Combining reward and M1 transcranial direct current stimulation enhances the retention of newly learnt sensorimotor mappings

Background: Reward-based feedback given during motor learning has been shown to improve the retention of the behaviour being acquired. Interestingly, applying transcranial direct current stimulation (tDCS) during learning over the primary motor cortex (M1), an area associated with motor retention, also results in enhanced retention of the newly formed motor memories. However, it remains unknown whether combining these distinct interventions result in an additive benefit of motor retention. Methods: We investigated whether combining both interventions while participants learned to account for a visuomotor transformation results in enhanced motor retention (total n = 56; each group n = 14). To determine whether these interventions share common physiological mechanisms underpinning learning, we assessed motor cortical excitability and inhibition (i.e. SICI) on a hand muscle before and after all participants learned the visuomotor rotation using their entire arm and hand. Results: We found that both the Reward-Stim (i.e. reward + tDCS) and Reward-Sham (i.e. reward-only) groups had increased retention at the beginning of the retention phase, indicating an immediate effect of reward on behaviour. However, each intervention on their own did not enhance retention when compared to sham, but rather, only the combination of both reward and tDCS demonstrated prolonged retention. We also found that only the Reward-Stim group had a significant reduction in SICI after exposure to the perturbation. Conclusions: We show that combining both interventions are additive in providing stronger retention of motor adaptation. These results indicate that the reliability and validity of using tDCS within a clinical context may depend on the type of feedback individuals receive when learning a new motor pattern

Laboratory investigation of coal bottom ash modified warm mix asphalt

Bottom Ash (BA), a coal combustion by-product, found to be a potential material when used to produce asphalt mixture. However, some of its characteristics make it a questionable material for the surface course. Therefore, this study aims to evaluate the compatibility of BA in Warm Mix Asphalt (WMA) technology through the basic mechanical properties of the asphalt mixtures for binder course layer (AC 28). Two WMA chemical additives, Cecabase RT and Evotherm 3G, were used at the concentrations of 0.3, 0.4 and 0.5% from the binder's weight. The binder properties were assessed through penetration, softening point and viscosity tests. The Marshall mix design was used to determine the optimum binder content (OBC). The additive dosage and production temperature for WMA were determined through Marshall stability, flow, air voids and specific gravity. The results show that the additives did not significantly affect the binder properties, although, at 0.4% Evotherm 3G, a drop of 17.5% in penetration was observed. Cecabase RT produced WMA with promising results but did not enhance the workability of WMA containing bottom ash (BAWMA). By lowering the production temperature of 25 °C, WMA and BAWMA at 0.4 %, Evotherm 3G demonstrated comparable workability to the conventional Hot Mix Asphalt (HMA). The data achieved through this study would be a guiding approach towards the application of BA in WMA technology for sustainable pavements

Assessment framework for pavement material and technology elements in green highway index

Sustainability concept in highway development needs to be addressed critically in order to alleviate the effect of global warming and depletion of natural resources issues. In Malaysia, there are a lot of alternative pavement materials and technology that have been introduced to the industry so that green highway can be achieved. However, Malaysia does not have any tools to assess the level of greenness for any highway projects and still lacks of awareness in sustainable highway. Thus, the main objective of this study is to develop an assessment framework for pavement material and technology elements in Malaysia green highway index. An extensive literature were reviewed and expert discussion was conducted to identify the 13 vital elements of pavement material and technology which include regional materials; reuse of top soil; reused and/or recycled of non-hazardous materials; earthwork balance; usage of industrial by-products; subgrade improvement/soil stabilization, permeable pavement, pavement design life, quiet pavement, recycled pavement or new sustainable techniques; cool pavement; soil biotechnical engineering treatment; and green techniques. Questionnaires were distributed among the 109 highway practitioners to obtain their agreement level on these elements. Then, all the data were analyzed by using factor analysis approach which generated from Statistical Package for Social Science (SPSS) software. The assessment score of each element was calculated from the findings and assessment framework for pavement material and technology elements was established. Results show that all the elements were grouped into four main factor namely environmental control, economical resources, innovation technology and erosion control with four point was considered as a maximum point score to be achieved in green highway assessment framework. Hence, the research clearly indicates that these elements are essential to be implemented in Malaysia's highway development indirectly as an encouragement to improve the performance of transportation sector

