This invention relates to the process for the manufacture of rapid construction wall & floor modules & more particularly to such pre-engineered wall units which shall have provision for laying conduits tracks inside the modules for electrical cables, TV cables, computer cables and plumbing lines etc.
Rapid Construction Modules
INTRODUCTION
Panels in the building industry have been made with a variety of ingredients, and used with some specific property characteristics in mind. None of the available varieties have the comprehensive coverage of the wide range of properties desired in the final product. For versatility of application and consistency with various environmental and property requirements that come into play while ultimately selecting any of these panels a number of factors need to be considered. These factors could be the surrounding atmosphere with regard to humidity, temperature, ground conditions taking into account seismic activity, fungal exposures and incidence of termites, possibility of fire hazards in industrial and commercial applications, wind loads in turbulent atmospheric zones or areas with excessive rainfall, and similar aspects along with the customer preferences with regard to color, surface texture, workability on the products chosen. This leads to the creation of a variety of end-use segments for the prefabricated building products.
A review of the available options exposes the limited applicability of the different varieties offered in the market. Plywood panels which have been used for quite some decades, has time and again proven very susceptible to fire hazards, besides being poor in water resistance which gives swollen and aesthetically unappealing appearance leading to periodic repairs, replacements. They are poor sound barriers too.
Gypsum boards are rather fragile for load-bearing applications though they have some better sound absorbent property.
Resin-bonded boards with wood shavings do not have any significant fire retardant property and neither much water/moisture resistance because of the wood shavings content. Boards with the core of expanded polymeric plastic substrates are also not robust enough for usual load bearing applications and impact resistance, and are also rather unstable in the case of high temperature impact, and do not have any significant fire retardant property.
Deformation due to higher flexibility of the softer plastic core and quite often the appearance of cracks caused by impact on surface, or discoloring of the joints impairs the visual appeal too especially for the interior applications.
Durability of most of these available panels are not much when compared to traditional masonry walls, though it may be argued that most interiors generally
undergo some change with time, to comply with recent fashionable trends or alterations desired by corporate customers.
Pre-cast concrete panels are quite heavy and require quite heavy-duty material handling equipment while erecting walls. They are also difficult to work on with conventional hand tools.
Aerated concrete blocks and panels are comparatively lighter, but wall panels in large sizes are vulnerable to chipping and damage at the edges and also breakage due to low impact resistance in its basic form as a panel without strengthening claddings or adhesive covering substrates. The use of asbestos sheet claddings is not environment friendly with health hazard implications.
Generally, all panels recently available require significant labor-intensive repair-work during erection and skilled finishing operations to achieve aesthetically acceptable external cosmetic finish. Moreover they all subscribe to visible external wiring channels on the surface of the wall which are generally carried out once the wall panels are erected in position to form the wall or partition, resulting in repeated repair work, and aesthetically unappealing wiring channels running over the surface of the wall.
Considering the desired functional, aesthetic and property attributes of such panels, be it for interior applications or exterior facades, no available panel can be recommended as versatile enough to satisfy all the property parameters. There are various degrees of compromise or neglected exclusions on properties like strength and workability, insulation characteristics, lightness for easy handling, in-built features of concealed electrical wiring and plumbing lines, neat and smooth surface to minimize subsequent finishing operations to achieve the finished look to the satisfaction of the architects and fastidious designers.
INVENTION INCENTIVE
It requires careful selection of constituent ingredients, innovative planning of operation sequences, laying down strictly controlled processing parameters, as variations in one of these can result in a product with different or undesirable property characteristics in the final product.
It is with such specific considerations, the proposed inventive process has been established to offer a superior product hitherto unavailable in the market, offering a comprehensive wide range of properties from the extensive range of desired properties keeping in view the ever increasing customer demand characteristics, with special reference to the precisely controlled process sequence, operational parameters and ingredient characteristics.
This inventive and innovative planned process parameters enables the production of pre-engineered rapid construction modules with different core property characteristics based on the ingredient composition that consists of cement, pulverized fly-ash, lime, vermiculite, pearlite, cellulose fiber, PVA fiber, and even expanded styropor globules in certain cases, and an aeration agent.
