Performance improvement of asphalt concretes using fiber reinforcement.

This study reports on the laboratory performance, field performance and cost analysis of fiber-reinforced asphalt concrete (FR-AC) pavement using AC60/70 and polymer modified asphalt (PMA) as binders. The performance testing included indirect tensile resilient modulus, indirect tensile strength modulus, indirect tensile fatigue life, dynamic creep and wheel-tracker tests. Field trials of AC60/70 and PMA mixtures, were undertaken with and without fibers and the International Roughness Index, texture depth, and rutting of the mixtures were measured over time. The PMA + Fiber mixture exhibited the best performance among the materials tested. The performance of AC60/70 + Fiber mixture were comparable to PMA mixture. The improvement of both fatigue cracking and rutting were similar for AC60/70 + Fiber mixtures while the improvement of fatigue cracking was higher than rutting for the PMA mixtures. Since the performance of FR-AC was similar for both laboratory and plant mixed specimens, the laboratory mix design results can be used to interpret the field performance. The fiber reinforced AC60/70 mixture was found to be the most economical. The outcome of this research can be used as a guide, for establishing the specification of FR-AC pavement in Thailand and other countries using similar mix design.

Permanent Deformation and Rutting Resistance of Demolition Waste Triple Blends in Unbound Pavement Applications.

Virgin quarried materials are becoming increasingly scarce in our environment, and these materials are no longer a viable or economical solution for the construction industry. The construction industry is constantly seeking new markets for recycled waste in civil engineering applications. This research's primary focus is the optimization of the usage of recycled materials such as recycled glass (RG), crushed brick (CB), and crushed concrete (CC), in pavement base/sub-base applications. Various percentages of RG, up to 40%, were blended with two types of CC in this research. The CC and CB, which were used as triple blends in this research, were utilized for the upper (100% CC) and lower sub-bases (up to 50% CB). This study sought to establish the maximum amount of RG that could be incorporated in the triple blends with CB and CC whilst maintaining an acceptable performance. Thus, a comprehensive series of fundamental and advanced geotechnical laboratory tests, including repeated load triaxial (RLT) and wheel-tracker (WT) tests, were performed to assess the engineering properties and permanent deformation characteristics of these triple blends. The particle-size distribution curve and California Bearing Ratio (CBR) values of all the blends met the minimum requirements. Results of RLT tests confirmed that all the nominated blends were found to provide the resilient modulus value required to be used as pavement materials. The WT results on the triple blend with 15% RG showed that the specimen performed exceptionally well during the test and comfortably met the requirements to be used in pavement applications. Based on the engineering properties and permanent deformation results, up to 15% RG can be suggested for incorporation as an accompanying material in unbound roadwork applications. Subject to the outcomes of future field testing, there might be potential to increase the percentage of RG added in the blends up to 30%.

Environmental and geotechnical suitability of recycling waste materials from plasterboard manufacturing.

This paper presents the geotechnical and environmental suitability of recycling gypsum-based waste material produced from plasterboard manufacturing. Most of the current plasterboard manufacturing industries are dumping these wastes to landfills. Among the major impediments to recycling such waste are environmental concerns around using such recycled material, as well as proper and suitable places to use it. To investigate these, such a waste from an Australian plasterboard manufacturing company was collected and a series of geotechnical properties were tested to evaluate the materials' suitability for any engineering construction. It was found that the tested gypsum-based plasterboard materials are suitable to use as road subgrade, pipe bedding and pipe backfill material. To ascertain the environmental safety of using such material in regards to manual handling as well as contaminants' leaching into the surrounding environment, materials were thoroughly tested for more than a hundred different contaminants. Tests were conducted to evaluate both the contaminants' concentrations in the sample as well as the leaching behaviour of those contaminants. It was found that concentrations of the tested contaminants were either below the individual detection limit or the safe limit defined by the local regulatory authority.

Nanoparticles in Construction Materials and Other Applications, and Implications of Nanoparticle Use.

