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Study on the metakaolin-based geopolymer pervious concrete (MKGPC) and its removal capability of heavy metal ions
Abstract
A metakaolin-based geopolymer pervious concrete (MKGPC) was developed to reduce the pollution of groundwater. In addition to the compressive strength, void ratio and permeability, the capacity of MKGPC on the removal of heavy metal ions in solution was focused. Its mechanisms were revealed from two aspects: the characteristics of binder and the volume structure of pervious concrete. The results showed that MKGPC has an excellent removal capacity of the heavy metal ions. In addition, we found that a low SiO2/Al2O3ratio at 2.0 could significantly improve the MKGPC's capability of removing heavy metal ions in solution, due to the formation of Natrolite. We also found that the decreases in the open void ratio and the permeability of MKGPC extend the contact time between the solution containing heavy metal ions and the MKG binder, thus improving the capacity of removing heavy metal ions in solution. Finally, the result indicated that pores of smaller size facilitate the adsorption of the heavy metal ions on MKGPC. To manufacture MKGPC which can purify water effectively, it is necessary to improve the adsorption ability of MKG binder and keep the balance between the open void, the permeability and the pore structure of MKGPC.
... Huang et al. [15] reported that the optimum GBFS contents were 10% and 30% for the AAM and AAF pervious concretes, respectively. Chen et al. [11] indicated that the alkali-activated based pervious concrete had a more substantial capability for water purification than OPC, and the AAM pervious concrete increased the capacity of removing heavy metal ions with the decrease in the void ratio and permeability. Overall, the alkali-activated based pervious concretes have satisfactory mechanical properties and water purification, which are appropriate for applying in pavements. ...
... Previous studies have reported the use of alkali-activated materials in pervious concrete, which is a type of pavement with void ratio of 15-30% and shows many benefits in storm water management, tire-pavement noise reduction, and water purification [11]. Zaetang et al. [12] reported that the mechanical properties and abrasive resistance of the alkali-activated fly-ash (AAF) pervious concrete improved with the increase in the curing temperature and OPC content. ...
... A constant head method was adopted to evaluate the water permeability for the pervious concretes [11,13,39]. The cylindrical specimens with 100 mm diameter and 50 mm height were used in the tests. ...
... Examination of pervious concrete for its ability to remove heavy metals with metal removal efficiencies of Cu (II) (85%-95%), Zn (II) (30%-95%), Cd (II) (60%-90%) and Pb (II) (95+%) and retention of particulate matter loaded column was reported by Vadas et al. (2017). Heavy metals have been found to adsorb onto geopolymer-based pervious concrete due to the formation of a geopolymeric gel with a zeolite (Chen et al., 2019;Al-Zboona et al., 2011;Cheng et al. 2012). Such systems have significant metal adsorption capability also due to their high surface area and well-defined pore size distribution. ...
... Murugan et al. (2018) studied the effects of hydraulic retention time and carbonation on reduced graphene oxide incorporated pervious concrete and found that the pervious concrete had a Pb (II) removal efficiency of 97.2 to 99.1%. Chen et al. (2019) studied the effects of metakaolin-based geopolymer pervious concrete to systematically remove heavy metals such as Pb (II) (>95%), Cd (II) (60%-90%), Cu (II) (85%-95%) and Zn (II) (30%-95%). Murugan et al. (2019) conducted column studies on reduced graphene oxide-incorporated pervious concrete and examined the influence of operating water heads on heavy metal removal and obtained removal efficiencies of Pb (II) (77%-96%), Cu (II) (76%-92%), Cd (II) (62%-98%) and Zn (II) (58%-96%). ...
The effects of partially adding iron-oxide-modified aggregate to OPC-based pervious concrete filter on the mechanical properties, heavy metal removal and leaching were investigated. Up to 10% of both coarse and fine aggregates were coated with iron oxide and filters (IOMA-C, coarse alone modified, IOMA-F fines alone modified and IOMA-CF) were prepared. Compressive strengths of the concrete improved while the permeability decreased by up to 13%. Simulated wastewater containing 15 ppm lead Pb (II) ions was passed through the control and IOMA-filters for 8 h under trickling water head. Iron-oxide-modified filter (IOMA-CF) showed maximum removal efficiency of 99.1% (87.3% for control). Desorption studies with 1M HNO3 indicated that iron oxide complexed the Pb (II) ions more irreversibly, reducing the extent of their leaching. Batch studies were carried out at 1 g/L adsorbent loading (crushed control and IOMA-CF) with solutions containing 5 to 25 ppm Pb (II). Langmuir isotherm fit adsorption results on both the control and IOMA-CF systems while Temkin isotherm was the best fit for IOMA-CF, indicating the stronger, more irreversible chemisorption of Pb (II) on iron oxide. Theoretical adsorption capacities based on Langmuir isotherms for the control and IOMA-CF were 18.21 and 20.66 mg/g, respectively. Kinetics studies indicated that a pseudo second order kinetics model fit the results of all systems with a slightly slower rate of adsorption than the control system. Effects of pH and coexisting ions have been examined. These preliminary results indicate the potential of applying pervious concretes either as water filters or pretreatment units.
... Recent studies related to porous concrete pavement includes, application of PCP in Municipal waste treatment [9] and blending Geopolymer with porous concrete to remove heavy metals [10].For environmental ecosystem protection it is essential to removed or reduced heavy metal pollutant. Remove heavy metalcontaminated wastewater pollutant is very difficult and costly. ...
... The porous concrete pavement (PCP) consisted with 7 layers, i.e. surface layer, base layer, subbase layer, coarse sand filter layer, fine sand filter layer and two layers of Geotextile. The PCP model was designed as per AASHTO, 1993 [11] guideline and followed typical layer thickness used for porous concrete pavements [10]. In this study, we used thickness of 4", 8", 8", 4" and 6" for surface layer, base layer, sub-base layer, coarse sand layer and fine sand layer respectively ( Figure 1). ...
