

"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."