Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The UNFCCC (United Nations Framework Convention on Climate Change), enabled by the Kyoto Protocol, set enforced responsibilities on industrialised countries to reduce the amount of emissions (greenhouse gases) produced. This global call for the reduction of greenhouse gas emissions ensured that the manufacturing sector commit to emission reduction. The asphalt industry has embarked on a quest to find alternative methods of producing and constructing asphalt mixes which will release less greenhouse gasses into the atmosphere. These new methods include the reduction in production and construction temperatures which in turn will reduce the amount of greenhouse emissions produced. These new methods introduced the concept of warm mix asphalt (WMA) to the alternative hot mix asphalt (HMA). To produce a WMA mix at lower temperatures the binder needs to be in a workable state so to effectively coat the aggregate and produce a good quality mix. WMA technologies have been developed to enable production of mixes at lower temperatures (effectively reducing emissions) whilst retaining the required binder viscosity and properties needed to produce a quality mix. The question which needs to be answered is whether the performance of these WMA mixes can compare with that of HMA mixes. In this study several WMA mixes (with different WMA technologies) are evaluated against their equivalent HMA mixes in terms of fatigue life and flexural stiffness. Phase angle results were also considered. Flexural stiffness is a mix property which is dependent on loading time and temperature. It is used to measure the load spread ability of a mix and also influences fatigue behaviour. Fatigue cracking occurs in the material as a result of repeated cyclic loading. The evaluation and analysis conducted in this study show that WMA mixes can compare favourably and even exceed that of HMA mixes in certain cases, although some WMA mixes resulted in lower fatigue life or flexural stiffness than its corresponding HMA mixes, which could be attributed to differences in mix components and variables. In this study a literature study, methodology, laboratory test results, a comparison of mix results and conclusions and recommendations are made. / AFRIKAANSE OPSOMMING: Die UNFCCC (United Nations Framework Convention on Climate Change) was in staat gestel deur die Kyoto Protocol om verantwoordelikhede op geïndustrialiseerde lande te forseer om die hoeveelheid van nadelige kweekhuisgasse wat geproduseer word te verminder. Hierdie globale oproep tot die vermindering van kweekhuisgasse verseker dat die vervaardigingsektor hulself verbind tot emissie vermindering. Die asfalt industrie het begin met 'n soektog na alternatiewe metodes van vervaardiging en die bou van asfaltmengsels wat minder kweekhuisgasse sal vrystel in die atmosfeer. Hierdie nuwe metodes sluit die vermindering in produksie en konstruksie temperature in wat op sy beurt die hoeveelheid kweekhuisgasse geproduseer verminder. Hierdie nuwe metodes het die konsep van warm mengsel asfalt (WMA) bekendgestel teenoor die alternatiewe ‘hot’ mengsel asfalt (HMA). Om ‘n WMA mengsel te produseer by laer temperature, moet die bindmiddel in 'n werkbare toestand wees om die aggregaat heeltemal te bedek en 'n goeie gehalte mengsel te produseer. WMA tegnologie is ontwikkel om die produksie van mengsels teen laer temperature te realiseer (vermindering die uitlaatgasse), terwyl die vereiste bindmiddel viskositeit en eienskappe wat nodig is om 'n kwaliteit mengsel te produseer behou word. Die vraag wat beantwoord moet word, is of die prestasie van hierdie WMA mengsel kan vergelyk word met dié van HMA mengsel. In hierdie studie is 'n paar WMA mengsels (met verskillende WMA tegnologie) geëvalueer teen hul ekwivalent HMA mengsels in terme van vermoeiing en buig styfheid. Fase hoek resultate is ook in ag geneem. Buig styfheid is 'n mengsel eienskap wat afhanklik is van die laai tyd en temperatuur. Dit word gebruik om die las verspreiding vermoë van 'n mengsel te meet en beïnvloed ook vermoeiing gedrag. Vermoeidheid krake kom voor in die materiaal as gevolg van herhaalde sikliese laai. Die evaluering en ontleding in hierdie studie toon dat WMA mengsels goed vergelyk en selfs in sekere gevalle meer as dié van HMA mengsels, hoewel sommige WMA mengsels laer vermoeidheid lewe of buig styfheid as die ooreenstemmende HMA mengsels gewys het, wat toegeskryf kan word tot verskille in mengsel komponente en veranderlikes. In hierdie studie word 'n literatuurstudie, metodiek, laboratorium toets resultate, 'n vergelyking van die mengsel resultate en gevolgtrekkings en aanbevelings gemaak.

