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Lightweight fill materials, including foamed aggregates are increasingly being used in civil engineering and infrastructure applications. This research assessed the engineering properties of foamed recycled glass through a laboratory evaluation to ascertain this novel recycled material as a lightweight fill material in civil engineering applications. The engineering assessment included particle size distribution, particle density, water absorption, minimum and maximum dry densities with a vibrating table, California Bearing Ratio (CBR) and Los Angeles (LA) abrasion tests. Shear strength properties of the recycled foamed glass were studied through large-scale direct shear tests. This recycled foamed glass is classified as a gap graded material. Due to high porosity, the coarse particles of this material have high water absorption of 60% and low particle density of 4.54 kN/m3, which is much lower than that of water. The minimum and maximum dry densities of this material are very low of 1.67 and 2.84 kN/m3, respectively. The LA abrasion of foamed recycled glass is lower than the requirement for pavement base/subbase material, being of 94%. The shear resistance at small shear displacement is thus low as shown by low CBR value of 9–12%. However, the shear resistance at large shear displacement is high as shown by high cohesion and friction angle of 23.36 kPa and 54.7°, respectively. The environmental assessment included pH value, organic content, total and leachate concentration of the material for a range of contaminant constituents. All the hazardous concentrations in the leachate are far lower than 100 times of those of the drinking water standards, indicating the foamed recycled glass as a non-hazardous material. The energy savings assessment demonstrates that the use of foamed recycled glass as engineering material has much lower energy consumption relative to a conventional aggregate-cement material in construction projects. The lightweight properties of the foamed recycled glass coupled with its satisfactory engineering and environmental results, particularly its high friction angle, indicates that the material is ideal for usage as a lightweight construction material in engineering applications such as non-structural fills in embankments, retaining wall backfill and pipe bedding.

Lightweight Cellular Cemented (LCC) material has wide applications in infrastructure rehabilitation and in the construction of new facilities. The roles of water content, cement content, air content, and fly ash (FA) replacement on the engineering properties, including unit weight, flow and strength of LCC clay−FA material, are investigated, analyzed and presented in this article. The engineering properties are strongly controlled by the generalized stress state, w/wL, where w is the water content and wL is the liquid limit. The FA replacement reduces wL, resulting in a change in w/wL. The workable state, recommended to produce the LCC clay−FA material, is w>1.5wL. The flowability is independent of cement content and approximated in terms of w/wL and air content in logarithmic function. The void/cement ratio (V/C), defined as the ratio of the void volume to the cement volume in the mix, is found to be the dominant parameter governing the strength development in LCC clay−FA material. The fabric (arrangement of clay particles, clusters and pore spaces) reflected from both air foam content and water content is taken into consideration by the void volume while the inter-particle forces (levels of cementation bond) are governed by the input of cement (cement volume). A strength equation in terms of V/C at a particular curing time is introduced using Abrams’ law as a basis. From the critical analysis of test results, a mix design method to attain the target unit weight, flowability and strength is suggested. This method is beneficial from both engineering and economic viewpoints.

Permeable pavements are increasingly being used as urban stormwater management systems. Permeable pavement systems enable stormwater to infiltrate through the pavement surface and into the filter layer. Three common recycled construction and demolition (CD crushed brick (CB), recycled concrete aggregate (RCA) and reclaimed asphalt pavement (RAP) were investigated in combination with nonwoven geotextile to assess their suitability as filter materials in permeable pavements. A series of laboratory tests was undertaken to assess the geotechnical and hydraulic characteristics of the CD however has potential to cause more clogging due to continuous accumulations of sediments in a long period. In terms of usage in permeable pavement filter layer, C&D materials were found to have geotechnical and hydraulic properties equivalent or superior to that of typical quarry granular materials. The Model for Urban Stormwater Improvement Conceptualisation (MUSIC) was furthermore employed to predict the pollutant removal efficiency of the C&D materials and the predicted results were validated with the laboratory experiments.

The viability of using waste materials such as clay and fly ash (FA) for developing a sustainable Lightweight Cellular Cemented (LCC) construction material is investigated in this paper. LCC clay has a wide range of applications in infrastructure rehabilitation as well as in the construction of new facilities. The durability against wetting–drying (w–d) cycles is an important parameter for service life design of LCC clay; however, studies on this aspect to date are very limited. The role of cemented soil structure (fabric and cementation bond) on w–d cycle strength of LCC clay are investigated, analyzed and presented in this paper. The strength reduction with increasing number of w–d is attributed to degradation of the cemented structure. The degradation index, qualifying the rate of degradation with number of w–d cycles, is proposed in term of initial soaked strength (without w–d cycle). Using the degradation index, the predictive w–d cycle strength equation at different number of w–d cycles is furthermore proposed. The applicability of the proposed equation is validated using a separate test data. This approach of predicting w–d cycle strength is beneficial from both engineering and economic points of view.

Tire particles in the form of shreds, chips, or crumbs, are normally mixed with sand to make suitable alternative backfill or embankment materials. This mixture of soft (tire) and rigid (sa...

