Cleaner Materials最新文献

The effect of supplementary cementitious materials (SCMs) such as fly ash (FA), GGBS and silica fume (SF) on the geotechnical index and engineering properties of expansive clays (EC) are studied in this research work. This manuscript aims to determine the workability (consistency limits (CL)), swellability (free swell index (FSI)), compaction properties, strength characteristics (UCS) and hydraulic conductivity (HC) of varied eighteen mix proportions of FA-EC (P-series), FA-GGBS-EC (Q-series) and FA-GGBS-SF-EC (R-series) are experimentally studied as a bottom liner in landfills. From the test results, CL and FSI significantly decreased in P, Q and R series, this is due to the effect of flocculation, a process that increases the average particle size of mix blends and also depletion of the double-diffusive layer thickness of EC by promoting the Ca2+ ions in the pore water from SCMs. The compaction parameters such as optimum moisture content decreased in all the series, due to the higher flocculation of mixes. However, maximum dry unit weight increased in Q and R and decreased in the P series. The UCS values increased with an increase in optimum SCMs quantities and with curing intervals tested at 0, 7, 14 and 28 days. The higher UCS value is attained at 40 %FA with EC (i.e. P2), 60 %FA-GGBS with EC (i.e. Q3) and 60 %FA-GGBS-SF with EC (i.e. R3) in R-series which confirmed to be optimum due to the loss of cementation action/reduced cohesion in the matrix. In the case of HC, P2, Q3 and R3 mixes are confirmed to be optimum and fall under the criterion standards of landfill liner as per USEPA recommendation. Overall, this work proves to be a novelty and shows the feasibility of various collated SCMs blended with EC as landfill liner material, furthermore, these mixes are optimized to combine with EC to create a sustainable landfill liner that fits with the United Nations sustainable goals of 2030

The search for cost-effective substrates for the manufacturing of valuable products has led to the use of agrowastes as alternative sources of reducing sugar. Numerous bacteria build up polyhydroxyalkanoates (PHAs) as storage materials. This research aimed to produce PHA from Pseudomonas aeruginosa using agrowastes as carbon sources. The agrowastes (corncob, plantain peduncle and sugarcane bagasse) were treated with 1 % NaOH and analysed. The agrowastes were hydrolysed using cellulase produced by Aspergillus niger isolated from agrowastes dumpsite. The agrowaste hydrolysate was used in place of glucose for PHA production in a submerged fermentation. Nile blue A test and Sudan black test showed positive results for the isolate with a bright orange fluorescence on irradiation with UV light and was identified as Pseudomonas aeruginosa (accession number 0L405443). Sugarcane bagasse gave the highest potential for PHA production with PHA values of 5.86 mg/mL, followed by corn cob (5.29 mg/mL) and the least was obtained in plantain peduncle with a yield of 3.58 mg/mL. The findings using response surface methodology (RSM) for optimization show that all the four factors (carbon source, pH, temperature and incubation time) were statistically significant (P < 0.05) for PHA production. The optimum PHA production was attained under culture conditions of 24 h, 38 °C, pH 6.5, and 3 % carbon source. The PHA produced from 10 L of MSM was quantified to be 10.57 g under these conditions. The study revealed that Pseudomonas aeruginosa 0L405443 is a local bacterial strain utilized for the production of PHA using affordable, sustainable and easily available agrowastes hydrolysate as substrate.

The scarcity of natural resources, and energy demand/carbon footprints related to their processing and transportation, has led to the quest for alternate materials for road/pavement construction and other infrastructure development. On the other side, landfill mined soil like fraction (LMSF) forms significant proportion of mined legacy landfill waste that exists at different locations around the world; however, it has found limited applications. The present study explores the utilization of LMSF in development of novel asphalt road subbase layers for resilient road infrastructure. 30–60% of LMSF replacement has been studied, and findings based on gradation analysis, compaction tests and California bearing ratio (CBR) tests are quite encouraging. Most combinations of subbase layers studied exceed the design requirements for low volume roads in Indian scenario (rural and outer urban roads); while 30% LMSF in wet mix macadam satisfies the requirements of Indian and other international codes. The cost-benefit analysis shows significant saving in material cost due to utilization of LMSF in road subbase layer. The potential utilization of low cost and sustainable LMSF in asphalt road subbase layer would allow design of superior roads with CBR exceeding design values, resulting in better life cycle performance of road infrastructure with high resilience to fatigue effects, water inundation and overloading conditions.