Nanoparticles are defined as ultrafine particles sized between 1 and 100 nanometres in diameter. In recent decades, there has been wide scientific research on the various uses of nanoparticles in construction, electronics, manufacturing, cosmetics, and medicine. The advantages of using nanoparticles in construction are immense, promising extraordinary physical and chemical properties for modified construction materials. Among the many different types of nanoparticles, titanium dioxide, carbon nanotubes, silica, copper, clay, and aluminium oxide are the most widely used nanoparticles in the construction sector. The promise of nanoparticles as observed in construction is reflected in other adoptive industries, driving the growth in demand and production quantity at an exorbitant rate. The objective of this study was to analyse the use of nanoparticles within the construction industry to exemplify the benefits of nanoparticle applications and to address the short-term and long-term effects of nanoparticles on the environment and human health within the microcosm of industry so that the findings may be generalised. The benefits of nanoparticle utilisation are demonstrated through specific applications in common materials, particularly in normal concrete, asphalt concrete, bricks, timber, and steel. In addition, the paper addresses the potential benefits and safety barriers for using nanomaterials, with consideration given to key areas of knowledge associated with exposure to nanoparticles that may have implications for health and environmental safety. The field of nanotechnology is considered rather young compared to established industries, thus limiting the time for research and risk analysis. Nevertheless, it is pertinent that research and regulation precede the widespread adoption of potentially harmful particles to mitigate undue risk.

Amazing Types, Properties, and Applications of Fibres in Construction Materials.

Fibres have been used in construction materials for a very long time. Through previous research and investigations, the use of natural and synthetic fibres have shown promising results, as their presence has demonstrated significant benefits in terms of the overall physical and mechanical properties of the composite material. When comparing fibre reinforcement to traditional reinforcement, the ratio of fibre required is significantly less, making fibre reinforcement both energy and economically efficient. More recently, waste fibres have been studied for their potential as reinforcement in construction materials. The build-up of waste materials all around the world is a known issue, as landfill space is limited, and the incineration process requires considerable energy and produces unwanted emissions. The utilisation of waste fibres in construction materials can alleviate these issues and promote environmentally friendly and sustainable solutions that work in the industry. This study reviews the types, properties, and applications of different fibres used in a wide range of materials in the construction industry, including concrete, asphalt concrete, soil, earth materials, blocks and bricks, composites, and other applications.

Land Subsidence Control Zone and Policy for the Environmental Protection of Shanghai.

Land subsidence was once a major geo-hazard in the city of Shanghai, China. From 1921 to 1965, the maximum cumulative land subsidence in the urban areas of China reached 2.6 m. This large subsidence has resulted in high economic losses for Shanghai. The Regulation of Prevention and Control of Land Subsidence of Shanghai Municipality was published in 2013 (simply cited as the 2013-regulation in the following context). The characteristics of the 2013-regulation included the combination of the subsidence monitoring network and the groundwater detection network due to both the effects of groundwater withdrawal and construction. In addition, the setting up of a supervision system was also incorporated in the 2013-regulation. To control the land subsidence, Shanghai demarcated three land subsidence control zones, where special measures have been implemented. From a strategic environmental assessment (SEA) point of view, the 2013-regulation attains a high total score, indicating that the control of groundwater withdrawal and recharge is effective. The observed land subsidence over the past six years also confirms the effectiveness of the 2013-regulation with the most consideration of SEA for sustainable environment protection in Shanghai. However, more effort should be made in the implementation of SEA in land subsidence control in the future.

In-situ solidification/stabilization of heavy metals contaminated site soil using a dry jet mixing method and new hydroxyapatite based binder.

In this study, in-situ treatment using dry jet mixing construction method and SPC (single superphosphate and calcium oxide) new binder are used to solidify/stabilize a heavy metal contaminated site soil with relatively high content of organic matters. Time-dependent field performance of the soils at 41 and 326 days after treatment is evaluated, which includes electrical conductivity (EC), leachability of heavy metals and chemical oxygen demand (COD), soil penetration resistance, acid neutralization capacity (ANC), and chemical speciation of heavy metals. The results indicate that the stabilized soils exhibit satisfactory performance which is comparable with the laboratory study. In-situ SPC treatment significantly decreases EC values and increases penetration resistance values of the soils. Leachability of lead, zinc, cadmium and COD decreases with increasing SPC content or curing time. Large percentages of heave metals in the soils are transformed from exchangeable fractions to residual fractions after treatment. These, coupled with the improved ANC, result in low heavy metal leachability in stabilized soils.

Environmental changes in Ariake Sea of Japan and their relationships with Isahaya Bay reclamation.

This paper reviews the recent environmental deterioration in Ariake Sea, Japan, including an increased frequency of red tides and hypoxic waters and decreased fishery production. Analysis of the mechanisms of environmental deterioration suggests that it is possibly induced by the decrease in tidal flat area, decreases in the tide and tidal current and changes in the sediment environment. The Isahaya Bay reclamation project resulted in the loss of 1550 ha of tidal flats, and is one of the possible reasons for the decreases in the tide and tidal current. Therefore, some fishermen and researchers believe that opening the reclamation project dike's floodgates is an effective environmental restoration countermeasure for Ariake Sea. However, the central government decided not to open the floodgates at present due to strong opposition from local farmers, and some researchers believe that the influences of the Isahaya Bay reclamation project on the environmental changes outside of Isahaya Bay are minor. Several lawsuits regarding these relationships and the opening of the dike's floodgates are currently under dispute. To revive Ariake Sea as a sustainable ecosystem, other countermeasures for environmental restoration are suggested and discussed in this paper.

