Indian Concrete Journal

Life cycle assessment as a tool in sustainability assessment of concrete systems: Why and How? Anusha S. Basavaraj, Ravindra Gettu

The production and use of concrete are responsible for natural resource consumption and adverse environmental effects. Evaluating sustainability aspects of concrete could help the industry identify processes with higher impacts, and work on them to perform in a holistic manner. This paper explores the environmental impact of concrete, with the evaluation based on the life cycle assessment (LCA) technique, the principles of which are outlined with illustrations relevant to the production of concrete. The synthesis of the LCA literature reveals that differences in goal and scope, system boundaries, inventory data, and impact assessment methods can induce significant variations in the environmental impact results. The justification is detailed as to why the carbon footprint and the embodied energy are used as the impact indicators. Further, the impacts of the different constituents of concrete and their contributions are discussed briefly. Finally, a framework, denoted as ‘ab initio’, for the LCA methodology, is proposed to assess the environmental impact of concrete, which could be adopted in cases where data is not readily available. This framework can be extended to any other systems, including concrete system components or products, such as blocks, prefabricated elements and recycled aggregates.

Performance assessment of calcium nitrite based corrosion inhibiting admixture in reinforced concrete Suresh Chandra Pattanaik, Sanjaya Kumar Patro, Bitanjaya Das

The durability of the reinforced concrete structures in the marine environment can be achieved by adding corrosion inhibitors in the concrete mix. Performances of concrete specimens were evaluated for control and having corrosion inhibiting admixtures of calcium nitrite at 30 % concentration of the active ingredient without induced corrosion environment. The various tests performed were concrete resistivity, rapid chloride permeability test (RCPT), compressive strength, and microscopic analysis of concrete specimens at normal exposure condition. The reinforced concrete specimens were prepared of M30 grade concrete with and without calcium nitrite based chemical admixture of varying dosages of 1 and 2 % by weight of cement. The corrosion probability was found low and negligible in concrete specimens with corrosion inhibiting admixtures as compared to control samples when tested for electrical resistivity. There was also marginal improvement in the 28-days compressive strength of samples having corrosion inhibiting admixture as compared to control samples. Alternatively, no such appreciable improvement was noticed in any samples made with corrosion inhibiting admixture for corrosion resistance while tested by RCPT. Thus, the RCPT result may mislead the performance of inhibiting admixtures to protect the corrosion in reinforced concrete. Moreover, the concrete resistivity test reveals the effectiveness of inhibiting admixture in corrosion prevention of reinforced concrete. Further, the microscopic study by petrographic examination disclosed that samples made with corrosion inhibiting admixture helped to reduce shrinkage cracks, reduces air voids and strong bond between aggregate-cement paste as compared to control sample.

A nanotechnology approach on self-cleaning material: A review Naveen Thakur, S.B. Singh, Anshuman

As we know that mostly pollution comes from the industry and the vehicles have badly affected the aesthetic view of structures. Cement manufacturing mainly emit much CO₂ (carbon dioxide) into the atmosphere, contributing to global warming. Because of climatic changes caused due to global warming, innovative concepts are needed to control the performance measures of sustainability, stability, and safety to the development of civil engineering. Nanotechnology is an essential method for increasing the durability of cement-based products. This study reviews the problem, challenges and benefits of selfcleaning construction materials. Recently researches based on self cleaning materials have provided option for traditional concrete use. Researchers conducted numerous investigations regarding self-cleaning concretes. Self-cleaning concrete would be a viable option for creating a cleaner environment that contributes towards sustainability and environmental protection. The incorporation of photo catalytic elements like zinc oxide (ZnO) and titanium (TiO₂) induces the concrete’s self-cleaning characteristics. First the photo catalysts in self-cleaning concrete are powered by ultraviolet (UV) radiation, Secondly, photo induced hydrophilicity makes it look clean, the pollutant is organic and causes dirt over the surface, It is easily removed by rain fall or manual rinsing. As a result, the integrity of buildings could be sustained, and air pollution in the surrounding area could be reduced. It is concluded that Bi₂O₂CO₃ photo catalyst gives better result in self cleaning than TiO₂

Assessment of a methodology for design of SCC mixes by robustness studies Sunitha K. Nayar, Premavathy A., Manu Santhanam, Ravindra Gettu, Pascal Boustingorry

A major deterrent to the large-scale use of self-compacting concrete (SCC) in the industry has been its limited robustness or susceptibility to deviate from expected performance with slight errors in the proportions of the constituents. In this study, a methodology for SCC mix design, which includes the empirical optimization of the phases, and subsequent assessment of the robustness of design SCC mixes by an experimental program, is presented. The mix design strategy involved separate optimization of paste and aggregate phases. The SCC mixes were developed with raw materials, including binders and aggregates, from two different geographical regions in India. Robustness assessment was done by varying the water content by ± 10 kg/m³, keeping all other proportions as constant. It was observed that the mixes developed are tolerant to an increase in water content up to 5 %, which is significant considering the fact that, in actual circumstances, errors in dosing of water are more common. It was also observed that mixes with higher water/powder (w/p) ratio exhibit better robustness with both increase or decrease in water content, with respect to the base mix. The performance of the SCC mixes formulated suggests that the mix designs with a combination of high paste content and low water powder ratio may have low robustness. The results also indicate that the performance of the mix varied with other constituents except with the two superplasticizers (SP) used (which belong to the same family of polycarboxylic ether (PCE) but with different characteristics), indicating that the SPs are efficient for developing robust SCC.