The process involves the homogeneous mixing and blending of a specific grade of finely ground cement (OPC/Gr43) with silica-rich material in a pre-estimated proportion stated hereafter in the phased break-up of process highlights. It has been observed with extensive experimentation, that the proportion of constituents plays a significant role in imparting the finished property characteristics. Just the economic consideration to increase the proportion of low cost ingredient like fly-ash beyond one third of the total solids content adversely affects the final mechanical property characteristics of the said module core. The other constituents follow in a pre-defined sequence of well-researched operational timings before aerating the mixture, which goes to form the core of the lightweight module. This process sequence, unique combination of ingredients and the operational parameters established is a highlight of the invention procedure being hereby presented. The process parameters are enumerated in the following passages conforming to the established sequence of operations in this invention. The ingredient constituents can include different fibrous additives in the form of cellulose fiber or some man-made fiber in finely expanded fluff and/or expanded styropor globules or even a combination of these additives. With this hitherto unused ingredient content of cellulose / man-made fiber and styropor globules, along with the option of customized built-in conduit passages within the thickness of the modular unit, these rapid construction wall/floor modules become a unique new product.
A unique edge profile is also incorporated for versatile adaptability during erection, and it gives a neat flush wall appearance with only the switchboards visible for operation. The cladding material is chosen from environment friendly totally asbestos-free Fiber-cement sheets or Calcium Silicate sheets, or even compressed fiber-cement boards for more aesthetic and sophisticated exterior facades and interior appearances. The cladding material can also be customized to different colored fiber cement sheets to suit a clients color preferences. This will also enable to save on the subsequent surface preparation and painting expenses that follow, to provide the desired exterior or interior finish to the wall surface.
The precisely controlled procedure with attributed features to the finished panel is presented hereafter for process parameter information.
PROCESS FLOW
The process parameters are derived with priority consideration to the composition uniformity, reaction time for ingredients, and the ultimate property attributes desired in the finished Rapid Construction Module.
The solids to water ratio for this complete process is strictly controlled between 32:16 to 33:26. The solids content comprising of the ingredients like cement, fly-ash, lime, vermiculite, cellulose fiber etc. shall constitute 31 to 33 parts by weight as compared to 18 to 21 parts by weight of water. The water used in the process is also maintained within a controlled temperature range between 25-50 degrees Celsius.
For the desired quality of blending and mixing of ingredients selected, the process is split into specifically delineated different phases for precise quality conformity in the final composite Module. The phased break-up of the blending and mixing operations becomes necessary to make the process adaptable to different ingredient mixes that can cater to different core compositions. This also makes the process amenable to be customized to include additives to achieve customer desired product characteristics.
PHASED MANUFACTURING OPERATIONS
FIRST PHASE - Preparation of Basic Core-mix :
In the first phase, early high strength finely ground OPC/Gr53 Cement and pulverised silica-rich material of superfine mesh size is taken in a pre-determined ratio between 1.5:1 to 3:1 and constitutes the bulk portion of the solid content of the core-mix by weight. These are blended in a slow speed blender-cum-mixer along with the requisite proportion by weight of a mix of man-made and cellulose fiber or only one of these. In this first phase 60-75%, depending upon the constituent mix ratio, of the total water requirement at a controlled temperature is added. The cellulose / man-made fibrous content is added in the beginning of the phase to allow for the water absorption by the cellulose fibres if included as an ingredient, while being stirred in the blender. The cement is added dry in pre-weighed quantity thereafter. The powdered silica-rich material can be added dry or even as slurry. In that case the water constituent of 60-75% is broken up into two phases of addition at the controlled temperature range, wherein a part of the water is included in the slurry, and the balance of the total water requirement of this phase, at the same temperature, is taken in the beginning of the phase before adding cement. This mixture forms the basic core mix which is further mixed with other additives like Lime, Vermiculite, Pearlite and the aeration agent in precisely controlled batch sizes in the subsequent phases of the core mixing process.
SECOND PHASE - Adaptable / Customization phase :
The basic core mix from the first phase is then taken in a measured batch size to the main mixer where it is mixed with the next group of ingredients like Lime and the Vermiculite / Pearlite in a specified sequence :
a) 10 to 20% of the water requirement within the controlled temperature range is also added before the next additive is added in the mixer.
b) Powdered Lime in a pre-estimated proportion by weight of the total solids content (1 to 5 % ) is added while churning the mix.
c) Exfoliated vermiculite in a pre-estimated proportion by weight is added after a stipulated time of mixing, and the mixing continued thereafter for a short period of before the mix is ready for aeration.
d) The mix is finally ready for aeration to lighter density and small casting/pouring batches are pumped to the final blender or holding tank for aeration and subsequent pumping into specially fabricated stainless steel hoppers from which they are poured into the stack of multiple moulds of a batch waiting underneath the hoppers.
