Damage identification in concrete under impact loading at varying temperatures using voltage strain relations technique: an experimental and numerical study

Impact-loaded concrete structures cause severe and rapid damage, resulting in significant property and human life loss. As the temperature rises, the damage caused by impact loading becomes increasingly severe. Concrete structures need structural health monitoring (SHM) to avoid this damage and loss. In this study, the voltage strain relation technique was used to identify the damaged state of concrete under impact loads at various temperature conditions experimentally and numerically. For this purpose, an experimental study was performed on concrete cube specimens in which different piezo configurations (surface bonded, non-bonded, and jacketed) were installed to acquire the voltage data. Before applying an impact load to the top surface of the concrete specimen, it was preheated at 50 °C, 100 °C, and 150 °C to provide the temperature effect, and then a free-falling iron ball was dropped from 3 m heights on the top of the specimens. Furthermore, finite element analysis has been carried out to validate the experimental results with analytical results. The experimental results show that the voltage strain relation technique is well capable of detecting the damage in concrete under the temperature and impact loading conditions. The maximum absolute voltage value (Vp) of 17.11 V was recorded for the jacketed sensors under an impact height of 3 m at 100 °C. All the piezo sensor configurations are capable of finding the damage. Jacketed sensors are more efficient in the health assessment of concrete in terms of voltage strain relations. In terms of strain values, the analytical results are in good agreement with the experimental results

An overview of the opportunities and challenges in sustaining the energy industry in Afghanistan

Energy access is not only crucial for economic growth but also important for any strategy to improve the health and social welfare of a nation. Afghanistan’s energy industry is in poor condition due to many years of war and negligence. Despite international agencies’ support and energy policies adopted in the last few years, Afghanistan has no universal access to power. Besides, the residences suffer from an irregular distribution of power supply. There is a growing gap between demand and supply, and the current predictions of demand do not show reality due to hindered economic growth. Afghanistan’s domestic power transmission is limited, which must be extended for the country to enjoy a stable and sustainable energy supply. Sustainability and security of Afghanistan’s power sector would rely on its ability to become self-reliant in power generation. Overall, the objective of this paper is to summarize the current energy status of Afghanistan and to identify energy opportunities for self-sufficiency and challenges in various aspects of energy sources. To meet energy demand, Afghanistan can develop its autochthonous hydrocarbon and renewable energy resources. By improving its domestic energy potential from natural resources, Afghanistan can fulfill its primary energy requirement. Further, along with policy formulation, appropriate and planned implementation of renewable energy policy, energy efficiency targets, and strategies, Afghanistan can reach energy self-sufficiency goals with socio-economic development

Investigation of dry-wet cycles effect on the durability of modified rubberised concrete

For communities and property in flood-prone locations, the performance of construction materials during flood occurrences is important. Limited investigations are available on the influence of dry-wet water cycles on rubberised concrete after rubber crumbs treatment. Several tests are done to assess rubberised concrete's mechanical and durability characteristics and compare it to conventional concrete. An optimum amount (15%) of rubber crumbs are utilised for partially replacing fine aggregate in concrete. Physical appearance, surface cracks, compressive strength, mass difference and ultrasonic pulse velocity of RuC have been tested under water dry-wet cycles. After dry-wet cycles, RuC gains its compressive strength, mass and ultrasonic pulse velocity. No harmful effect is found under dry-wet cycles of water. After rubber crumbs treatment and using pozzolana-based cement, the rubberised concrete can struggle with dry-wet water cycles during flood conditions for a long duration

Evaluation of the Feasibility of Recycled Concrete Aggregate for Producing Structural Concrete

When sustainability has become a primary measure of the selection of the building materials in the construction industry over the past decades, researchers all around the world have been looking upon for alternatives to reduce the overall environmental impact of the construction materials while not compromising the strength and durability. The factors like manufacturing, reusability, recyclability, disposal etc, are the criteria of utmost attention affecting the overall life cycle impact of the construction materials. In this prospect the Recycled Concrete Aggregate (RCA) has shown up as an exceptionally viable contender for the manufacturing of concrete with several environmental benefits over the Natural Aggregate (NA) and has already been identified by industry and several government agencies across the globe. The efficient material use of RCA can potentially deliver an inferior though competent concrete in comparison to the NA while averring the criteria of sustenance. The present study delves into the calculation of the proportion of the RCA in a mix design for achieving maximum compressive strength. The experimental setup constituted the casting of concrete cubes of control mix design of M40 grade with proportions of RCA varying from 0-100 percent spread over a space of 10% with NA which were later put to tests. The thorough investigation on the casted concrete cubes lead to the conclusion that the mix design with 50% proportion of RCA in addition to 50% proportion of NA delivered the maximum compressive strength, an average value of 8.23% higher than that of the normal concrete and the highest Rebound Number, an average value of 53.92 for the M40 grade concrete thereby showcasing the feasibility of producing structural concrete with RCA. The results are asserted to be governed by the better bonding between the RCA and NA and due to the significant increase in the water retention capacity by the provision of RCA in the mix

