State-ofthe-Art Report on Fiber-Reinforced Lightweight Aggregate Concrete Masonry

Masonry construction is themost widely used buildingmethod in the world. Concretemasonry is relatively low in cost due to the vast availability of aggregates used within the production process.*ese aggregate materials are not always reliable for structural use. One of the principal issues associated with masonry is the brittleness of the unit. When subject to seismic loads, the brittleness of the masonry magni1es. In regions with high seismic activity and unspeci1ed building codes or standards, masonry housing has developed into a death trap for countless individuals. A common approach concerning the issue associated with the brittle characteristic of masonry is addition of steel reinforcement. However, this can be expensive, highly dependent on skillfulness of labor, and particularly dependent on the quality of available steel. A proposed solution presented in this investigation consists of introducing steel 1bers to the lightweight aggregate concrete masonry mix. Previous investigations in the 1eld of lightweight aggregate 1ber-reinforced concrete have shown an increase in 7exural strength, toughness, and ductility. *e outcome of this research project provides invaluable data for the production of a ductile masonry unit capable of withstanding seismic loads for prolonged periods.


Introduction
e earliest application of lightweight aggregate concrete dates back to the Roman Empire.Lightweight aggregate concrete was the primary manufactured material, using Greek or Italian pumice aggregates mixed with limestone paste.Today, modern lightweight aggregate concrete consists of lightweight aggregate held together by a paste consisting of Portland cement and water [1,2].Fiber has been used as a reinforcing material throughout history in the form of mudbricks containing straws, horsehairs, and corresponding natural bers [3,4].Lightweight aggregate ber-reinforced concrete is a relatively new material [5].Although lightweight concrete and bers have been previously employed in construction, their use in modern days dates back to the second half of the nineteenth century.However, it was not until later in the 20th century that the usage and detailed study of properties associated with lightweight aggregate concrete became more signi cant.
is new understanding of the behavior of ber-reinforced concrete and crack propagation paved the way for the development of new technology.Stronger and lighter concrete sections permitted reductions in the cost of manufacturing, transportation, and foundation design.One of the latest elds a ected by the development of lightweight aggregate ber-reinforced concrete includes the seismic strength of structures.

Lightweight Aggregate Fiber-Reinforced Concrete versus
Lightweight Aggregate Concrete.For countless years, lightweight aggregate concrete (LWAC) was utilized for aesthetical or insulation purposes only. is was because of one of the main disadvantages found in both normal and highstrength lightweight concretes: low tensile-to-compressive strength ratio, low exural strength, low fracture toughness, high brittleness, and large shrinkage [6].Furthermore, lightweight aggregate concrete is brittle in nature, and when subjected to external loading, a sudden failure under stress occurs.
e addition of bers, however, will allow overcoming the issue associated with the brittleness of the material.e incorporation of bers into a brittle cement matrix serves to increase the fracture toughness of the composite, through the crack-arresting process, and increase the tensile and exural strengths.Lightweight aggregate ber-reinforced concrete would fail only if bers break or are drawn out of the cement matrix due to tensile forces.e strength mechanics of ber-reinforced concrete and mortar, extending from the elastic precrack state to the partially plastic postcracked state, is a continuing research topic [7].