This study aimed to investigate the heavy metals, i.e. Cu, Pb, Ni, and Zn removal efficiency from stormwater runoff of a porous concrete pavement (PCP). A model of PCP was designed with the porosity and co-efficient of permeability of the pavement were 27.2% and 1.83 cm/sec, respectively. Artificial stormwater containing heavy metals are passed through the pavement at a constant rainfall rate to mimic the stormwater rainfall-runoff condition. The artificial stormwater infiltrated through the pavement were then collected at two different pavement layers at different time instances. From the experimental investigations, it is observed that Cu, Pb, Ni and Zn concentrations are significantly reduced in the treated stormwater. At the first collection point which is located below the sub-base layer and coarse sand layer of the pavement, the concentrations of Cu, Pb and Zn reduced 56%, 67% and 93% respectively compared to their initial concentration, Ni concentration reduced only 20%. At the second collection point which is located below the coarse and fine sand layers beneath the pavement, the concentrations of Cu, Pb, Zn, and Ni are reduced 92%, 89%, 100%, 100%, respectively.
... The research findings indicate that the utilization of RM in GP-based pervious concrete presents a viable and ecologically sustainable resolution that has tangible implications for the purification of water. In another study, Chen et al. [76] revealed the water purification capacity by heavy metal ion removal potential (specifically, Pb 2+ and Cr 3+ ) of MK-based pervious GP concrete (MKGPC). The results of this study indicate that a significant portion of heavy metal ions present in rainwater can be adsorbed by MKGPC when the runoff flows over porous pavement, even when the duration of infiltration is very short. ...
Alkali-activated/geopolymer pervious concretes represent a recent and significant area of research within the pavement construction and materials science domains. A comprehensive, systematic literature study on this area is presented in this article. By leveraging its ability to handle massive volumes of data without causing additional complexities, systematic review with scientometrics will address the fundamental shortcomings of earlier traditional review methodologies. Hence, this all-encompassing review is dedicated to the "systematic" examination of prior research with an added focus on bibliometric analysis to enrich the review insights. Hence, a meticulous curation of a total of 81 pertinent documents available to date from the esteemed Scopus database was undertaken in the scope of the study. The "Preferred Reporting Items for Systematic Reviews and Meta-Analyses," i.e., the PRISMA technique, was applied for methodical review, thereby shedding light on concepts, developments, and trends in the novel field of pervious concretes were systematically undertaken. Additionally, the "VOSviewer software" package was employed as a valuable tool for bibliometric analysis, delivering a comprehensive overview of the scholarly landscape. Further, this article provides an in-depth analysis of the properties of alkali-activated/geopolymer pervious concretes, especially shedding light on the latest advancements in activating solution, materials and mix design, mechanical properties, durability aspects, and micro-structural properties. Furthermore, it explores into the various studies on the applications of such special concretes and their potential impact on the field of pavement construction engineering. The future research scopes were highlighted through the research gaps, linking the key findings from the existing developments in the prior art to help potential future researchers. Overall, this review serves as a valuable resource for researchers , scholars, and practitioners interested in advancing their knowledge base of developments in alkali-activated and geopolymer-based pervious concrete systems from the quick fundamentals to their potential applications , which can be further used for their research, thus contributing to the future evolution of this sustainable and innovative pavement construction material.
... Compared with cement concrete, it can reduce carbon dioxide emissions and the heat energy consumed in production, with obvious advantages in carbon emission reduction [12,13]. In addition, GPC has high early strength, higher strength than ordinary concrete, excellent mechanical properties, good acid and alkali corrosion resistance, outstanding high-temperature resistance, and can solidify heavy metal ions [14][15][16][17][18]. At present, China's construction waste production is huge, and the recycling of recycled aggregate is a key issue. ...
Geopolymeric recycled concrete (GRC) is a new low-carbon building material that uses both construction and industrial solid waste to replace natural aggregate and cement. GRC is similar to geopolymeric concrete (GPC) in that it has good mechanical properties but needs to be improved in terms of frost resistance. Previous studies have shown that polyoxymethylene fiber (POM fiber) can improve the shrinkage and durability of concrete and is superior to other commonly used fibers. Therefore, this paper explores adding POM fiber to GRC to improve its frost resistance. In this paper, the influence of different volumes and lengths of POM fiber on the frost resistance of geopolymeric recycled concrete (PRGRC) is studied. By measuring the changes in mass loss rate, relative dynamic elastic modulus, and compressive strength of PRGRC under different cycles, the improvement effect of POM fiber on the freeze-thaw damage of GRC is analyzed, and the strength attenuation model of PRGRC is established. The results show that the increase in POM fiber content can effectively slow down the mass loss of PRGRC in the freeze-thaw cycles, the reduction rate of relative dynamic elastic modulus, and the reduction rate of compressive strength. This shows that POM fiber can effectively improve the frost resistance of PRGRC, and the effect of 6 mm POM fiber on the freeze-thaw damage of PRGRC is better than 12 mm POM fiber. According to the test results, the existing strength attenuation model is further modified, the attenuation model of PRGRC compressive strength under the freeze-thaw cycle is obtained, and the model fitting effect is good. The strengthening mechanism of POM fiber is explained by the structural relationship between POM fiber and concrete matrix in the SEM micrograph of PRGRC. The research results provide a scientific basis for the applicability of POM fiber in geopolymeric cementitious materials and improving the frost resistance of PRGRC.
... [139,144,145] Earlier studies suggested that PCPs involved several layers, including the surface layer (in porous concrete), base layer, subbase layer, coarse sand filter layer, fine sand filter layer and subgrade. PCP models have been proposed based on the AASHTO (1993) [146] guidelines and the regular layer thickness of porous concrete pavements [147]. Rahman et al. [26] applied the thicknesses of 8, 4, 4, and 8 inches to the base layer (choker coarse and filter sand layer), the surface layer (porous concrete pavement), fine sand layer (filter blanket) and sub-base layer (coarse reservoir), respectively, as shown in Figure 2. The researchers at the University of New Hampshire Stormwater Center (UNHSC) studied pavement structural layers in the pavement system. ...