In recent years, efforts have been made by various researchers to explore the sustainable use of Construction and Demolition (C&D) materials as a construction material in civil engineering applications. Recycled crushed brick is a commonly found material from demolition activities and works to date on this material in pavement applications have been limited to its usage in unbound pavement layers. This research was undertaken to evaluate the performance of crushed brick as a supplementary material in cement stabilized recycled concrete aggregates. An extensive suite of tests were undertaken on the crushed brick and recycled concrete aggregate blends stabilized with 3% cement. The laboratory evaluation comprised pH, plasticity index, foreign materials content, particle size distribution, linear shrinkage, California Bearing Ratio, modified Proctor compaction, Repeated Load Triaxial test, Unconfined Compressive Strength Test and Flexural Beam Tests. The cement stabilized blends with up to 50% crushed brick content and 3% cement were found to have physical properties, which comply with the local state road authority requirements. The results of Repeated Load Triaxial tests indicated the Recycled Crushed Aggregate/Crushed Brick (RCA/CB) blends performed well with 50% Crushed Brick (CB) content just on the border line for bound pavement material. Unconfined Compression Strengths met the minimum requirement for 7 days of curing for all blends, while the 28 day strength of the blends also improved significantly. The results of the flexural beam tests were noted to be consistent with past works with cement stabilized quarry produced crushed rock products. The modulus of rupture and flexural modulus for all the cement-stabilized blends were found to be consistent with the previous works, which indicate that these blends are suitable for applications such as cement-stabilized pavement subbases. The fatigue life was also within the range that has been previously reported for quarry materials. The cement-stabilized blends with crushed brick as a supplementary material with up to 50% brick content and 3% cement were found to have physical and strength properties, which would comply with road authority requirements.

Calcium Carbide Residue (CCR) and Fly Ash (FA) are waste by-products from acetylene gas and power plant production, respectively. The liquid alkaline activator studied in this research is a mixture of sodium silicate solution (Na 2 SiO 3 ), water and CCR. The primary aim of this research is to investigate the viability of using CCR, a cementitious waste material, as an alkaline activator and FA as a precursor to improve the engineering properties of a problematic silty clay to facilitate its usage as stabilized subgrade material. The influential factors studied are Na 2 SiO 3 /water ratio, FA replacement ratio, curing time, curing temperature and soaking condition for a fixed CCR content of 7%. Strength development is investigated via the unconfined compression test. Scanning Electron Microscopy (SEM) observation is used to explain the role and contribution of influential factors on strength development. CCR dissolves the silicon and aluminum in amorphous phase of FA and the Na 2 SiO 3 acts as a binder. The maximum soaked strength of the clay-FA geopolymer is found at Na 2 SiO 3 /water ratio of 0.6 and FA replacement ratio of 15%. The optimal Na 2 SiO 3 /water ratio is approximated from index test, which is a very practical approach. The clay-FA geopolymers with 40 °C curing exhibit higher strength than those with room temperature curing, indicating the possibility of using clay-FA geopolymer for pavement subgrade applications. The 7-day soaked strength at the optimal ingredient meets the strength requirement for subgrade materials specified by the local national road authority. CCR is found to be a sustainable alkaline activator for geopolymer stabilized subgrade materials, which will result in the diversion of significant quantities of this by-product from landfills.

Construction and Demolition (C&D) materials are increasingly used as construction materials in engineering applications. Their usage currently includes applications such as pavements, ground improvement, engineered fills, pipe bedding, backfill and aggregates in concrete. A comprehensive laboratory evaluation of physical and shear strength characteristics of recycled C&D materials was undertaken using gradation, Los Angeles Abrasion, unconfined compression, California Bearing Ratio (CBR), direct shear and consolidated drained triaxial tests. The recycled C&D materials evaluated were recycled concrete aggregate (RCA), crushed brick (CB), reclaimed asphalt pavement (RAP), waste excavation rock (WR), fine recycled glass (FRG) and medium recycled glass (MRG). All the recycled C&D materials are classified as well-graded materials and their compaction curves are controlled by water absorption and surface characteristics. RAP, FRG and MRG exhibit flat compaction curves while RCA, WR and CB exhibit bell-shaped compaction curves. The shear responses of the recycled C&D materials are classified into two groups: dilatancy induced peak strength and dilatancy associated strain-hardening behaviors. RCA, WR and CB are dilatancy induced peak strength materials in that their peak strength is clearly observed after the maximum dilatancy ratio occurs. Higher dilatancy ratios in these materials are associated with higher peak friction angles. RAP, FRG and MRG on the other hand are dilatancy associated strain-hardening materials, which exhibit strain-hardening behavior even with a relatively high magnitude of dilatancy. Based on the evaluation of the shear strength characteristics, it is ascertained that the compacted C&D materials have the potential to be used in pavement base/subbase applications as they have the required minimum effective friction angles. RCA, CB and WR in particular are found to also meet the physical and shear strength requirements for aggregates in pavement base/subbase applications.