Lightweight Aggregates and Fiber Types
2.2.1.Lightweight Aggregate.Lightweight aggregates are the most important components in the production of lightweight aggregate concrete, with relatively low particle density due to their cellular pore system.Heating certain raw materials, particularly clays, develops the cellular structure within the particles by incipient fusion.At this temperature, gasses are evolved within the pyroclastic mass causing expansion that retains a particular shape upon cooling. is fast cooling creates voids or pores that reduce the total weight of the aggregate.Strong aggregates have pore sizes ranging from 5 to 300 µm.e American Concrete Institute (ACI 213 Committee 2005) provides a detailed report on the characteristics of lightweight aggregate concrete [8].
Two primary sources of lightweight aggregates exist: natural and manufactured.Natural lightweight aggregates like pumice, a froth-like volcanic rock, occur when lava expelled to the air from a volcanic source cools at a relatively fast rate [9].e most widely used synthetic lightweight aggregate is called expanded clay.Manufacturing of expanded clay consists of heating the clay particles in a rotatory kiln.e term "expanded clay" is commonly used to describe the three main materials used for the fabrication of arti cial lightweight aggregates: shale, clay, and slate.Campione et al. stated that the experimental results from the tests performed on lightweight ber-reinforced concrete show improvements within the application of expanded shale aggregate as oppose to the use of pumice stone.Nonetheless, pumice stone performance was also desirable due to its relatively low cost and suitability in various regions, including seismic areas [9].
One alternative to these expanded clay aggregates is the utilization of lightweight waste materials.is results in the reduction of the overall cost of construction as well as solid waste.One such material is the oil palm shells (OPSs) or palm kernel shells (PKSs), a material available in vast quantities within tropical regions.In the past, some experiments of OPS lightweight aggregate concrete have produced concrete with a grade of 20-50.e compressive strength at 28 days of the OPS concrete varies between 20 and 24 MPa [10].

Fiber Reinforcement.
Fiber reinforcement can substantially increase the energy absorption and impact strength of concrete, resulting in improvements within ductility, tensile-to-compression strength ratio, seismic behavior and earthquake resistance, resistance to cracking, and fracture toughness [11].ACE Committee 544 de nes steel bers as "a short, discrete length of steel having an aspect ratio (length/diameter) from about 20 to 100, with any cross section, and that is su ciently small and randomly dispersed in an unhardened concrete mixture using usual mixing procedures" [12].
ASTM 820 provides calci cation of ber as follows [13]: (i) Type I-Cold-drawn wire (ii) Type II-Cut sheet (iii) Type III-Melt-extracted (iv) Type IV-other bers Currently, there are many types of reinforcing bers that can be used in the production of LWAFRC including (i) steel, (ii) glass, (iii) polypropylene, (iv) natural.
More information about other types of ber reinforcement can be found in ACI 544 Chapter 2 [12].
Natural bers exhibit many advantageous properties as reinforcement for composites, especially signi cant reductions in costs and thermal conductivity.
e use of natural bers could facilitate the reduction and conservation of energy and thereby protect the environment.e principal sources for natural bers come from coconut husk, sisal, sugarcane bagasse, bamboo, jute, wood, akwara, elephant grass, water reed, plantain and musamba, and cellulose bers [14].e disadvantage of adding natural bers to the concrete mix is reductions in workability due to high amount of bers leading to a high volume of entrapped air.Similarly, the inclusion of palm ber results in obtaining a higher density at 0.8% ber volume.is increment in bers provided the optimum ber volume percentage for the mix in which small amount of air bubbles are present.An excessive quantity of the ber at 1% or more leads to a reduction in bonding strength and disintegration [14].
In summary, bers improve the ductility of concrete and avoid congestion of secondary reinforcement [15].e inclusion of bers develops a more homogeneous and isotropic mixture, transforming the concrete from brittle to a more ductile material.In fact, previous investigations have shown that the unit weight of concrete increases with increasing ber ratios [16].

