Hydration and properties of hydrogen-based mineral phase transformation iron ore tailings as supplementary cementitious material.

Almost all iron ore tailings (IOTs) required activation prior to use as SCMs, which limited their application in building materials. This study investigated HMPT-IOTs and discovered that they possess latent hydraulic and pozzolanic properties. In order to better utilize as SCM, mechanical properties, hydration reactions, hydration products, microstructure, and pores were comprehensively studied through mechanical tests, hydration heat tests, XRD, SEM, TG, and MIP. The results show that when HMPT-IOTs replace cement at 10 wt%, 20 wt% and 30 wt%, the compressive strength at 28 days is 41.9 MPa, 47.9 MPa and 37.5 MPa, respectively. When the substitution amount reaches 30 wt%, it will reduce the cumulative heat of hydration and promote early hydration reactions. The main hydration products are ettringite and Ca(OH)2. As the nucleation site of C-S-H, hydration products are interconnected, making the microstructure denser. At this substitution level, Ca(OH)2 consumption was about 2% at 28 days of age. Simultaneously, the total pore volume was only 0.01 mL/g greater than that of the control group, and the number of micropores and transition pores decreased by approximately 3%.

Strength development and self-desiccation of saline cemented paste backfill.

Given that many mines around the world are located in areas where fresh water is scarce, and companies are being held to increasingly stringent sustainability and environmental responsibility standards, many mines are looking to use locally available saline groundwater or seawater as mixing water in cemented paste backfill (CPB). However, the impacts of this decision on key engineering properties of CPB (e.g. strength and self-desiccation) that affect its mechanical stability need to be better understood to allow confident selection of this practical and more sustainable solution. Thus, the effect of mixing water salinity and binder type on the strength (unconfined compressive strength, UCS) development and self-desiccation (measured by suction and volumetric water content) of CPB is explored in this research. NaCl concentrations from 0 to 300 g/L were used in CPB made with silica tailings and Portland cement type I (PC). Concentrations of 10 and 35 g/L were found to moderately increase UCS, while a concentration of 100 g/L had comparable UCS to non-saline CPB and a concentration of 300 g/L was found to significantly decrease UCS over all curing times. The overall trend is 10 g/L > 35 g/L > 0 g/L > 100 g/L > 300 g/L. The UCS of the 60-day-old CPB with a NaCl of 300 g/L is significantly lower, registering a 26% decrease compared to the UCS of the 60-day-old CPB without salt. In contrast, the UCS of the 60-day-old CPBs containing 10 g/L and 35 g/L of salt exhibits a notable improvement, being 15% and 10% higher, respectively, than the UCS of the 60-day-old CPB without salt. Water content and suction monitoring were conducted up to 28 days of curing time, and it was found that suction only slightly contributed to UCS gain of the saline CPB, and high salt contents (100 and 300 g/L) significantly inhibited the self-desiccation ability of CPB due to inhibition of cement hydration by the excessive amount of salt. The increase in strength of both saline and non-saline samples was attributed primarily to the increase in cement hydration products, while the increased strength of the samples with salinities of 10 and 35 g/L was mainly attributed to the enhancement of the binder hydration due to the low amount of salt and the presence of Friedel's salt in the pores. The effect of PC replacement by 25 to 75% with slag on CPB with 35 g/L mixing water salinity was also studied. Slag replacement of 50% and higher resulted in significantly higher UCS over most curing times. Suction likely moderately contributed to UCS of the saline CPB with slag, in addition to the presence of Friedel's salt in the pores and the acceleration of cement and slag hydration by the presence of NaCl.

Characterization of textile effluent treatment plant sludge and its industrial application in fired clay bricks with health risk assessment.

