Moisture susceptibility and environmental impact of warm mix asphalt containing bottom ash

Warm Mix Asphalt (WMA) is recognised as a sustainable pavement construction technology due to its economic and environmental benefits. However, there are still some major concerns related to its performance properties, like moisture susceptibility. Certain researchers have reported desired performances using waste and by-products as constituent material in the WMA mixture. Therefore, this study was proposed to assess the Bottom Ash (BA) impact on WMA mixtures moisture susceptibility and environmental properties because its potential has widely been reported in HMA. It was limited to 20 % of fine aggregate substitution with BA and granite stone dust as a filler. Evotherm 3G was used as a WMA additive, and the Hot Mix Asphalt (HMA) mixtures were treated with 2 % hydrated lime by replacing stone dust. The Marshall mix design was followed to fabricate asphalt mixtures, where HMA and WMA specimens were mixed at 165 °C and 140 °C, respectively. The indirect tensile strength, tensile strength ratio, toxicity characteristic leaching procedure (TCLP) and pollutant emission of mixtures were investigated through laboratory tests. The mixtures containing BA improved the indirect tensile strength of mixtures, while Evotherm 3G potentially improved the tensile strength ratio of WMA mixtures containing BA. The results showed that BA as a constituent of asphalt mixture coupled with Evotherm 3G produced a compatible blend for WMA. The findings of the TCLP test showed that the compound of heavy elements found in BA does not leach out if introduced in the asphalt mixtures. Heavy elements concentrations were either undetectable or below the minimal level. However, the presence of BA in the asphalt mixture slightly increased the level of Carbon dioxide (CO2). However, the carbon monoxide (CO) of the WMA mixture containing BA was reduced to approximately 75 %

Mechanical performance of asphalt mixture containing cup lump rubber

The use of cup lump rubber as an additive in asphalt binder has recently become the main interest of the paving industry. The innovation helps to increase the natural rubber consumption and stabilize the rubber price. This study evaluates the mechanical performance of cup lump rubber modified asphalt (CMA) mixture in terms of resilient modulus, dynamic creep and indirect tensile strength under aging conditions. The CMA mixture was prepared using dense-graded Marshall-designed mix and the observed behavior was compared with that of conventional mixture. From the results, both mixtures passed the volumetric properties as accordance to Malaysian Public Work Department (PWD) specification. A comparable result was obtained for stability and indirect tensile strength. The addition of 5% cup lump rubber provides better resistance against permanent deformation through the enhanced properties of resilient modulus and dynamic creep by 27% and 126% respectively under unaged condition. Furthermore, lower permanent strain was also observed for CMA compared to conventional mixture

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

Properties of dense-graded asphalt mixture compacted at different temperatures

Poor compaction work is one of the identified causes of road failure and has always been a concern to the asphalt industry. The use of compaction machinery, compaction temperature, weather factor and the type of mixture used could potentially affect the asphalt pavement performance. This study measures the properties of hot mix asphalt (dense-graded AC10) prepared at different compaction temperatures. Various compaction temperatures were selected for the laboratory slab samples preparation i.e. 152°C, 142°C, 132°C and 122°C. A 60/70 pen bitumen was used to prepare the slab with the size of 305mm x 305mm x 50mm. Thermocouple was used to monitor the temperature of the mix. The slab samples were then cored for cylindrical samples at the approximate size of 100mm diameter for mechanical tests. The core samples were tested for volumetric properties, degree of compaction (DOC), Marshall stability and resilient modulus. It was found that low compaction temperature increases the air void in the total mix (VTM) and decreases the air void filled with bitumen (VFB) due to the increase in bitumen viscosity. In other words, reduction in compaction temperature resists the compactibility of the loose mix and resulted in low final DOC and low modulus