Applications.
e added bers can be used as a substitution for the required transverse reinforcement, where large quantities of steel con ning reinforcement are needed.e use of bers can reduce both the weight and cost of structures. is reduction in weight and increase in material strength are useful where seismic codes require higher ductility performance [17].
e brittle nature of lightweight aggregate concrete leads to sudden and precipitated failure.erefore, adding ber reinforcement improves the ductility of the lightweight concrete or normal-weight high-strength concrete.Combining lightweight concrete with conventional steel 2 Advances in Civil Engineering reinforcement and steel or polypropylene bers reduces the brittleness in the lightweight concrete.Addition of bers to lightweight aggregate concrete increases the peak and residual frictional stresses.Furthermore, ber reinforcement may prevent congestion when additional steel reinforcement is required to provide ductility.e main purpose of using lightweight aggregate ber-reinforced concrete in seismic zones is to improve the seismic behavior of the structures [9,17,18].Moreover, its lightweight characteristic makes this concrete useful in reducing the dead load on high-rise buildings, slabs, and joists, permitting a direct reduction in the foundation size, especially in soils with low bearing capacity [17].In fact, the lightweight and higher ductility of lightweight aggregate ber-reinforced concrete make structural members such as marine structures, slabs, joists, bridge girders, and bridge decks both desirable and cost e cient [19].In addition, lightweight aggregate ber-reinforced concrete is increasingly being used in precast concrete structures, providing higher strength members and facilitating transportation.e addition of bers to a concrete mix improves the engineering characteristics of the concrete, for example, ductility, impact strength, and toughness [18].Properly designed nonstructural ber-reinforced ultralightweight concrete can be easily cut, sawed, and nailed like wood for decorative or insulation purposes [20].e applications of a lightweight aggregate berreinforced concrete mix vary depending on the required strength, workability, cost, and feasibility.e primary use of ber-reinforced concrete is to improve tensile strength, the behavior of earthquake resistance, cracking resistance, and fracture toughness [6].
e main purpose of using lightweight aggregate ber-reinforced concrete in seismic zones is to improve the ductility behavior of the structures under a seismic load.e brittle nature of lightweight aggregate concrete leads to sudden and precipitated failure, and adding reinforcement increases the ductility of the lightweight aggregate ber-reinforced concrete.

Introduction.
e lightweight aggregate ber-reinforced concrete production consists of the combination of Portland cement, lightweight aggregates such as pumice or expanded manmade clays, steel bers, water, and other chemicals used to enhance workability and other mechanical properties.e addition of bers to the concrete mix improves the engineering characteristics of the concrete: ductility, impact strength, and toughness [16,18].

Physical Properties.
e physical properties of lightweight aggregate ber-reinforced concrete mainly depend on the characteristics of the aggregates, in particular, the density, ber strength, and ber-cement bond.Any increase in the mentioned components will a ect the nal product strength, workability, ductility, density, and physical appearance.In fact, lightweight concrete requires large amounts of transverse reinforcement steel due to its brittle nature [17].e strength of the material increases with the use of expanded shale aggregates, while the natural pumice aggregate showed no substantial increase in strength.Nonetheless, pumice stone performance was acceptable in some cases, making this material suitable for regions of seismic activity due to its low cost [9].

Compressive Strength.
e failure mode for lightweight aggregate ber-reinforced concrete matrices depends mostly on the aggregate and not on the cement paste.e main parameters in the experimental compressive strength test include volume percentage of bers, the type and the volumetric ratio of transverse steel reinforcement, the shape of the specimen (whether a prism, cube, or cylinder), and the length of the specimen.Furthermore, the main parameters a ecting the test results include frictional restraints between the load platens, the specimens, and the allowable rotations of the loading platens prior to and during the test.e loading platens should be xed against rotation once a signi cant load is applied.Often, capping of specimen ends is used to ensure plane and parallel ends [17].
e addition of bers increases the maximum compressive strength of LWAFRC expanded clay by 30%.Concrete made of pumice stones with the same dimension and size showed no signi cant increment in compressive strength.is low strength resulted from the ber-matrix bond mechanism in concrete and the low strength of the aggregate.is bonding depends principally on the quality of the cement mortar and the ber properties.Higher strength concrete provides better ber-matrix interface bonding.Moreover, hooked-end steel bers in uence the compressive strength of concrete [9].
For high-strength LWAFRC, the bers did not signicantly contribute to the compressive strength [21].In addition, there was no signi cant increase in the compressive strength of the hardened lightweight self-compacting concrete due to the addition of polypropylene bers [22].Steel bers have a signi cant e ect on energy absorption.As a result, they have a signi cant impact on the compressive toughness in lightweight aggregate ber-reinforced concrete since the descending part of the strain-stress curve depends on the addition of bers [18].

