REINFORCED CONCRETE ELEMENT

Abstract: A system for walls and structural slabs is disclosed. It consists of units of a pre-cast reinforced concrete element that has a special form design, fabrication methods and utilisation. The element has a circular section, variable lengths and flat surface on the top and bottom sides (2). It has a sectional area of 4170 sq mm. The optimum preferred dimensions of the cross section are 64 mm high and 75 mm wide (1). The element has an optimum shape that reduces the materials used yet provides the structural performance required. When stacked vertically between two structural framing columns, the elements form non-load-bearing walls system (3). The elements form structural diaphragm when horizontally laid side by side in a butt-jointed manner, supported on both ends by means of structural framing beams. Plain concrete topping to the necessary thickness is cast over the diaphragm/elements, forming an integral reinforced concrete structural slab system (4). The elements are fabricated mechanically or manually. Manual fabrication using PVC moulds produces individual elements of various lengths. Machine fabrication allows production of jointed elements forming slabs of various widths and lengths.

Description: Reinforced Concrete Element 1 . BACKGROUND The following document describes an innovative technology in the design, fabrication and construction of a reinforced concrete element, referred to herein as Locrete. Locrete is used as a building construction material for walls and slabs in addition to few other functions. It presents an effective solution for the efficient use of reinforced concrete material and offers a substantial cutback in cost, time, equipment, formwork, labour and the need of extensive technical know-how. Generally, the main contributors to the cost of reinforced concrete include areas such as: □ Technical expertise, cost of design, supervision and skilled labor α Cost of materials and material handling o Equipment and labor □ Formwork and related labor α Construction time The predominant techniques used in reinforced concrete construction are mostly based on previously set models. The technical research on reinforced concrete as a building construction material is extensive with particular emphasis placed on its physical performance. Most of the applications in the field utilise heavy equipment, extensive amounts of formwork or a combination of bot Advanced technical know how is required but may not be readily available. All of these factors result in prohibitive or redundant costs. Locrete addresses some of the identified issues of the existing systems by maximising the benefits of the material and concurrently reducing its cost. The innovative design of Locrete and its mode of production and easy construction lead to a substantial elimination of some of the redundant cost factors that are deep-seated in the standard modus operandi. Locrete, as a building construction system, offers the following : α The elimination of formwork for reinforced concrete slabs, resulting in direct cost saving and a positive environmental impact. □ The elimination of mandatory use of heavy equipment, intensive labor and advanced technical expertise. α The substantial reduction in capital investment as a result of major savings achieved through the use of Locrete as an alternative building system. α Substantial reduction in the time required for fabrication and construction of walls and slabs. 2. DISCLOSURE OF INVENTION The proposed invention is a pre-designed, pre-cast reinforced concrete element that is characterised by its cross sectional form, variable lengths, mode of reinforcement and mode of production. The Locrete elements once combined, form a system. The system is used for construction of flat reinforced concrete slabs. In its individual form, the element can be utilised for other purposes such as walls of a building structure, partition walls, fencing, planters, tree support posts, pavements, retaining walls , etc. Locrete is easily produced, in fact, it does not require a major technical know how to either produce or construct. It is easy to transport and handle without the use of heavy equipment. Locrete is economical to fabricate and build and it is maintenance free. 2.1 Brief Description of Drawings Figures 1- 4 include model drawings illustrating the Locrete element designs, dimension and areas of utilisation . Figure 1 shows the sectional details of the Locrete element. The mould details, slab alternatives and wall sections. The gross sectional dimensions are 64 mm high and 75 mm wide. The cross section area of the element is 4170 square millimetres. The length of the element varies anywhere between 100 mm to 5000 mm. The gross width and height of the cross section can be varied to suit the required increase in the bearing capacity of the elements. The system allows optimal combination