Clean water is a vital need for all living creatures during their lifespan. However, contaminated stormwater is a major issue around the globe. A wide range of contaminants, including heavy metals, organic and inorganic impurities, has been discovered in stormwater. Some commonly utilized methods, such as biological, physical and chemical procedures, have been considered to overcome these issues. However, these current approaches result in moderate to low contaminant removal efficiencies for certain classes of contaminants. Of late, filtration and adsorption processes have become more featured in permeable concretes (PCs) for the treatment of stormwater. As nanoparticles have vast potential and unique characterizations, such as a higher surface area to cure polluted stormwater, employing them to improve permeable concretes’ capabilities in stormwater treatment systems is an effective way to increase filtration and adsorption mechanisms. The present study reviews the removal rate of different stormwater contaminants such as heavy metals, organic and other pollutants using nanoparticle-improved PC. The application of different kinds of nanomaterials in PC as porous media to investigate their influences on the properties of PC, including the permeability rate, compressive strength, adsorption capacity and mix design of such concrete, was also studied. The findings of this review show that different types of nanomaterials improve the removal efficiency, compressive strength and adsorption capacity and decrease the infiltration rate of PC during the stormwater treatment process. With regard to the lack of comprehensive investigation concerning the use of nanomaterials in PC to treat polluted stormwater runoff, this study reviews 242 published articles on the removal rate of different stormwater contaminants by using PC improved with nanoparticles.
High porosity endues pervious concrete with outstanding performances as water permeability, pollutant removal, and noise reduction, which make pervious concrete a sustainable material for wide application fields, but a uniform mix design method for pervious concrete is not established yet. This review is conducted to integrate the useful findings in the publication and search the efficient method for the mix design of pervious concrete. The quantitative relationships between the mechanical and hydraulic properties and the mesoscopic parameters of pervious concrete provides the foundation for the property estimation during the mix design of pervious concrete, and the existing model could quantitatively characterize the mesostructure of pervious concrete consisting of cement paste and aggregate. The paste thickness is an important parameter to the final mesostructure of pervious concrete. The film-forming ability test provides an effective approach to select the suitable W/C and dosage of chemical admixture. Based on the previous finding in the publications, the mixture of pervious concrete could be quantitatively controlled from fresh to hardened state, and a systematic mix design method for pervious concrete is suggested. The suggested method would conduce to better control the quality of pervious concrete and greatly reduce the number of trail batching.
Cement paste coating is closely related to the water purification performance of porous concrete. The properties of metakaolin (MK) based cement paste coating and the effects of the metakaolin on removing methylene blue in water were investigated. The results showed the fluidity of the cement paste decreased and the cohesiveness increased with increase of the content of MK. It is found that the MK promoted the hydration of cement, which not only refined the pore structure of the cement paste, but also improved the interface transition zone. Besides, MK increased the adsorption capacity of the cement paste coating to methylene blue in water. The results showed that the content of MK is an important factor for affecting the methylene blue removal rate of the cement paste coating. Under the same MK content, the thickness of the cement paste coating had little positive effect on the methylene blue removal rate of the cement paste coating. The study is expected to provide a new approach for preparing cement paste coating with good methylene blue removal.
The EU has the ambitious goal to transition from linear to circular economy. In circular economy, the old saying of “one’s waste is the other’s treasure” is being implemented. In this chapter, valorisation of industrial side streams, traditionally branded as waste, is discussed with respect to their applications as raw materials for new adsorptive products – geopolymers (GP) and alkali-activated materials (AAM) – as adsorbents in wastewater treatment. The chemical nature and structure of materials generally have great influence on GP/AAM adsorption capability. The approaches used for the raw materials preparation (chemical or physical) prior geopolymerization to increase the adsorption capacity of the final products will be discussed. Adsorption properties and performance of GPs/AAMs towards various contaminants are described, and the latest research on testing those materials as water remediation are reviewed. Special attention is paid to regeneration of exhausted materials and available resource recovery options that the regeneration approach opens. New forms of geopolymer adsorbent such as foams or core-shell structures are described and in the last part of the chapter, a short economic evaluation of resource recovery models is provided.
A kind of alkali-activated slag pervious concrete (AAS-PC) was designed to purify rainwater to prevent it from polluting groundwater resources. The pervious concrete was designed from two aspects: the cementitious material and the volumetric structure parameters of pervious concrete. Chitosan was used in the cementitious material paste to enhance the adsorption capacity for heavy metal ions and other pollutants. In consideration of adsorption, composition parameters of the cementitious material paste such as the chitosan content, the mole ratio of SiO2/Na2O, and the concentration of alkali activator wereoptimized by orthogonal experiment. The influences of the bulk porosity of aggregate (BPA) and the ratio of paste to aggregate (P/A, mass ratio) on water purification capability, water permeability, and mechanical properties of the AAS-PC were investigated. It is found that, with the BPA increasing, the adsorption to Pb²⁺ and the compressive strength of pervious concrete decreased gradually but its water permeability improved; meanwhile, with the P/A increasing, its adsorption to Pb²⁺ and the compressive strength increased, but its water permeability decreased. There is a negative correlation between the water purification and the water permeability of the pervious concrete. Considering the water purification, water permeability and strength properties of the pervious concrete, the optimum BPA was 30% and the optimum P/A was 0.25.
One source of water is rainwater. It is a pure solvent if not polluted. It has diverse functions in humans, animals and other materials. For rainwater not to be polluted, it means the values of cations, anions and particulate matter should be below water permissible limits. In this paper, we have characterized metals in rainwater harvested in Akure, Ondo State, Nigeria using standard methods of analyses. The physico-chemical parameters and metals were below WHO water guidelines. The variation of the metals was as follows: Ca>K>Na>Mg>Zn>Fe>Cu>Pb>Cr. Cd was absent and the Pb content was low. Principal Component Analysis showed that factors 1, 2 and 3 showed high loadings for Cr and Zn; Pb and Ca; and Cu, Mn and Mg respectively. Sources of these metals were due to anthropogenic activities.
Fast urbanization and industrialization in developing countries result in significant stormwater runoff pollution, due to drastic changes in land-use, from rural to urban. A three-year study on the stormwater runoff pollutant loading distributions of industrial, parking lot and mixed commercial and residential catchments was conducted in the Tongsha reservoir watershed of Dongguan city, a typical, rapidly industrialized urban area in China. This study presents the changes in concentration during rainfall events, event mean concentrations (EMCs) and event pollution loads per unit area (EPLs). The first flush criterion, namely the mass first flush ratio (MFFn), was used to identify the first flush effects. The impacts of rainfall and catchment characterization on EMCs and pollutant loads percentage transported by the first 40% of runoff volume (FF40) were evaluated. The results indicated that the pollutant wash-off process of runoff during the rainfall events has significant temporal and spatial variations. The mean rainfall intensity (I), the impervious rate (IMR) and max 5-min intensity (Imax5) are the critical parameters of EMCs, while Imax5, antecedent dry days (ADD) and rainfall depth (RD) are the critical parameters of FF40. Intercepting the first 40% of runoff volume can remove 55% of TSS load, 53% of COD load, 58% of TN load, and 61% of TP load, respectively, according to all the storm events. These results may be helpful in mitigating stormwater runoff pollution for many other urban areas in developing countries.