The rapid growth of population and climate change has subjected our civil infrastructures to high load demands and fast aging or degradation over time. Temperature plays a key role in the performance of the aging infrastructure in form of thermal stress and cracking, temperature-induced material aging and degradation, temperature-dependent deformation, and softening. Thus, the importance of predicting the consequent behavior of the infrastructures under environmental conditions becomes imperative. This research characterizes three infrastructure surface materials, namely asphalt pavement, solar panels, and phase change materials (PCM), models the efficacy of modifiers and novel methods to improve their performance and uses these materials in the design and testing of thermal management systems for different applications. The connection between these materials is the thermal management in pavement overlays, which can be extended to other infrastructure surfaces. Asphalt pavement modified with recycled crumb rubber (CR) is a sustainable way to reuse the millions of tires that used to end in landfills. However, the ultraviolet (UV) rays from the sun have been shown to adversely affect the asphalt’s performance in the long run. The severe photo-oxidation can cause changes in the volatile components of the asphalt and result in hardening, aging, and thermal cracks in it. The effect of UV rays on the rubber-modified asphalt may be even more complex due to the presence of crumb rubber particles and their chemical/physical incompatibility and changes in the glass transition. In order to examine these effects, a PG 64-22 is modified with two percentages of 16.6 wt.% and 20.0 wt.% crumb rubber. Results show the specific heat capacities increase with UV aging with 16.6% having the highest value. The addition of the rubber particles does not change the chemical composition of the binder as confirmed by the elemental analysis. However, after UV exposure, peaks associated with carbonyl and sulfoxide are observed, proving that the rubber-modified binder is subject to photo-oxidation as well. The 16.6. wt.% shows the best performance against aging with the lowest sulfoxide index and the highest aliphatic index. Another advantage of adding crumb rubber particles is the formation of a matrix due to the crosslinking of the rubber particles with the binder after being heated, as approved by microscopic images. The carbon nanotubes (CNT) are used to modify the asphalt binder to improve its rheological characteristics while also enhancing the thermal conductivity of the mixture to facilitate the transfer of heat to the surface. In this study, two samples of 3% and 6% multi walled carbon nanotubes (MWCNTs) are prepared using a foaming technology. Foaming the asphalt via water lowers its viscosity and temperature resulting in the saving of the base material and consumed energy while increasing the coating of the aggregates. The results show the CNTs can improve the thermal conductivity of the foamed binder by almost 2X while not negatively affect its rheology. For the other end of the thermal management system, a new hydronic system is introduced for the building integrated photovoltaics and thermal (BIPVT) silicon module that acts for the dual objectives of collecting heat to be used for the thermal management of the pavement and controlling the surface temperature of the solar module itself for the optimal efficiency under different operating conditions. The BIPVT panel with different flow rates of 100 to 600 ml/min were tested for the effectiveness of the cooling design. The results from experiments and simulations show that at 200 ml/min, an optimal balance for the performance of the panel is achieved to not only reduce the temperature of the panel from 88°C to 65°C, but also generate a partially heated water outlet of 37°C (compared with the 23°C inlet) that can be used for the hot water system of the building, or as the inlet feed to the hydronic cooling/heating pavement system. In addition, the BIPVT design proves to restore the power of the solar module by 24.6% at a 200 ml/min flow rate, as confirmed from the I-V curves. Finally, the feasibility study of converting the waste animal fat to a phase change material (PCM) is explored. In PCMs, the high latent heat characteristics are used to store or release energy during the phase change. The use of PCMs can significantly lower the temperature variation of buildings and the consequent energy use. While most common PCMs are paraffin-based and too expensive for large scale applications, a bio-based and more economic alternative could be the key to its vast use in infrastructure systems. However, more research is needed to achieve an animal fat PCM with high latent heat values. In this study, characterizing the raw fat shows a ~20% saturated content. After hydrolysis, the saturated portion has been increased to 65%, but the improvement in the latent is not significant. However, after separation of the fatty acids by use of crystallization, the resulting fully saturated fatty acids (palmitic and stearic acids) show a 3.5X increase in the value of the latent heat, increasing it from ~55 J/g for free fatty acids to ~195 J/g for saturated fatty acids. The promising results of the high latent heat values make the current bio-based PCM a good alternative that needs to be further explored in the future to be used for applications in buildings and BIPVT panels. Overall, the results of this PhD study provide a comprehensive understanding of materials and systems for thermal management of asphalt pavements and enable the design and development of durable self-heated pavements, which can be immediately extended to other infrastructure applications such as wall panels, net-zero buildings, and solar panels.