between the element cross sectional dimension and its bearing capacity. Generally the only constant in the cross section is its design form. The element dimensions are the inventor's choice. They are the dimensions used in the structural analysis enclosed in Appendix ii). The linear metre weight of a single element, the load bearing capacity, the square metre cost are prime factors dictating the choice of the said dimensions. Figure 2 presents a three dimensional representation of the element . The top and bottom of the cross section are made flat to allow the construction of the elements in the vertical direction as walls or the horizontal direction as slabs. Figure 3 shows a three dimensional representation of the potential areas of use of the element in building construction, such as walls, floors, roofing slabs, fences, planters, etc.. Figure 4: shows the details of a roof slab with Locrete elements supported by the structural frame, beams and columns. The Locrete elements in turn support the topping cast in situ concrete producing a monolithic roof slab of the Locrete system. 2 .2 Reinforcement Deformed steel bars are used for the reinforcement of the elements. The diameter of the steel bars could vary from 6 mm to 12 mm depending on the desired length of the bar and the required bearing capacity. In mechanised production pre-stressed steel reinforcement can be used, in which case the span and bearing capacity of the element can be increased without any addition in the raw material. 2.3 Weights in Units of Length The following table is based on a specific gravity of 2350 kg/cubic meter Length Weight in kg 0.50 meter long 04.90 1.00 meter long 09.80 1.50 meter long 13.70 2.00 meter long 18.60 2.50 meter long 24.50 3.00 meter long 29.40 3.50 meter long 34.30 4.00 meter long 39.20 4.50 meter long 44.10 5.00 meter long 49.00 2 . 4 Crushing strength Depending on the structural requirements of the element, the Locrete units crushing strength can vary between 25 K e.g. for walls to 40 K as in roof slabs. 2 . 5 The concrete mix The physical characteristics of the ingredients; sand, gravel, cement, water and the weather temperature are basic contributors to the mix proportions. In most cases the crushing strength of the concrete shall be the decisive factor in identifying the various proportions of the mixes. Appendix i presents a table suggesting the concrete mix design to be used for building a pilot project. 2.6 The structural design parameters The Locrete element has an optimum shape to reduce the materials used without compromising the required structural performance. The element is designed utilising the requirements of the ACI-318 code of practice. Appendix ii; shows tables of calculations identifying the various structural design parameters for Locrete and the equation used in the design calculations. 3. MODE OF PRODCUCTION 3.1 Manual Production: The manual production is well suited for a limited production of the Locrete elements. For an individual, wishing to construct his/her own home unit, the means and the process of production are simple and straightforward. In fact any one person can produce Locrete elements in his/her own backyard. The technique is dependent on moulds made out of material that allows multiple use and minimal deterioration . Locrete elements are produced as follows: α Procurement or fabrication of moulds α Arranging moulds in batteries □ Placing reinforcement steel α Mixing of concrete □ Placing concrete in the mould and vibrating as per standards. □ Casting the reinforced concrete α Curing and storing The first step is crucial in the process. Since the invention is intended to minimise the cost of reinforced concrete, it is important that the mould material is obtainable and that moulds fabricated from such material can be repeatedly used without deterioration. The most suitable materials found for the purpose are GRC or GRP or PVC or Polyethylene moulds cast to the form. The PVC or Polyethylene moulds are made in one piece. And because the mould material is flexible, it allows casting of formwork without disturbing the moulds and or the elements. Moulds may be fabricated to order by any PVC pipe extrusion factory. If pipes of the required measurements are available they may be cut to the form shown in Figure 1. Moulds are arranged on specially prepared level casting floor. Reinforcement is set in position. Concrete is then mixed and cast into the moulds. Small size vibrator may be used to vibrate the concrete. Concrete shall be retained in the moulds for a period of three days, during which time the concrete will be regularly cured. The elements would be cast off the moulds and stacked for future use. The moulds will then be rearranged for another cast. It would be beneficial if the Locrete units are cast to the lengths required. This can be easily achieved by means of restraining the mould on both ends with