This research was undertaken to investigate the suitability of recycled construction and demolition materials as alternative pipe backfilling materials for stormwater and sewer pipes. Three commonly found recycled construction and demolition waste materials, (crushed brick, recycled concrete aggregate and reclaimed asphalt pavement) were investigated to assess their suitability as a pipe backfilling material. The physical, geotechnical and chemical properties of these construction and demolition materials were compared with local engineering and water authorities specifications for typical quarried materials so as to assess their performance as a viable substitute for virgin quarried aggregates in pipe backfilling applications. Physical and geotechnical characterisation tests such as particle size distribution, specific gravity, water absorption, Los Angeles abrasion, California Bearing Ratio and modified Proctor compaction tests were undertaken. Chemical properties were also determined, including organic content, pH, trace element or total concentration and leachate testing of the construction and demolition materials for a range of contaminant constituents. In terms of physical, geotechnical and chemical assessment for pipe backfilling applications, recycled concrete aggregate and crushed brick were found to have the properties recommended by environmental protection authorities while reclaimed asphalt pavement material did not meet some of the specified requirements. Also shear strength properties were found to be equivalent or superior to those of typical quarry backfilling materials. This research indicates that traditional considered waste materials can be reused viably as alternate pipe backfilling materials.

In recent years, efforts have been made to incorporate reclaimed asphalt pavement (RAP) into pavement base or subbase applications by means of cement binder stabilization. This approach, however, may not be an environmentally friendly solution due to the high carbon footprint involved in the production of Portland cement. Recycled concrete aggregate (RCA), on the other hand, has been widely accepted in pavement applications. The sustainable solution of blending RAP with RCA was investigated in this research in an attempt to facilitate the usage of this blend as an alternative pavement subbase material. An extensive suite of geotechnical laboratory tests was undertaken on RAP with contents of 100, 50, 30 and 15% in blends with RCA. Results of the research study indicated that RAP/RCA blends with a low 15% RAP content meet the repeated load triaxial requirements for use in pavement subbase layers. Results of field performance of a pavement subbase constructed with untreated 100% RAP, at a private haul road field-demonstration site, confirmed that it had insufficient strength requirements to meet local road-authority pavement-subbase requirements. RAP and RAP/RCA blends, although found in this study to be not fully compliant with the local road-authorities requirements, could be potentially considered for lower traffic usage, such as haul roads and footpaths.

In-situ tests were undertaken with a BAT permeameter as part of a hydrogeological study to determine the horizontal hydraulic conductivity of Singapore marine clay at Changi. BAT permeameter tests were undertaken in marine conditions prior to land reclamation at a Test Site. An additional series of tests were undertaken after land reclamation and subsequent ground improvement works with prefabricated vertical drains after 23 months of surcharge loading. The BAT permeameter results were compared to laboratory test results carried out using a Rowe consolidation cell as well as hydraulic conductivity tests interpreted from other in-situ dissipation tests including Piezocone Penetration Test (CPTU), Dilatometer Test (DMT) and Self-Boring Pressuremeter Test (SBPMT). The BAT permeameter was found to be suitable for horizontal hydraulic conductivity measurements. The BAT permeameter has the advantage that it measures horizontal hydraulic conductivity directly whereas other in-situ test methods require the introduction of additional parameters to evaluate the hydraulic conductivity indirectly. The horizontal hydraulic conductivity measured using the BAT permeameter was however lower than that expected which is attributed to smear effect. The horizontal hydraulic conductivity was found to decrease in the vertical drain treated area as compared to the prior to reclamation results which is attributed to the significant void ratio reduction at the vertical drain treated area.

Coordination number can be used to quantify the particle connectivity and deformability of a granular material. However, it is a local feature of particles at the microscale, and the use of an average coordination number does not allow for full characterization of the microstructural variation in the granular material. Mesoscale structures can be used to overcome this limitation: triangular-like structures at the mesoscale tend to be rigid, whereas square-like structures tend to be deformable. However, the effect of these structures on heat transfer has not been studied in deforming granular materials. A better understating of how microstructure variation affects effective thermal conductivity is necessary. This work constructs contact networks representing the granular materials with particles as nodes and linking neighbouring nodes with edges that represent particle contacts. Then, ‘3-cycles’ (i.e., a triangular structure) and ‘clustering coefficients’ are extracted from the contact network. As contact thermal conductance is vital to heat transfer and affected by particle shape, microscale three-dimensional particle shape descriptors are also calculated. To compute the effective thermal conductivity of the granular assembly, a thermal network model is established by adding ‘near-contact’ edges to the contact network and assigning a thermal conductance to each edge. The results show that mesoscale local clustering coefficients can indicate the rigidity of granular materials and, together with particle shape descriptors, can be used to predict well the effective thermal conductivity of granular materials under deformation.

Results of an extensive series of repeated load triaxial tests performed on three major recycled construction and demolition (C&D) materials at various moisture contents and stress levels were analysed to ascertain their performance in pavement subbases. The development of the resulting permanent deformation that accumulates with the repeated loading and the determination of resilient modulus by two phases of the test are described. The experimental study shows that the C&D materials perform satisfactorily at a moisture content of about 70% of their optimum moisture contents. Furthermore, the C&D materials also satisfy the two-parameter and three-parameter models. The results of this study indicate that, at a density ratio of 98% compared to maximum dry density obtained in the modified proctor test and with moisture contents in the range of 65–90% of the optimum moisture content, most of the recycled C&D materials produce comparatively smaller permanent strain and greater resilient modulus than na...