Flexural Strength. Gao et al. indicated the following improvement areas due to the addition of bers to lightweight high-strength concrete [6]:
(i) Flexural strength: the fracture process of steel ber-reinforced concrete consists of progressive debonding of ber, during which slow crack propagation occurs.Final failure occurs due to unstable crack propagation when the ber pulls out, and the interfacial shear stress reaches the ultimate bond strength.After mix cracks, ber will carry the load that the concrete took before cracking by the interfacial bond between ber and matrix.(ii) Flexural Load: the de ection corresponding to the ultimate load increases with the increase of ber volume fraction and aspect ratio, and descending Advances in Civil Engineering branch of the exural load-de ection curves decreases gently after reaching the maximum load for the ber volume fraction and aspect ratio.(iii) Flexural Toughness: cracks rst occur in lightweight aggregate concrete rather than in the cement paste under load.In general, bers serving as crack arrest or barriers increase the tortuosity of an advancing crack.erefore, the addition of steel bers to concrete e ectively increases the postcracking behavior of steel ber-reinforced high-strength lightweight concrete.
For concrete mixes with higher ber steel ratio, 1-2%, strain hardening was observed, and consequently, there is an increase in maximum strain corresponding to failure.At failure, bers ensure high levels of deformation without a signi cant reduction in the bearing capacity.For exural strength, addition of bers resulted in slow crack propagation and progressive debonding of bers at high levels of postpeak stress [9].
e increase in exural strength due to the addition of bers in lightweight concrete is 91%, 182%, and 260% relative to the increase in specimen size.As stated previously, ber reinforcement enhances compressive and tensile strength as well as fracture energy absorption, largely improving exural strength for lightweight aggregate concrete [11].

Splitting Tensile Strength.
Cylinder splitting tensile strength increased for lightweight aggregate ber-reinforced concrete through the addition of steel bers.Cylinder splitting tensile strength of lightweight aggregate berreinforced concrete is about twice as high as that of plain concrete and lightweight concrete.Specimens with diameter sizes varying from 76, 100, 150, and 200 mm increased in splitting tensile strength of 134%, 33%, 12%, and 0%, respectively, for normal concrete and 127%, 165%, 44%, and 29% for lightweight concrete, respectively [11].Fiber reinforcement signi cantly increases the tensile strength of lightweight aggregate concrete [21].

Shear Strength.
e addition of steel ber improves the ductility and energy absorption that causes ductile shear failure.e presence of bers reduces all deformations including de ection, slab rotation, concrete strain, and steel strain at all stages of loading.However, the e ects of bers are only apparent after the rst cracking occurs.Most of the research conducted in the area of shear strength of berreinforced concrete belongs to the slab-column mechanisms.Fibers delay the formation of inclined shear cracking in slabcolumn connections.As a result, the service load on the lightweight ber-reinforced concrete slab is increased from 15 to 40%, depending on the serviceability criterion.One of the signi cant contributions of the bers in slabs is the elimination of the failing brittle nature of the slab. is process created a failure surface that was very irregular.e fracture surfaces in ber-reinforced concrete were similar to those in plain concrete slab-column connections.However, the punching perimeter was much larger, resulting in a decrease in the angle of the surface of a maximum of 3 ° [23].
e major increase in strength of a lightweight concrete mix is a result of a combination of bers with conventional reinforcement.Fibers act as bridging agents between the inclined cracks produced by the local tensile forces when the strength of concrete around the stirrups surpasses the actual strength for the concrete.is phenomenon increases the shear strength of concrete enclosed between two consecutive stirrups [15].

Modulus of Elasticity.
Elastic properties of the aggregate have a substantial in uence on Young's modulus.
is e ect occurs mainly because of the bond existing between the aggregate particles and the cementing material.Young's modulus of elasticity for composite materials such as lightweight aggregate ber-reinforced concrete can be measured using eight models [24].

