The present study addresses the effective utilization of tannery sludge as a partial replacement of fly ash in brick manufacturing. The main objective of this research is to determine the optimal sludge content that can be incorporated in flyash bricks and thereby to assess the key engineering properties while mitigating potential radiological emissions. Sludge incorporated bricks were cast with the tannery sludge varying from 5% to 30 %. The bricks were tested for its compressive strength, water absorption, efflorescence and radiological tests. Samples were prepared for radiation test with varying percentage of tannery sludge. Various parameters, including internal and external hazard indices, radium equivalent activity (Req), annual effective dose rates, and absorbed dose rates, were thoroughly examined in this research. The results of various tests revealed that the newly formulated fly ash tannery bricks showed significant compressive strength upto 20% replacement. The water absorption and efflorescence were found to be within permissible limit as per BIS IS 3495. The gamma-ray spectrometry measurements of Primordial radionuclide activity concentrations, including Uranium-238, Thorium-232, and Potassium-K, in sludge bricks were found well within the permissible limits as per UNSCEAR 2000. The radium equivalent activity was found below the permissible limit of 370 Bq/kg. The absorbed gamma dose, radioactivity level index, external hazard index, indoor effective dose rate and outdoor effective dose rate, were all determined to be below the threshold of one (1.0), indicating that they were comfortably within the safety standards recommended. The results claimed the tannery sludge did not pose any serious radiation effect and it can be utilized as an eco-friendly as well as user- friendly construction material.

This paper presents an investigation of the bond performance of corrosion-free sand-coated glass fiber reinforced polymer bars (GFRP) implanted in two types of fly ash-based eco-friendly concrete. Steel reinforcement is prone to corrosion and is expensive to fix, therefore finding an effective alternative has become a must. One of these alternatives is GFRP bar. On the other hand, conventional concrete (CC) is not issueless, as it significantly affects the environment through its high-intensity CO₂ emissions. Thus, other alternatives have been looked into to mitigate the CO₂ problems. One of these alternatives is partially substituting Portland cement with another CO₂ emission-free material such as fly ash. In this study, two levels (50% and 70%) of high-volume fly ash concrete (HVFAC) were used to investigate their bond performance with GFRP bars. Cylindrical specimens were tested under the effect of pullout load. Furthermore, the bars were investigated chemically and microstructurally to see if the fly ash had some influence on the GFRP bar. For concrete, performance rank analysis was carried out to identify the best concrete mixture in terms of slump, unit weight, cost, and bond strength. In addition, to verify the experimental work, two-dimensional finite element models were built using translator elements to present the bond action between the concrete and its reinforcement. The results of the investigation showed that the bond strength of GFRP bars was less than that of mild steel owing to GFRP bar deformation. In addition, CC resulted in a higher bond strength than HVFAC. The bar analyses did not yield any obvious signs of microstructural deterioration or chemical attack.

Pavement subgrade is an in-situ material upon which the pavement structure is constructed. A soil with a high plasticity index will experience high shrinkage and swell depending upon its moisture content with detrimental impacts on its supported pavement structure. Removing and replacing the weak soil with better-quality soil is an alternative to stabilization of poor subgrade soil and may be a very expensive solution, typically for large road networks. Secondly, stabilization of weak soil -subgrade using conventional cement may not be sustainable due to its high CO₂ footprint. The feasibility of this non-conventional method using blended geopolymer binder for stabilization of weak subgrade soil was investigated compared to the conventional cement stabilization method. Laboratory testing of design mixes included unconfined compression test, maximum dry density, CBR and shrink & swell testing determining its feasibility and optimum extent. This research paper will present the findings on the effectiveness of blended geopolymer (fly ash and slag) as an alternative to conventional cement-based soil stabilizers for weak subgrade and its sustainability potential.

Supersulphated cements are considered to be some of the first alkali-activated cements. Ground granulated blast-furnace slag is activated with a small amount of Portland cement in the presence of gypsum, providing C-S-H gel and ettringite as the main reaction products. These materials exhibit some good properties; the most important of these being good sulphate resistance and also good environmental effects. Standard EN15743+A1 "supersulphated cement" describes the conditions for the composition of this binder. In this paper, the product after desulphurisation (PPR) from the Třebovice heating plant (Ostrava) was used as a source of gypsum. Strength development was recorded up to 91 days for different ratios of compounds. Early strengths are very low and are higher for higher ordinary Portland cement content. At 28 and 91 days of age, the strengths are almost the same for gypsum contents from 10 to 20% and all cement contents (2.5, 3.75, and 5%). These strengths are relatively high—around 50 MPa. Supersulphated cements can be a good choice for the use of waste material—the product after desulphurisation.

The recovery/recycling of solid industrial waste is a major environmental, economic and productive reality in the context of waste management activities. One of the main aspects related to the application of recovery technologies is the removal of waste from landfills and it is sufficient to observe the consequent proportional decrease in quantities of industrial waste in landfills in order to confirm the progressive development of recovery technologies related to the world of waste. Disposal and recovery/recycling aim at minimizing environmental impacts and promoting the efficient use of resources. In the current landscape of waste recycling, there are consolidated activities in constant search of technological improvements aimed at optimizing recovery efficiency. In this context, the final goal of this study is the production of lightweight artificial aggregates through the recycling of industrial solid waste, such as fly ash, blast furnace slag, and marble sludge. The results show that the aggregates produced can be classified as lightweight aggregates and are suitable for road paving.