Authors: Mr. M. K. Kamalakannan, K. Gowtham
Certificate: View Certificate
An improved qualitative arrangement of wire mesh which is thought to reflect more realistically the behavior of ferroce-ment in flexure is arranged. The presence of wire mesh reinforcement in ferrocement improves bending strength and crack resistance. The objective of the study is to investigate the behavior of material reinforced with varying mesh layers and orientations and to evelove its material properties. Tension tests were also carried out on meshes. Bending tests is to be conducted for specimen under two point loading. The effects of the varying reinforcement arrangements would replicates its response on strength and bending characteristics of ferrocement characteristics under tension and simple bending which to be studied experimentally, and those results also will be discussed in the paper.
Ferrocement is the composite of Ferro (Iron) and cement (cement mortar). Ferrocement can be considered as a type of thin walled reinforced concrete construction in which small-diameter wire meshes are used uniformly throughout the cross section instead of discretely placed reinforcing bars and in which Portland cement mortar is used instead of concrete. In ferrocement, wire-meshes are filled in with cement mortar. It is a composite, formed with closely knit wire mesh; tightly wound round skeletal steel and impregnated with rich cement mortar
With Ferrocement it is possible to fabricate a variety of structural elements, may be used in foundations, walls, floors, roofs, shells etc. They are thin walled, lightweight, durable and have high degree of impermeability. It combines the properties of thin sections and high strength of steel.
In addition it needs no formwork or shuttering for casting. Ferrocement have applications in all fields of civil construction, including water and soil retaining structures, building components, space structures of large size, bridges, domes, dams, boats, conduits, bunkers, silos, treatment plants for water and sewage.
II. LITERATURE REVIEW
A. Dr.T.S.Thandavamoorty and S.Durairaj Professor at Adhiparasakti Engineering college Melmaaruvathur
A hollow cored ferrocement floor panel of size 900 mm X 600 mm was precast with cement mortar 1:2 and cured for 7 days. Then it was arranged in a loading frame and tested under gradually increasing static loading till failure. The ultimate load sustained by the panel was 85 kN.
B. Mohamad Mahmood Civil Engineering department Mosul University Iraq
The paper describes the results of testing folded and flat ferrocement panels reinforced with different number of wire mesh layers. The main objective of these experimental tests is to study the effect of using different numbers of wire mesh layers on the flexural strength of folded and flat ferrocement panels and to compare the effect of varying the number of wire mesh layers on the ductility and the ultimate strength of these types of ferrocement structure. Seven ferrocement elements were constructed and tested each having (600x380mm) horizontal projection and 20mm thick, consisting of four flat panels and three folded panels. The used number of wire mesh layers is one, two and three layers. The experimental results show that flexural strength of the folded panels increased by 37% and 90% for panels having 2 and 3 wire mesh layers respectively, compared with that having single layer, while for flat panel the increase in flexural strength compared with panel of plan mortar is 4.5%, 65% and 68% for panels having 1, 2 and 3 wire mesh layers respectively. The strength capacity of the folded panels, having the particular geometry used in the present study, is in the order of 3.5 to 5 times that of the corresponding flat panels having the same number of wire mesh layers.
C. STRUCTURAL BEHAVIOR OF FERROCEMENT SYSTEM FOR ROOFING By Wail N. Al-Rifaie and Muyasser M. Joma’ah (1) University of Nottingham, U.K. and Professor Emeritus, University of Tikrit (2) Civil Engineering Dept, Eng. College, University of Tikrit
Experimental work: - Slab specimens S1 to S4, are square having overall dimensions of 500x500 mm. Specimens S1 and S2 are 20 mm thick, whereas S3 and S4 are 30 mm thick. Specimens S1 and S3 have two mesh layers while specimens S2 and S4 have four mesh layers. Hexagonal wire mesh with diameter of 0.7mm is used for both slab specimens and beam models. The moulds of slab specimens consists of a flat steel plate of which angle iron pieces having out-standing leg of 20 mm or 30 mm have been bolted to get square inside dimensions of 500x500 mm. Ink markings have been made all-round the inside periphery of the mould to indicate location of the mesh layers. The top surface has been leveled off by a trowel.
D. FERROCEMENT BOX SECTIONS-VIABLE OPTION FOR FLOORS AND ROOF OF MULTI-STOREYED BUILDINGS By A. Kumar Structural Engineering Division, Central Building Research Institute, Roorkee
A 5m x 9m size interior panel of a framed structure has been designed as beam-slab construction, flat slab construction and using ferrocement box sections for 5 kN/m2 live load. The self-weight, floor/ roof height and cost of these options have been compared. It is found that the flat slab option is comparable in weight to the beam-slab option, about 58.2% less in floor height and 17.7% costlier than the conventional beam and slab construction. The ferrocement box section alternative is found to be 56.2% less in weight, comparable in floor height and 15.6% cheaper than the beam - slab construction. The ferrocement box sections being light in weight need less strong supporting structures.