Advances in Civil Engineering
For a composite material, Kurugol et al. stated that the Hashin-Hansen model results are very similar to the experimental results.As a result, the model is better for predicting the modulus of elasticity.Likewise, the Counto and Maxwell models predict that Young's modulus for a composite material and give desired results.For the parallel phase model, Kurugol et al. stated that this model predicts acceptable results at low aggregate volume fractions, even though for high aggregate volumes this model overestimates the modulus of elasticity.However, this model is accepted and useful since it provides a simple linear expression [24].
Balaguru and Foden reported that by increasing the ber volume ratio in the mixture, the modulus of elasticity is enhanced by approximately 30%.Furthermore, by replacing the lightweight ne aggregate with sand, the modulus of elasticity is also expected to increase.As a result, berreinforced concrete exhibits ductility by the addition of coarse lightweight aggregate and bers [26].

Density of Lightweight Aggregate Fiber-Reinforced
Concrete.Due to the brittle nature of the lightweight aggregate concrete, the density of the lightweight concrete depends on the amount and density of the aggregate used.Utilizing aggregates with higher density has shown to improve the strength of the concrete signi cantly [9].Structural lightweight aggregate ber-reinforced concrete is 20-30% lighter than conventional concrete.In this respect, the term "lightweight" is relative.Lightweight aggregate ber-reinforced concrete bulk densities vary from 800 to 1400 kg/m 3 (50 to 87 lb/ft 3 ) [20].e unit weight of concrete decreased with the addition of lightweight aggregates and increased with the addition of bers [16].

Workability. Lightweight aggregates show two particular characteristics due to their lightness and inclusion of inner voids that can retain water and cause the aggregate to
oat during the mixing process.ese phenomena result in the decline in the workability of the concrete mix.Similarly, ber entangles together forming a network structure in the concrete mixture that restrains segregation of lightweight aggregates.In addition, the length of the bers requires more cement paste to wrap around the ber, in uencing the viscosity of the concrete mix a ecting the slump.Polypropylene bers reduced the slump by about 20%, whereas steel bers reduced the slump by 54%. is is due to the holding e ects of the bers [18,27].
Workability characteristics of steel ber-reinforced concrete are complex; shapes of bers, aspect ratio, and volume fraction are the most important factors a ecting the workability.e ber-reinforced concrete mixes were less workable than mixtures without bers.e V-funnel test results for plain concrete ranged from 15 to 20 seconds and 35 to 120 seconds for the ber concrete.e ber-reinforced concrete mixes with plain bers show the best compatibility followed by mix with paddle bers.Mixes with cramped and hooked bers show less compatibility than those with straight bers.In fact, hooked bers require the highest energy compaction.erefore, the compact ability of lightweight aggregate ber-reinforced concrete mixes depends on the shape and surface area of the bers.e compact ability of ber-reinforced concrete decreases as the design strength increases and decreases as their aspect ratio increases [28].
e presence of polypropylene bers signi cantly reduces the slump ow of concrete and increases the time of the V-funnel tests.In the same manner, increasing the amount of the ber volume ratio reduces the lling height of the U-box test [22].