The textile industry in Bangladesh faces environmental and health challenges due to the disposal of solid waste from Effluent Treatment Plants (ETPs). To address this issue, a study was conducted using soil from a brick industry near Dhaka, amending it with varying amounts of dry sludge to create clay bricks. The original soil had a loam texture and medium plasticity. The research found that adding 9 wt% of sludge resulted in Grade A commercial bricks with a compressive strength of 15.33 MPa and water absorption of 13.33 wt%, meeting BDS 208 standards. However, these sludge-incorporated bricks experienced more shrinkage during the burning process due to organic content, requiring additional soil to maintain conventional dimensions. Also, to assess the health hazards of these sludge-incorporated bricks, a leaching test was performed, revealing that no toxic heavy metals (Pb, Cd, Cr, Cu, Ni, and Zn) in the leachate exceeded the limits set by the United States Environmental Protection Agency (USEPA). The study indicates that textile ETP sludge can serve as a sustainable raw material for bricks, potentially reducing the environmental burden caused by textile sludge disposal by 28.75%. This innovative approach offers a promising solution to both environmental and health concerns associated with textile waste in Bangladesh's industrial sector.

Assessment of radioactivity concentration for building materials used in Babadogo Estate, Nairobi City County, Kenya.

Natural radioactive materials in certain conditions can get to hazardous radiological level. The aim of the present work was to evaluate the natural activity concentration from sampled building materials collected from different locations in Babadogo Estate within Nairobi City County. The analysis done using gamma ray spectrometer, which was put into action for spectral data acquisition and then analysis. The activity concentration levels of 238U, 232Th and 40K for the selected samples of building materials was measured by the use of gamma ray spectrometry method. The analyzed data compared with the standard acceptable values. The activity concentration in 40K varied from 55 ± 3 to 2647 ± 132 Bq kg-1, giving an average (sum of all values divided by 33) value of 831 ± 42 Bq kg-1; 238U varied from 39 ± 2 to 3602 ± 180 Bq kg-1, giving average figures of 378 ± 19 Bq kg-1 and 232Th ranged from 5.000 ± 0.300 to 4213 ± 211 Bq kg-1, giving average figure of 290 ± 15 Bq kg-1. The calculated average figures for activity concentration surpassed the world average values of 420, 33 and 45 Bq kg-1 in 40K, 238U and 232Th, respectively.

Analysis of internal gamma-ray dose to the public from brick as building material in Tamil Nadu, India.

Natural radioactivity due to 238U, 232Th and 40K in brick samples from Tamil Nadu was determined using gamma-ray spectrometry. The mean activity concentrations of 238U, 232Th and 40K, 69 ± 6, 62 ± 6 and 462 ± 23 Bq kg-1, are slightly greater than the world recommended limits of 35, 45 and 420 Bq kg-1, respectively, and they are compared with a similar work carried out across the world. The radiological parameters such as radium equivalent activity, Raeq (193 ± 17 Bq kg-1), internal hazard index, Hin (0.71 ± 0.06), and activity utilisation index, AUI (1.43 ± 0.13), was lower, whilst absorbed dose rate, DRin (89 ± 8 nGy h-1), annual effective dose equivalent, AEDEin (0.43 ± 0.04 mSv y-1), and excess lifetime cancer risk, ELCRin (1.52 ± 0.13 mSv y-1), are slightly greater than the world's recommended limit. Bi-variate statistical analysis was performed to corroborate the relationship between radionuclides and radiological hazards.

Self-assembled silk fibroin cross-linked with genipin supplements microbial carbonate precipitation in building material.

The process of microbially induced carbonate precipitation (MICP) is known to effectively improve engineering properties of building materials and so does silk fibroin (SF). Thus, in this study, an attempt was taken to see the improvement in sand, that is, basic building material coupled with MICP and SF. Urease producing Bacillus megaterium was utilized for MICP in Nutri-Calci medium. To improve the strength of SF itself in bacterial solution, it was cross-linked with genipin at the optimized concentration of 3.12 mg/mL. The Fourier transform infrared (FTIR) spectra confirmed the crosslinking of SF with genipin in bacterial solution. In order to understand how such cross-linking can improve engineering properties, sand moulds of 50 mm3 dimension were prepared that resulted in 35% and 55% more compressive strength than the one prepared with bacterial solution with SF and bacterial solution only, respectively with higher calcite content in former one. The FTIR, SEM, x-ray powder diffraction spectrometry and x-ray photoelectron spectroscopy analyses confirmed higher biomineral precipitation in bacterial solution coupled with genipin cross-linked SF. As the process of MICP is proven to replace cement partially from concrete without negatively influence mechanical properties, SF cross-linked with genipin can provide additional significance in developing low-carbon cement-based composites.