A total of 50 rainwater samples were analyzed in order to investigate trace elements in wet precipitation of Juiz de Fora City, during February, 2010 and February, 2011. Samples were analyzed for major cations (H3O+, Na+, NH4+, K+, Mg-2(+) and Ca-2(+)) and anions (NO3-, SO42-, Cl-and HCO3-), hydrogen peroxide (H2O2), some trace metals (Cu-2(+), Zn-2(+), Cd-2(+) and Pb-2(+)), as well as some other physicochemical aspects like pH, conductivity and redox potential. Rainwater pH mean was of 5.77 (+/- 0.52). Cations and anions mean values ranged from 7.12 mu Eq L-1 (K+) to 39.6 mu Eq L-1 (Ca2+). Principal Component Analysis (PCA) with Varimax normalized rotation was performed, grouping the major analyzed cations and anions into different factors. Mg2+, K+, Ca2+ and HCO3-were assigned to soil contribution, Na+ and Cl-to sea-salt contribution and NO3-, SO42-and NH4+ to anthropogenic sources. Hydrogen peroxide average concentration was of 19.2 +/- 17.5 mu mol L-1 with higher values in summer and lower in spring and autumn, reverse case was observed for H3O+ levels. Zn2+ (7.31 +/- 2.74) mu g L-1 and Cu2+ (4.07 +/- 0.74) mu g L-1 were within the range of other studied areas, while Cd2+ and Pb2+ were below the detection limit.
The work described in this paper provides an evaluation of an aged pervious concrete pavement in the Northeastern United States to provide a better understanding of the long-lasting effects of placement techniques as well as the long-term field performance of porous pavement, specifically in areas susceptible to freezing and thawing. Multiple samples were taken from the existing pavement and were examined in terms of porosity and unit weight, compressive and splitting tensile strength, and the depth and degree of clogging. It was concluded that improper placement and curing led to uneven pavement thickness, irregular pore distribution within the pervious concrete, and highly variable strength values across the site, as well as sealed surfaces that prevented infiltration.
Pervious concrete is a tailored-property concrete with high water permeability which allow the passage of water to flow through easily through the existing interconnected large pore structure. This paper reports the results of an experimental investigation into the development of pervious concrete with reduced cement content and recycled concrete aggregate for sustainable permeable pavement construction. High fineness ground granulated blast furnace slag was used to replace up to 70 % cement by weight. The properties of the pervious concrete were evaluated by determining the compressive strength at 7 and 28 days, void content and water permeability under falling head. The compressive strength of pervious concrete increased with a reduction in the maximum aggregate size from 20 to 13 mm. The relationship between 28-day compressive strength and porosity for pervious concrete was adversely affected by the use of recycled concrete aggregate instead of natural aggregate. However, the binder materials type, age, aggregate size and test specimen shape had marginal effect on the strength–porosity relationship. The results also showed that the water permeability of pervious concrete is primarily influenced by the porosity and not affected by the use of recycled concrete aggregate in place of natural aggregate. The empirical inter-relationships developed among porosity, compressive strength and water permeability could be used in the mix design of pervious concrete with either natural or recycled concrete aggregates to meet the specification requirements of compressive strength and water permeability.
Strength development of alkali activated slag (AAS) mortars, activated using alkali hydroxide and sodium silicate, was investigated at room and elevated temperatures. Heat evolution at room temperature was measured using isothermal calorimetry. Important differences were observed between critical activation parameters. Heat cured specimens gain strength rapidly, humid oven conditions being favorable, but given sufficient time room temperature curing yields comparable strengths. Both activators are needed for high strength at room temperature, NaOH solution is more critical and its concentration greatly influences strength. At 80°C however, sodium silicate is essential and even sufficient. KOH is more effective than NaOH at 80°C, but not at room temperature. Lower water-to-slag ratios give higher strength at early ages. AAS hydration evolves less heat than Portland cement hydration. Time to significant strength gain of mixtures can be predicted using their time and heat evolution at setting. Twenty eight-day strength of AAS mortars is roughly related to total evolved heat and increases nearly linearly with the amount of NaOH activator for fixed water glass content.
Monthly rainwater samples were collected during the summer of 1994 in eight arctic catchments in northern Europe (four in Russia, three in Finland, one in Norway), at different distances and wind directions from the emissions of the Russian nickel ore mining, roasting and smelting industry on the Kola Peninsula. Three stations consisting of five samplers each were placed in open areas in all the catchments. Results show that close to the smelters in Monchegorsk, rainwater is strongly enriched in Ni (633 x), Co, Cu, As, Mo, Al (36 x), V, Cd, Sb, Pb (11 x), Zn, Fe, Sr, Na, S/SO4 (6 x), Cl, Cr, Se (4 x) and Ag when compared to a Finnish background catchment. Three sources of elements can be differentiated: natural dust, sea spray and anthropogenic (smokestack emissions and dust). Correlation diagrams and element ratios can be used to identify the different industrial processes and even ore feed changes at one smelter.
Geopolymer with Si/Al ratios from 2 to 4 were prepared by adding different contents of fused silica into geopolymer matrix. Effects of Si/Al ratios on the structure, mechanical properties and chemical stability in air of the obtained geopolymer were systematically investigated. The results showed that all the geopolymer samples were XRD amorphous. Geopolymer with Si/Al ratios of 2 and 2.5 showed similar structure and property and they were classed as KGP-I; and geopolymer with Si/Al ratios of 3, 3.5 and 4 were similar and they were class as KGP-II. In alkaline solution, reactivity of fused silica were higher than that of metakaolin, resulting in higher content of both residual metakaolin and free alkaline cation in KGP-II than in KGP-I. Fused silica partially reacted with the alkaline solution in KGP-II indicating chemical interfacial bonding between silica and binder phase. With the increase in Si/Al ratios, KGP-II especially for geopolymer with Si/Al of 4 showed much higher mechanical properties than KGP-I due to the increased Si-O-Si bonds and residual silica as reinforcement. However, KGP-II showed worse chemical stability in air than KGP-I, with the presence of efflorescence on the surface, which was attributed to their higher residual free K þ .
