UCS and CBR behaviour of Perth sandy soil reinforced with waste tyre fibres and cement

Weak and unsuitable soil conditions have always caused problems for civil engineers during the construction of structures. To avoid problems in a cost-effective manner, proper and reliable solutions need to be developed. Fibre reinforcement and cement stabilisation are the most efficient and common methods in geotechnical engineering applications when engineers have problematic soil conditions. These methods can be used in different applications, such as pavement layers, retaining walls and slopes. Over the past three decades, many studies have been done to investigate the effects of adding synthetic and natural fibres to soil as the reinforcing material alone or with cement. The present work focuses on investigating the characteristics of local Perth sandy soil after inclusion of waste tyre fibres and cement. These wastes can be utilised in ground improvement projects in large quantities and could provide a cost-effective and environmentally friendly strategy that avoids tyre disposal problems. Fibres for reinforcement applications in soils are available in different types in terms of materials and their geometrical configurations. Using waste materials, which are present nowadays in large quantities and in different forms, such as used tyres and carpets, as reinforcing materials can be environmentally and economically beneficial. In the past, waste tyres have been used in some geotechnical applications, such as highway construction, retaining wall backfill and drainage layers for roads, but the efforts seem to be insufficient. Although much research has been conducted on cement stabilisation, but on fibre reinforcement, and their combination, no comprehensive research has been done to investigate the UCS and CBR behaviour of sandy soils mixed with cement and tyre fibres, especially on the sandy soils available in Perth and its surrounding areas. A series of laboratory tests including compaction, unconfined compressive strength (UCS) and California bearing ratio (CBR) tests were conducted to investigate the effects of adding tyre fibre and cement on the engineering behaviour of Perth sandy soil. The contents were varied from 0 to 5% of dried soil by weight for cement and 1% of dried soil by weight for tyre fibres. The cemented specimens were cured in for 3, 7, 14, and 28 days. This study aims at investigating the effect of different parameters, including cement content, tyre fibre content, curing time and confining pressure on the CBR behaviour of Perth sandy soils. Feasible, ecologically friendly, and economically reasonable solutions, both theoretically and practically, are studied in this research so that geotechnical/civil engineers can effectively use them in the construction projects. The compaction test results indicate that the maximum dry unit weight generally increases by adding cement and decreases by tyre fibres inclusion, while adding cement and tyre fibre results in a lower optimum water content. For the fibre-reinforced and unreinforced materials, the compressive strength increases with an increase in the cement content. Adding 1% of tyre fibres to mixtures increases the UCS of the soil approximately by 10-70%. The results also show that as the curing time increases, the UCS increases, and the effect of curing is more pronounced for higher stabiliser contents

Experimental and numerical investigation of footing behaviour on multi-layered rubber-reinforced soil

This paper describes the beneficial effects of multiple layers of rubber–sand mixture (RSM). The plate load tests, using circular plate of 300 mm diameter, were performed at an outdoor test pit, dug in natural ground with dimensions of 2000 × 2000 mm in plan and 720 mm in depth to facilitate realistic test conditions. The rubber used in the RSM layers was granulated rubber, produced from waste tires. The optimum thickness of the RSM layer was determined to be approximately 0.4 times the footing diameter. By increasing the number of RSM layers, the bearing capacity of the foundation can be increased and the footing settlement reduced. The influence of the number of RSM layers on bearing capacity and settlement become almost insignificant beyond three layers of RSM, particularly at low settlement ratios. At a ratio of settlement to plate diameter of 4%, the values of bearing pressure for the installation with one, two, three and four layers of RSM were about 1.26, 1.47, 1.52 and 1.54 times greater, respectively, than that for the unreinforced installation. Layers of the RSM reduced the vertical stress transferred through the foundation depth by distributing the load over a wider area. For example, at an applied footing pressure of 560 kPa, the transferred pressure at a depth of 570 mm was about 58, 45 and 35% for one, two and three layers of RSM, respectively, compared to the transferred stress in the unreinforced bed. By numerical analysis, it was found that the presence of soil-rubber layers resulted in expansion of passive zones in the foundation due to the effectiveness of the confinement provided by the rubber inclusions, and this tends to make the bed deflect less. On the basis of this study, the concept of using multiple RSM layers has not only been shown to improve the performance of foundations under heavy loading, but also, the environmental impacts of waste tires are attenuated by re-using their rubber as part of a composite soil material in civil engineering works

Potential of Tyre Derived Geomaterial as Alternative Material in Gabion Type Retaining Wall

The disposal of scrap tyre is a major problem in developing countries. Material recycling is adopted in order to promote safer disposal (beside conventional dump and thermal recycling). Tyre derived geomaterial (TDGM) are proposed to be used in construction of gabion type retaining wall to prevent slope failure that has been a serious geotechnical threat in many countries. The reason of choosing tyre is not only to help in reducing the stockpiling of scrap tyre generated in environmentally friendly way but also to reduce the dependency of gravel as the material to filled current gabion wall. In this study, various mixtures were considered in laboratory scale retaining wall namely, 100% gravel, 100% tyre and 50% of both materials. The retaining wall was functioned to retain a 60º of sand slope. The slope was then subjected to 0.8 mm/hour of artificial rainfall. The soil movement from commencement of the test until the slope failed was recorded. Several tests were carried out to determine basic characteristics (grains size distribution and standard Proctor test) of materials used in the study were conducted beforehand. The results showed that TDGM was able to mitigate slope failure as effective as using gravel. No significant horizontal movements were recorded compared to the slope without any countermeasure. However, slight settlement of gabion wall was recorded and need further testing for clarification