Characterization of industrial by-products as asphalt paving material

Most of the recent research is focusing on the utilization of industrial by-products in road construction. The intention is not only to mitigate the problem of waste being dumped to the landfills but to encourage their use as construction material without compromising quality and performance of the road. Steel slag and bottom ash are the industrial by-products generated in large quantity by industry. This study investigates the characteristics of steel slag and bottom ash to be utilized as aggregate in asphalt pavement. Both materials were characterized in terms of physical, chemical and morphological characteristics compared to the conventional granite aggregate. The results revealed that both materials have much potential to be used as aggregate in asphalt mix. The bottom ash was observed weaker in terms of strength, but the steel slag was found much stronger than the granite. The morphological structure of bottom ash and steel slag disclosed that these are made up of porous and rough-edged granular particles with slightly higher water absorption

Effects of titanate coupling agent on engineering properties of asphalt binders and mixtures incorporating LLDPE-CaCO3 pellet

This study was initiated to evaluate the performance of asphalt binders and mixtures incorporating linear low-density polyethylene- calcium carbonate (LLDPE-CaCO3) pellet, either with or without titanate coupling agent. The detailed manufacturing process of modifier pellets was displayed. The coupling agent was used to enhance the cross-linking between materials by means of winding up covalent bonds or molecule chains, thus improving the performance of composites. In the preparation of modified bitumen, the preheated asphalt binder was mixed with the modifiers using a high shear mixer at 5000 rpm rotational speed for 45 min. Experimental works were conducted to evaluate the performance of asphalt binders in terms of volatile loss, viscosity, rutting potential, and low temperature cracking. Meanwhile, the asphalt mixtures were tested using the flow number test and tensile strength ratio (TSR) test. The addition of LLDPE-CaCO3 modifiers and coupling agent does not significantly affect the volatile loss of modified asphalt binders. The addition of modifiers and coupling agent has significantly improved the resistance to permanent deformation of asphalt binders. Even though, the addition of LLDPE-CaCO3 modifier and coupling agent remarkably increased the mixture stiffness that contributed to lower rutting potential, the resistance to low temperature cracking of asphalt binder was not adversely affected. The combination of 1% coupling agent with 3% PECC is optimum dosage for asphalt binder to have satisfactory performance in resistance to moisture damage and rutting

Developing a Human Balance Test System (DETES) in Order to Investigate Control Mechanisms of Human Erect Posture

An originally designed 3-dof (2-dof perturbation platform and 1-dof cabin) human balance testing system (DETES) has been developed for delivering mechanical and perceptual stimuli in a controlled embedding environment in order to investigate sensory-motor control of human erect posture at physiological and/or pathological conditions. The human balance (especially studying vestibular system involved mechanisms) demonstrating complex (nonlinear) dynamical behavior in the context of postural adjustments having ecological roots/meanings (information) is to be tested (by means of quiet and perturbed stance) and analyzed for supporting (differential) diagnosis, monitoring/following the progress of the disease, and creating the new adaptive motor learning protocols for rehabilitation

A comparative assessment of the physical and microstructural properties of waste garnet generated from automated and manual blasting process

Cold mix asphalt (CMA) is an eco-friendly sustainable asphalt mixture, mostly for asphalt surface treatments (ASTs). However, material compatibility and poor adhesion leading to high voids, moisture damage susceptibility, and weak early strength remain challenging. Efforts to solve this limitation is beamed towards binder improvement and modification with modifiers, adhesion promoters, or polymers. Other forms of AST mixture improvement entail supplementary cementitious reinforcing or pozzolanic agents in the form of by-products. In this study, the physio-mechanical and microstructural desirability of spent garnet for use as fine aggregate in CMA was explored. Spent garnet is a by-product of abrasive blasting, often produced in large quantities and disposed of in landfills. Often, spent garnet waste gets contaminated with toxic elements either during usage or in landfills. This study aimed to investigate the properties of Automatically (AG) and Manually generated (MG) spent garnet grades. The physio-mechanical, morphologic, and chemical parameters of spent garnet were assessed to achieve this aim. The result compared with relevant specifications on cold mixtures plus Jabatan Kerja Raya (JKR) requirement. Moreover, crystallinity and composition were studied using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray Fluorescence (XRF). The presence of toxic heavy metals that often contaminate spent garnet deposits in landfills was evaluated too. Results suggested that both AG and MG's high sand equivalent and least water absorption of 98 %, 89 %, and 0.14 %, 0.23 % accordingly, and can replace sand in CMA. However, MG spent garnet is not desirable for chemically sensitive materials. The AG garnet was found to be Pyrope while the MG spent garnet is largely Almandine garnet – the strongest form of garnet, including traces of other garnet forms

