Evaluation of the compactive effort on the stripping characteristic of hot mix asphalt (HMA) mixtures

Generally, moisture susceptibility is a HMA mixture’s tendency towards stripping. To combat moisture susceptibility, proper mix design is essential. However if a mix is properly designed but not compacted sufficiently it could be also subjected to stripping. This study is to evaluate the relationship between different compactive efforts on stripping, as well as to suggest the most appropriate indicative test to envisage the stripping characteristic in HMA mixtures. Two test methods were carried out to assess the stripping, which are quantitative strength test for compacted specimens and qualitative test for loose uncompacted specimens. Samples compacted with 35, 50 and 75 blows of Marshall hammer were used to determine the stripping in HMA. For the quantitative test, moisture induce damage test (AASTHO T 283) is utilized to forecast the stripping while for qualitative test, Coating and Stripping of Bitumen-Aggregate Mixtures (ASTM D1664-80) and Effect of Water Bituminous-Coated Aggregate Using Boiling Water (ASTM 3625- 91) were used. The results show that increase in compactive effort would decrease the optimum asphalt content. In the moisture induce damage test, those 35 blows and 50 blows have larger TSR value, which the 35 blows is 24% and 50 blows is 14% higher than 75 blows. Similarly, the loose uncompacted specimens indicate that both of these lower blows have lesser stripping potential. This shows that, the lower the blow the larger optimum asphalt content thus decreases the stripping potential of the HMA. Besides that, it was also found that moisture induce damage test is a more appropriate method to use in evaluating of stripping characteristic of HMA

Settlement behaviour of biosolids stabilised with bauxsol in road embankment

This paper presents a study on an innovative and effective use of biosolids from the waste water treatment plant in Melbourne, Australia. Biosolids is a treated sewage sludge consisting of untreated organic slurry residue derived from waste water treatment process and the bauxsol is an inert stabilised by-product of the aluminium industry and is a carefully modified residue from alumina refineries, also known as red mud. The settlement behaviour of the road embankment using biosolids stabilised with 1%, 3% and 5% with bauxsol was analysed and presented in this paper. The primary and creep settlements were considered in this study. Furthermore the material model parameters from the laboratory experimental results which were used in this analysis, for the biosolids stabilised with bauxsol are also presented. The results obtained were positive, since settlements were found to be within an acceptable range

Geotechnical laboratory testing of biosolids

Biosolids is the end product of the wastewater treatment process. An innovative research project on biosolids is currently being undertaken in Melbourne, Australia to characterize its geotechnical characteristic which is essential to evaluate the performance of biosolids in various geotechnical applications. The geotechnical engineering characteristics of biosolids at Western Treatment Plant (WTP) in Melbourne, Australia was investigated and presented in this paper. The tests undertaken include consolidation, triaxial shear strength, hydraulic conductivity, compaction, California Bearing Ratio, Atterberg limits, particle density and particle size distribution

Laboratory evaluation of the geotechnical characteristics of wastewater biosolids in road embankments

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 tests. 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 assessment tests indicated that heavy metals, Dichloro Diphenyl Trichloroethane (DDT) and Organochlorine Pesticides concentration along with pathogens (bacteria, viruses or parasites) results were within acceptable limits for usage in geotechnical applications. With regards to contaminants containing nitrogen, phosphorus and total organic carbon, the biosolids were found to require special protection, in the event there is potential leaching/flow to adjoining water bodies. The geotechnical testing results indicate that untreated biosolids have insufficient bearing capacity to enable its usage as a fill material. The biosolids will have to be stabilized with an additive or blended with a high quality material to enhance its geotechnical properties to enable it to be considered as an engineering fill material

Geotechnical testing to determine the suitability of biosolids for embankment fill

Biosolids are an end product of municipal wastewater treatment and contain many of the constituents removed from the influent wastewater. The use of biosolids and other waste materials in a sustainable manner is currently being investigated in several countries around the world. A series of field tests were undertaken on biosolids stockpiles at Western Treatment Plant in Victoria. Following the field tests and sampling geotechnical laboratory tests were undertaken to assess the viability of using biosolids as fill material for embankment fills. Geotechnical properties of untreated biosolids and stabilised biosolids with 1%, 3% and 5% of cement were obtained from the laboratory tests. The field and laboratory test results were compared with the existing local road authority specification for fill material

Long-term settlement prediction for wastewater biosolids in road embankments

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

Stabilisation of biosolids with admixtures for potential use as an embankment fill material

Biosolids are an end product of the wastewater treatment process and contain many of the constituents removed from the influent wastewater. This paper is based on a project currently implemented in Victoria to assess the viability of using biosolids as engineered fill material for road embankments. A series of geotechnical lab tests were conducted to evaluate the engineering properties of biosolids samples retrieved from Western Treatment Plant (WTP) in Victoria, Australia. The laboratory tests undertaken include particle density, moisture content, organic content, Atterberg limits, particle-size distribution, proctor compaction, California Bearing Ratio (CBR) and consolidation tests. Geotechnical laboratory tests were carried out on untreated biosolids as well as biosolids stabilised with 1%, 3% and 5% by weight of cement and lime. The test results were subsequently compared with the existing local road authority specification for embankment fill material

Shear strength behaviour of recycled glassbiosolids mixtures

To enhance the shear strength properties of pure Fine Recycled Glass (FRG) and pure Biosolids (Bio), the innovative idea of blending these two materials was studied. The blended FRG-Bio material has the advantage of combining the high friction characteristics of recycled glass with the cohesive characteristics of biosolids. The Direct Shear Test results, California Bearing Ratio results along with other geotechnical test results indicated that 50FRG/50Bio, 60FRG/40Bio and 70FRG/30Bio blends provide a sufficiently high shear strength and friction angle for their usage as an embankment fill material. The findings showed the potential of blended recycled glass-biosolids to be used as a viable alternative to natural materials in road embankment applications

Field testing to determine the suitability of biosolids for embankment fill

Biosolids are defined as appropriately treated sewage sludge which consists of untreated organic slurry residue derived from wastewater treatment processes. The use of biosolids and other waste materials in a sustainable manner is currently being investigated in several countries around the world. This paper reports on results obtained from field investigations to assess the viability of using biosolids as stabilised fill for road embankments. Field tests were recently carried out on biosolids stockpiles at the Western Treatment Plant in Victoria, Australia. The field tests included field vane shear tests, standard penetration tests (SPT) and dynamic cone penetrometer (DCP) tests. Undisturbed tube samples and disturbed bulk samples were also collected for future laboratory testing. Geotechnical parameters from the field test were obtained and compared with the existing local road authority specification for fill material