Drying Shrinkage.
It is important to take into consideration the properties of the lightweight aggregate concrete if a prediction model for ultimate shrinkage is to be applied.Lightweight aggregate concrete made with sintered y ash aggregates displays a long-term drying shrinkage that was nearly twice the value for normal concrete.is drying shrinkage seems to be a result of the high volumetric value of y ash paste content.As the modulus of elasticity of concrete decreases, the shrinkage value is increased.For normal-weight concrete, a modulus of elasticity of 35 GPa (5076.3ksi) and ultimate shrinkage value of about 500 microstrains are expected.For lightweight aggregate ber-reinforced concrete, the expected shrinkage value was around 1000 microstrains and a modulus of elasticity was of 21 GPa (3045 ksi) [21].
e addition of ber to the concrete mix did not reduce shrinkage at an early state of setting.However, as the concrete cures, the increase in age showed that bers restrained shrinkage.A higher tensile strength alongside a low modulus of elasticity is believed to be e ective in reducing shrinkage cracking.For lightweight aggregate ber-reinforced concrete, mixes containing carbon ber combinations produce the greatest reduction of shrinkage [27].Also, the use of carbon steel ber combination in lightweight concrete mixtures showed lower brittleness of the concrete as well as a reduction of shrinkage [22].
3.2.9.Fiber-Cement Bond.When the concrete reaches its maximum load, and the rst cracks appear, the bers bridge the inclined cracks that form when overcoming the local concrete tensile strength.
e strength of the bridging mechanism will depend on the strength of the ber or the capacity of the bond between the ber and the concrete paste.Fibers also increase the shear strength of the concrete enclosed between two section heaves.e results showed that if the anchorage length increases, the extraction forces of longitudinal bers will also increase.e addition of bers ensures steel yielding that guarantees a better behavior.For cyclic loading, experimental results show that the highest degradation occurs at the rst cycle.is phenomenon is caused in part because the concrete around the rebar is locally crushed in compression reducing the bond strength [15].
A substantial amount of ber volume guarantees the proper bridging connection between bers and the concrete paste.e required amount of bers needed is called critical ber volume.High frictional bond strength and frictional surface depend on the amount and the physical properties of Advances in Civil Engineering the bers.e relationship between ber volume fraction and composite energy absorption can be given by where G tip is the composite energy absorption at crack tip, τ is the frictional bond strength, L f is the ber length, d f is ber diameter, and where V f and E f are the ber volume fraction and elasticity modulus of ber, respectively [29].
3.2.10.Ductility.Ductility is de ned as the characteristic of a material to withstand plastic deformation while being loaded beyond peak loads.In addition, ductility may be de ned based on bending and compressive resistance.As a primary characteristic of a ductile material, large deformation occurs prior to fracture.In the same way, energy absorption is de ned as the area under the load-de ection curve.
Incorporating lightweight aggregates to the concrete mix decreases the ductility of the concrete and at the same time increases the brittleness of the material.
e shear and exural de nition of ductility index μ consist of the ratio of the area of the load-de ection response.Shear ductility should only be measured on shear deformation [19].
For lightweight aggregate ber-reinforced concrete, ductility results from enforced crack resistance due to the ber bridging concrete layers.Pseudostrain hardening, or multiple cracking in ber-reinforced composites, occurs with the following sequence: rst microcracks appear, and then the concrete matrix transferred the load to the bers.Consequently, the bers perform a bridge connection and transfer the load back to the concrete through the interface bond.e load builds up again in the matrix forming another parallel crack.
e bers and the concrete matrix repeat this process until multiple cracking takes place.Eventually, the bers pull out or break causing total failure of the concrete specimen.e ber volume fraction of 1.5% or higher achieved strain hardening faster than lower ber volume fractions.By the addition of 10-20% y ash and silica-fume cement substitutes, the ductility and exural strength of lightweight ber-reinforced concrete are improved.is yields an increment of 50-150% exural displacement (ductility) at ultimate load [29].
Düzgün et al. concluded that the addition of bers to the concrete mixes increases the strain and peak stress of the specimens.In the same way, the strain capacity and deformation capability increase greatly as the volume of bers were increased from 0% to 1.5%.
is increase in stress de nes the descending portion of the stress-strain curve [16].
eodorakopoulos and Swamy stated that the addition of bers to a brittle lightweight concrete generates an increase in ductility of 125%-158% and an increase in energy absorption of 216%-237% [23].Libre et al. provided a complete work on the ductility of lightweight aggregate ber-reinforced concrete based on the exural strength of this material.Specimens tested for exural strength contained a combination of steel and polypropylene bers at 0%, 0.5%, and 1% ber volume.e mix composed of 1% steel bers and 0.4% polypropylene bers yield a exural strength of 7.3 MPa (1058.8psi), the prepeak energy of 11,920 N mm, and the total energy of 71,112 N mm [18].Gao et al. worked with high-strength lightweight aggregate ber-reinforced concrete and observed that the de ection curve is greatly a ected by the introduction of steel bers; it increases with the increase of ber volume fraction and aspect ratio.In fact, the result showed that plain concrete reached a peak load of 20 kN (4.5 kip) and a de ection of approximately 0.2 mm (0.079 inch).e de ection for a lightweight aggregate berreinforced concrete with a ber volume fraction of 2% and aspect ratio of 70 reached a peak load of 40 kN (8.99 kip) and a measure de ection of 2.0 mm (0.079 inch) [6].
Arisoy and Wu revised the e ects that the lightweight aggregate concrete has on ductility at a constant ber volume of 1.5%.Ductility increases when lightweight aggregate content is between 40 and 60% of the specimen mix.However, the concrete mix with less than 20% lightweight aggregate showed good ductility.Meanwhile, high volumes of lightweight aggregate concrete resulted in a weak matrix and poor ber distribution yielding premature failure of the specimens [29].