removable wooden planks. Reinforcement bars are laid in the mould and suspended in the required position by means of thin tie wires. The wires keep the reinforcement bars properly positioned while the concrete mix is poured. The reinforcement bars protrude beyond the wooden planks on both ends of the moulds through a hole that is provided for the purpose. The length of the steel protrusion is a matter of choice and will be used to better tie the Locrete bars to the structural frame. The structural frame can be pre-cast concrete and or cast in situ columns and beams, bearing walls, or steel frame 3.2 Mechanised mode of production The mechanised mode of production of the Locrete elements allow production of either: α Individual elements of lengths that are limited by the span, the deflection allowed and the bearing capacity required, or □ Attached units forming slabs as in Figure 1 with any practical width that is limited by the width of the machine and the casting bed, and to the length that is limited by the safe span and bearing capacity required of the slabs in production. The factory set up can be similar to the production line of the hollow core slabs. It follows the same principles of mixing, handling and casting of concrete, i.e. concrete extrusion kind of operation. The reinforcement bars for the elements are either normal tension bars or pre-stressed bars. The specifications of this invention show the design calculations of the normal reinforcement bars. The performance of the reinforced concrete element is analysed for normal reinforcement and presented in appendix ii. In case of mass production for wide scale commercial purposes, the elements are produced in slabs of various widths and lengths. The slabs range from 1 meter long up to 5 meters long and the width is anywhere between 0.6 meter wide up to 2 meters wide. All dimensions will be limited only by the deflection allowable in relation to the length of the slabs. The elements can be stacked in a storage yard and sold on order. This allows spontaneous delivery of required material thus contributing to substantial reduction of construction time. For more efficient operation, slabs or wall elements can be produced to lengths and widths extracted from any building design drawings that are suited to the system. 4. APPLICABILITY : Mode of Construction The two main uses of the elements are for constructing walls and structural slabs. In the first case, the Locrete units can be built with or without mortar, depending on the final treatment of the walls. (Figure iii). For the slabs, the Locrete units will have to be built on structural frames that are either cast in place, or pre-cast or steel frames (Figure iv). After arranging the Locrete units or slab units in place, the concrete topping shall be poured to the thickness required. 4. 1 Walls In wall construction the element is built horizontally, with or without mortar. In both cases the Locrete units shall be restrained on both ends by means of a properly sized groove in the concrete columns. The Locrete elements are laid horizontally. They are either dry or with mortar. The elements will be stacked one on top of the other. The flat face on top of the unit will act as a base for the following unit. Dry construction of Locrete elements on walls i.e. without mortar mandates that the elements will be plastered in order to weather tighten the walls. Casting the concrete framing columns on site after building the Locrete elements will allow an integral structural bonding between the Locrete elements and the frame. This adds substantial structural rigidity to the building frame. If the columns are built in situ ahead of the Locrete elements, then the Locrete elements will have to be bonded to the columns by means of mortar. Enough space will be provided in the pre-moulded groove in the column to allow for the bonding mortar. Windows may be opened in the wall simply by casting the Locrete units to the specific dimensions of the design to allow the window opening to be formed. The Locrete elements on the window sides are cut to size on site or better pre-fabricated to the required lengths. No special framing system is required for the windows and no lintels will be needed. The Locrete elements once plastered will produce the required window frame thickness. Depending on the insulation standards required for the building, the necessary insulation material is constructed. Alternatively if the insulation of the exterior is not required, the inner face may be left without any treatment and / or may be plastered to produce a good internal finish face with plaster and paint as per the standard practice. Depending on the design requirements, the exterior walls can be clad with marble, stone, granite, bricks or can be plastered and painted. Locrete elements can be used as internal partitions too. 15-millimeter thick plaster on each side of the