An extensive suite of geotechnical laboratory tests were undertaken on wastewater biosolids to evaluate their sustainable usage as a fill material in road embankments. Geotechnical tests undertaken include particle size distribution, specific gravity, Atterberg limits, compaction, consolidation, hydraulic conductivity, California bearing ratio (CBR), field vane shear, direct shear, and triaxial shear. The geotechnical tests indicated that biosolids are equivalent to organic fine-grained soils of medium to high plasticity with high moisture content and liquid limit values. Consolidation tests indicate that biosolids have similar consolidation characteristics to that of organic soils. Shear strength tests on compacted biosolids samples indicated relatively high internal friction angles, comparable to that of inorganic silts. Compacted biosolids samples exhibit a modest cohesion comparable to organic clays. CBR tests results indicate high deformation potential of biosolids. Chemical and environmental...

An innovative research study was undertaken to characterize the settlement characteristics of aged wastewater biosolids to facilitate its long-term settlement prediction when used as fill material in road embankment applications. Settlement can be sub-divided into compression due to consolidation and deformation attributed to biodegradation. Results of an extensive geotechnical laboratory evaluation including compaction characteristics, shear strength parameters, coefficient of consolidation, compression index, swell index and coefficient of secondary consolidation were used to predict the consolidation settlement of biosolids in road embankments. Other relevant parameters for biodegradation settlement prediction, such as organic content, pH and electrical conductivity of the biosolids were also determined. The biodegradation induced settlement of a road embankment built with aged biosolids was subsequently analyzed by applying an analytical method used previously for municipal solid waste landfills. The adopted model shows that the rate of biodegradation settlement reduces with the reduction in pH values of biosolids. The model also suggests that the time taken for full process of biodegradation decreases dramatically with pH value of the biosolids between 0 and 6 and then increases exponentially with pH value of the biosolids between 8 and 14. A framework has been developed to predict the total settlement of wastewater biosolids in road embankments for end-users.

Piezometers are commonly used for monitoring the dissipation of pore water pressure and therefore the determination of degree of consolidation of soft soils after ground improvement in land reclamation projects. This paper compares the degree of consolidation obtained using pore pressure monitoring data from vibrating wire piezometers and pneumatic piezometers installed in a test site in the Changi East Reclamation project in Singapore. The test site consisted of a vertical drain sub-area at which prefabricated vertical drains were installed at 2.0 m × 2.0 m square spacing as well as an adjacent control sub-area where no prefabricated vertical drains were installed. Pneumatic piezometers were installed at the same elevations as the vibrating-wire piezometers in both sub-areas for comparison purposes. During the surcharge period of 32 months, the piezometer monitoring data were analysed at various periods to determine the degree of consolidation of the underlying soft marine clay. The degree of consolidation values interpreted from both types of piezometers were compared with predictions from neighbouring settlement plates to evaluate their performance. The findings of the comparison between pneumatic and electric vibrating-wire piezometers indicate that both types of piezometer are suitable for monitoring the consolidation behaviour of soft soil under land reclamation fills.

Laboratory and field experiments were undertaken to investigate the possible application of recycled crushed glass blended with crushed basaltic waste rock as a footpath base material. The laboratory experimental program included basic and specialized geotechnical tests including particle size distribution, modified Proctor compaction, particle density, water absorption, California bearing ratio (CBR), Los Angeles abrasion, pH, organic content, and triaxial shear tests. A field demonstration footpath comprising two sections of recycled glass-waste rock blends with 15% and 30% recycled glass content and a third control section with only waste rock was subsequently constructed on the basis of the outcomes of the initial laboratory tests. Subsequently field tests with a nuclear density gauge and Clegg impact hammer were undertaken, as well as laboratory testing of field samples to assess the geotechnical performance of the trial sections. The field and laboratory test results indicated that adding crushed glass may improve the workability of the crushed waste rock base material but subsequently results in lower shear strength. The blend with 15% glass content was found to be the optimum blend, in which the material presented good workability and also had sufficiently high base strength. Higher recycled glass content (30%) resulted in borderline, though still satisfactory, performance. The research findings indicate that recycled crushed glass in blends with crushed waste rock is a potential alternative material to be used in footpath bases. A separate study is recommended to evaluate the environmental risks associated with the usage of these recycled materials.

The increase in generation of waste from construction activities along with significant increase in global population has led to increasing focus and research on reuse of waste material. In this paper, the application of construction and demolition (C&D) materials in road works is reviewed and discussed. C&D materials were evaluated by laboratory testing methods to assess their viability for reuse in roads and footpaths. Several unique field case studies where C&D materials have been used are also reported. C&D materials studied include recycled concrete aggregate (RCA), crushed brick (CB), reclaimed asphalt pavement (RAP), fine recycled glass (FRG), and waste rock (WR). C&D materials were found to be suitable for road and footpath applications such as embankment fills, pavement base/subbase, and pipe bedding applications.