An investigation on the effect of curing conditions on the mechanical and microstructural properties of the geopolymer concrete

Geopolymer concrete represents the future of green and sustainable concrete. It has a large impact on the construction industry owing to its better performance than that of conventional Portland cement concrete. This study aimed to identify the effect of curing conditions on the physical, mechanical, and microstructural properties of specimens using ambient curing and oven-curing. In the experimental analysis, we tested slump and setting time for physical properties, density and drying shrinkage for chemical properties, compressive strength, indirect tensile strength, modulus of rupture, Poisson’s ratio, and elastic modulus for mechanical properties, rebound strength, and UPVT for nondestructive and x-ray diffraction, and thermogravimetric analysis for microstructural analysis. After the experimental analysis, it was concluded that the density, Poisson’s ratio, and dry shrinkage were higher for ambient-cured specimens than for oven-cured specimens, whereas the compressive strength, indirect tensile strength, modulus of rupture, and elastic modulus of oven-cured specimens were higher than those of ambient-cured specimens. The nondestructive tests, rebound tests, and UPVT show that the oven-cured specimens are better in quality and strength than the ambient cured specimens. In microstructural analysis, x-ray diffraction showed that the oven-cured specimens had a lower intensity of mineral oxides than the ambient-cured specimens in microstructural analysis. The matrix of the ambient-cured specimens was thermally stable up to 800 °C and retained 92% of its original mass, whereas the matrix of the oven-cured specimens retained 94% of its mass up to 800 °C in the thermogravimetric analysis

Geopolymer Concrete: A Material for Sustainable Development in Indian Construction Industries

Geopolymer concrete (GPC) is a new material in the construction industry, with different chemical compositions and reactions involved in a binding material. The pozzolanic materials (industrial waste like fly ash, ground granulated blast furnace slag (GGBFS), and rice husk ash), which contain high silica and alumina, work as binding materials in the mix. Geopolymer concrete is economical, low energy consumption, thermally stable, easily workable, eco-friendly, cementless, and durable. GPC reduces carbon footprints by using industrial solid waste like slag, fly ash, and rice husk ash. Around one tonne of carbon dioxide emissions produced one tonne of cement that directly polluted the environment and increased the world’s temperature by increasing greenhouse gas production. For sustainable construction, GPC reduces the use of cement and finds the alternative of cement for the material’s binding property. So, the geopolymer concrete is an alternative to Portland cement concrete and it is a potential material having large commercial value and for sustainable development in Indian construction industries. The comprehensive survey of the literature shows that geopolymer concrete is a perfect alternative to Portland cement concrete because it has better physical, mechanical, and durable properties. Geopolymer concrete is highly resistant to acid, sulphate, and salt attack. Geopolymer concrete plays a vital role in the construction industry through its use in bridge construction, high-rise buildings, highways, tunnels, dams, and hydraulic structures, because of its high performance. It can be concluded from the review that sustainable development is achieved by employing geopolymers in Indian construction industries, because it results in lower CO2 emissions, optimum utilization of natural resources, utilization of waste materials, is more cost-effective in long life infrastructure construction, and, socially, in financial benefits and employment generation

Improvements in the Engineering Properties of Cementitious Composites Using Nano-Sized Cement and Nano-Sized Additives

The findings of an extensive experimental research study on the usage of nano-sized cement powder and other additives combined to form cement–fine-aggregate matrices are discussed in this work. In the laboratory, dry and wet methods were used to create nano-sized cements. The influence of these nano-sized cements, nano-silica fumes, and nano-fly ash in different proportions was studied to the evaluate the engineering properties of the cement–fine-aggregate matrices concerning normal-sized, commercially available cement. The composites produced with modified cement–fine-aggregate matrices were subjected to microscopic-scale analyses using a petrographic microscope, a Scanning Electron Microscope (SEM), and a Transmission Electron Microscope (TEM). These studies unravelled the placement and behaviour of additives in controlling the engineering properties of the mix. The test results indicated that nano-cement and nano-sized particles improved the engineering properties of the hardened cement matrix. The wet-ground nano-cement showed the best result, 40 MPa 28th-day compressive strength, without mixing any additive compared with ordinary and dry-ground cements. The mix containing 50:50 normal and wet-ground cement exhibited 37.20 MPa 28th-day compressive strength. All other mixes with nano-sized dry cement, silica fume, and fly ash with different permutations and combinations gave better results than the normal-cement–fine-aggregate mix. The petrographic studies and the Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) analyses further validated the above findings. Statistical analyses and techniques such as correlation and stepwise multiple regression analysis were conducted to compose a predictive equation to calculate the 28th-day compressive strength. In addition to these methods, a repeated measures Analysis of Variance (ANOVA) was also implemented to analyse the statistically significant differences among three differently timed strength readings