Received Date: November 04, 2016; Accepted Date: December 27, 2016; Published Date: January 17, 2017
Citation: Rifaie WN, Fayadh NK, Ahmed WK (2017) Nanomaterial to Improve Ferrocement Properties for Green Buildings. J Nanosci Curr Res 2: 108.
Copyright: © 2017 Al-Rifaie WN, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Nowadays, nanomaterial has been used extensively worldwide to improve the properties of the constructional materials due to many advantages that can be achieved especially improving strength/weight ratio which is highly desired by the engineers towards a green building concept by minimizing the material used and increasing the stresses levels that the structure can carry. The present research examined the mechanical properties of nano cement mortar which can lead to improvements in ferrocement to be used in the green building system. Thus 90 cubes, 50 mm, and 500×50 mm prisms varying thickness (t=4, 6, 8 and 10 mm) were cast and tested to determine the compressive strength, and modulus of rupture, for nano cement mortar at curing age of 28 days, In addition, 50 nano-ferrocement prisms (500×50 mm) with varying the thickness (t=4, 6, 8 and 10 mm), number of fine wire mesh layers, mix proportions were cast and flexural tests were carried out to determine the composite modulus of elasticity and modulus of rupture. It was observed that the compressive and flexural strengths were increased for the nano-ferrocement samples in comparison with the normal one which refers to the importance of developed mixture toward sustainable building.
Nanomaterial; Ferrocement building; Cement mortar
ACI: American Concrete Institute; ASTM: American Society for Testing and Materials; CNT: Carbon Nano Tube; CNF: Carbon Nano Fibre; NSCSC: Nano Sand Cement Silica Fum Clay; MWCNT: Multiwall Carbon Nano Tube
In general, a green building which is also known as green construction or sustainable building, refers to both a structure as well as adopting processes that are environmentally friendly and uses the resources efficiently during the life cycle of the building that from the design, material, construction, air quality, maintenance and even demolition. Green buildings must be designed to meet one of certain objective such as the use of energy more efficiently which eventually will influence positively on the reduction of the CO2 emission, and hence minimize the impact of the global warming. Many constructional trends have been implemented around the world to fulfill the green buildings requirements through the design and the material used. However, a structural system based on generic services facilities is introduced by Al-Rifaie and prefabricated ferrocement cavity walls/ and roofs within the proposed system present a series of possibilities for the solution of building construction at maximum reduction of the electrical energy. Ferrocement is recognized as a composite material of great potential made of cement- sand mortar and layers of very fine steel wire meshes. The material was found wide applications because of high tensile strength, imperviousness to water and crack free performance. The relationship between several elements such as building materials of natural and manufactured building materials and renewable energy sources and energy sources depleted should be determined.
Ferrocement is a type of thin reinforced concrete with great potential, made of cement–sand mortar and reinforced with layers of fine wire meshes with or without skeletal reinforcement [1-3]. Ferrocement is an excellent construction material due to its mechanical properties, and low cost, and it is considered to possess a high cracking strength. Cement mortar is a material used in construction of ferrocement which is cement composite material made up of Portland cement, sand, water and sometimes admixtures.
Investigators and researchers have been focusing on the substantial scientific background of the nanomaterial, where a continuous efforts have been done to improve the durability and the sustainability of concrete, and improving the mechanical properties of cementitious materials by using nano-materials [4,5]. The addition of some metal oxide nanoparticles to concretes can both reduce the permeability of concrete to ions and increase the strength of concrete, thereby improving durability. The addition Fe2O3 nanoparticles , SiO2 nanoparticles  and metal oxide containing nano clays  have all been shown to improve concrete and/or cement mortar properties. Properties of the cement-based composites made from the CNTs/CNFs-grown cement/ mineral admixture were presented. Experimentally, Li et al.  studied the mechanical properties of nano-Fe2O3 and nano-SiO2 cement mortars.
The flexural strength of a very thin ferrocement element, by using NSCSC mortar as a replacement to the normal cement mortar, usually used in ferrocement elements was examined. The measured results showed an increase the flexural strength of a very thin ferrocement using NSCSC mortar . Zhang and Li  found that the addition of 1% by weight of binder of 15 nm diameter TiO2 to concrete refined the pore structure and increased the resistance to chloride penetration by 31%.
Oscar et al.  studied the effect of the reagglomeration process of Multi-Walled Carbon Nanotubes (MWCNT) dispersions on the activity of silica nanoparticles at early ages when they are combined in cement matrixes. MWCNT/water/superplasticizer dispersions were produced via sonication and combined with nano silica particles in the mixing water of the cement samples. The methods and theories of in situ growth of CNTs/CNFs on cement/mineral admixture, including chemical vapour deposition method and microwave irradiating conductive polymers method, were summarized . The addition of SiO2 nanoparticles is widely reported to be effective for strengthening concrete; both normally vibrated concrete and self-compacting concrete .
