16-Sep-2021: Low carbon bricks developed using construction and demolition waste for energy-efficient walling envelopes
Researchers have developed a technology to produce energy-efficient walling materials using construction and demolition (C&D) waste and alkali-activated binders. These are called low-C bricks, do not require high-temperature firing, and avoid the use of high-energy materials such as Portland cement. The technology will also solve the disposal problems associated with C&D waste mitigation.
Conventionally, building envelopes consist of masonry walls built with burnt clay bricks, concrete blocks, hollow clay blocks, fly ash bricks, lightweight blocks, and so on. The envelopes spend energy during their production, thus incurring carbon emission (i.e., possess embodied carbon) consume mined raw material resources which lead to unsustainable constructions. The masonry units are manufactured either through the process of firing or using high-energy/embodied carbon binders such as Portland cement. As a result, the annual consumption of bricks and blocks in India is about 900 million tonnes. Besides, the construction industry generates vast amounts (70 – 100 million tonnes per annum) of construction and demolition waste (CDW). In order to promote sustainable construction, two important issues need to be addressed while manufacturing the masonry units – conserving mined raw material resources and emission reduction.
Moving towards this target, scientists of the Indian Institute of Science (IISc) developed a technology for producing alkali-activated bricks/blocks by utilising fly ash and furnace slag. The team of researchers developed low embodied carbon bricks from CDW waste through an alkali activation process using fly ash and ground slag and characterizing the thermal, structural, and durability characteristics of Low-C bricks and their masonry. After ascertaining the Physico-chemical and compaction characteristics of the CDW, the optimum mix ratios of the materials were obtained, and then the production process was evolved to produce low-C bricks. Based on the optimum binder proportions, the compressed bricks were manufactured. The bricks were examined for engineering characteristics.
The major beneficiary of this development undertaken by IISc Bangalore with funding from the Department of Science and Technology, Govt. of India, is the construction industry in general and the building sector in particular. This technology will also mitigate the disposal problems associated with the C&D wastes.
“A start-up has been registered which will be functional within 6-9 months to manufacture low-C bricks and blocks with IISc technical help. The start-up unit will act as a technology dissemination unit through training, capacity building, and providing technical know-how for establishing such commercial units across India,” remarked Prof. B V Venkatarama Reddy, IISc Bangalore.
15-Sep-2021: High-quality transparent ceramics developed for the first time in India can be used in thermal imaging and personal protection equipments
Indian researchers have developed transparent ceramics, reaching theoretical transparency through a technique called colloidal processing followed by simultaneous application of temperature and pressure, for the first time in India. The material can be used for thermal imaging applications, especially in harsh service conditions and personal protection systems such as, helmets, face shields, and goggles.
Transparent ceramics is a new class of advanced materials with unique transparency and excellent mechanical properties. These materials can be designed not only for transparent to visible light but also for ultraviolet (UV), Infrared (IR), and Radiofrequency (RF), giving opportunity for diverse applications. Though produced by different countries globally, transparent ceramics are restricted in supply as they can be used for strategic applications. Though several attempts were made in the country, the transparent ceramics produced were either on a laboratory scale or low transparency. Currently developed process is able to produce the sizes usable for several applications and on a pilot scale.
Generally, prepared from the high purity powders through a line of critically engineered processing steps, transparent ceramics needs preparation processes that will help achieve theoretical transparency by eliminating defects. Chemical Vapour Deposition (CVD) involving reactions of the precursors in the vapor phase at elevated temperatures and Hot Isostatic Pressing (HIP) involving simultaneous application of temperature and pressure are a few advanced processing techniques generally practiced to address the above challenges. An enhanced diffusion process at high temperature under pressure is suggested as the possible mechanism to eliminate the defects.
Researchers at the ARCI have produced magnesium aluminate spinel ceramics with colloidal processing followed by HIP technique which involves the simultaneous application of temperature and pressure. Spinel is currently emerging as a transparent ceramic based on the outstanding optical properties of transmission – more than 75 % in the visible and more than 80% in the infrared range. It also has higher strength of 200 megapascal and hardness of more than 13 Gigapascal. This research has been published in the journal ‘Materials Chemistry and Physics’ recently.
With potential applications in infantry personal protection systems involving thermal imaging such as helmets, face shields, and goggles, these transparent ceramics developed in India is a step towards Atmanirbhar Bharat.
10-Sep-2021: Noise Control Sheet Absorber developed by mimicking bee hives
An Indian researcher has fabricated paper honeycomb and stronger polymer honeycomb structure as sound-absorbing panels that dissipate acoustic energy to low-frequency ranges. The technology can be used in building acoustics and also as environmental noise control solution.
Many traditional materials have been found to be good at controlling higher frequencies. However, natural bee hives have been found to efficiently control high as well as low frequencies because of their geometry. It has been found from theoretical analysis and experimental investigations that this behaviour was owing to the conversion of acoustical energy into vibration energy. This vibration energy is dissipated in the form of heat due to wall damping property. Mimicking this property as an engineering solution could offer a cost-effective method for controlling noise pollution.
Dr. B. Venkatesham and Dr. Surya, faculty at Mechanical and Aerospace Engineering Department at IIT Hyderabad, fabricated low thickness and strong acoustic panels mimicking this property using biomimetic design methodology. The design methodology involves understanding the physics of bee hive sample acoustic energy dissipation and then mimicking its design. The team developed a mathematical model and calculated optimized parameters, and then fabricated the test samples using systematic, controlled parameters. Subsequently, fabrication of a large sample was done. They have used two different approaches and their respective prototype machines with two different kinds of materials. One prototype is for paper honeycomb based on indexed -Honeycomb Before Expansion (HOBE) process, and another prototype machine is for polymer honeycomb structure based on hot wire technique.
The panels were made by slicing stacked extruded polypropene straws. The slicing process is done with the help of hot wire, which also bonds the straws together. The developed technology provides a mechanism of acoustic energy dissipation with lower thickness and higher specific strength of acoustic panels. A test facility to measure the absorption coefficient of large samples has also been established as part of this work.
This technology, supported by the Advanced Manufacturing Technologies programme of the Department of Science & Technology (DST), Government of India, is in the 6th stage of Technology Readiness Level, and Dr B. Venkatesham has allied with Eaton PVT Ltd, Maharashtra Industrial Development Corporation Kharadi Knowledge Park, Pune. He plans to further scale up the technology demonstration, develop a batch production machine for polymer materials, fabricate with newer alternative self-damping materials, and compliance with other safety requirements like flame retarding capacities, weather ability and so on. Dr Venkatesham says that it may create an opportunity to capture 15% of the traditional sound-absorbing acoustic material market based on the low-frequency applications.