The reuse of recycled construction and demolition (C&D) aggregates in civil engineering infrastructure applications has been considered a low-carbon solution to replace conventional pavement aggregates. Evaluating the strength development mechanism and interparticle flow of forces in geopolymer stabilized C&D aggregates will provide fundamental understanding of the behavior of stabilized C&D aggregates. The C&D aggregates studied are reclaimed asphalt pavement (RAP), recycled concrete aggregate (RCA), and crushed brick (CB). The performance of alkali-activated fly ash (geopolymer) on the stabilization of C&D aggregates, under different curing conditions and sample preparation methods were studied. Fly ash was used as the precursor for the alkali-activated binder that was used to stabilize the C&D aggregates. The effect of low and high content of fly ash–based geopolymers on strength development of recycled materials is investigated for the first time. Sodium silicate and sodium hydroxide were used, with different ratios, to intensify the alkaline environment for fly ash to accelerate the strength development of the mixture. The effect of static and dynamic compaction on the density and strength development was investigated for both low-content fly ash and high-content fly ash. Temperature treatment of geopolymer stabilized C&D aggregates up to 40°C and humidity curing in the moisture chamber for 7 days indicated improvement of the strength development of the mixture. The results of unconfined compressive strength (UCS) and resilient modulus testing of geopolymer-stabilized C&D aggregates indicate that alkali-activated fly ash is a viable binder for the stabilization of C&D aggregates.

The use of recycled construction and demolition (C&D) materials in unbound and cement stabilized pavement base/subbase applications has generated growing interest in recent years. C&D materials consisting of crushed brick (CB), recycled crushed aggregate (RCA), and reclaimed asphalt pavement (RAP) have been investigated in unbound and cement stabilized pavement base/subbase applications. However, the high carbon footprint of using cement for pavement base/subbase stabilization has led to this research to seek alternative low-carbon binders. This study evaluates the behavior of C&D materials when stabilized with geopolymers. Fly ash (FA) and ground granulated blast furnace slag (S) were used as pozzolanic binders and a different alkaline activator solution to pozzolanic binder ratio was tested. A maximum of 4% of dry weight of soil was used for geopolymer stabilization of the C&D materials. The binders used were either 4% FA, 2% FA+ 2% S, or 4% S. The geotechnical engineering and strength propertie...

The drinking of coffee forms a deep-rooted pastime in many communities worldwide. However, the culture of coffee drinking generates vast quantities of organic waste that ends up in landfills. Current research trends are inclined towards recycling of waste materials into alternative construction materials, hence the need to research sustainable uses for spent coffee grounds. Coffee grounds (CG) are highly organic with a very high percentage of biodegradable material. The objective of this research was to study the strength development of CG when used as a geopolymer stabilized embankment structural fill material aiming for a better understanding of geopolymer stabilization of highly organic material. Fly ash (FA), being a silica and alumina rich material, was used as a precursor. A liquid alkaline activator, L, being a sodium hydroxide-sodium silicate solution was used for alkali activation of FA in the CG-FA geopolymer. Factors found to affect strength development of the CG-FA geopolymer were: (1)...

Soft subgrades are not strong enough to provide the required degree of compaction for a pavement embankment’s foundation. Therefore, it is required to treat the subgrade soil or construct a working platform on top of the soft subgrade to ensure proper compaction of the subsequent layers. The constriction sizes of the granular materials used for a working platform are comparatively higher to restrict the erosion of overlying embankment materials. This condition would lead to severe material loss in the embankment layer in cases where the embankment is constructed with dispersive soil, which becomes structurally unstable in wet conditions and appears to disperse in water. This paper investigates the contact erosion failure at the foundation of a pavement embankment constructed with dispersive soil as a result of groundwater fluctuation. Experimental studies were conducted on a laboratory model test apparatus designed to simulate the conditions in the pavement embankment’s foundation. The experimenta...

Recycled crushed glass is the main by-product of the glass recycling industry. Insufficient knowledge of the geotechnical characteristics of recycled glass and its environmental risks are the primary barriers in its application in road works. An extensive suite of geotechnical and environmental tests were undertaken on two common types of recycled crushed glass (fine recycled glass and medium recycled glass) to study the potential of using them in road works as alternatives to natural aggregates. Recycled glass was found to exhibit either equivalent or superior workability, hydraulic conductivity and shear strength to natural aggregates within the same soil classification and demonstrated the potential to substitute natural sand and gravel mixtures in a range of road applications. To address the environmental concerns of using recycled glass in road work applications, a comprehensive series of chemical and environmental tests including total and leachate concentration for a range of contaminant constituents including heavy metals and aromatic hydrocarbons were carried out. Test results were compared with environmental protection authorities’ requirements and indicated that no leaching hazard will be experienced during the service life of recycled glass in road work applications. Other possible environmental risks along with health and safety precautions and management suggestions have also been discussed.

