Mechanical behaviour of stress absorbing membrane interlayers

This study assesses the contribution of some selected stress absorbing membrane interlayers (SAMIs) on overlaid pavement performance in delaying the offset of reflective cracking using laboratory and full scale testing. Materials characterization were carried to have knowledge of the properties of the SAMIs and overlay and some of the properties were required as input for the finite element modelling. The characterization tests include the particle size distribution, penetration and softening point tests, dynamic mechanical analysis, indirect tensile stiffness modulus test (ITSM), indirect tensile fatigue test (ITFT) and repeated load axial test (RLAT). The interface bond was investigated using the Leutner shear test and pull off test. The assessment of the contribution of selected SAMIs on overlaid pavement performance in delaying offset of reflective cracking was carried out using a wheel tracking test supported by finite element modelling, a large scale pavement test facility test and a thermal cycling test. The Leutner shear test and pull-off test were used to examine the strength and stiffness of the overlay-SAMI interface. The interface strength/stiffness was determined because it is one of the factors that influence the crack resistance of SAMIs. The wheel tracking test was carried out to evaluate the effects of the thickness and stiffness of SAMI, thickness of overlay, SAMI composition, interface stiffness, load level and temperature on the performance of SAMIs under traffic loading. To study the performance of SAMIs under conditions close to the field, a large pavement test facility test was carried out. The finite element analysis of the wheel tracking test was carried out to evaluate the deflection, stress and strain distribution in a cracked pavement with and without SAMIs. The performance of SAMIs under thermal loading (temperature variation) was investigated using the thermal cycling test. The study shows that SAMI composition, SAMI thickness and stiffness, overlay thickness, interface stiffness, temperature and load levels influence the performance of SAMIs under traffic loading. It also demonstrates that the main factor that influences the performance of SAMIs under thermal loading is the interface stiffness. Design guidelines for the successful use of SAMIs against reflective cracking were prepared and the OLCRACK software was used to demonstrate the benefits of SAMIs in an overlay over a cracked pavement

Geotechnical Properties of Lateritic Soil Stabilized with Ground-Nut Husk Ash

This study assesses the geotechnical properties of lateritic soil stabilized with Ground-nut Husk Ash. Preliminary tests were carried out on the natural soil sample for identification and classification purposes, while consistency limits tests were thereafter carried out as well. Engineering property tests such as California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS) and compaction tests were performed on both the natural soil sample and the stabilized lateritic soil, which was stabilized by adding Ground-nut Husk Ash, GHA, in percentages of 2, 4, 6, 8 and 10 by weight of the soil.  The results showed that the addition of GHA enhanced the strength of the soil sample. The Maximum Dry Density (MDD) reduced from 1960 kg/m3 to 1760 kg/m3 at 10% GHA by weight of soil. The Optimum Moisture Content (OMC) increased from 12.70% to 14.95%, also at 10% GHA by weight of soil. The unsoaked CBR values increased from 24.42% to 72.88% finally, the UCS values increased from 510.25 kN/m2 to 1186.46 kN/m2, for both CBR and UCS, the values were at 10% GHA by weight of soil. It was therefore concluded that GHA performs satisfactorily as a cheap stabilizing agent for stabilizing lateritic soil especially for subgrade and sub base purposes in road construction

Evaluation of the effects of waste glass in asphalt concrete using the Marshall test

The study investigates the use of waste glass as filler in asphalt concrete. Waste glass constitutes a significant proportion of the waste generated in both developed and developing countries. Successful utilization of the waste glass in asphalt will reduce the problem faced by environmental agencies at ensuring safe disposal of the non-biodegradable waste and may improve the asphalt properties. In the study, a waste glass in form of a filler was introduced into the asphalt mix at 8%, 10%, 12%, 14%, 16%, 18% and 20% of the total mix. The asphalt concrete samples with and without waste glass as filler were subjected to the Marshall test to determine the stability, flow, air voids, void in mix aggregate and void filled with bitumen. The Marshall test results show that stability increases when increasing glass filler up to 18%, although the values were lower than of the asphalt concrete without waste glass. This implies improved resistance to fatigue for higher waste glass content. Also, the flow increases with increasing glass filler, which implies the resistance to permanent deformation which did not improve. Generally, the introduction of waste glass in the asphalt concrete is environmentally friendly, and it will aid the sustainable management of waste glass

Geotechnical and microstructural properties of cement-treated laterites stabilized with rice husk ash and bamboo leaf ash