The water purification characteristics of pervious concrete fabricated with calcium sulfoaluminate cement and coal bottom ash aggregate are investigated. Reduction ratio of nitrogen and phosphorus by the pervious concrete was investigated, and the results were discussed with filtering and adsorption effects. A series of tests including a batch adsorption, BET and XRD was conducted for this purpose. The calcium sulfoaluminate cement contributed to the slightly rapid strength development of the pervious concrete, while its purification performance was similar to that of ordinary Portland cement. Suspended nitrogen and phosphorous contents were significantly reduced by the physical filtration of voids in the pervious concrete, resulting in an improvement of the turbidity. The dissolved phosphorous could be adsorbed by the formation of hydroxyapatite in both cements.
This study examined metal leaching and retention in pervious concrete with or without embedded particulate matter. Particulate matter was collected from an adjacent parking lot and from a nearby parking garage as examples of weathered and un-weathered particulate matter. Particle size distributions were similar, but metal content was 3–35-fold higher and organic matter content was 3-fold higher in the parking garage particulate matter compared to the parking lot particulate matter. Replicate columns were established with either no particulate added as the control, or 20 g of parking lot or parking garage particulate matter. Synthetic rainwater was passed through the columns at variable rainfall intensity or fixed intensity to assess leaching. Metals were leached at higher concentrations from the parking garage particulate amended column, but from all columns less than 1% of the metal mass leached. Rainfall intensity did not have a large effect on leached metal concentrations, only varying effluent by about 2-fold. Synthetic stormwater with elevated dissolved Cu, Zn, Cd and Pb concentrations was passed through the same columns and metal removal efficiencies were on the order of 85–95%, 30–95%, 60–90%, and 95+% for each metal, respectively. After loading the column with a year's worth of stormwater metal exposure, removal efficiencies in the no particulate and parking lot particulate amended columns decreased, while parking garage particulate amended columns performed similarly with a small drop in Cu and Pb removal efficiencies. Generally, columns with no particulate and parking lot particulate amendments performed similarly, suggesting the pervious concrete is responsible for the majority of the initial metal retention. The parking garage particulate amended columns retained more metals from stormwater, perhaps due to an increase in pH that promoted surface precipitation as hydroxides or carbonate species on the pervious concrete, or due to complexation in the higher concentrations of organic matter and iron oxides in the particulate matter. Overall, metal retention was aided by the presence of organic matter in the particulate matter, but the pervious concrete itself was more important than particulates for metal retention. A strategy to increase metal retention and removal from the environment could involve amending pervious concrete with mixtures of well-defined sorbents to enhance metal retention.
Pervious concrete is a sustainable pavement with high permeability. The purpose of this study is to evaluate physical and mechanical properties of the pervious concrete including density, strength, porosity, and permeability. Taguchi design of experiments was used to optimize the performance of these characteristics. The relationship between properties dependent on coarse aggregate size. As the maximum size of the coarse aggregate increases, both the permeability and porosity grows up. Also, it results in a significant decrease in compressive strength. There is a trade-off between strength and permeability which should be considered to meet the minimum requirements for the pervious concrete.
In this study, self-developed laboratory apparatus was devised to investigate filtration effects of permeable asphalt pavements (PAP) and their mechanisms. The filtration effect of PAP is specified by measuring 16 pollutant indices in influent and effluent samples. Results show that the PAP is highly effective in removing copper (Cu), zinc (Zn), lead (Pb) and cadmium (Cd), and relatively less effective on petroleum pollutants (PP), animal & vegetable oil (AVO), biochemical oxygen demand (BOD), chemical oxygen demand (COD) and ammonia nitrogen (NH4-N). The effect on removing total phosphorus (TP), chloride (Cl-) and total nitrogen (TN) is marginal. Influences of sampling time on pollutant concentrations were investigated as well, which indicates that the increases of sampling time reduce the pollutant concentrations to some extent. The decreases of pollution concentrations can be attributed to the interception and physisorption of porous materials used in the PAP.
Mix ratios of liquid-to-binder (L/B), fly ash-to-binder (FA/B), nanoSiO2-to-binder (NS/B) and NaOH concentration (NH) of fly ash-nanoSiO2-cement geopolymer pastes were optimized for the flow of paste and the compressive strength simultaneously. Optimum mix design was found at 50% L/B, 60% FA/B, 0.04% NS/B and 1.71 M NH resulting in a maximum achievable compressive strength at 22.2 MPa after a 7-day curing under ambient temperature (25 ± 5 °C) and the desired flow of paste at 110%. It was found that NH had the greatest effect on the flow of paste: the higher NH, the smaller the flow of paste was. On the other hand, NS/B showed the least effect on the compressive strength. Pervious geopolymer concrete made with the optimum mix was able to reduce fecal coliforms and phosphorus by 54-100 and 25-85%, respectively, depending on the contact time (0.5-8 h). A greater FC and P removal % was achieved at a higher pH caused by pervious geopolymer concrete.
In this research, the ability of pervious concrete pavement material to reduce pollutant concentrations and purify water was investigated. This project mainly aims to study the ability of pervious concrete pavement material to reduce pollutant concentrations such as those in diluted sulfuric acid, seawater, and motor oil. The results demonstrated that the ability of pervious concrete pavement material to reduce pollutant concentrations and purify water was effective in diluted sulfuric acid, artificial seawater, and motor oil tests. After flowing through pervious concrete pavement, a diluted sulfuric acid solution (pH value 2.0) could dramatically increase its pH value to approximately 7.0. A pervious concrete pavement system could greatly decrease the content of an artificial seawater solution (salinity 36%) to about 1%, and the oil content of motor oil combined with certain types of water could also be significantly decreased to 1%. The study demonstrates that pervious concrete pavement holds potential for environment conservation and hydrologic consideration. (C) 2014 American Society of Civil Engineers.