Crafting Styrene-Butadiene-Styrene (SBS) polymer into the bitumen can notably improve the elastic response of the polymer modified bitumen (PMB), which will significantly enhance the overall performance of bituminous pavement. But the molecular mechanism of the PMB’s unique entropy elasticity has not been fully understood yet. The prominent entropy-elasticity of SBS polymer modified asphalt was investigated in this study. To do so, Fourier Transform Infrared (FTIR), Gel Permeation Chromatography (GPC) and Dynamic Mechanical Analysis (DMA) were conducted to investigate the molecular modification mechanism of PMB. Afterwards, polymer molecular model with a polymerization degree over 2000 is constructed and dynamic simulation is conducted to reveal the mesoscopic mechanism of SBS polymer’s entropy elasticity. As for macroscopic evaluation, a series of creep and recovery tests associated with different testing temperatures (10 °C to 100 °C with a 6 °C gap), recovery times (0.01 s, 0.1 s, 1 s, 4 s and 9 s) and SBS dosages (0 %, 2.5 %, 4.2 %, 7.5 %) were carried out to characterize the elasticity of various PMBs. The results show that plain bitumen mainly shows energy-elasticity, which is small, instantaneous and highly temperature-dependent, while PMB mainly shows entropy-elasticity, which is strong, delayed and less temperature-dependent. Under the condition of low temperature and short recovery time, the bitumen molecules freeze and prevent the SBS polymer to demonstrate its entropy-elasticity, hence the energy-elasticity dominates. Higher temperatures and long recovery time render the SBS molecule more time to relax and thus the entropy-elasticity dominates. The predominant influence of entropy-elasticity in PMA leads to a unique increasing recovery rate within a specific high-temperature range. This phenomenon can be utilized as a fingerprint approach for the identification of the entropy-elasticity and polymer modification.

Recycled aggregates, obtained from construction and demolition waste (C&DW), are currently underutilized in the production of new concrete given the incidence of widespread leftover cement paste adhering to the surface. C&DW sorting facilities based on optical technology can be developed and applied on an industrial scale, improving the overall quality of this secondary raw material. In this study, we present a novel approach based on image analysis and mineralogical laboratory methods to determine the residual attached mortar volume. Through clustering analysis, we classify C&DW samples with a comparable cement content determined by the image analysis. The leftover cement paste from these C&DW classes is mechanically extracted and examined using X-ray Powder Diffraction and Rietveld refinement. To estimate the attached mortar volume and the carbonation of the cement paste, we present a novel mathematical model based on the mineralogical data. To overcome the bottleneck associate with the image analysis, we further incorporate a deep learning model to automate the determination of the mortar volume, which enables high-throughput screening of C&DW in real production.

After the 2015 Nepal earthquake, numerous human casualties resulted from the collapse of substantial brick walls. Concurrently, the proliferation of air pollution attributed to brick kilns has become a pressing concern in urban areas of Nepal. The dual challenge of fortifying building structures and safeguarding the urban environment necessitates innovative solutions. This paper outlines the development of aerated lightweight mortar, incorporating diverse proportions of aluminium powder and various powder-to-sand combinations, aiming to achieve a density below 1000 kg/m³. Three fundamental mixtures, characterized by water-powder ratios (W/P) of 63.3 %, 57.9 %, and 35.3 %, and total powder to sand ratios (P/S) of 0.344, 0.520, and 1.275 (by weight) were employed. The aluminium powder content ranged from 0 % to 1.2 % (by weight of cement). Standard-sized cubes and cylinders were prepared to evaluate the impact of aluminium powder on density, strength, and water absorption. From the test results, the most suitable mixture for aeration proved to be the mortar with a W/P of 35.3 % and P/S of 1.275. This formulation demonstrated a significant 50 % density reduction (<1000 kg/m³) with 0.6 % aluminium powder, accompanied by a 58 % decrease in 28-day compressive strength, a 52 % drop in modulus of elasticity, and a 44 % reduction in splitting tensile strength. The study emphasized the critical role of both aluminium powder content and powder-to-sand ratio in mortar aeration. The developed aerated lightweight mortar not only enhances seismic resilience by reducing building weight but also serves as an eco-friendly alternative to traditional burnt clay bricks, mitigating environmental impact.