partition will produce a 100-mm thick partition wall. 4.2 Structural slabs The Locrete elements are used in the structural slabs as follows: Based on the slab plans and the finishing beneath the slabs, the length and the reinforcement of the Locrete elements are decided. All fabrication of the elements shall be to the pre-designed, required length. Moreover, cutting the elements to the required length on site is easy and can be achieved by means of an electric disc saw. In such case some waste will have to be allowed for. The Locrete elements are laid horizontally in a butt-joint manner to the full length and width of the slab area. If the clear span between the two end supports of the element is more than 2.5 meters, an intermediary support will have to be temporarily provided until the plain concrete slab topping of the Locrete units is poured and cured. Details of the structural characteristics with normal reinforcement are provided in Appendix ii. 4.3 Other Functional Utilisations Further to the established functional utilisation of the Locrete element in the building construction there are other areas of use that are also functional, these include: □ Fencing posts and runners α Warehouse wall closure. □ Warehouse roof trusses α Shoring panels closing between vertical structural supports. □ Pavements substructures α Fruit trees groves and vineyards. 5. COST IMPLICATIONS : Comparative Analysis The following table and figures draw a comparative analysis between the Locrete element and other concrete products, emphasising the economic implications Table 1: Walls and Slabs Analysis Based on the above table: α Locrete walls are 61.60% of the standard 100mm thick sand cement blocks. □ Locrete slabs are 42.37% of the standard 120mm thick reinforced concrete slabs. Cost analysis of one cubic meter of Locrete 1 α Concrete material $ 42.00 □ Reinforcement steel 55 kg. @ $ 249 / Metric Ton $ 13.695 α Allow for casting, curing and transport to site $ 15.00 α Allow for site handling and construction in walls $ 15.00 α Subtotal cost / cubic Meter $ 85.695 α Add 25% for over head and profit $ 21.42 α Locrete total cost / cubic meter $ 107.20 The following logistic factors are not catered for in the calculations: Walls α The block work construction is a wet trade. Locrete on the other hand is a dry trade. This will minimise the messiness on sites and will save on water consumption. □ The block work requires plastering in most cases considering the aesthetic side of construction. Locrete can stay without plaster on the interior when providing for low cost housing, and still maintains an aesthetically acceptable look, α Block work requires seven days curing time before it is allowed to be plastered. Locrete can be plastered instantly. □ Transportation and mechanical handling costs are also reduced when simply considering that light and less material will be transported. Slabs □ The labor rate for the carpenters forming slabs estimated at a minimum of US$ 42.80 per cubic meter is eliminated with the Locrete system □ The need for wood and other sundries for formwork at US$ 18 per cubic meter is also eliminated. Cost is calculated on basis of Kuwait market prices α A minimum of 30% of the concrete used in the similar span solid slabs will be reduced by one third, yielding a saving in concrete quantity and in reinforcement of US$ 35.00/ cubic meter. α Total direct saving of labor, formwork and the reduction in quantities in slab concrete and reinforcement steel is US$ 95.80 This will produce a yield saving of approximately 64% of the prevailing cost of cubic meter of concrete of the classical slab system. In consideration of the substantial direct saving in quantities, there is an indirect saving effect that results from the reduction in the concrete and reinforcement quantities and the dead load resulting from the partitions. A proportional reduction to the foundation and the framing structure will result from the elimination of dead weights on walls and on slabs. This will yield a minimum saving of 25% of the concrete and reinforcement value for the foundations and the framing of the structure. US$ 15.00 per cubic meter in the foundation and the framing system are allowed for in this calculation. To that, one need to add the benefits listed under the previous point of analysis. 6. CONCLUSION Reinforced concrete is globally considered one of the most utilised material in the construction industry. It is also expensive to acquire in its final form. People in the low- income bracket are the first to suffer from this factor. The introduction of Locrete is meant to reach such segment of the world population by giving them a cost-effective and economically viable solution in order to address the issue. The Locrete solution will help build more for less time and money. Locrete curbs the difficulties involved in the technology to a major extent. It does not eliminate all the problems but makes the solution much more attainable by the end user. It provides a standard solution to the walls and slabs in any standard structure and in particular modular structures. The fact that the formwork for slabs, and in many parts of the world for wall construction, is relatively eliminated, a major saving on the use of wood for concrete construction purposes is achieved. This, on its own merit, will reflect positively on the issue of world forestry depletion. 