A comprehensive suite of geotechnical laboratory tests was undertaken on samples of recycled crushed glass produced in Victoria, Australia. Three types of recycled glass sources were tested being coarse, medium and fine sized glass. Laboratory testing results indicated that medium and fine sized recycled glass sources exhibit geotechnical behavior similar to natural aggregates. Coarse recycled glass was however found to be unsuitable for geotechnical engineering applications. Shear strength tests indicate that the fine and medium glass encompass shear strength parameters similar to that of natural sand and gravel mixtures comprising of angular particles. Environmental assessment tests indicated that the material meets the requirements of environmental protection authorities for fill material. The results were used to discuss potential usages of recycled glass as a construction material in geotechnical engineering applications particularly road works.

Fine recycled glass is the main by-product of the glass recycling industry in Victoria, Australia. Holding the maximum particle size of 4.75 mm, it mainly comprises of sand size particles with a sm...

In the original publication of the article, the reference Wray et al. (2005) was cited incorrectly in the text and in References list. The correct citation is “Wray et al. (2005),” and the correct reference is provided in this erratum.

This paper describes laboratory testing to investigate the suitability of recycled construction and demolition (C&D) materials as alternative subbase materials for permeable pavements. Permeable pavements are increasingly being used as urban stormwater management systems. Three commonly found recycled C&D waste materials, crushed brick (CB), recycled concrete aggregate (RCA), and reclaimed asphalt pavement (RAP), were investigated to assess their suitability as permeable pavement subbase materials. Geotextile was also used in this research to trap pollutants. The laboratory tests included basic physical characterization such as particle size distribution, specific gravity, water absorption, Los Angeles abrasion, California Bearing Ratio (CBR), and modified Proctor compaction tests. In addition, hydraulic conductivity tests were undertaken in a laboratory test setup with different influent suspension percentages and moisture contents. Temporal variations of effluent suspension percentages were investigated to assess clogging effects. It was found that the geotextile layer did not have any effect in terms of permeability of the C&D materials. The chemical assessment included organic content, pH value, trace element, and leachate concentration for a range of contaminant constituents and compared with maximum allowable limits in soil and natural water as well as with the environmental protection authorities' requirements. In terms of geotechnical and chemical assessment for permeable pavement applications, RCA was found to be a suitable alternative construction material for permeable pavements, while CB was borderline and RAP did not meet some of the specified requirements.

Construction and demolition (C&D) materials constitute a major proportion of waste materials present in landfills worldwide. With the scarcity of high-quality quarry aggregates, alternative materials, such as C&D materials, are increasingly being considered as a replacement for traditional road-construction materials, particularly as the sustainable usage of these C&D materials has significant environmental benefits. In this research, an extensive laboratory evaluation was carried out to determine the engineering properties of cement-treated C&D materials. The C&D materials investigated were reclaimed asphalt pavement (RAP), recycled concrete aggregate (RCA), and crushed brick (CB). The geotechnical properties of cement-treated C&D materials were evaluated to assess their performance in pavement base/subbase applications. The effect of curing duration on the strength of the C&D materials was analyzed by conducting unconfined compression strength and repeated load triaxial tests. The RAP required 2% cement (by weight) and either 7 or 28 days of curing to meet the local road-authority requirements, whereas RCA and CB required 4% cement and 28 days of curing. The RAP exhibited the highest strength in all cases, with the same cement content and for the same curing duration, followed by RCA and CB. The resilient moduli of C&D materials increased with an increase in cement content, curing duration, and confining pressure. Humidity curing was found to play an important role in the strength development of cement-treated C&D materials. This study indicates that cement-treated C&D materials are viable construction materials for pavement base/subbase applications.

© 2015 Techno-Press, Ltd. A nonlinear creep function incorporated into the elastic visco-plastic model may describe the long-term soil deformation more accurately. However, by applying the conventional procedure, there are challenges to determine the model parameters due to limitation of suitable data points. This paper presents a numerical solution to obtain several parameters simultaneously for a nonlinear elastic visco-plastic (EVP) model using the available consolidation data. The finite difference scheme using the Crank-Nicolson procedure is applied to solve a set of coupled partial differential equations of the time dependent strain and pore water pressure dissipation. The model parameters are determined by applying the algorithm of trust-region reflective optimisation in conjunction with the finite difference solution. The proposed method utilises all available consolidation data during dissipation of the excess pore water pressure to determine the required model parameters. Moreover, the reference time in the elastic visco-plastic model can readily be adopted as a unit of time; denoting creep is included in the numerical predictions explicitly from the very first time steps. In this paper, the settlement predictions of thick soft clay layers are presented and discussed to evaluate and compare the accuracy and reliability of the proposed method against the graphical procedure to obtain the model parameters. In addition, comparison of the available experimental results to the numerical predictions confirms the accuracy of the numerical procedure.

Conventionally, high quality quarry materials are used for base and sub-base materials of the pavements. Traditional road building materials are becoming scarce in some regions. Moreover, rate of consumption of high strength aggregates is increasing rapidly in different industries. The use of traditional quarry materials at current rate of consumption is unsustainable from both environmental and cost perspective. The engineering characteristics of various cement-treated recycled Construction and Demolition (C&D) materials obtained from extensive laboratory testing are presented in this paper. Unconfined Compression Strength (UCS) tests shows that cement treated recycled material can be considered satisfactorily as a pavement base or sub-base material in the field. The Laboratory result shows that conditions of temperature and humidity curing play a very important role in strength development in cement-treated materials. The Los Angeles abrasion loss tests indicated that the cement treated recycled materials are durable.