High performance C-A-S-H seeds from fly ash-carbide slag for activating lithium slag towards a low carbon binder.

In this work, one-step synthesis of high-performance C-A-S-H (calcium alumina silicate hydrate) seeds from low-calcium fly ash (FA) and carbide slag (CS) by 7 days of mechanochemical mixing was proposed and used to activate lithium slag (LS) cement. The results showed that the seeding effect of C-A-S-H seeds was increased with the increasing Ca/Si (i.e. from 1.0 to 1.5), i.e. the mortar compressive strength of 1 day and 28 days were increased by 67% and 29% with the addition of 1.0% C-A-S-H nano-seeds at Ca/Si = 1.5 in the presence of polycarboxylate superplasticizer (PCE), respectively. Moreover, the chloride resistance of lithium slag cement was improved significantly, i.e. the electric flux was decreased by more than 30% than that of plain lithium slag cement mortar. The performance difference of various C-A-S-H seeds is mainly attributed to their high proportion and polymerization degree, more stretch and three-dimensional foil-like morphology at high Ca/Si. This study provides guidance for obtaining low-cost and high-performance C-A-S-H seeds from wastes and the highly efficient utilization of LS as supplementary cementitious materials (SCMs) in the future.

Assessment of 222Rn, 226Ra, 238U, 218Po, and 214Po activity concentrations in the blood samples of workers at selected building material factories in Erbil City.

The objective of this research is to assess the impact of radon concentration on workers at certain construction material industries in Erbil, Kurdistan Region of Iraq. The CR-39 solid-state track detector was used in this experiment to monitor radon levels and their daughters. For this purpose, as a case study group, 70 workers were divided into seven subgroups (gypsum, cement plant, lightweight block, marble, red brick 1, crusher stone, and concrete block 2), and 20 healthy volunteers were selected as a control group. The findings demonstrate that the mean concentrations of radon, radium, uranium, and radon daughters deposited on the detector face (POS) and chamber walls (POW) for the case study group were 9.61 ± 1.52 Bq/m3, 0.33 ± 0.05 Bq/Kg, 5.39 ± 0.86 mBq/Kg, 4 ± 0.63, and 16.62 ± 2.64 mBq/m3, whereas for the control group, they were 3.39 ± 0.58 Bq/m3, 0.117 ± 0.03 Bq/Kg, 1.91 ± 0.32 mBq/Kg, 1.41 ± 0.24, and 5.88 ± 1 mBq/m3, respectively. The statistical analysis revealed that radon, radium, uranium, and POW and POS concentrations were statistically significant (p ≤ 0.001) in the samples for the case study groups of cement, lightweight block, red brick 1, marble, and crusher stone factories in comparison to the control group; however, the results for gypsum and concrete block 2 factories were not statistically significant in comparison to the control group. Intriguingly, the radon levels in every blood sample examined were far lower than the 200 Bq/m3 limit established by the International Atomic Energy Agency. Hence, it may be argued that the blood is devoid of contaminants. These results are crucial for determining whether or not an individual is exposed to substantial quantities of radiation and for demonstrating a link between radon, its daughter, uranium, and the prevalence of cancer among workers in the Kurdish region of Iraq.

A review on fabricating functional materials by electroplating sludge: process characteristics and outlook.

As the end product of the electroplating industry, electroplating sludge (ES) has a huge annual output and an abundant heavy metal (HM). The effective disposal of ES is attracting increasing attention. Currently, the widely used ES disposal methods (e.g. landfill and incineration) make it difficult to effectively control of HMs and synchronously utilise metal resources, leading to a waste of metal resources, HMs migration, and potential harm to the environment and human health. Therefore, techniques to limit HMs release into the environment and promote the efficient utilisation of metal resources contained within ES are of great interest. Based on these requirements, material reuse is a great potential means of ES management. This review presents an overview of the process flows, principles and feasibilities of the methods employed for the material reuse of ES. Several approaches have been investigated to date, including (1) additions in building materials, (2) application in pigment production, and (3) production of special functional materials. However, these three methods vary in their treatment scales, property requirements, ability to control HMs, and degree of utilisation of metal resources in ES. Currently, the safety of products and costs are not paid enough attention, and the large-scale disposal of HMs is not concordant with the effective management of HMs. Accordingly, this study proposes a holistic sustainable materialised reuse pattern of ES, which combines the scale and efficiency of sludge disposal and pays attention to the safety of products and the cost of transformation process for commercial application.