This study investigated the geotechnical and microstructural properties of cement-treated laterites stabilized with rice husk ash and bamboo leaf ash. In going about the tests, the soil sample was subjected to compaction, California Bearing Ratio (CBR) and preliminary tests; such as specific gravity, particle size distribution and Atterbergs limits to determine its index properties. Thereafter, the soil sample was mixed with cement at varying proportions of 0–12% at 2% intervals and also, separately mixed with bamboo leaf ash (BLA) and rice husk ash (RHA) in proportions of 0–16% at 2% intervals. The mixes at each stage were subjected to compaction, Atterberg limits and CBR tests. The highest values were 66.7% and 54.8% for unsoaked and soaked CBR at 6% cement+8% BLA and 78.5% and 63.8% for unsoaked and soaked CBR at 8% cement+8% RHA. Samples at these optimal CBR values were subjected into Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) tests. Results showed that new compounds were formed and there were changes in the microstructural arrangements. It can therefore be concluded that pozzolanic and cement hydration reactions actually took place in the course of stabilization

Effects of Coarse Aggregate Size on the Compressive Strength of Concrete

This study investigates the effect of aggregate size on the compressive strength of concrete. Two nominal mixes, that is, 1:2:4 and 1:3:6 were used in the study. Concrete cubes were produced with 6, 10, 12.5, 20 and 25 mm aggregates for the two nominal mixes and they were subjected to compressive strength test after curing for 7, 21, 28 and 56 days. It was found in the study that the strength development follows the same trend for both nominal mixes. Also, the results show that the compressive strength increases with increasing aggregate size up to 12.5 mm, while the concrete produced using 20 mm had greater compressive strength than those produced using 25 mm aggregate. This established the importance of ensuring that the right aggregate size is used in the production of concrete. Therefore, it is recommended that careful attention must be paid to the sizes of aggregates used in the production of concrete for structural purposes

Mechanical behaviour of stress absorbing membrane interlayers

This study assesses the contribution of some selected stress absorbing membrane interlayers (SAMIs) on overlaid pavement performance in delaying the offset of reflective cracking using laboratory and full scale testing. Materials characterization were carried to have knowledge of the properties of the SAMIs and overlay and some of the properties were required as input for the finite element modelling. The characterization tests include the particle size distribution, penetration and softening point tests, dynamic mechanical analysis, indirect tensile stiffness modulus test (ITSM), indirect tensile fatigue test (ITFT) and repeated load axial test (RLAT). The interface bond was investigated using the Leutner shear test and pull off test. The assessment of the contribution of selected SAMIs on overlaid pavement performance in delaying offset of reflective cracking was carried out using a wheel tracking test supported by finite element modelling, a large scale pavement test facility test and a thermal cycling test. The Leutner shear test and pull-off test were used to examine the strength and stiffness of the overlay-SAMI interface. The interface strength/stiffness was determined because it is one of the factors that influence the crack resistance of SAMIs. The wheel tracking test was carried out to evaluate the effects of the thickness and stiffness of SAMI, thickness of overlay, SAMI composition, interface stiffness, load level and temperature on the performance of SAMIs under traffic loading. To study the performance of SAMIs under conditions close to the field, a large pavement test facility test was carried out. The finite element analysis of the wheel tracking test was carried out to evaluate the deflection, stress and strain distribution in a cracked pavement with and without SAMIs. The performance of SAMIs under thermal loading (temperature variation) was investigated using the thermal cycling test. The study shows that SAMI composition, SAMI thickness and stiffness, overlay thickness, interface stiffness, temperature and load levels influence the performance of SAMIs under traffic loading. It also demonstrates that the main factor that influences the performance of SAMIs under thermal loading is the interface stiffness. Design guidelines for the successful use of SAMIs against reflective cracking were prepared and the OLCRACK software was used to demonstrate the benefits of SAMIs in an overlay over a cracked pavement.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

An Investigation Into The Use Of Lime-Stabilized Clay As Subgrade Material

ABSTRACT: This study involves the collection of clay sample at a site along Ise / Ikere Road at Ikere-Ekiti region and evaluation of its properties in natural state and after stabilization with lime. The major objective of the study is to determine the optimum lime content that will stabilize the clay soil adequately. Also, it investigates the level of improvement that could be achieved by stabilizing clayey soil with lime. The tests carried out include mechanical sieve analysis and hydrometer test, specific gravity, moisture content, Atterberg limit test, compaction test, and California bearing ratio test. The high moisture content of the natual clay soil clearly shows its high water absorption capability. The addition of lime reduces the plasticity index at 8% and 10 % lime content. The maximum dry density (MDD) increases with an increase in lime content from 0 to 8%, while a reduction in the MDD was observed at 10%. The maximum optimum moisture content (OMC) was recorded at 10 % lime content. The California bearing ratio (CBR) of the lime stabilized clay increases for lime content of 2 % to 8%, with the maximum value obtained at 8%, while a reduction in the CBR was observed at 10%. The reduction in the CBR at 10 % might be due to the excess lime in the clay not required for the early strength gain as a result of flocculation