7. APPENDICES Appendix i Table 1: Concrete mix design for the pilot project Type of concrete K40 Type of cement OPC. Type of mix PRODUCTION Water/Cement Ratio: W/C: 0.44 Aggregate/Cement Ratio: A/C: 3.96 □ 3.5% of the sand cement weight polymer is added to the mix to achieve early curing. Appendix ii : Structural parameters and analysis of the Locrete element under different conditions The design of the element considers the loads and stresses from the following stages: □ Handling □ Casting of concrete topping □ Full service loading in its permanent location The element is designed utilising the requirements of the ACI-318 code of practice. The reinforcement percentage in the section is calculated as per the following equation: As = p bd 100 p = steel percentage fy = steel yield strength fc' = concrete cylindrical strength at 28 days φ = 0.9 Deflection limitations as governed by the limits stipulated in ACI - 318 Code of Practice, Chapter 9. Other criteria like general detailing, cover to reinforcement etc. are as per ACI- 318 Chapter 7. Local code requirements can be implemented keeping the ACI requirements as the minimum acceptable. Notes: □ "a" is the top and bottom flat face dimension of the Locrete element. "As" is the area of steel section used in reinforcement of the Locrete units. "d" is the dimension from the bottom of steel reinforcement to the element top face. α The structural design tables are formulated to provide alternatives of cross sectional dimensions, reinforcement, lengths and load bearing capacity. The tables enables the user choose the optimum dimensions of the cross section, the length of the element, The reinforcement and the thickness of the topping required to safely achieve the loading criterion within the permissible deflection limits. Locrete: optimisation table and tnals for various options Table 1 : section properties dame 7 51 [ depth I 64 | cm2 cm cm4 cm cm kg/cm2 kg/cm2 kg/cm2 cm kg-cm 13 Table 2: Maximum Element Span Before Cracking Table 3: Variation of Reinforcement Steel Diameter, Concrete Topping, Element Length, Allowable and Actual Deflection and Load Bearing Limit Table 3: cont'd Table 3: cont'd Table 3: cont'd LOCRETE DESIGN DRAWINGS α Figure 1/4: Details for wall & ceiling moulds cross section dimensions, wall & ceiling element cross section dimensions, pre-cast slab and walls cross sections representation, individual elements slab cross section representation. Q Figure 2/4: 3-D representation of element in walls. □ Figure 3/4: 3-D representation of element applications in walls, slabs, internal partitions, fence and planters etc. α Figure 4/4: 3-D representation of element and topping in roof slabs.

Claims: THE CLAIMS The claims defining the invention are as follows: 1. A pre-cast reinforced concrete element comprising a particular design in terms of form, dimensions, single bar reinforcement and method of fabrication and construction. The pre-cast reinforced concrete element of claim 1 with its specific cross section design and dimensions, provides an optimum form that renders efficient utilisation of the pre-cast reinforced concrete material, in that it reduces the material used while it fulfils the requirements of the structural performance. The pre-cast reinforced concrete element of claim 1, when combined, forms a non- load bearing wall and structural slab system. 4. The wall and structural slab system of claim 2 wherein walls are constructed by stacking the elements in vertical direction with the flat surfaces horizentally laid and the ends of each element are fitted with sand-cement mortar in a specially provided groove in the framing columns. 5. The wall and structural slab system of claim 2 wherein slabs are constructed by horizentally placing individual elements in a butt-jointed manner, supported on both ends by structural framing beams to form a diaphragm , over which plain concrete of predetermined thickness, is cast in situ to achieve a monolithic structure. 6. The pre-cast reinforced concrete element of claim 1, when manually produced, is best poured in moulds made of PVC or similar durable, reusable material . A pre-cast reinforced concrete element substantially as herein described with reference to the accompanying drawings.

Inventors: KASSIS FAHIM, KASSIS, FAHIM
Applicants: KASSIS FAHIM, KASSIS, FAHIM
Application year: 1999
Main classification: E04B2
IPC codes: E04B2, E04B5, E04C2, E04C3