Is Policy the Necessary or Sufficient Driving Force of Construction and Demolition Waste Recycling Industry Development? Experience from China.

Policies have long been considered the essential driving force in promoting construction and demolition waste (CDW) recycling. However, the policy instruments adopted in different economies have varied greatly, which contributes to the difficulty in quantitative discernment of their effect. This study aims to examine whether the holistic employment of policy measures determines the development of CDW recycling around China. To accurately measure the holistic adoption of CDW policies, this study assessed policy strength via a proposed three-dimensional evaluation model. The spatiotemporal differences in policy strength among the 52 sample cities were further defined using K-means clustering and the Gini coefficient. Next, the driving effect of policy on the initial establishment of CDW recycling industry practices was examined by event history analysis (EHA). Finally, fuzzy set qualitative comparative analysis (fsQCA) was used to analyze the sufficiency and necessity of policy for the initial establishment of CDW recycling practices. The results indicated that the establishment of a first CDW recycling plant is only slightly correlated with policy measures, whereas it is highly correlated with the pilot city and per capita GDP. Furthermore, application of policy is neither a necessary nor sufficient condition for the establishment of a CDW recycling industry facility.

Effects of the addition of fatty acid from soybean oil sludge in recycled asphalt mixtures.

Recycling agents provide better additions of reclaimed asphalt pavement (RAP) in the production of new asphalt mixtures. Alternative and residual materials that have the potential as asphalt binder viscosity reducers have gained visibility in the field of paving due to the perspective of circular economy in recycled mixtures. Soybean oil sludge fatty acid is a material produced from soybean oil sludge, a waste generated in the soybean oil refining step. Thus, this paper investigated the physical, chemical, and rheological effects of the asphalt binder PG 64-XX modified by the fatty acid of soybean oil sludge in the contents of 6% and 7% by weight of the binder. The modified binder samples were submitted to penetration tests, softening point, rotational viscosity, performance grade (PG), before and after short-term aging (RTFO), and multiple stress creep and recovery (MSCR). A control asphalt mixture and recycled asphalt mixtures produced with 40% RAP and fatty acid-modified binders were subjected to tensile strength, induced moisture damage, resilient modulus, and fatigue life. A Student's t statistical test verified the significance of the data, as well as the estimation of production costs of these asphalt mixtures. The use of the fatty acid significantly reduced the stiffness and viscosity of the control asphalt binder, decreasing the mixing temperatures at 14 °C and 17 °C to 6% and 7%, respectively. Using higher fatty acid contents from soybean oil sludge significantly improved the performance of recycled mixtures in tensile strength, moisture damage, and fatigue life. The production cost of recycled asphalt mixtures was lower than that of the control mixture.

Struggles over waste: Preparing for re-use in the Danish waste sector.