This paper focused on the usage and behavior of slag sand by investigating the fresh, mechanical, durability, and microstructural properties of M40 grade concrete. However, in India, more research on the effect of slag on mechanical strength is needed with in-depth microstructure & durability investigation. To fill this research gap and promote slag sand usage, a systematic and scientific investigation was conducted in which 9 concrete mixes with partial and total replacement of fine aggregate with slag sand were prepared. Compressive, split tensile strength & UPV tests are performed at 3, 7, 28, and 90 days of curing to know the mechanical properties. Linear regression analysis is done to correlate and predict the strength of concrete using different mechanical properties. According to test results, workability and mechanical properties improve with the increase in the replacement of slag sand. Slag sand concrete forms a dense network at an optimum replacement achieving Maximum rise in strength of about 17 to 33 %, referring to the control mix resulting in an environmentally friendly material. Thereby reducing the disposal of industrial effluent. Conversely, increased replacement beyond 40 % of slag sand in concrete caused a reduction in the slump and mechanical properties with increased curing age. Microstructure results revealed the formation of CSH, CASH, ettringite, calcite, and good bonding with an aggregate. Slag sand tends to absorb more water with its increased percentage due to its shape, texture, and surface area, as evidenced in its SEM images & workability. The durability of slag sand concrete has performed better and is economically feasible than M−sand mixed concrete. Hence, recycling slag sand in concrete yields an economical, eco-friendly material and proves to be a robust substrate for various construction activities in sustainable waste management.

This study develops and presents an Artificial Neural Network (ANN) model employing the Levenberg-Marquardt Backpropagation (LMBP) training algorithm to predict the compressive strength of both normal and high strength concrete. The model's robustness was evaluated using an extensive dataset comprising 1637 samples. Eight input variables, including the cement content, blast furnace slag, fly ash, fine aggregate, coarse aggregate, water content, superplasticizer, and testing age, were considered. The optimal number of hidden layers and neurons in the layer were identified through analysis, and the effectiveness of the model was assessed through k-fold cross-validation and statistical measures, including correlation coefficient (R), coefficient of determination (R²), Root Mean Square Error (RMSE), and Mean Absolute Error (MEA). Comparison with other models was carried out, and the perturbation/super-position method was employed for parametric studies to investigate the effect of each input variable on the output variable. The k-fold cross-validation confirmed the generalizability of the model, and statistical measures showed good results, with unit cement content and superplasticizers having the highest impact on compressive strength. The findings demonstrate that the suggested ANN model is an extremely precise, economical, and practical predictive tool for concrete compressive strength.

Sustainable infrastructure is one of the fastest growing sectors and is concurrently producing huge amount of construction demolition waste (CDW). Correspondingly, industrial activities also result in generation of similar wastes, out of which slag from iron industries pose a serious threat to the environment. This study attempts to incorporate both of the above-mentioned wastes in concrete, thereby an attempt to encourage and contribute towards sustainability. The experimental program comprises the evaluation of strength and water absorption behaviour along with the prediction and validation of iron slag (IS) and recycled aggregate concrete (RAC). The replacement levels for IS range from 10 to 30% while those for recycled concrete aggregates (RCA) range from 0 to 50%. Based on the experimental outcomes, the predicted equations for strength and water absorption characteristics were established. Furthermore, the statistical analysis was performed, indicating the desired responses thereby validating the efficiency of the tested properties of IS–RAC concrete. The successful analysis indicates the optimum constituent mix of 24.8% IS and 26.9% RCA for maximum strength and water absorption behaviour. Finally, a comparative environmental estimation was performed by life cycle assessment, describing a reduction of nearly 12.28% and 22% in carbon dioxide emissions and eco-cost in optimized concrete respectively.

The metallurgical and cement industries contribute significantly to anthropogenic carbon dioxide emissions. Utilizing oxidic by-products from the metallurgical industry as supplementary cementitious materials (SCMs) can improve resource efficiency and reduce emissions from cement production. Iron silicate copper slags have been studied as SCMs, but mainly in systems where Portland cement is used as an activator. There is limited research on the inherent reactivity of the slag under changing processing conditions. The present study offers insight into the effect of granulation temperature and grinding on the inherent reactivity of an industrially produced iron silicate copper slag. The results showed that granulation temperature had an insignificant effect on reactivity, while grinding generated substantial improvements. The latter effect was concluded to stem from the increased specific surface area, increased number of sites for nucleation and growth of hydrates, and changes in the inherent reactivity owing to structural changes induced by the grinding.