This research investigated whether pervious concrete is effective in removing dissolved zinc and copper contaminants from stormwater runoff. Pervious concrete cylinders were loaded in the laboratory with simulated runoff, and influent and effluent concentrations and volumes measured. In one set of tests, stormwater was dispensed at typical concentrations (100 mu g/L Zn and 20 mu g/L Cu) simulating ten consecutive storm events of 12 mm (0.5 in.) of rain to test initial removal performance. Another set of cylinders was loaded at forty times the typical concentration to simulate accelerated longterm metal loading indicative of several years of typical use. Cylinders were removed after 15 and 24 accelerated events respectively for further typical concentration performance testing. Performance for the typical concentration tests both pre and post accelerated loading were calculated as a percent metals retained and also as a percent decrease in effluent versus influent concentration. The pre accelerated metal loading results indicate averages of 93% and 91% retained, and 90% and 87% concentration decreases for Zn and Cu respectively. Similar percentages were retained post accelerated metal loadings with slightly lower averages for copper after 24 accelerated loading events, although this was probably due to a higher infiltration rate. Removals were seen to be effected by both physical (water trapping) and by chemical (sorption and complexation) processes.
Pervious concrete is increasingly used in the pavements and overlays subjected to heavy traffic and in cold weather regions. In the present study, strength, fracture toughness and fatigue life of two types of pervious concrete, supplementary cementitious material (SCM)-modified pervious concrete (SPC) and polymer-modified pervious concrete (PPC), are investigated. The results indicate that high strength pervious concrete (32–46 MPa at 28 days depending upon the porosity) can be achieved through both SCM-modification, using silica fume (SF) and superplasticizer (SP), and polymer-modification, using polymer SJ-601. For both SPC and PPC, porosity significantly affects compressive strength, but it has little effect on the rate of strength development. Flexural strength of pervious concrete is more sensitive to porosity than compressive strength. Pervious concrete has more significant size effect than conventional concrete. PPC demonstrates much higher fracture toughness and far longer fatigue life than SPC at any stress level.
This study evaluates the properties of pervious concrete made of high-calcium fly ash geopolymer binder. Pervious geopolymer concretes (PGCs) were prepared from lignite fly ash (FA), sodium silicate (NS), sodium hydroxide (NH) solution, and coarse aggregate. The FA to coarse aggregate ratio of 1:8 by weight, constant NS/NH ratio of 0.50, alkaline liquid/FA (L/A) ratios of 0.35, 0.40, and 0.45, and NH concentrations of 10, 15, and 20 M were the PGC mix proportions. The curing temperature of 60 °C for 48 h was used to activate the geopolymerization. The results showed that the high-calcium fly ash geopolymer binder could be used to produce pervious concrete with satisfactory mechanical properties. The relationships of the density-void content, compressive strength-density, and compressive strength-void content of the PGCs were derived and found to be similar to those of conventional pervious concrete.
Since porous materials often function as adsorbents, this study chose to investigate the adsorption of heavy metals by geopolymers. The geopolymer was made by condensing a mixture of metakaolin and alkali solution at a fixed ratio at room temperature and then pre-crashed to a fixed-radius size. This paper examined the adsorption efficiency of the geopolymer for different heavy metals (i.e., Pb2+, Cu2+, Cr3+, and Cd2+) in aqueous solutions under discrete experimental parameters. The experimental results verified that the geopolymer could adsorb heavy metals. Of the metals tested, optimal adsorption with the implementation of the geopolymer occurred with Pb2+. The data fit both the pseudo-second-order and the Langmuir equations. This discovery may facilitate the development of optimized procedures for wastewater treatment, thus providing an alternative solution to environmental damages caused by heavy metal pollutants.
The results of an experiment on the compressive strength and water purification properties of porous concrete are reported in this paper. Two sizes of coarse aggregate were used, namely 5 to 10 mm, and 10 to 20 mm. Three absolute volume ratios of paste–aggregate were used, namely 30%, 40% and 50% for a given size of aggregate. The compressive strength is found to be higher when the size of the aggregate is smaller, and when the paste–aggregate ratio (P/G, vol.%) is smaller. In the water purification experiment, the amount of organisms attached on the porous concrete surface is indirectly examined by the consumption of the dissolved oxygen (DO, mg/l). Water purification of the porous concrete is evaluated by the removal amount of the total phosphorus (T-P, mg/l) and total nitrogen (T-N, mg/l). A porous concrete with a smaller size of aggregate and a higher void content was found to have superior ability of the removal of the T-N and T-P in the test water. This is due to the large specific surface area of the porous concrete. Results from this study show that porous concrete using industrial by-products is able to purify water efficiently.
The solution of three-dimensional diffusion equations is discussed with respect to the applicability of a √t relationship to describe diffusion. The kinetics of the rates of H2O sorption and of D2O-H2O exchange have been followed in the zeolites chabazite, gmelinite and heulandite in the temperature range 30–80°C, and intrinsic diffusion coefficients and self-diffusion coefficients of water in the crystal evaluated from the respective sets of measurements. Self-diffusion coefficients in all three zeolites have values intermediate between the self-diffusion coefficients of liquid water, at the same temperature, and ice near its melting point. Small changes in total water content near saturation produce a slight decrease in the self-diffusion coefficients in chabazite and gmelinite and a more marked decrease in heulandite. Using equilibrium sorption data it is shown that the equation is a reasonably satisfactory description of the relationship between the diffusion coefficients and this provides an indication that both intrinsic and self-diffusion processes involve molecules as diffusing units.
The structure of natrolite, Na2Al2Si301o' 2H20, proposed by PAULING and TAYLOR has been confirmed and refined by Fourier and least-squares methods using three-dimensional data obtained with CuKcx radiation. The water is linked to oxygen atoms of the framework by hydrogen bonds having a length of 2.85 and 2.99 A, respectively. The refined structure gives interatomic distances of 1.62 ::I: 0.01 A for the tetrahedral Si-O bond, 1.75 ::I: 0.02 A for the tetra- hedral AI-O bond, and 2.37 ::I: 0.02 Afor the Na-O bond. The openings between neighboring chains of the fibrous zeolites provide a system of open, intersecting channels. The dehydration and cation exchange phenomena must be attributed to these channels and not, as has long been supposed, to the much narrower channels parallel to the fiber axis.