Al-Rifaie et al.  examined the compressive and flexural strength of nano cement mortar by using micro cement, micro sand, nano silica and nano clay in developing a nano cement mortar which can lead to improvements in ferrocement construction. In addition, the influence of heating on compressive strength of cement mortar, whereas ferrocement eco-housing system was able to produce very energy efficient dwellings .
Generally, cement-based materials containing SiO2 nanoparticles are stronger than those containing SiO2 fume . This is attributed to the accelerated cement hydration, increased pozzolanic activity, reduced pore size and improved interfacial bonding between the hardened cement paste and aggregate that is associated with the decreased average particle size of the SiO2 . The effect of elevated temperatures on chemical composition, microstructure and mechanical properties of high strength mortars with nano alumina was investigated . Effect of nano clay particles on mechanical, thermal and physical behaviours of waste-glass cement mortars was investigated . Finite element method was used to investigate the impact of inclusion in hypothetical nano composite , cracked nano composite , debonding between the nanofiber and the matrix , pre-crack existence in nanocomposite  as well as studying the impact of the mismatch properties . Moreover, FEA has been used to investigate the effect of the nanoinclusion , interfacial debonding defects , interfacial defects  and fractured particulate composite  on the characteristics and failure of the nano composite, whereas the development of nano structural element called “nano-polymercement” which can be used for different applications , whereas effect of nanomaterials in cement mortar characteristics was studied by Al- Rifaie and Ahmed .
Towards impenimg a green building concept by improving the ferrocement properties which will reduce the material used for the construction and hence maximize the allowable stresses that can be adopted in the design of a building, the authors present a research work to examine the mechanical properties of nano particles in developing a cement mortar which can lead to improvements in the performance of ferrocement as structural elements in the structural system for green housing. Cubes and prisms were cast and tested for determining compressive strength, and modulus of rupture of nano cement mortar. The parameters considered during the investigation were micro sand, micro cement, and wire mesh layers.
α) Micro Portland cement, conforming ASTM C150 type I.
β) Micro sand 600 μm, conforming ASTM C33-01.
χ) Fumed silica, the chemical composition is given in Table 1.
δ) Metakaoline clay (200-3) μm by burning kaoline clay up to 700°C for a period of 2 hrs. The chemical composition is given in Table 2.
ε) Wire mesh: welded square mesh used in the present work had an average wire diameter and aperture of 0.25 mm and 2.5×2.5 mm respectively. The yield strength Fy, elastic modulus Ew, and ultimate tensile strength Fu, were obtained using direct tensile tests. The test was conducted on wire mesh according to ACICode 549. The average values of modulus of elasticity (Ew), upper yield stress (Fy), and ultimate tensile stress (Fult) of wire mesh are 66100 MPa, 320.5 MPa, and 350 MPa respectively.
|200(160-240)||Specific surface, m2/g|
|3||Loss on drying, %|
|>99.0||SiO2- concentration, %|
|Burn Loses%||SO3 %||SiO2,Al2O3,Fe2O3%|
The nano cement mortar matrices considered during the present investigation may be summarized in the following groups:
• Group A: Micro sand/ micro cement ratio 1/ 1, 1.5/1, 2/ 1, 2.5/1, 3/1 with w:c ratio=0.4.
• Group B: Micro sand/ micro cement ratio 1/ 1, 1.5/1, 2/ 1, 2.5/1, 3/1, each with fumed silica (1% of micro cement by weight) and 10% of micro cement by weight was replaced by metakaoline clay. w:c ratio=0.4.
Compressive strength, the following tests were conducted according to ASTM C109:
a) Compressive strength at age of 28 curing days:
Twenty five 50 mm mortar cube specimens with mortar group A.
b) Compressive strength at age of 28 curing days:
Seventy five 50 mm mortar cube specimens with mortar group B.
Modulus of rupture:
The prisms considered in the present work are detailed in Table 3.
a) Four point bending tests were performed on 30 prisms 160×40×40 mm of mortar groups A and B after 28 curing days according to ASTM C348.
b) Four point bending tests were performed on 50 ferrocement prisms 500×50×t (t=4, 6, 8, 10 mm) using the developed nano cement mortar (Figure 1).
Each ferrocement prisms has been tested with its two ends simply supported over as span of 450 mm as shown in Figure 1. The load from a Universal testing machine with a capacity of 150 kN with a least count of 0.01 kN was applied. During the test, the deflections at the third point of the ferrocement prisms were provided by the testing machine with a least count of 0.01 mm. Each group of prisms was cast together with three cubes of 50 mm to determine the compressive strength (fcu) at a curing age of 28 days. The following expression is used to determine the deflection at mid span:
δ(1/2)-span = 1.15 δ(1/3)-points
Ultrasonic Pulse Velocity Test (UPV) for measuring static and dynamic modulus of elasticity: Ultrasonic Pulse transit times were measured by direct transmission method . This test was carried out according to reference . The Velocity of Ultrasonic Pulse transmitted through cubes 50 mm made of nano cement mortar as developed in the present investigation at 28 curing days to determine the elastic modulus of elasticity (static and dynamic) using portable ultrasonic concrete tester known as (PUNDIT). A thin layer of grease was applied on the surface to prevent dissipation of transmitted energy. The time of transit was recorded to the order of 0.1 microsecond and the path length was measured accurately in mm, after obtaining the pulse velocity (km/sec), then the elastic modulus can be estimated .