Loose granular soils placed during a land reclamation process require densification to enhance their engineering properties. In a mega-land reclamation project in the Republic of Singapore, techniques such as Muller resonance compaction (MRC), vibroflotation, and dynamic compaction were employed to densify the land reclamation sand fills. The efficacy of densification was subsequently verified by cone penetration tests (CPT). The MRC technique results in the sand mass being rearranged due to the application of high vibrating energies. The vibroflotation technique results in a densified column of soil forming at and surrounding the probe point. The dynamic compaction technique results in the centroid point being the most compacted point, provided the selected spacing is efficient. The aging effect in the vibroflotation technique was found to be significant, in contrast to the MRC and dynamic compaction techniques. The usage of these three deep compaction techniques was found to be effective for the densification of deep deposits of loose sand fills in this mega-land reclamation project.

Fine particles may migrate in the preexisting pores of an internally unstable soil matrix caused by water flow. This migration changes the fine particle distribution and content at different zones and can affect the mechanical properties of these soils. Due to the different roles that fine particles can play in the force chains of an internally unstable soil, the available geometrical assessment methods do not predict post-erosion behavior of the soil. The fine particles may sit loose in the voids, provide lateral support for the primary soil matrix, or participate directly in stress transfer. This will depend on the fine content, particle size distribution, constriction size, relative density, stress path, and particle shape. However, to evaluate the post-erosion behavior accurately, computational modelling or experimental investigation needs to be conducted. A modified triaxial apparatus connected to a water supply system and collection tank was developed to investigate the post-erosion behavior of an internally unstable cohesionless soil under different loading patterns in undrained conditions. This system allowed all test phases to be completed, including erosion inside the triaxial chamber to remove any possible impact of specimen disturbance. The results suggest that the undrained shear strength of the eroded specimen increased at small vertical strains (0–4 %) under monotonic and cyclic loadings, whereas the initial modulus of elasticity remained unchanged. Also, the eroded specimen showed much higher resistance against cyclic loadings, whereas the non-eroded specimen was liquefied during less than five cycles of loading. This improvement was due to a better interlock between coarse particles due to erosion of fine particles. The hardening strain behavior of the non-eroded specimen changed to limited flow deformation due to a decrease in the fine content. The flow deformation of the eroded specimen at medium strain may be due to the local increase in lubrication effect of fine particles in the eroded specimen.

Grain breakage is of paramount importance for understanding the behaviour of granular materials used in various engineering applications, such as pavements, roads, rail tracks, the oil and gas industry, and mineral processing. Changes to grain properties of a uniformly graded sand specimen stemming from breakage during compression were studied with the aid of three-dimensional Synchrotron Radiation-based Micro-Computed Tomography. The fast scanning and high-resolution 4D imaging were utilised to capture images from the interior body of the granular assembly during loading. The fractal distribution of the sand assembly showed that breakage becomes dominant in smaller grains rather than larger ones, where an increase in the amount of newly generated fine fragments leads to high coordination number surrounding the larger grains. More importantly, the results of morphological changes in the particulate assembly revealed that there is a reversal trend in the grain morphology evolution with increasing stress. The sand grains tended to create more spherical fragments with higher aspect ratio whereas by increasing the stress this trend completely shifted.

Lightweight cellular cemented clays have wide range of applications in the infrastructure rehabilitation and in the construction of new facilities. Since the inception of this method, the developments in the plant and machinery as well as associated field techniques have surpassed the basic understanding of strength developments in lightweight cellular cemented clay. In this paper, an attempt is made to identify the dominant parameter, governing the unit weight, strength, and compressibility characteristics of lightweight cellular cemented clay, which helps control input of water, air foam, and cementing agent to attain unit weight and strength development with curing time. From this research, it is discovered that water-void/cement ratio, wV/C is the dominant parameter for the above purposes. From the critical analysis of test results, a mix design method to attain the target strength and unit weight is suggested. This method is useful from both engineering and economic perspectives.

Loose granular sand deposits formed during the land reclamation process are vulnerable to liquefaction upon imparting seismic forces. These loose granular sand fills could encounter bearing failures or compress beyond tolerable limits under static and dynamic loads. To eliminate such failures, loose granular soils require densification to enhance their engineering properties. Deep compaction is the only means to improve these thick deposits of loose sand fill in many foreshore land reclamation projects. Muller resonance compaction (MRC) and vibroflotation are deep vibratory compaction techniques, which are suitable to densify thick layers of loose granular fills. This paper describes the applications of deep compaction vibratory techniques in a mega-land reclamation project in the Republic of Singapore where the efficacy of densification was verified by cone penetration tests (CPT) undertaken in a pilot test area. In the MRC technique, high vibrating energies are used, which results in the whole m...

