New paradigm : Bamboo for precast structures in road infrastructure
Col Atul Kumar
1.1 Bamboo, like wood, is a natural composite material with a high strength-to-weight ratio useful for structures. One of the most useful varieties of bamboos, Bambusa is native to the Indian subcontinent. Also famous as Indian timber or Bengal bamboo, it can reach up to a height of 15-25 feet and has a dull green color. Tropical bamboos generally grow taller and bigger than temperate bamboos and have thicker walls, which often results in better structural and mechanical properties
1.2 India is the world’s second largest cultivator of bamboo after China, with 136 species and 23 genera spread over 13.96 million hectares. According to the Union Ministry of Agriculture and Farmer Welfare, India’s annual bamboo production is estimated at 3.23 million tones. One of North East state Mizoram is said to be the Bamboo Queen of the country, The State has abundant natural bamboo resources which cover around 57% of its geographical area. With about 3,268 square kms of area covered by bamboo forests, Manipur is also one of India’s largest bamboo producing states.
2.1 To enhance quality & capacity builder the revue the infrastructure etc.
3. “BRC” GENERAL IDEA
(a) Concrete is the most widely used material in building construction. It is very strong in compression but weak in tension. Due to this, it is often reinforced with steel bars wherein these bars provide the tensile strength to the concrete. But use of steel as reinforcing material has some disadvantages like higher cost and non-renewability of steels. Apart from these, production of steel is responsible for a major source of greenhouse gas emission.
Hence, attempts are being made by several researchers to provide a low-cost sustainable alternative of steel by using locally available material. In this regard, many researchers investigated the possibilities of using vegetable fibers materials as reinforcement in concrete.
The typical vegetable fibers materials which have been studied in the past includes, jute, coconut coir, sisal, babadua, date palm, raffia palms , bamboo, and bamboo fibers etc.
Although most of these studies yielded good results still bamboo has a clear advantage over other natural reinforcing materials.
Bamboo is a fast growing wood-like substance belonging to the grass family Poaceae. It reaches its optimum strength in just three to four years and attains maturity in five years. The tensile strength of bamboo is very high and for some of its species the ultimate tensile strength is the same as the yield strength of mild steel while the strength to specific weight ratio is six times greater than that of steel.
Like steel bars, bamboo can take both tension as well as compression whereas many other vegetable reinforcing materials cannot carry compression loading. Furthermore, the energy required to produce one cubic meter per unit stress of bamboo is 50 times lower than the energy required by steel. Due to these properties bamboo has drawn the attention of many researchers for use as reinforcement in concrete.
(b) North East states in the extreme climatic conditions, development of National Highway infrastructure is progressing at a pace which was never seen before.
In the next few years, a Huge total of Rs. 1.5 lakh Cr. will be invested to seamlessly connect the 8 sister states (Incl Sikkim) of the North East to the rest of India.
(c) The precast concrete casting can be carried on simultaneously with other works on site such as earthwork, survey, etc. and thus saves time.
Quality Assurance: The key factors which regulate the quality of construction such as curing, temperature, mix design, formwork, etc can be monitored.
4. BAMBOO SELECTION
The following factors should be considered in the selection of bamboo culms (whole plants) for use as reinforcement in concrete structures:
(a) Use only bamboo showing a pronounced brown color. This will insure that the plant is at least three years old.
(b) Select the longest large diameter culms available.
(c) Do not use whole culms of green, unseasoned bamboo.
(d) Avoid bamboo cut in spring or early summer. These culms are generally weaker due to increased fiber moisture content.
5. TREATMENT Without proper seasoning and treatment of the bamboo, the material is vulnerable to fungus and insects. We can treat bamboo through a chemical process, which primarily uses borax and synthetic wood sealers. Or we can cure bamboo poles by natural methods, involving heat or saltwater and to increase the bond strength at the interface of the bamboo concrete composite. Adhesive Araldite has been used for treatment purposes.
6. “BRC” CASTING Precast 1 Mtr BRC model casted with 30 mm Bamboo strips with 100 mm spacing and concrete ratio of 1: 1.5 : 3 as under:-
Advantages of adopting “Bamboo Reinforced Concrete (BRC)” in precast structures in road infrastructure like R/walls, B/walls & Lined drains etc are as under-
a) Thinner sections Vis a vis Stone structures reduce material consumption.
b) Employment generated for locals in the NE region.
c) Durability and strength more than plain concrete.
d) Eco friendly.
e) Win win situation.
f) Manufacture of precast elements concurrent with commencement of early site work.
g) Expedited construction.
h) Reduce time on site.
i) Reduces site defects.
j) Reduces propping and scaffolding costs.
k) Lower site labour cost.
l) Reduce plant, amenities, tools and materials storage on sites.
m) Most precast products are trafficable after installation.
n) Uninterrupted manufacture of precast structures in any weather.
o) Concrete curing time will not affect project time.
In view of all the above advantages in terms of quality, environmental redundancy, simultaneity & economy in construction “Bamboo Reinforced Concrete (BRC)” in hill roads for R/walls, B/walls & Lined drains etc can be implemented in NE region to attain Win-Win environmentally conducive solution/impetus to the requisite infrastructure.
References: Elsevier journal, A. Agarwal et al. / Construction and Building Materials 71 (2014) 610–617.