Properties of high strength concrete containing spent garnet as sand

Spent garnet is a waste resulting from abrasive media known as garnet and disposed into the landfill which can become threat to the environment. Meanwhile, the step of substituting sand by spent garnet can reduce sand exploitation activities which have been ongoing to fulfil the continuous development and construction. This work attempts to investigate the mechanical properties of specimens made of concrete that contains spent garnet. This new material replaces sand partially at different percentages of 10% and 20% by weight. The compressive strength test as well as splitting tensile test have been both conducted after 7 days and 28 days water curing. The results show an improvement of the strength during the compressive test. The increment appears to be in positive relationship with the replacement percentage. Meanwhile, splitting tensile strength testing shows that 20% performs better than 10% sand replacement. In conclusion, the inclusion of spent garnet in reasonable amount to take place instead of sand has improved the concrete's properties

Effect of black rice husk ash on asphaltic concrete properties under aging condition

The scarcities of natural resources and increment in waste production rates have promoted efforts to investigate the potential incorporation of various by-products in roads construction. Reusing of waste materials such as black rice husk ash (BRHA) in asphaltic concrete was considered as one of the proper management of the waste, which ensures economic and environmental benefits. Hence, this study investigates the effect of black rice husk ash on asphalt mixtures properties under different aging condition. BRHA was added in the asphalt mix in a proportion of 0%, 2%, 4% and 6% by weight of bitumen. 5% optimum bitumen content with 60/70 penetration grade binder was selected for this study. The asphalt mixtures for each fraction was prepared in three different aging conditions i.e. un-aging (UA), short term aging (STA) and long term aging (LTA). The properties of asphalt mixtures were evaluated by voids, stiffness and dynamic creep tests. The results indicate that asphalt mixtures consisting of BRHA have exhibited better performance in term of voids, stiffness and creep modulus when compared to the conventional asphalt mixtures. The STA and LTA mixtures modified with BRHA produced higher performance than the unmodified mixtures. It can be concluded that the optimum additional percentage of BRHA was in the range of 4% to 6%

Enhanced dry process method for modified asphalt containing plastic waste

In recent years, the proliferation of plastic waste has become a global problem. A potential solution to this problem is the dry process, which incorporates plastic waste into asphalt mixtures. However, the dry process often has inconsistent performance due to poor interaction with binder and improper distribution of plastic waste particles in the mixture skeleton. This inconsistency may be caused by inaccurate mixing method, shredding size, mixing temperature and ingredient priorities. Thus, this study aims to improve the consistency of the dry process by comparing the control asphalt mixture and two plastic waste-modified asphalt mixtures prepared using the dry process. This study used crushed granite aggregate with the nominal maximum aggregate size of 14 mm whereas the shredded plastic bag is in the range of 5–10 mm. Quantitative sieving analysis and performance tests were carried out to examine the effects of plastic waste added into the asphalt mixture. The volumetric and performance properties combined with image analysis of the modified mixtures were obtained and compared with the control mixture. In addition, the moisture damage, resilient modulus, creep deformation and rutting were evaluated. This study also highlighted in detail the distribution of plastic particles in the final skeleton of the asphalt mixture. Based on the analysis, an enhanced dry process of mixing procedure was proposed and evaluated. Results showed that the addition of plastic particles using the conventional dry process leads to the deviation in the aggregate structure as high plastic content is added. Furthermore, the enhanced dry process developed in this study presents substantial enhancement in the asphalt performance, particularly with plastic waste that accounts for 20% of the weight of the asphalt binder

Short term aging effect of asphaltic concrete incorporating charcoal ash from coconut shell

Numerous studies have been conducted to improve the performance of asphalt mixture properties in comparison with conventional mixes. One of the alternatives is utilizing waste agriculture product as additive or replacement into bitumen mixture. Coconut shell is one of the agricultural wastes that can be utilized. This paper aims to study the effect of asphaltic concrete incorporating charcoal ash from a coconut shell under short term aging condition. Charcoal coconut shell ash (CCSA) was added into a bitumen with 0%, 2%, 4%, 6%, and 8% by weight. The original CCSA was initially ground until getting the particles sizes less than 0.075mm. Laboratory simulation of aging was applied in this investigation. Marshall Stability, volumetric properties, resilient modulus, and dynamic creep test were performed to analyses asphalt mixture containing CCSA. It was observed that the addition of CCSA in asphaltic concrete gives the significant development in stability, modulus of resilient and creep stiffness. This study suggests that 4% and 6% of CBA as a supplementary binder could improve the mechanical properties of asphaltic concrete even under aging conditions