Aluminosilicate geopolymers with SiO2/Al2O3 ratios ranging from 0.5 to 300 have been prepared from mixtures of dehydroxylated kaolinite with either ρ-Al2O3 or fine Aerosil SiO2, with the ratios Na2O/SiO2 and H2O/SiO2 kept constant throughout the series. All the compositions hardened at ambient temperature, but the high-alumina compositions were of low strength and did not display typical XRD and NMR geopolymer characteristics, by contrast with the compositions of S/A between 2 and 300 which showed typical amorphous geopolymer XRD traces and 27Al, 29Si and 23Na NMR spectra. The samples with increasing SiO2 content (S/A > 24) showed increasingly elastic behaviour, deforming rather than crushing in brittle fashion, and upon heating at 100–250 °C, their hydration water was expelled as bubbles, forming stable foamed materials at about 300 °C.
Statistical analysis of a systematic series of geopolymers with varying alkali type (sodium and potassium) and Si/Al ratio after 7 and 28 days ageing has been used as a basis for observing the development of mechanical properties with time. Minimal change in the compressive strength of specimens was generally observed in specimens of different alkali or between 7 and 28 days of ageing. However, mixed-alkali specimens with high Si/Al ratio exhibited significant increases in strength, while pure alkali specimens displayed decreased strength. The development of Young's modulus of geopolymers between 7 and 28 days was observed to be dependent on alkali, with the Young's moduli of Na-specimens decreasing at low Si/Al ratio, but increasing at high Si/Al ratio, while K-specimens exhibited the opposite effect. Mixed-alkali specimens all exhibited nominal change in Young's moduli, without any significant effect of Si/Al ratio being observed.
This investigation is focused on the effect of curing temperature on microstructure, shrinkage, and compressive strength of alkali-activated slag (AAS) concrete. Concrete prepared using sodium silicate and sodium hydroxide as the activator had greater early and flexural strength than ordinary Portland cement concrete of the same water/binder ratio, but it also had high autogenous and drying shrinkage. Heat treatment was found to be very effective in reducing drying shrinkage of AAS concrete and promoting high early strength. However, strength of AAS concrete at later ages was reduced. Microstructural study revealed an inhomogeneity in distribution of hydration product in AAS concrete that can be a cause of strength reduction. Pretreatment at room temperature before elevated temperature curing further improved early strength and considerably decreased shrinkage in AAS concrete.
A 0.05 ha highway subcatchment located within a larger 243 ha separately sewered residential estate in NW London has been investigated to evaluate the relative pollutant contribution of highway surfaces to total urban runoff discharges.Mass balances for both solid and soluble metal loadings for the subcatchment are ‘scaled-up’ to estimate the potential impact of rooftop, road surface and roadside gullypots on stormwater loadings discharged to the receiving stream from the parent catchment. The scaling-up procedure predicts a 46%, 78%, 47% and 13% contribution of total Cd, Cu, Pb and Zn loadings respectively from road runoff with ratios of soluble to insoluble metal being 4.0, 1.8, 0.2 and 3.0 respectively for these metals.The analysis confirms the importance of belowground, in-pipe processes in modifying the inherent geochemical characteristics of road runoff quality as well as highlighting the potential deleterious effect of uncontrolled highway discharges on receiving stream quality.
In this paper, a pervious concrete pavement material used for roadway is introduced. Using the common material and method, the strength of the pervious concrete is low. Using smaller sized aggregate, silica fume (SF), and superplasticizer (SP) in the pervious concrete can enhance the strength of pervious concrete greatly. The pervious pavement materials that composed of a surface layer and a base layer were made. The compressive strength of the composite can reach 50 MPa and the flexural strength 6 MPa. The water penetration, abrasion resistance, and freezing and thawing durability of the materials are also very good. It can be applied to both the footpath and the vehicle road. It is an environment-friendly pavement material.
The purpose of this review paper is to summarise the wide-range but diffuse literature on predominantly permeable pavement systems (PPS), highlight current trends in research and industry, and to recommend future areas of research and development. The development of PPS as an integral part of sustainable drainage systems is reviewed in the context of traditional and modern urban drainage. Particular emphasise is given to detailed design, maintenance and water quality control aspects. The most important target pollutants are hydrocarbons, heavy metals and nutrients (i.e. nitrogen and phosphorus). The advantages and disadvantages of different PPS are discussed with the help of recent case studies. The latest innovations are highlighted and explained, and their potential for further research work is outlined. Recent research on the development of a combined geothermal heating and cooling, water treatment, and recycling pavement system is promising.
The aim of this work was to synthesis highly amorphous geopolymer from waste coal fly ash, to be used as an adsorbent for lead Pb(II) removal from aqueous wastewater. The effect of various parameters including geopolymer dosage, initial concentration, contact time, pH and temperature on lead adsorption were investigated. The major components of the used ash in the current study were SiO(2), Al(2)O(3) and Fe(2)O(3) representing 91.53 wt% of its mass. It was found that the synthesized geopolymer has higher removal capacity for lead ions when compared with that of raw coal fly ash. The removal efficiency increases with increasing geopolymer dosage, contact time, temperature, and the decrease of Pb(2+) initial concentration. The optimum removal efficiency was obtained at pH 5. Adsorption isotherm study indicated that Langmuir isotherm model is the best fit for the experimental data than Freundlich model. It was found also that the adsorption process is endothermic and more favorable at higher temperatures.
Geopolymers consist of an amorphous, three-dimensional structure resulting from the polymerization of aluminosilicate monomers that result from dissolution of kaolin in an alkaline solution at temperatures around 80 degrees C. One potential use of geopolymers is as Portland cement replacement. It will be of great importance to provide a geopolymer with suitable mechanical properties for the purpose of water storage and high adsorption capacity towards pollutants. The aim of this work is to investigate the effect of using Jordanian zeolitic tuff as filler on the mechanical performance and on the adsorption capacity of the geopolymers products. Jordanian zeolitic tuff is inexpensive and is known to have high adsorption capacity. The results confirmed that this natural zeolitic tuff can be used as a filler of stable geopolymers with high mechanical properties and high adsorption capacity towards methylene blue and Cu(II) ions. The XRD measurements showed that the phillipsite peaks (major mineral constituent of Jordanian zeolite) were disappeared upon geopolymerization. The zeolite-based geopolymers revealed high compressive strength compared to reference geopolymers that employ sand as filler. Adsorption experiments showed that among different geopolymers prepared, the zeolite-based geopolymers have the highest adsorption capacity towards methylene blue and copper(II) ions.