Strength behaviour of kaolin treated by demolished concrete materials

Kaolin has claynite structure in nature, presenting several properties which may justify in many engineering and industrial applications. However, this type of soil is categorised as problematic soil because the presence of claynite properties eventually resulting the kaolin to have low shear strength and high compressibility as other clay soil. Due to that weakness, kaolinite does not meet the requirements necessary for any construction purposes particularly at the preliminary stage. Hence, to overcome this issue, soil stabilisation process is needed prior any construction works. The aim of this study is to determine the strength characteristics of stabilised soft clay soil (Kaolin S300) with demolished concrete materials (DCM). The selection of DCM as the stabilizer for the purpose reutilisation of waste materials that currently has been a great concern for the environmental sustainability. The percentages of DCM content used were 5%,10%,15%20%,25%,30% with varying curing time of 7days, 14 days and 28 days, respectively. Based on the result it was reported that, the unconfined compressive strength (UCS) test shows that the highest strength value obtained of 595.6 kPa kaolin treated with 30% DCM at 28 curing days. It is equivalent to 92% increment from the untreated kaolin sample at 0 days. However, the optimum amount of DCM which provides significant strength improvement was found when more than 20% of DCM is presented after 14 curing days. Hence, it shows the possible usage of DCM as waste material to effectively stabilize kaolin at specific amounts sufficiently

The influence of PelletRAP™ rejuvenator on the mechanical properties of reclaimed asphalt pavement

In the last decade, the use of reclaimed asphalt pavement (RAP) resulted from asphalt milling process has been widely increased for economic and environmental reasons. However, RAP mixtures have undesired characteristics, such as higher stiffness and low flexibility. In this case, the rejuvenators should be used for restoring the properties of RAP which were lost during service life. In the present research, the mechanical properties of 100% RAP incorporating various percentages of PelletRAP™ rejuvenator were evaluated via stability, flow, stiffness, indirect tensile strength (ITS), moisture damage and Cantabro loss measurements. The results showed that the rejuvenated mixtures containing 4% of PelletRAP™ exhibited better performance in terms of stability, cracking and moisture damage resistance, as well as durability, compared with virgin mixtures. Thus, it can be concluded that 100% RAP can be renovated and re-used in the pavement if it is mixed with an appropriate prescription of PelletRAP™. The proposed of incorporating PelletRAP™ with RAP is beneficial in the improvement of sustainability and cost-efficiency of the asphalt mixtures industry

Evaluating the performance of reclaimed asphalt pavement incorporating pelletrap as a rejuvenator

In the recent years, the use of reclaimed asphalt pavement (RAP) in the pavement has become inevitable for economic and environmental reasons. However, the brittleness property of aged asphalt in the RAP restrict its usage in a high percentage. Nevertheless, the rejuvenators are introduced into the mixtures to reverse the effect of ageing processes, decrease the stiffness and increase the workability of RAP mixture. In the present research, various percentages of PelletRAP rejuvenator were added to 100% of RAP mixtures. The performance characteristics of rejuvenated mixtures were investigated via resilient modulus (MR), dynamic creep, and wheel tracking tests. The results showed that when the PelletRAP was included into the mixture, the MR values and the creep stiffness modulus (CSM) decreased, while the permanent creep, the creep strain slope (CSS) and the rutting depth increased. However, all the rejuvenated mixtures exhibited better results than that of virgin mixture. Such a trend of findings suggested that PelletRAP can be used as a rejuvenator without a negative effect on the high-temperature performance of asphalt mixtures