The Use of Geogrids in Mitigating Pavement Defects on Roads Built over Expansive Soils

This study was conducted to investigate the potential benefits of using geogrids in mitigating pavement defects notably roughness and longitudinal cracking on pavements built over expansive soils. The seasonal changes of expansive soils (periodic wetting and drying) cause detrimental effects on the overlying road pavements. Such detrimental behavior of expansive soils was simulated in a controlled laboratory environment through allowing cyclic wetting and drying of an expansive soil underlying a pavement section. The shrink/swell effects of the expansive soil subgrade were examined through monitoring its change in moisture, and measuring deformation of overlying pavement section. The experimental study suggested that a geogrid layer in a reinforced pavement section can reduce surface differential shrinking and swelling deformation resulting from underlying expansive soils by a factor of 2 and 3 respectively in comparison to unreinforced section. Given that an oedometer test which is typically used to predict swelling potential of expansive soils is known to overpredict in-situ soil swell, experimental program also investigated quantitatively the extent to which the oedometer can overestimate swelling behaviour of the real-field scenarios. It was found that oedometer percent swell can overpredict in-situ swelling behaviour of the expansive soil by a factor ranging between 2 and 10 depending upon the period over which the in-situ expansive soil has been in contact with water

Municipal incinerated bottom ash (MIBA) characteristics and potential for use in road pavements

The characteristics of municipal incinerated bottom ash (MIBA) and its performance in road pavement applications is assessed through systematic analysis and evaluation of the global experimental data. MIBA has been used in unbound, hydraulically and bitumen bound forms. As unbound material, after processing, MIBA exhibits suitable mechanical properties for use as capping, fill and sub-base material, which has been successfully demonstrated in field testing. In hydraulically bound form, MIBA can be a viable aggregate component in subbase and roadbase layers at low to moderate contents, depending on the performance requirements and binder content. As bituminous bound aggregate in roads, the material can be fit for use at low contents, which is reinforced by a number of completed case studies, with the allowable MIBA fraction controlled by the voids contents, abrasion resistance and bitumen content requirements. Keywords: Municipal incinerated bottom ash, Road pavements, Sustainability, Recycled construction material

Remediation of Acid Generating Colliery Spoil Using Steel Slag – Case Studies

One of the legacies of the coal mining industry is the existence of numerous colliery spoil mounds. Run-off waters from some of these mounds result in oxidation of sulphur compounds causing pH to drop to perhaps as low as 2.5. At this pH, mobility for metals increases and it results in destruction of both flora and fauna. In order to reduce acidity, a number of solutions have been investigated with varying degree of success. A recent study to reduce acidity in spoil run-off water included the use of Basic Oxygen Steel slag. Its slow release of lime resulted in longer term remediation compared with other techniques. In addition to this, steel slag contains elements which are essential for plant growth and can be regarded as a weak fertiliser. This was substantiated in two field trials, which had the aim of not only remediating acidity from two different types of colliery spoils, but also to develop a composition that supports grass growth. The objectives were achieved at both sites and some of the results of over 5000 chemical tests conducted during these studies are reported in this paper

Rainfall induced erosion of soils used in earth roads

Earth roads in rural areas of the developing world are key engines to the development of countries. They give access to education and health services, sustain agriculture and businesses, and promote social interactions between communities. However, earth roads suffer substantially from poor engineering and funding for construction and maintenance. Rainfall is probably their most dangerous enemy resulting in soil particle detachment leading to the loss of surface material. A laboratory rainfall simulator was used to identify the performance of an earth road surface compacted at the maximum dry density against rainfall energy and surface flow. Under the rain intensity of 30mm/hr, erosion increased with rain duration from 0 to 30 minutes. Fine sand (0.06 – 0.02mm) and medium sand (0.02 – 0.6mm) particles eroded faster than coarse sand (0.6 – 2mm) and gravel (> 2mm) particles of the sediments collected at 5 minutes intervals of time. Additionally, a 20cm x 20cm photograph at the same place was analysed using ImageJ software and showed reduction in number of particles from 18554 at 10 min to 5803 at 25 min as smaller particles had eroded in the meantime

Properties of concrete prepared with waste tyre rubber particles of uniform and varying sizes

Investigations and research into the recent use of rubber particles in concrete has been well documented. However, information on the rubber particle sizes or their distributions within concrete which may also influence the concrete properties is still limited. In this study, three groups of singly-sized rubber particle samples (3 mm, 0.5 mm and 03 mm) and one sample of continuous size grading (prepared by blending the three singly-sized samples to form the same particle distribution curve of sand) were used to replace 20% of the natural fine aggregate by volume. The reference concrete containing 100% sand was also prepared to compare its properties with those of the samples in terms of workability, fresh density, compressive strength, tensile splitting strength, flexural strength and water permeability. The experimental results demonstrated that the rubber particle size affects the concrete's workability and water permeability to a greater extent than the fresh density and strength. Concrete with rubber particles of larger size tends to have a higher workability and fresh density than that with smaller particle sizes. However, the rubber aggregates with smaller or continuously graded particle sizes are shown to have higher strengths and lower water permeability. (C) 2015 The Authors, Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license