The development, processing and application of Ferrocrete Channels within the context of sustainable development and building technologies has thus far been fairly successful. The process of manufacturing the channels, the materials used in this process and the livelihoods that are maintained through this process are of significant value. The ferrocrete channels, being currently propagated, are primarily used to replace steel girders and stanchions, and in this the outcome has been commendable. Currently, these channels are used in conjunction with the pre-cast ferrocrete vaults to make roofing structures. Therefore, the ferrocrete channels are inherently efficient and viable materials for building construction.
 
These channels, because of their design, cannot be used with the MCR roof tiles, as there are no provisions made within the structure of the channel for attachments to other support elements like rafters and purlins. The applications of these channels are also limited because of their bulk as large components, which means that they cannot be used for different purposes where smaller sizes of beams are required (like rafters and purlins). Further, these channels are not small-scale products and cannot be viably produced outside of large towns. Thus, the levies and expenditures associated with industrial production are reflected in the production of these channels. There is, therefore, a need to modify these ferrocrete channels so that they can compliment the MCR tiles by replacing timber as rafters/purlins and manufactured at the micro level.
 
Modified ferrocrete channels, when used to compliment the MCR tiles, result in the utilization of two appropriate products thereby illustrating the use of appropriate technology. The use of timber in roof construction is expensive and the extraction of timber from the environment has unfortunate repercussions at both the micro and macro levels. The modified ferrocrete channels would, thus, have all the advantages of timber (i.e. versatility, flexibility), at the same time being more cost effective and environmentally efficient. For example, when the cost of a cubic foot of cement (as compared to a cubic foot of timber) is at a ratio of 1:3 or 1:4 (etc.) then the use of cement becomes a more viable option. Further, ferrocrete mixtures comprise one-third cement and two-thirds fine aggregate, which is locally and readily available. Fine aggregate, being an inexpensive additive, offsets the cost of m.s. welded mesh that is used in the ferrocrete channels. Therefore it is more feasible, wherever possible, to replace timber products with appropriate ferrocrete products.
 
The practical solution to this problem is through simple modifications in the structure of the ferrocrete channel. The ‘I’ beam shape of the channel is appropriate for bearing roof loads, but with some changes it could become a more viable, efficient and appropriate building material, in conjunction with MCR tiles.
 
Ferrocrete Rafters and Purlins
The following suggestions, along with the diagrams, illustrate modifications to ferrocrete channels, using existing technologies, to make Ferrocrete Rafters and Purlins:
 
n The length of the ferrocrete rafters and purlins could be available in modular lengths of 1.0m, 1.25m, 1.5m (Fig. 1).

n The sections could be multiples of 35mm x 75mm or 50mm x 100mm and so on. By making the sections smaller and multiples of each other, the rafters and purlins become more versatile in their application. For example, where bigger sections are required these rafters/purlins can be stacked and efficiently joined together to form the required section. (Fig. 2)

n The modular rafter and purlin ‘I’ sections could be closed at both ends using ferrocrete with mild steel (ms) plates anchored into the ends. In this way, modular rafters and purlins can be welded end-to-end in areas where longer lengths are required. (Fig. 3, Fig. 4, and Fig. 5)

n During the process of fabrication, timber dowels could be inserted at regular intervals into the web of the ‘I’ section. These dowels can be removed later to expose holes through which ties (i.e. wire or rope) can be passed. An example of this is in the case of tying rafters to purlins or stacking them to make larger sections, a technique that is similar to conventional methods of timber construction used in villages.
 
Using the existing structure of marketing, these modified ferrocrete rafters and purlins can eventually replace timber beams, rafters and purlins in roof construction. Existing timber merchants can keep stocks of these products and actually enhance their trade by providing viable options to buyers. As these rafters and purlins are made in varying modular sizes, they can be lengthened and the depth and width can be controlled depending on structural requirements, making them an efficient alternative to timber. Ferrocrete products are durable, easy to manage and easy to store and although they are somewhat heavier than timber products, they are highly resistant to mishandling. Since ferrocrete production units can be locally set-up, managed and produced and since material and labour resources are also locally available, supplies for the merchant could be reliable and controllable. This would mean that the small-scale producer of the ferrocrete rafters and purlins would be more accountable to the merchant and builder and vice-versa, leading to a more efficient and reliable process of manufacture, trade and application. In contrast, reliance at the micro level on external resources such as the industrial sector, and timber suppliers (i.e. macro level) proves to be both inefficient and contrary to sustainable development.
 
By taking into account these suggested modifications to the existing ferrocrete channels, the resulting modular rafters and purlins would be feasible alternatives to timber beams for roofing construction. In the process, existing technologies and machinery, as well as local materials and resources can all be used and sustainable livelihoods can be maintained, especially at the micro level, as in the case of MCR tile production. Thus, the entire process of manufacturing, distributing, and applying ferrocrete rafters and purlins in conjunction with MCR tiles, maintains a system of sustainable development using Appropriate Technology. q

The Author is the CEO of Anangpur Building Centre, Haryana.