Mechanical and microstructural characterization of ceramic-laterized concrete composite

Ceramics is one of the solid wastes generated from construction and demolition sites, or industries that can constitute nuisance to the environment. Hence, reusing this kind of waste could be of immense benefit not only to the construction industry but also to the environment. This research focused on the mechanical and microstructural characterization of ceramic-laterized composite. The mechanical properties of mortar and concrete elements produced using cementitious composite, comprising of blended ceramic-cement as binders, ceramic aggregate, laterite and conventional aggregates, were determined after the samples have been cured by immersion in water. Non-destructive tests were performed on the hardened mortars, using X-ray CT scan and Ultrasonic Pulse Velocity (UPV) techniques. Also, dry bulk density, water absorption due to capillarity, compressive and flexural strength of mortars were determined. Mechanical properties of concrete such as compressive, split-tensile and flexural strength of concrete cubes, cylinders and prisms were determined. Next, predictive models for determining the compressive and split-tensile strength of ceramic-laterized concrete were developed using the Artificial Neural Network (ANN) technique. The results of compressive and split-tensile strengths obtained from this study and those of related studies were utilized for the model development. Finally, micro scale analysis was performed on mortar fragments from selected mixes, which revealed the hydration mechanism and pore structure of the concrete, as they relate to the strength properties. The concrete specimens were characterized using more advanced analysis techniques, comprising of Scanning Electron Microscopy, in secondary and backscattered electron modes, X-ray Diffractometer, mercury intrusion porosimetry (MIP), and thermogravimetric analysis (TGA). From the results, a mortar sample which was composed of 10% powdered ceramics as cement replacement, and 100% fine ceramics as sand replacement developed better strength characteristics than the reference mortar. The micro scale analysis showed that the best mortar mix developed larger peaks of Ettringite, Portlandite and Calcite minerals than the reference mortar. This could be the cause of its high strength. While for concrete, the reference mix yielded higher mechanical properties than the concrete containing secondary aggregates. However, a laterized concrete mix comprising both 90% of ceramic fine and 10% of laterite as the fine aggregate provided the optimal strength out of all the modified mixes, and this was the case whether the coarse aggregate was 100% granite or 100% coarse ceramics. Although, the strength reduction was about 9% when compared with the reference case, this reduction in strength is acceptable, and does not compromise the use of these alternative aggregates in structural concrete. Thus, this has shown that ceramic aggregate could be adequately used to supplement or totally replace natural aggregate in concrete while laterite could be sparingly used as replacement for river sand

Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields

Innovations in Road, Railway and Airfield Bearing Capacity – Volume 3 comprises the third part of contributions to the 11th International Conference on Bearing Capacity of Roads, Railways and Airfields (2022). In anticipation of the event, it unveils state-of-the-art information and research on the latest policies, traffic loading measurements, in-situ measurements and condition surveys, functional testing, deflection measurement evaluation, structural performance prediction for pavements and tracks, new construction and rehabilitation design systems, frost affected areas, drainage and environmental effects, reinforcement, traditional and recycled materials, full scale testing and on case histories of road, railways and airfields. This edited work is intended for a global audience of road, railway and airfield engineers, researchers and consultants, as well as building and maintenance companies looking to further upgrade their practices in the field

2018 Scholarly Productivity Report

https://scholarsmine.mst.edu/care-scholarly_productivity_reports/1001/thumbnail.jp

Interfacial shear strength of rubber-reinforced clays: a dimensional analysis perspective

The present study aims towards the development of practical dimensional models capable of simulating the interfacial shear strength of rubber-reinforced clays. Two types of recycled tire rubbers (of fine and coarse categories) were each incorporated into the soil at four different contents (by weight), and statically compacted at their respective Proctor optimum condition for direct shear testing. The rubber inclusions amended the soil through improvements achieved in two aspects: (i) frictional resistance generated as a result of soil–rubber contact; and (ii) mechanical interlocking of rubber particles and soil grains. In general, both amending mechanisms were in favor of a higher rubber content, and to a lesser degree a larger rubber size. The dimensional analysis concept was extended to the soil–rubber shear strength problem, thereby leading to the development of practical dimensional models capable of simulating the shear stress–horizontal displacement response as a function of the composite's basic index properties. The predictive capacity of the proposed models was examined and validated by statistical techniques. The proposed dimensional models contain a limited number of fitting parameters, which can be calibrated by minimal experimental effort and hence implemented for predictive purposes.A. Soltani, A. Deng, A. Taheri, M. Mirzababaei, H. Nikra

Advanced Testing and Characterization of Bituminous Materials, Two Volume Set

Bituminous materials are used to build durable roads that sustain diverse environmental conditions. However, due to their complexity and a global shortage of these materials, their design and technical development present several challenges. Advanced Testing and Characterisation of Bituminous Materials focuses on fundamental and performance testin