The removal performance and the selectivity sequence of mixed metal ions (Co(2+), Cr(3+), Cu(2+), Zn(2+) and Ni(2+)) in aqueous solution were investigated by adsorption process on pure and chamfered-edge zeolite 4A prepared from coal fly ash (CFA), commercial grade zeolite 4A and the residual products recycled from CFA. The pure zeolite 4A (prepared from CFA) was synthesized under a novel temperature step-change method with reduced synthesis time. Batch method was employed to study the influential parameters such as initial metal ions concentration, adsorbent dose, contact time and initial pH of the solution on the adsorption process. The experimental data were well fitted by the pseudo-second-order kinetics model (for Co(2+), Cr(3+), Cu(2+) and Zn(2+) ions) and the pseudo-first-order kinetics model (for Ni(2+) ions). The equilibrium data were well fitted by the Langmuir model and showed the affinity order: Cu(2+) > Cr(3+) > Zn(2+) > Co(2+) > Ni(2+) (CFA prepared and commercial grade zeolite 4A). The adsorption process was found to be pH and concentration dependent. The sorption rate and sorption capacity of metal ions could be significantly improved by increasing pH value. The removal mechanism of metal ions was by adsorption and ion exchange processes. Compared to commercial grade zeolite 4A, the CFA prepared adsorbents could be alternative materials for the treatment of wastewater.
Pervious concrete is an alternative paving surface that can be used to reduce the nonpoint source pollution effects of stormwater runoff from paved surfaces such as roadways and parking lots by allowing some of the rainfall to permeate into the ground below. This infiltration rate may be adversely affected by clogging of the system, particularly clogging or covering by sand in coastal areas. A theoretical relation was developed between the effective permeability of a sand-clogged pervious concrete block, the permeability of sand, and the porosity of the unclogged block. Permeabilities were then measured for Portland cement pervious concrete systems fully covered with extra fine sand in a flume using simulated rainfalls. The experimental results correlated well with the theoretical calculated permeability of the pervious concrete system for pervious concrete systems fully covered on the surface with sand. Two different slopes (2% and 10%) were used. Rainfall rates were simulated for the combination of direct rainfall (passive runoff) and for additional stormwater runoff from adjacent areas (active runoff). A typical pervious concrete block will allow water to pass through at flow rates greater than 0.2 cm/s and a typical extra fine sand will have a permeability of approximately 0.02 cm/s. The limit of the system with complete sand coverage resulted in an effective system permeability of approximately 0.004 cm/s which is similar to the rainfall intensity of a 30 min duration, 100-year frequency event in the southeastern United States. The results obtained are important in designing and evaluating pervious concrete as a paving surface within watershed management systems for controlling the quantity of runoff.
High-performance materials for construction, waste immobilisation and an ever-growing range of niche applications are produced by the reaction sequence known as 'geopolymerisation'. In this process, an alkaline activating solution reacts with a solid aluminosilicate source, with solidification possible within minutes and very rapid early strength development. Geopolymers have been observed to display remarkable chemical and thermal stability, but due to their largely X-ray amorphous nature have only recently been accurately characterised. It has previously been shown that both fly ash and ground granulated blast furnace slag are highly effective as solid constituents of geopolymer reaction slurries, providing readily soluble alumina and silica that undergo a dissolution-reorientation-solidification process to form a geopolymeric material. Here a conceptual model for geopolymerisation is presented, allowing elucidation of the individual mechanistic steps involved in this complex and rapid process. The model is based on the reactions known to occur in the weathering of aluminosilicate minerals under alkaline conditions, which occur in a highly accelerated manner under the conditions required for geopolymerisation. Transformation of the waste materials to the mixture of gel and nanocrystalline/semicrystalline phases comprising the geopolymeric product is described. Presence of calcium in the solid waste materials affects the process of geopolymerisation by providing extra nucleation sites for precipitation of dissolved species, which may be used to tailor setting times and material properties if desired. Application of geopolymer technology in remediation of toxic or radioactive contaminants will depend on the ability to analyse and predict long-term durability and stability based on initial mix formulation. The model presented here provides a framework by which this will be made possible.
Solid-state conversion of fly ash to an amorphous aluminosilicate adsorbent (geopolymer) has been investigated under different conditions and the synthesised material has been tested for Cu2+ removal from aqueous solution. It has been found that higher reaction temperature and Na:FA ratio will make the adsorbents achieving higher removal efficiency. The adsorbent loading and Cu2+ initial concentration will also affect the removal efficiency while the adsorption capacity exhibits similarly at 30-40 degrees C. The adsorption capacity of the synthesised adsorbent shows much higher value than fly ash and natural zeolite. The capacity is 0.1, 3.5 and 92 mg/g, for fly ash, natural zeolite, and FA derived adsorbent, respectively. The kinetic studies indicate that the adsorption can be fitted by the second-order kinetic model. Langmuir and Freundlich isotherms also can fit to the adsorption isotherm.
The study was carried out on the sorption of heavy metals (Ni2+, Cu2+, Pb2+, and Cd2+) under static conditions from single- and multicomponent aqueous solutions by raw and pretreated clinoptilolite. The sorption has an ion-exchange nature and consists of three stages, i.e., the adsorption on the surface of microcrystals, the inversion stage, and the moderate adsorption in the interior of the microcrystal. The finer clinoptilolite fractions sorb higher amounts of the metals due to relative enriching by the zeolite proper and higher cleavage. The slight difference between adsorption capacity of the clinoptilolite toward lead, copper, and cadmium from single- and multicomponent solutions may testify to individual sorption centers of the zeolite for each metal. The decrease of nickel adsorption from multicomponent solutions is probably caused by the propinquity of its sorption forms to the other metals and by competition. The maximum sorption capacity toward Cd2+ is determined as 4.22 mg/g at an initial concentration of 80 mg/L and toward Pb2+, Cu2+, and Ni2+ as 27.7, 25.76, and 13.03 mg/g at 800 mg/L. The sorption results fit well to the Langmuir and the Freundlich models. The second one is better for adsorption modeling at high metal concentrations.
Concrete. Specification, performance, production and conformity
- Bs En
Pervious high-calcium fly ash geopolymer concrete. Construction and Building Materials, 30
- Tho-In
- Tawatchai
Experiment on adsorptive capacity of permeable concrete pavement materials for runoff pollutants
- Junling Wang