E. PERFORMANCE OF PRECAST FERROCEMENT PANEL FOR COMPOSITE MASONRY SLAB SYSTEM BY Y. Yardim, Universiti Putra Malaysia
This study investigates the performance of inverted two-way ribs precast ferrocement thin panel. The two-way inverted ribs in the ferrocement panel enhanced its flexural stiffness, as well as providing link between the precast layer and the in situ elements. Flexural behaviors of two precast panels and two composite slabs are investigated under two line load and distributed load. Test results indicate that the thin panel with suitable ribs layout and support distance can be used as permanent formwork. Typical load from construction worker and in situ elements could be sustained by the panel. The panel also acts as good composite component with in situ brick and concrete. Composite full slab can sustain typical design loads for residential buildings and until ultimate load and no separation or any horizontal cracks between the layers were observed.
III. MATERIAL AND PROPERTIES
A. Materials use Dinferrocement Structures
Skeletal steel in the form of angles, steel bars, welded wire fabrics or pipes. b) Steel wire meshes for forming cages. c) Rich cement mortar, as matrix in form of micro-concrete. All these three raw materials are those which are commonly used in practice in construction of conventional buildings.
B. Skeletal Steel
In the form of steel bars: Skeletal steel as the name implies is generally used to give basic shape and size to the structure. If used only to give the form to the structure, the steel rods may be spaced wide apart, say even up to 500 mm. When they are not treated as structural reinforcement, they also act as spacers to the layers of meshes. In highly stressed structures, where the skeletal steel acts also as reinforcement, their spacing will be as per the structural design of the structure. Steel bars of 4 to 10 mm dia. are generally used. Sometimes angle framework may be used to support the structure.
C. In Form of Welded bar Fabric
Welded bar fabric may be used as skeletal steel for Ferrocement panels of large size. A wide range of permutations of bar sizes and spacings is available, from which the required design can be chosen. Welded bar fabric is available for bar diameters from 4 to 10mm, with spacing of bars from 50 X 50 to 300 X 300 mm square or rectangular in shape.
Steel bars to be used should be according to I. S. Specifications as follows: i.Mild steel bars confirming to IS-432(Part I) 1982, ii.Hard drawn steel wires confirming to IS-432 (Part II) 1982 and iii.Hard drawn steel wire mesh fabric IS 1566-1982.
E. Practical Hints in Selecting the Skeletal Steel
i.The steel area particularly at the location of welding of cross bars should not be more than 50% of the cross-sectional area of ferrocement. It is observed that when large diameter steel bars are used or angles are used, temperature cracks are formed along the line of steel bars. ii.Bars of 6 or 8 mm diameter could be used for small structures, to maintain the rigidity of framework, the edge-bars may be 8mm dia. tor-steel, while the other bars may be 6mm dia. mild steel. iii.The following table 3.1 and table 3.2 will be useful in placing an order in the market for steel bars:
F. Steel Wire Meshes
Fine wire mesh reinforcement is the basic element of ferrocement, it controls the specific surface, which is an important factor in design. The number of layers of meshes, decide the thickness of the composite. Four basic types of meshes are in use. a. Weldmesh b. Fine wire mesh (woven square mesh/interlocked hexagonal wire mesh/Chicken wire mesh) c. Expanded metal. d. Crimped wire mesh
Welded wire mesh of rectangular pattern as shown in fig. 3.1 is formed by aligning wires perpendicularly and welding them at their intersections. Weldmesh is tied on skeletal steel framework and it provides a base for tying fine wire meshes on it. Its surface area is considered in calculating the specific surface of the composite. Weldmesh is designated by the spacing of wires or the size of openings, followed by the gauge of the wire in longitudinal and transverse directions. Thus a 100 mm x 100 mm x 12 g x12 g means a weldmesh of opening size of 100 mm x 100 mm and wire gauge used in longitudinal and transverse directions are 12 gauge. Weld meshes generally used in ferrocement structures are having opening sizes in mm as 25 x 25, 50 x 50,75 x 75, 100 x 100, and 150 x 150. The wire gauges may vary from 10 to 16. Rolls of weld meshes are available in widths of 900, 1200 and 1500 mm and in lengths of 15 m or 30 m
H. Cement Mortar
The matrix used in ferrocement primarily consists of mortar or micro concrete with hydraulic cement as binder, sand as fine aggregate and water. Normally the aggregate consists of well graded fine sand passing IS 2.36 mm sieve. If permitted by the size of the mesh and the distance between the mesh layers, small size coarse aggregate may be added to the sand. The mortar matrix usually comprises of more than, 90 percent of the ferrocement volume, and hence has a great influence on the behavior of the final product. Hence a great care should be exercised in choosing the constituent materials and in mixing and placing them.