Toughness Index.
Toughness is an important characteristic of ber-reinforced concrete.Fibers increase their energy-absorbing capability and are more suitable for use in structures subjected to impact and earthquake loads [25,27].
e toughness de nition consists of the ratio of the amount of energy needed to cause a de ection of a speci c amount and is expressed as a multiple of the rst crack de ection.e toughness is calculated based on the load-de ection behavior of a 100 mm × 1000 mm × 360 mm prism tested under a fourpoint load stated on ASTM C1018 procedure [30].
e increase of ber content will yield an increase in the toughness index and postcrack resistance, and lightweight aggregate ber-reinforced concrete beams can sustain large loads and greater de ections, indicating strain hardening.Fibers with a length of 50 mm (2 inch) show the best improvement of toughness.Evaluation of toughness behavior depends on the values I 50 and I 100 .
Area under load deflection curve up to 3δ Area under load deflection curve up to δ .(12) e calculation of these values depends on the loadde ection curve and properly measured small increments.
e toughness index magnitude for lightweight aggregate ber-reinforced concrete is very similar to that magnitude for normal weight concrete of the same strength [26].
Lightweight aggregate ber-reinforced concrete toughness indexes are not sensitive to specimen size.For highstrength LWAFRC, postpeak loads drop at a faster rate than normal-strength LWAFRC. is change in toughness index indicates that to achieve similar ductility for high strength and low strength, lightweight concrete requires an increase 6 Advances in Civil Engineering in ber volume fraction or the addition of bers with higher strength and hook end [11].

Preparation Technologies
3.3.1.Scope.e main purpose of the utilization and production of LWAFRC is to provide a lightweight material capable of withstanding greater loads but reducing member size.In order to achieve the required ductile capacity, a very strict material proportion must be followed.
e most common manner to design a LWAFRC mixture is to follow ACI 213 in combination with ACI 554 and the experimental research work previously approved by ACI [8,12].

Mixture Proportion Criteria.
Laboratory experimental results show that uidity of concrete is reduced by the addition of bers; this concludes that slump test does not provide an accurate evaluation of workability of fresh concrete.Polypropylene bers show lower e ect on workability of fresh concrete, while for steel bers the e ect was higher.
e traditional slump test fails to evaluate workability of ber-reinforced concrete; therefore, it is recommended to utilize the inverted slump cone test for the evaluation of workability of FRC using standardized test ASTM C995 [31].