Tables 4 and 5 give the outcomes of the measured values of compressive strength fcu and modulus of rupture fr at 28 curing days. It may be noted that the normal cement mortar is usually used in producing ferrocement elements .
|Mix proportion (cement: sand) by weight||fcu (MPa) for normal cement mortar*||fcu (MPa) for nano cement mortar*|
|Mix proportion (cement: sand) by weight||fr (MPa) for normal cement mortar*||fr (MPa) for nano cement mortar*|
Compressive strength fcu=P/A in which P (N) is the maximum axial load, and modulus of rapture fr=3PL/2bd2 in which P (N) is the maximum flexural load, A=2500 mm2, L(mm) is the tested span, b=width of the prism (mm) and d=thickness of the prism (mm).
Table 6 gives the measured values of compressive strength of nano cement mortar used for producing ferrocement prisms, volume fraction of reinforcement Vf, specific surface Sr, (P/δ)av., Icomp., Ecomp., Mcr., and fr.comp. of ferrocement prisms after 28 curing days.
|Sep.||fcu (MPa)||Vf (%)||Sr (mm-1)||(P/δ)av. (N/mm)||I com (mm4)||E com (MPa)||M cr (N.mm)||f r-com (MPa)|
Table 6: Measured values of nano ferrocement prisms.
It may be noted that each of the compressive strength and modulus of rapture value is the average of three values and each of (P/δ)av is the average of two measured values of identical prisms.
Where, Icom is determined from the following expression:
Es: Modulus of elasticity of steel wire mesh
Em: Modulus of elasticity of cement mortar
N: Number of layers of mesh reinforcement
db: Diameter of mesh wire (mm)
h: Thickness of ferrocement panel (mm)
Dl: Spacing of wires aligned longitudinally in mesh (mm)
Dt: Spacing of wires aligned transversely in mesh (mm)
As it was mentioned above the static and dynamic elastic modules are determined from the curves given in Figure 2. The Ultrasonic Pulse Velocity (UPV) is determined using the following expression:
V: Ultrasonic Pulse Velocity (km/sec)
L: Path length (mm)
T: Transit time (microsecond)
The measured values of Ultrasonic Pulse Velocity and elastic modulus values are presented in Table 7 together with values of static and dynamic of normal ferrocement mortar given in reference [32,33].
|Mix proportion (cement/fine aggregate) by weight||Nano cement mortar as developed in the present investigation||Ordinary cement mortar used in ferrocement (reference )*|
|Pulse velocity (km/sec)||Modulus of elasticity (GPa)||Pulse velocity (km/sec)||Modulus of elasticity (GPa)|
Table 7: Measured values of static and dynamic modulus of elasticity.
In Table 8 the Pu/Pcr and the ductility ratio μ=δu/ δcr in which Pu, Pcr, δu and δcr are the measured values of first cracking, ultimate loads, and first cracking, ultimate deflections respectively of nano ferrocement prisms are tabulated.
|Spe.||Load, kN||Pu/Pc||Mid-span deflection, mm||µ = δu/δcr|
Table 8: Ductility ratio of nano ferrocement prisms.
In general, It is seen from the above tables that the highest values can be achieved by using cement mortar as developed in the present investigation with the ratio of sand/ cement=1.5.
In reference  tests were carried out to determine the flexural strength of normal ferrocement prisms with 22 mm thickness and 4, 6, 8, 10 wire mesh layers and mix proportion plain sand/ cement ratio of 1.5 and the measured flextural strength were 5.74, 8.42, 8.48, 10.9 MPa respectively.
It may be seen that the flexural strength values of nano ferrocement prisms as tabulated in Table 9 is higher than that of normal ferrocement.
|Spe.||t, mm||n||fr-com, MPanano ferrocement|
t: prism thickness, mm; n: number of wire mesh layers
Table 9: Modulus of rupture of nano ferrocement using sand/ cement ratio=1.5.
The mechanical properties of nano cement mortars as developed in the present work to improve ferrocement properties were experimentally investigated. The measured results showed that the compressive and flexural strengths measured at 28 curing days of the developed nano cement mortars were higher than that of a plain cement mortar. In addition, the flexural strength of nano ferrocement using nano cement as developed in the present investigation is higher than that of normal ferrocement prisms having 22 mm thickness and reinforced by 10 layers of wire mesh.