Flood risk assessment in metro systems of mega-cities using a GIS-based modeling approach.

Metro system is a vital component of mass transportation infrastructure, providing crucial social and economic service in urban area. Flood events may cause functional disruptions to metro systems; therefore, a better understanding of their vulnerability would enhance their resilience. A comparative study of flood risk in metro systems is presented using the analytic hierarchy process (AHP) and the interval AHP (I-AHP) methods. The flood risk in the Guangzhou metro system is evaluated according to recorded data. Evaluated results are validated using the flood event occurred in Guangzhou on May 10, 2016 (hereinafter called "May 10th event"), which inundated several metro stations. The flood risk is assessed within a range of 500 m around the metro line. The results show that >50% of metro lines are highly exposed to flood risk, indicating that the Guangzhou metro system is vulnerable to flood events. Comparisons between results from AHP and I-AHP show that the latter yields a wider range of high flooding risk than the former.

High calcium fly ash geopolymer stabilized lateritic soil and granulated blast furnace slag blends as a pavement base material.

Granulated Blast Furnace Slag (GBFS) was used as a replacement material in marginal lateritic soil (LS) while class C Fly Ash (FA) was used as a precursor for the geopolymerization process to develop a low-carbon pavement base material at ambient temperature. Unconfined Compression Strength (UCS) tests were performed to investigate the strength development of geopolymer stabilized LS/GBFS blends. Scanning Electron Microscopy and X-ray Diffraction analysis were undertaken to examine the role of the various influencing factors on UCS development. The influencing factors studied included GBFS content, Na2SiO3:NaOH ratio (NS:NH) and curing time. The 7-day soaked UCS of FA geopolymer stabilized LS/GBFS blends at various NS:NH ratios tested was found to satisfy the specifications of the Thailand national road authorities. The GBFS replacement was found to be insignificant for the improvement of the UCS of FA geopolymer stabilized LS/GBFS blends at low NS:NH ratio of 50:50. Microstructural analysis indicated the coexistence of Calcium Silicate Hydrate (CSH) and Sodium Alumino Silicate Hydrate products in FA geopolymer stabilized LS/GBFS blends. This research enables GBFS, which is traditionally considered as a waste material, to be used as a replacement and partially reactive material in FA geopolymer pavement applications.

Evaluation of Environmental Risk Due to Metro System Construction in Jinan, China.

Jinan is a famous spring city in China. Construction of underground metro system may block groundwater seepage, inducing the depletion risk of springs. This paper presents an assessment of the risk due to metro line construction to groundwater in Jinan City using Analytic Hierarchy Process (AHP) and Geographic International System (GIS). Based on the characteristics of hydrogeology and engineering geology, the assessment model is established from the perspectives of surface index and underground index. The assessment results show that the high and very high risk levels of surface index exceed 98% in the north region; and high and very high risk levels of underground index exceed 56% in urban center and southern region. The assessment result also shows that about 14% of the urban area belongs to very high risk level; regions of high risk are 20% in urban area, 9% in Changqing County and 43% in Pingyin County. In the high risk region, metro lines R1 to R3, which are under construction, and metro lines L1 to L5, which are planned, have very high and high risk. Therefore, risk control measures are proposed to protect the groundwater seepage path to spring.

Development of groundwater vulnerability zones in a data-scarce eogenetic karst area using Head-Guided Zonation and particle-tracking simulation methods.

Delineation of groundwater vulnerability zones based on a valid groundwater model is crucial towards an accurate design of management strategies. However, limited data often restrain the development of a robust groundwater model. This study presents a methodology to develop groundwater vulnerability zones in a data-scarce area. The Head-Guided Zonation (HGZ) method was applied on the recharge area of Oemau Spring in Rote Island, Indonesia, which is under potential risk of contamination from rapid land use changes. In this method the model domain is divided into zones of piecewise constant into which the values of subsurface properties are assigned in the parameterisation step. Using reverse particle-tracking simulation on the calibrated and validated groundwater model, the simulation results (travel time and pathline trajectory) were combined with the potential groundwater contamination risk from human activities (land use type and current practice) to develop three vulnerability zones. The corresponding preventive management strategies were proposed to protect the spring from contamination and to ensure provision of safe and good quality water from the spring.