A circular economy (CE) aims to reduce waste and encourages keeping products, components, and materials circulating in the economy. Furthermore, following the European waste hierarchy, preparing for re-use (PfR) is regarded as a better waste management option than recycling. Nevertheless, too many products with a reuse potential end up as waste. This includes residuals from products that have no major value and are therefore not demanded by the current system. As a result, products are prematurely recycled. This contradicts both the priority order of the waste hierarchy and the principles of a CE. This article investigates the potential of and constraints to reusing products that are disposed of at municipal recycling stations. It aims to improve our understanding of these issues and offers possible solutions that could enable municipal waste companies to transition from waste to resource management and reach the upper levels of the waste hierarchy, preparing waste for re-use. Interviews with relevant stakeholders, desk studies and knowledge obtained from participating in waste conferences over the past 3 years are all used to analyze PfR practice at five municipal waste management companies in Denmark. Pioneers with respect to circularity in the waste sector, which have been experimenting with and initiating PfR schemes concerning a range of products, including building materials, furniture, white goods and bicycles, are considered because they support the inner cycles of the CE. However, results reveal that the current transition consists of complex processes connected to an ambivalent legal framework and struggles over access and rights to resources. Further, a more coherent conceptual understanding of PfR is needed as the current understanding has a too narrow focus on restoring product value rather than coupling PfR processes to the market. Thus, challenges to achieving higher PfR rates seem to go beyond engaging in strategic partnerships, creating financial incentives and setting separate targets for PfR. Consequently, a more holistic investigation appears to be necessary to deepen our understanding of processes of resource management and use and the contestation that exists over these. Furthermore, a wider mapping of the actors operating in the tension area of PfR, including their willingness to cooperate and negotiate a zone of agreement, could prove beneficial to practitioners and policy developers alike.

A review of comprehensive utilization of red mud.

Red mud (RM) is a solid waste generated during the process of alumina production. RM has already posed a serious environmental threat with the development of the alumina refining industry. The comprehensive utilization of RM has attracted much attention due to its large-scale generation and harmful nature. This paper introduces the characteristics and state of RM and summarizes the relevant research on the comprehensive utilization of RM. The results show that comprehensive utilization of RM is mainly focused on the preparation of building materials, the extraction of valuable metals, catalyst synthesis and environmental protection. Besides, the article discusses the existing problems while utilizing RM. Prospects and suggestions for different utilization methods of RM are proposed.

Stabilization of Waste-to-Energy (WTE) fly ash for disposal in landfills or use as cement substitute.

This study investigated two approaches for managing Waste-to-Energy (WTE) fly ash (FA): (i) phosphoric acid stabilization of FA and disposal in non-hazardous landfills, so that it can pass the U.S. TCLP procedure and meet the U.S. Resource Conservation and Recovery Act (RCRA) standards; (ii) use of FA or phosphoric acid stabilized fly ash (PFA) as cement substitute in construction for avoiding disposal in landfills and reducing the consumption of Portland cement. The effect of stabilization was identified by TCLP tests and XRD quantification (QXRD), which showed that the economically optimal concentration for PFA to pass the RCRA was 1 mol/L H3PO4 (equivalent to 0.4 mol of H3PO4/kg of FA). Zn/Pb-phosphates were formed in treated ash by using high concentration H3PO4 (e.g., 3 mol/L). Thus, the hazardous FA was chemically stabilized to PFA, that were both discussed as cement substitute. QXRD and SEM results showed that both FA and PFA (1 mol/L H3PO4) chemically reacted with cement and water. Up to 25 vol% of the cement can be replaced by FA or PFA, with similar mechanical performance of cement mortars than that of reference. Testing by LEAF Method 1313-pH dependence showed that the FA and PFA cement mortars exhibited the same leachability of heavy metals; therefore, this study demonstrated the technical feasibility of utilizing either raw FA or stabilized PFA as supplementary cementitious material. The leachability of heavy metals in optimal FA or PFA 25 vol% cement mortar was under the U.K. WAC non-hazardous limits.

A review on sustainable use of agricultural straw and husk biomass ashes: Transitioning towards low carbon economy.

In order to mitigate the problems associated with the deposition of biomass ashes, it becomes essential to use these materials efficiently. One solution to the problem is utilization of these wastes in the concrete industry. Due to the massive development of infrastructure, the demand for cement is tremendously rising which results in the surge of cement concrete by 30 billion tonnes every year. Plant-based straw and husk ashes are residual waste containing high amounts of silica, which can also be accommodated as a pozzolanic material in concrete. This study presents a complete review of various husk and straw ashes and their impacts on the fresh and hardened properties of concrete including its preparation, microstructure, workability, compressive strength, splitting tensile strength and flexural strength. Special emphasis has been given to the durability characteristics of concrete focussing on porosity, water penetration, carbonation, acid resistance, sulphate, and chloride attack. The data gathered shows that fineness of ashes provides filler and pore refinement effect and gains additional hydration products, resulting in an improvement of the mechanical and durability properties of concrete. The addition of ashes as supplementary cementitious materials in concrete enhances the mechanical performance up to a certain replacement. The optimum level of replacement for rice husk ash, wheat straw ash, and sugarcane straw ash was observed at 10-20%. While wheat husk ash, groundnut husk ash, rice straw ash, and millet husk ash provide optimum strength gains at 10% replacement of OPC. An increase in the replacement content of mostly ashes has a positive effect on water absorption and resistance to acid, sulphate, and chloride attacks.