This paper presents the findings of a field and laboratory evaluation on the use of recycled glass blends as unbound pavement base/subbase materials. The parent recycled aggregates studied in this research were fine recycled glass (FRG), recycled concrete aggregate (RCA), and waste rock (WR). The geotechnical performance of the recycled aggregate blends of particular interest in this research were FRG blended with RCA (FRG/RCA) and FRG blended with WR (FRG/WR) in pavement base applications. The geotechnical performance of a trial road pavement was assessed by means of initial laboratory tests and subsequently field tests. The initial laboratory experimental program included specialized geotechnical tests including repeated load triaxial and triaxial tests to characterize the recycled materials. The subsequent trial road pavement constructed comprised seven different sections of FRG blends in the pavement base varying from 10 to 30% recycled glass content as well as two control sections with RCA an...

A valuable conceptual framework for the characterisation of seepage-induced internal instability was provided in the article under discussion, particularly for the ‘suffusion and suffosion’ phenomena. A few modifications are suggested here to clarify the definitions in the original paper.

Construction and demolition materials such as recycled crushed rock and recycled glass account for a major proportion of the waste materials present in landfills in Australia. Using recycled glass and crushed rock in road pavement applications would significantly reduce the need for quarry-based virgin materials. Furthermore, recycled materials could be used in parts of the country where aggregate sources are scarce. This paper discusses the suitability and applicability of recycled glass when used in blends with crushed rock for road pavement applications. Performance of the blends was measured using an extensive suite of geotechnical engineering laboratory tests including basic classification tests along with modified compaction, California Bearing Ratio and Los Angeles abrasion tests. Repeated load triaxial tests were also conducted on blends. The test results indicated that the recycled glass could be blended with recycled crushed rock by up to 30% by mass and provide satisfactory engineering performance to be used as a pavement subbase material.

The select chemical and engineering characteristics of biosolids produced at a wastewater treatment plant in Eastern Australia were investigated to assess its suitability as structural fill material in road embankments. Results of comprehensive set of geotechnical experimentation including compaction, consolidation, creep, hydraulic conductivity and shear strength tests implied that biosolids demonstrate behavior similar to highly organic clays with a higher potential for consolidation and settlement. Results of chemical study including heavy metals, dichloro diphenyl trichloroethane (and derivatives) and organochlorine pesticides, indicate that biosolids samples are within the acceptable limits which allows their usage under certain guidelines. Results of tests on pathogens (bacteria, viruses or parasites) also indicated that biosolids were within the safe acceptable limits. Technical and management suggestions have been provided to minimize the possible environmental risks of using biosolids in road embankment fills.

Salazar et al. (2015) presented a new method to measure the volume and volumetric strains of soil specimen during the triaxial test. To eliminate the optical distortions due to refraction at the fluid-cell wall and cell wall-atmosphere interfaces, they installed a camera-based system inside the triaxial cell. The discussers wished to highlight some points about taking into account the refraction of light and other related issues in image processing for evaluating the volumetric strains and show that there is another simple way to overcome this problem.

Contact erosion failure beneath the pavement layer is frequently under-estimated. The risk of contact erosion failure is high at the interface of pavement embankment constructed on granular working platform material, particularly due to the higher constriction size than the embankment material. In addition, this type of failure occurs in the long-term process and it is furthermore difficult to identify, assess, and mitigate these failures initially. A new laboratory erosion test apparatus was developed in this research and its suitability for determining the risk of pavement deformation due to contact erosion failure as a result of vertical ground water fluctuations at the pavement embankment foundation was assessed. The suitability of this apparatus for the study of contact erosion failure below the pavement layer was examined by studying the erosion rate of dispersive clayey soil placed on the coarse aggregate layer. The soil layer was saturated in five different water cycles and water was allowed to draw down after saturation period for each cycle. The erosion test apparatus developed in this study was found to be suitable and reliable for determining the contact erosion failure under vertical ground water fluctuation beneath the pavement layer.

Laboratory large-scale direct shear tests were carried out on five different recycled construction and demolition materials, such as crushed concrete (CC), crushed rock (CR), crushed brick (CB), reclaimed asphalt pavement (RAP), and recycled glass (RG). The shear strength parameters were evaluated with a large shear test machine for different values of normal stress ranging from 30 to 200 kPa. Resulting values of cohesion were found to vary in a wide range between 8.55 kPa to 284.5 kPa, whereas coefficient of internal friction varies between 44.6° to 52.1°. The failure envelopes for all materials investigated are straight-line failure envelopes. Crushed rock and crushed concrete showed high cohesion of 284 kPa and 154 kPa, respectively, whereas reclaimed asphalt pavement and recycled glass showed low cohesion of 8.55 kPa and 14 kPa, respectively. Meanwhile, crushed brick showed a medium cohesion of 61.2 kPa. Further, the volumetric behaviours of the recycled materials are dilatancy except for reclaimed asphalt pavement at low normal stress. The results of the shear strength tests indicate that CR, CC, and CB and blends of RAP and medium recycled glass (MRG) with other materials can be viable materials to be sustainably used in pavement sub-base applications.