THIRD PHASE - Aeration and Moulding phase :
Aeration
The aerating agent in a desired concentration in solution with water at the desired temperature is hereafter added to small pouring batches of the mix in precisely calculated volume of the solution for every kilogram of solid contents of the mix and blended for a short period. Thereafter it is immediately poured into the waiting moulds and the expansion due to aeration is allowed to take place within the moulds.
Preparation of Mould
The rapid construction wall/floor modules are cast in precisely fabricated moulds that can be stripped after the setting and initial hardening of the core and reused for subsequent batches of production. These moulds incorporate the unique mating edge profile and also the provision for alignment grooves for vertical mounting assembly of the said modules.
The provision for concealed conduit passages, if desired within these rapid construction modules, is provided with precise orientation and alignment within the moulds and the finished module has only to be mounted with the visible switch board after drawing the wires through these conduit passages.
This provision for conduit passages, when desired by any customer, incorporated right at the stage of pouring the core mix, gives a finished module, ready with in-built conduit tracks for easy and quick wiring by the electrical contractor, thereby giving a neat flat surface and saving the cost of external wiring channels and covers.
FOURTH PHASE - Curing :
The curing of the said modules after pouring and testing thereafter forms the longest time segment for the production cycle-time for these modules. Any compromise in the minimum required timings for setting of the core mix and subsequent curing within moulds can affect the resultant strength characteristics of the final module. Special care is taken to ensure adequate moisture retention within the modules while the initial curing takes place, and also after the stripping of the moulds and subsequent stacking of the modules for the final prolonged curing period and hardening of the core. This is ensured by providing for moisture barrier enclosing of the stacks to retard water evaporation and prevent any rapid loss of moisture content.
The setting time and initial curing time is within the cladding cement sheets, held in the same stationary condition without any disturbance or movement for at least 9-12 hours. Thereafter the moulds and holding accessories can be stripped from the rapid construction wall/floor modules. Within 12-14 hours after pouring, the said modules are ready to be stacked vertically in curing bays under shower or in the ambient atmosphere with enveloping moisture barrier coverings for air curing, for the final curing period. The careful stripping and gentle handling operations thereafter are very strictly ensured to avoid any loss due to mishandling & breakage.
The said modules are stripped from the moulds after the initial setting and curing for minimum of 9-12 hours, and thereafter they are stacked vertically under showers for the final curing period of 25-28 days. This prolonged curing gradually builds up the maximum strength attainable in the core as well as the bonding between the skin sheets and the core. This also ensures minimal finishing/repairing operations at the time of erection.
Ensuring stage-wise quality parameters is of high significance, and every stage of operation is closely monitored, followed by interim sample tests with regard to desired property characteristics and documented for future reference and research data. Even a semi-cured said module after the initial setting and curing of 24 hours is tested at random for strength parameters and density assessment. After the 25-28 days of either water-spray curing or atmospheric air curing, final testing of the said modular unit is done for its structural strength and flexural rigidity besides the final density assessment.
PRODUCT CHARACTERISTICS HIGHLIGHT
It is the result of the unique selection of ingredient combination and strict enforcement of process and material quality parameters that the Everest Rapid Construction Module stands out as a novel innovative product with desired comprehensive property characteristics.
The general characteristic features of the rapid construction modular wall & floor units can be broadly enumerated below : -
a) Size of modular unit : 0.3Mx0.3M to 3.05Mx0.61 M
b) Thickness ranges of modules : 40mm - 125mm
c) Weight per Sq.Mtr. : variable from 34-35Kg/m2 to 90-95Kg/M2
d) Composite Density : 0.5 - 1.2
e) Flexural Strength : 50 Kg/cm2
f) Max Deflection (span=300mm) : 0.9-1.0mm
g) Water Penetration : Negligible, h) Linear Expansion : 1.2mm/Mtr.