Recycling of phosphogypsum and red mud in low carbon and green cementitious materials for vertical barrier.

MgO activated slag and bentonite (MASB) slurry is a new and promising vertical barrier material along with excellent performances. Some solid wastes, such as phosphogypsum (PG), red mud (RM), fly ash and so on, show a positive effect on the performances of alkali activated slag. However, few studies focus on the recycling of these solid wastes in the system of MgO activated slag. The purpose of this paper is to study the incorporation of phosphogypsum and red mud on the mechanical property, permeability and hydration process of MASB slurry. The results showed that the addition of PG could significantly improve the mechanical strength and anti-permeability of the MASB slurry at early age (7 days), where the unconfined compressive strength (UCS) increased from 793.1 kPa to 1395.7 kPa and the permeability coefficient declined from 16.1 × 10-7 cm/s to 1.7 × 10-7 cm/s. In contrast, the introduction of RM had some negative effects on its macroscopic properties, resulting the UCS decreased to 580.4 kPa and the permeability coefficient rose to 25.9 × 10-7 cm/s at 7 days. The ettringite formed in the PG blended MASB slurry led to a notable increase in the absolute solid volume, which could satisfactorily fill the pores and block the pore channels. The combined addition of RM and PG had a synergistic effect on the promotion of hydration process and optimization of the pore structure, contributing to establish a low permeability and high mechanical strength matrix. The overall findings indicate that the use of solid wastes in the MASB slurry can not only improve its engineering properties, but also promotes its sustainability and economical efficiency, holding a great potential for popularization and application.

The influence of palm oil fuel ash heat treatment on the strength activity, porosity, and water absorption of cement mortar.

The current study aims to explore the impact of palm oil fuel ash (POFA) heat treatment on the strength activity, porosity, and water absorption of cement mortar. The cement mortar mixtures were typically comprising cement or cement in combination with ultrafine treated POFA (u-TPOFA) which is the final form of the treated POFA, sand, water, and a superplasticizer. Before utilizing the u-TPOFA in mortar mixtures, the treatment processes of POFA were undertaken via five steps (drying at 105 ℃, sieving, grinding, heat treatment, re-grinding) to form u-TPOFA. The heat treatment was performed at three different heating temperatures (i.e., 550 ℃, 600 ℃, and 650 ℃). The ratio on mass/mass basis of the blended ordinary Portland cement (OPC) with u-TPOFA was OPC:u-TPOFA of 70%:30%. A total of four mixtures were prepared, consisting of a plain control mixture (designated as PCM) and three mixtures containing 30% of u-TPOFA treated at three different temperatures designated as M1 "550 ℃," M2 "600 ℃," and M3 "650 ℃". The results show that the optimum mixture was M2 which achieved the highest strength activity index (SAI) of 101.84% and 107% among all mixtures at 7 days and 28 days, respectively. Meanwhile, the porosity (P%) and water absorption (Abs%) of M2 exhibited the lowest values of 9.3% and 4.5%, respectively, among all the mixtures at 28 days. This superior performance of u-TPOFA treated at 600 ℃ represented in the M2 mixture was due to the formation of more binding phases consisting of calcium silicate hydrate (C-S-H) type gel originated from a higher pozzolanic reaction and the filler effects caused by the fine u-TPOFA microparticles. These observations were further confirmed by the improved performance of the M2 mix among all the designed mixes which also exhibited better results in terms of bulk density (BD), ultrasonic pulse velocity (UPV), X-ray diffraction (XRD) as well as thermogravimetry (TGA) and field emission scanning electron microscopy (FESEM-EDX) analyses.