Effect of fly ash on properties of crushed brick and reclaimed asphalt in pavement base/subbase applications.

Fly Ash (FA), an abundant by-product with no carbon footprint, is a potential stabilizer for enhancing the physical and geotechnical properties of pavement aggregates. In this research, FA was used in different ratios to stabilize crushed brick (CB) and reclaimed asphalt pavement (RAP) for pavement base/subbase applications. The FA stabilization of CB and RAP was targeted to improve the strength and durability of these recycled materials for pavement base/subbase applications. The Unconfined Compressive Strength (UCS) and resilient modulus (MR) development of the stabilized CB and RAP aggregates was studied under room temperature and at an elevated temperatures of 40°C, and results compared with unbound CB and RAP. Analysis of atomic silica content showed that when the amount of silica and alumina crystalline was increased, the soil structure matrix deteriorated, resulting in strength reduction. The results of UCS and MR testing of FA stabilized CB and RAP aggregates indicated that FA was a viable binder for the stabilization of recycled CB and RAP. CB and RAP stabilized with 15% FA showed the highest UCS results at both room temperature and at 40°C. Higher temperature curing was also found to result in higher strengths.

Recycled asphalt pavement - fly ash geopolymers as a sustainable pavement base material: Strength and toxic leaching investigations.

In this research, a low-carbon stabilization method was studied using Recycled Asphalt Pavement (RAP) and Fly Ash (FA) geopolymers as a sustainable pavement material. The liquid alkaline activator (L) is a mixture of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH), and high calcium FA is used as a precursor to synthesize the FA-RAP geopolymers. Unconfined Compressive Strength (UCS) of RAP-FA blend and RAP-FA geopolymer are investigated and compared with the requirement of the national road authorities of Thailand. The leachability of the heavy metals is measured by Toxicity Characteristic Leaching Procedure (TCLP) and compared with international standards. The Scanning Electron Microscopy (SEM) analysis of RAP-FA blend indicates the Calcium Aluminate (Silicate) Hydrate (C-A-S-H) formation, which is due to a reaction between the high calcium in RAP and high silica and alumina in FA. The low geopolymerization products (N-A-S-H) of RAP-FA geopolymer at NaOH/Na2SiO3=100:0 are detected at the early 7days of curing, hence its UCS is lower than that of RAP-FA blend. The 28-day UCS of RAP-FA geopolymers at various NaOH/Na2SiO3 ratios are significantly higher than that of the RAP-FA blend, which can be attributed to the development of geopolymerization reactions. With the input of Na2SiO3, the highly soluble silica from Na2SiO3 reacted with leached silica and alumina from FA and RAP and with free calcium from FA and RAP; hence the coexistence of N-A-S-H gel and C-A-S-H products. Therefore, the 7-day UCS values of RAP-FA geopolymers increase with decreasing NaOH/Na2SiO3 ratio. TCLP results demonstrated that there is no environmental risk for both RAP-FA blends and RAP-FA geopolymers in road construction. The geopolymer binder reduces the leaching of heavy metal in RAP-FA mixture. The outcomes from this research will promote the move toward increased applications of recycled materials in a sustainable manner in road construction.

Possible environmental impacts of recycled glass used as a pavement base material.

In theory, glass diverted or recovered from the municipal solid waste (MSW) stream can be used as feedstock (glass cullet) in the production of new glass containers. However, post-consumer glass typically contains a mixture of clear and coloured material and is often contaminated with other wastes; characteristics that are impediments to the production of new containers. Sorting and cleaning of glass diverted from MSW to make it feasible for use in bottle industries are also time consuming and costly tasks. There is, however, the potential to use recycled glass as a sub-base material for road pavement construction. Geotechnical investigations to date suggest that use of recycled glass as a roadway sub-base could be cost-effective, and thus preclude the need for expensive sorting. There is, however, the necessessity to further investigate the potential short- and long-term toxicity, health hazards, and/or environmental pollution associated with use of mixed glass cullet as an aggregate, considering conditions during stockpiled storage and after placement. The results of laboratory tests on recycled glass regarding its potential to release pollutants to the environment via leaching are presented herein. Five random samples of crushed glasses were collected from a recycling company in Melbourne, Australia. The parameters tested for each sample were total organic matter, heavy metals, sulfates, chlorides, conductivity, pH and surfactant levels. It wais found that in most cases, the contamination levels were within the State of Victoria's Environmental Protection Agency-specified limits for manual handling, thus indicating that recycled glass could probably be safely used in pavement sub-bases.