Materials.
e materials utilized in the production of lightweight aggregate ber-reinforced concrete consist of the following: (i) Portland cement type II or higher and/or y ash (ii) Lightweight aggregates (expanded clay or natural) and normal weight aggregates (sand and ne gravel) (iii) Fibers (steel, polypropylene, glass, and natural) (iv) Plasticizers 3.4.eoretical Modeling.For lightweight aggregate berreinforced concrete, the procedures followed in order to measure and analyze its mechanical properties are very similar to those utilized for normal-weight concrete.e main variation occurs in the workability and modulus of elasticity calculations.

Design Considerations.
In order to design a member made of LWAFRC, the procedures in ACI 544.R [12] must be followed, including the mix selection, placing, nishing, and quality control procedures.While some training is necessary, the equipment used for normal concrete can be used in the production of LWAFRC.

Applications.
e brittle nature of lightweight aggregate concrete leads to sudden and precipitated failure.erefore, adding ber reinforcement improves ductility of lightweight concrete or normal-weight high-strength concrete when combined with conventional steel reinforcement and reduces the characteristic brittleness of these materials.e addition of bers to lightweight aggregate concrete increases the peak and residual frictional stresses.Furthermore, ber reinforcement may prevent congestion when additional reinforcement is required to provide ductility.
e main purpose of using lightweight aggregate ber-reinforced concrete in seismic zones is to improve the seismic behavior of the structures [9,17,18].Moreover, the lightweight reduced the dead load on buildings supported by low bearing capacity soil [17].Also, the low weight and higher ductility of LWAFRC make structural members such as marine structures, slabs, joist, bridge girders, and bridge decks very desirable and cost e cient [19].In addition, LWAFRC is increasingly being used in precast concrete structures, providing higher strength members and facilitating its transportation.erefore, the addition of bers is important to improve the engineering characteristics of the concrete, for example, ductility, impact strength, and toughness [18].
Properly designed nonstructural ber-reinforced ultralightweight concrete can be easily cut, sawed, and nailed like wood for decorative or insulation purposes [20].
e application of a LWAFRC mix varies depending on the required strength and workability.
ey are mainly viewed in improvements in the tensile/compression ratio, behavior of earthquake resistance, resistance to cracking, and fracture toughness [6].
e main purpose of using lightweight aggregate ber-reinforced concrete in seismic zones is to improve the behavior of the structures.e brittle nature of the lightweight aggregate leads to sudden and precipitated failure.

e
following items list important research needs in the area of LWAFRCM: (i) Further studies need to be conducted on the bonding behavior of bers and cement paste.(ii) More research is needed in order to optimize the mixture proportions and examine the e ects of hybrid steel and polypropylene bers on other properties of pumice lightweight aggregate concrete such as shrinkage, creep, durability parameters, and re resistance.(iii) Studies on the e ect of hybrid ber mechanical properties of LWAC are warranted based on recent advancement in this area.us, more research is needed in order to optimize the mixture proportions and examine the e ects of hybrid steel and polypropylene bers on other properties of pumice lightweight aggregate concrete such as shrinkage, creep, durability parameters, and re resistance.(vi) More studies are required to investigate the e ects of shear forces on LWAFRCM.
Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with ird-Point Loading).ASTM C192: Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory.ASTM C330: Speci cation for Lightweight Aggregate for Structural Concrete.ASTM C331: Speci cation for Concrete Masonry Units.ASTM C469: Test for Static Modulus of Elasticity and Poison's Ratio of Concrete in Compression.ASTM C495: Test Method for Compressive Strength of Lightweight Insulation Concrete.ASTM C496: Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens.ASTM C567: Test Method for Determining Density of Lightweight Aggregate Concrete.ASTM C995: Standard Test Method for Time of Flow of Fiber-Reinforced Concrete through Inverted Slump Cone.ASTM C1116: Speci cation for Fiber-Reinforced Concrete.ASTM C1399: Obtaining Average Residual Strength of Fiber-Reinforced Concrete.ASTM C1550: Test Method for Flexural Toughness of Fiber-Reinforced Concrete.ASTM C1609: Test Method for Flexural Performance of Fiber-Reinforced Concrete.