A holistic assessment of the use of emerging recycled concrete aggregates after a destructive earthquake: Mechanical, economic and environmental.

This study aims to examine the mechanical, environmental, and economic properties of recycled aggregate concretes produced using emerged recycled concrete aggregates from the buildings that were demolished in a controlled way after the 24 January 2020, Elazig-Sivrice earthquake. For this purpose, 24 series of recycled aggregate concretes were produced, water-to-cement ratios of 0.30-0.35-0.40-0.45-0.50, and cement dosages were chosen as 320-370-420 kg/m3. 100% recycled concrete aggregate was used in the prepared concrete mixtures. Analyses were made on the response surface method using the mixture ratios and test results of 24 series. The effectiveness of the developed models was examined on 6 Control recycled aggregate concrete. Then, Energy Consumption, Global Warming Potential, Waste Generation, and Abiotic Depletion were considered to assess the environmental impacts of recycled aggregate concretes. In order to make environmental and economic comparisons of recycled aggregate concretes and natural aggregate concretes according to these impact categories, 4 different scenarios were developed. Then, a detailed feasibility analysis was made for 4 different scenarios, and the economic results of recycled aggregate concretes and natural aggregate concretes were evaluated. Regarding the arisen millions of tons of waste materials and newly constructed buildings after the earthquake, recycling waste materials is considered crucial. Therefore, a holistic assessment was taken with this study, and the usability of recycled concrete aggregates was examined in detail.

A review of cementitious alternatives within the development of environmental sustainability associated with cement replacement.

The environmental conditions of sustainable improvement in manufacturing consist of the application of secondary raw materials in the design and structure of new structures. Presently, the demand to construct new structures is growing rapidly, especially in the developed world. All of the construction and demolition (C&D) waste is deposited in open landfills in easily reachable spaces, which leads to numerous environmental problems. The utilization of this waste in concrete will help in sustainable and greener development. The main goals of using waste, by-products, and recycled materials to develop sustainable concrete are to reduce carbon dioxide emissions, which are a cause of environmental pollution and climate change, and to enhance exploitation of waste, which creates problems of disposal that can be solved by completely or partially replacing concrete components. This paper aims to provide a comprehensive overview of the published literature on the replacement of cement in concrete such as rice husk ash (RHA), olive stone biomass ash (OBA), recycled coal bottom ash (CBA), and recycled palm oil fuel ash (POFA), and its effects on the characteristics of concrete like workability, density, compressive strength, splitting tensile strength, flexural strength, shrinkage, and durability. Also, this paper aims to review the impact of the replacement of cement on sustainability. The author has also included recommendations for future research.

Aerogel and expanded perlite incorporated lightweight cementitious composites containing crushed glass: Evaluation of the drying shrinkage and alkali-silica expansion.

Lightweight cementitious composite (LCC) produced by incorporating lightweight silica aerogel was explored in this study. Silica aerogel was incorporated as 60% replacement of fine aggregate (sand/crushed glass) in producing the LCC. The effect of aerogel on the drying shrinkage and alkali-silica expansion of LCC was evaluated and compared with those of lightweight expanded perlite aggregate. At the density of 1600 ± 100 kg/m3, the aerogel/ expanded perlite LCC had attained compressive strength of about 17/24 MPa and 22/26 MPa in mixtures with sand and crushed glass as a fine aggregate, respectively. The inclusion of aerogel and expanded perlite increased the drying shrinkage. The drying shrinkage of aerogel LCC was up to about 3 times of the control mixtures. Although the presence of aerogel and expanded perlite could reduce the alkali-silica expansion when partially replacing crushed glass, the aerogel-glass LCC still recorded expansion exceeding the maximum limit of 0.10% at 14 days. However, when 15% cement was replaced with fly ash and granulated blast furnace slag, the alkali-silica expansion was reduced to 0.03% and 0.10%, respectively. Microstructural observations also revealed that the aerogel with fly ash can help in reducing the alkali-silica expansion in mixes containing the reactive crushed glass aggregate.