The various aspects of product differentiation which can be highlighted are :-
1) Lightweight Modular Units - The Rapid Construction Module is lighter than other concrete panels considering the composite resultant density of the aerated core and the cladding sheets. These panels are 10%-15% lighter than other cement-concrete panels. The density offered can also be varied to some extent as per customer's requirement regarding the usage environment and strength requirements vis-a-vis the lightweight easy-handling feature of the module.
2) Ease Of Handling- Unique Edge Profile - Keeping in mind the ease of the erector and speedy assembly of the said modules, the mating edge details are so designed that the edges automatically align themselves holding each other, and the erector does not have to worry about the inner or outer face of the wall except, if the opposite faces of the said modules are differently colored. Upside-down or inside-out, anyway the modular unit edges mate and flush neatly.
3) Concealed Wiring - The said Modules also have unique in-built conduit tracks within the thickness of the panels and no external wiring and visible electrical wiring channels and covers need to be fixed over the surface of the panels which stands out as a protrusion on the surface of the said Modules and adversely affect the aesthetic appearance of a clean flat wall.
4) Vertical Assembly - The said Modules have the built-in provision for alignment strips in case increasing of the height of enclosures is required by mounting panels vertically above another. The same provision can be utilized for holding and aligning panels used for the ceiling wherever so chosen with the help of fixtures and accessories used for ceiling erection. These fixtures are also exclusively designed for ease of assembly and can be made available to the end user by Everest Industries Ltd.
5) Asbestos Free - The fiber-reinforced cement sheets or the calcium silicate sheets used for cladding as the skin of the said Modules are Asbestos-free and exhibit good fire resistance properties also. As the said Modules can be worked upon with general carpentry tools, the dust of the cladding sheets generated during sawing/drilling or similar working, pose no environmental health hazard as compared to the asbestos containing similar products and can be dispensed with as any other domestic dust.
PROCESS FLOW DIAGRAM RAPID CONSTRUCTION LIGHTWEIGHT MODULAR WALL & FLOOR UNITS.

We Claim :
1) Process for the manufacture of Rapid Construction Modules comprising
the following steps :
a) High strength finely ground OPC/Gr43 cement and Pulverized Silica-rich material of superfine mesh size is taken in a predetermined ratio of 1.5:1 to 3:1 and constitute bulk portion of solid content of core mix by weight blended in a blender cum mixer with 0.25 % to 0.8 % by weight of man-made fiber and/or cellulose fiber.
b) 60%-75% of the total water requirement at 25-50°C is added for fiber soaking, if cellulose fiber is chosen as an ingredient in the first phase.
c) Cement is added in pre weighed quantity, controlled by PLC (Programmable Logic Controller).
d) Silica-rich ingredient is added similarly controlled by PLC.
e) Cement & Silica-rich ingredient is mixed for pre-estimated period, forming basic core mix and then mixed with other additives in controlled batch size in the subsequent phases of said core mixing process. The said core mix is taken to main mixture with next group of ingredients in a specified sequence. 10-20% of water at 25-50° C is added before the next constituent is added in the mixture. Powdered line in a pre -estimated proportion by weight of total solid content to the tune of about 2-3% is added during the mixing in main mixture.
f) Exfoliated vermiculite in a pre-estimated proportion by weight is added after a specified period of mixing and further blended for a short duration. The said mix is finally ready for aeration to lighter density. Aeration is carried out here by the addition of the aerating agent. Small casting/ pouring batches are pumped to the final blender or holding tank for aeration & subsequently pumped into specially fabricated stainless steel hoppers & poured into stacks of multiple moulds having unique in-built matting edge profile and provision for alignment grooves for vertical mounting assembly of Modules. Provision for concealed conduit tracks within the thickness of the Modules is incorporated for easy & quick wiring.
g) Curing of Rapid Construction Modules.

2) Process for the manufacture of Rapid Construction Modules as claimed in claim 1 wherein blender is having slow speed below 60 RPM.
3) Process for the manufacture of Rapid Construction Modules as claimed in claim 1 wherein Silica-rich ingredient is added dry.
4) Process for the manufacture of Rapid Construction Modules as claimed in claim 1 wherein Silica-rich ingredient is added with 30 - 45% of water to form slurry.
5) Rapid Construction Modules as claimed in claim!
6) Process for the manufacture of Rapid Construction Modules as herein descptee*) with examples & flowchart.