Repeatability of reclaimed asphalt pavement

Usage of fresh bitumen and aggregates in pavement construction and rehabilitation can be minimised by utilising reclaimed asphalt pavement (RAP). RAP is a waste material generated from old or damaged pavement surface. Although it has been practiced since 1970s and several suggestions on the usage of RAP in the new mixture have been introduced, there is a limited number of research has been found, discussing on the issue of second recycling of RAP (R2AP). Pavement made with RAP will reach the end of service life and there is a need to recycle again. This study focused on investigating the performance of mixtures incorporating RAP and R2AP. It was carried out in three phases. In the first phase, three ageing procedures consisted of eight laboratory ageing methods were conducted to select suitable method that produced most severe ageing effect. Ageing methods used were combination of rolling thin film oven (RTFO), pressure aging vessel (PAV), short term oven ageing (STOA) and long term oven ageing (LTOA). In the second phase, mixture tests were conducted to evaluate the performance of asphaltic concrete with 14 mm nominal maximum aggregate size (AC 14) mixture incorporating RAP and R2AP. Final phase involved the physical, rheological and chemical property tests of aged bitumen. Penetration, softening point, viscosity, dynamic shear, elemental analysis and Fourier transform infrared (FTIR) tests were performed on the bitumen which were extracted from the selected mixtures. Three mixtures consisted of 20, 40 and 60% RAP were evaluated in the first cycle and four mixtures consisted of 20, 40, 60 and 80% R2AP were evaluated in the second cycle. Results show that seven days of LTOA is the most suitable ageing method for AC 14. Mixture consisted of 40% RAP shows a better performance when it was mixed with 80-100 PEN (B1) bitumen whereas mixture with 60% RAP performed better with 60-70 PEN (B2) bitumen compared to other mixtures. After seven days of LTOA, mixture consisted of 40% R2AP mixed with B1 and 40% R2AP mixed with B2 show better performance compared to other recycled mixtures. Physical, rheological and chemical analyses of the extracted bitumen also indicated that there were acceptable differences between first and second cycle. Hence, it is proven that R2AP is suitable to be used as an alternative material to minimise the usage of fresh bitumen and aggregates. Based on regression model of aged bitumen properties, it can be concluded that RAP was suitable to be recycled up to second time

Development of software for rigid pavement thickness design

Rigid pavement is frequently misunderstood form of construction. Many people assume that rigid pavement is costly and not effective. However, it has been proven that it is good in term of the strength and durability to cater high traffic load compare to flexible pavement. However, in order to have good rigid pavement, the design procedures of the pavement should be properly applied. The vital issue in pavement design is thickness. There are two main approaches of design the rigid pavement thickness which are Portland Cement Association (PCA) method and American Association of States Highway and Transportation Officials (AASHTO) method. However, both methods are difficult to conduct manually and may produce inaccurate result. The difficulties can be expressed in term of time consuming and tedious calculation. Hence, it is very important to computerize the methods in order to make it more accurate and quicker. Although there are available software in the market but the software may not be user-friendly enough. It also does not allow the user to compare between methods. Generally, both methods have their own concept but there are still several same parameters considered. Therefore, the significance comparison between both methods can be done to select most economical pavement thickness design. Microsoft Visual Basic 6.0 was the tools used to develop the new software. Software named as AnP Pave was successfully developed. Moreover, based on the verification result there are only small difference between the software and manual calculation. However, an improvement needs to be applied to make the software capable to design pavement reinforcement and produce printable design report