The cement should be fresh, of uniform consistency and free from lumps and foreign matter. It should be stored under dry conditions for as short duration as possible. Types of cement are ordinary Portland cement of various grades, rapid hardening cement, sulphate-resisting cement, white and coloured cement and pozzolana cement. The choice of any particular cement depends upon the site conditions.
Generally Ordinary Portland Cement of 43 or 53 grades is used in ferrocement. In coastal areas or for structures exposed to sea water or acidic industrial wastes sulphate resisting cements are recommended. If sulphate-resisting cements or admixtures are not available, rich cement mortar should be used and later the structure should be coated. Cement content in ferrocement is higher than in conventional reinforced concrete. For Ordinary Portland cement IS 8112: 2015 and IS 12269: 2015 should be referred.
J. Aggregates: Sand
Well graded and washed river sand passing 2.36mm IS sieve is most commonly used as fine aggregate in ferrocement. The maximum size of aggregate depends upon the size of mesh openings and the spacing between the layers of mesh. For 13mm mesh openings, 1/4th its opening size, that is less than 3.25 mm, should be the maximum size of the fine aggregate. For proper gradation fineness modulus of sand should be between 2.4 to 2.5 for maximum grain size of 1.18mm and it should be 2.9 to 3.0 for maximum grain size of 2.36 mm. As shown in fig 3.5, proper control over the grain size and fineness modulus will result in the least water requirement, with better workability and higher strength. Grading of sand, with cement of 43 grade and aggregate as crushed sand confirming to IS 383-1970
K. Grading of sand for Grading zone II
Ttt Sieve Size
90 to 100
4 4. 8
75 to 100
55 to 90
35 to 59
8 to 30
0 to 10
The fine aggregate should be clean, free from organic matter and relatively free from clay and silt. Hard, strong and sharp silica will give strong mortar, while rounded grains of river sand will result in smooth mortar finishes. IS 383-1970 for coarse and fine aggregates from natural sources should be referred to for specifications of natural sands.
L. Crushed Sand or Manufactured Sand
Crushed sand is a good substitute for natural sands. It is manufactured from quarried rock, by bringing down its particle size in the range of 4.75mm to 150 microns. Crushed sand is quite different than stone dust, which is a waste from stone crushers. Crushed sand has two important features; one is its gradation and the second is its particle size. Crushed sands are successfully used for various grades of concrete from M15 to M40.
The mixing water should be fresh, clean and potable. It should be free from organic matter, silt, oil, sugar, chlorides and acidic materials. The value of pH should be close to 7.0. The salt water is not acceptable but chlorinated drinking water will do.
Chemical admixtures in ferrocement serve four purposes:
O. Proportioning of Cement Mortar
Normally rich cement mortars of mix proportions of (1:1.5) to (1:4) by volume are used in ferrocement. When sand content is increased, its water requirement goes up to maintain the same workability. To obtain strong, dense and mortars of such a consistency, which can easily penetrate the layers of meshes, trial mixes should be taken. Fineness modulus of the sand, water cement ratio and the sand cement ratio for the mix should be determined and used. Due to dispersion of wires throughout the body of ferrocement, problem of shrinkage is not there. Depending upon the method of application of mortar, its plasticity plays an important role. Normally the slump of cement mortars should not exceed 50 mm to provide stiff mortar mix, which can penetrate meshes. For most applications, the 28 days compressive strength of moist cured cement mortars should not be less than 35 MPa. Generally the mix proportions are specified by their weight but on small jobs mixes are made on volume basis. The bulging effects of moist sands must be allowed for, when the mixes are based on volume basis.
P. Practical Hints for Proportioning and Mixing of Cement Mortars.
Q. Guidance of Proportion of Mortar
A quick guide for various mortar mixes by volume measure and by weight
R. Cement Mortar mix by Volume
Dry mix of mortar = 1.33 x (wet mortar mix)
(Quantities per m3 of wet mortar)
Mix by volume
IV. ADVANTAGES OF FERROCEMENT
Ferrocement has following basic advantages over RCC
V. SCOPE OF FUTURE STUDY
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Copyright © 2023 Mr. M. K. Kamalakannan, K. Gowtham. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.