Marshall Stability Test Research Articles

Investigating the Possibility of Using Roof Shingles Waste and Fibers in Stone Mastic Asphalt Pavements

In order to study the mechanical properties of stone mastic asphalt mixtures (SMA) which are used in roads pavement , the current study added various proportion of shingles (bituminous tiles with mineral aggregate coating) roofing (RAS), that are commonly used in sloping roofing, to SMA mixture containing 0.3% of added fibers. The percentage of 1, 2, 4, and 6% shingle particle wastes were respectively added to the SMA mixture samples on which Marshall Stability, moisture damage, dynamic creep and fatigue tests were performed. The comparison of the results revealed an agreement between the results from samples containing up to 4% of waste and normal samples. In addition, the mentioned samples were capable of providing the restrictions determined in the regulations. Thus, based on the results, it is suggested to use shingle wastes according to the suggested percentage. However, increasing the number of wastes will lead to a downward trend due to the disruption of uniform texture in the mixture.

Improvement in bituminous surface course using waste plastic in acid-rain susceptible area’s

Acid rain as an important environmental issue has negative impact on bitumen performance, thereby shortening the service life of bituminous pavements. Rapid industrial and economic developments causes negative changes in the environment, including acid rain. Acid rain consisting of sulphuric acid and nitric acid has adverse effects on bituminous pavements. Both these acids react with the bitumen and adversely effect’s the properties of the bitumen leading to degradation of pavements at early stage of life. Early degradation of such pavements can be reduced to some extent by using waste plastic in bituminous surface course. Besides acid rain puts an adverse effect on the properties of bitumen, it also percolates deep down in the various down layers of pavements and reduces the serviceability of our pavements & its foundation. Waste plastic such as PET water bottles cannot only prevents the early degradation of pavements but also can prevents entry of acid rain into deep down layers of pavement as it absorbs acid rain water which makes it hydroscopic as because of it acid rain water does not percolate deep down into below pavement layers. In this paper, interaction between constituents of acid rain and bitumen is being investigated by analyzing the effect of sulphuric acid and nitric acid on control mix (mix without plastic content) & 6% WPET mix (mix with 6% waste plastic PET content) by using Marshal stability test. Also, it’s evaluated how improvement in bituminous surface course can be done by using waste plastic on acid rain area’s so that our pavements show good safety & serviceability.

Evaluation of Fatigue Potential for Crumb Rubber Modified Bitumen in Stone Mastic Asphalt Mixes

SMA is a gap graded mix composed of a high concentration of coarse aggregate that is held together in a thick asphalt film by a matrix of mineral filler and stabilizers. Since natural aggregates have become expensive, hence Reclaimed Asphalt Pavement (RAP) can be reused in pavement construction to reduce the environmental hazardous due to disposal problems. Since the RAP contains used aggregates, it is highly prone to fatigue, thermal and reflective cracking effect. Rheological and chemical properties of aged bitumen in RAP can be enhanced by use of untreated waste oils such as waste engine oil as rejuvenators. This research presents a study on fatigue performance of SMA mix with Reclaimed Asphalt Pavement (RAP) materials with and without rejuvenators and results were compared with conventional SMA mix. The materials used were first characterized by common laboratory tests. Then the three SMA mixes are tested using several laboratory test procedures: Marshall Stability, indirect tensile strength, moisture susceptibility, and indirect tension fatigue test. The optimum proportions of the of the mixes with highest stability are selected from the Marshall stability test. The indirect tensile strength test results show that the SMA mix replaced with RAP without rejuvenators showed higher tensile strength ratio and resistance to moisture damage when compared to conventional mix and optimum RAP replacement mix with rejuvenators. The fatigue test was conducted for the three optimum mixes at different temperature and stresses. The fatigue test results showed that at lower temperature and stresses, the RAP replaced SMA without rejuvenator offered better fatigue resistance than those with rejuvenator and conventional SMA mix. At higher temperatures, the RAP replaced SMA mix with rejuvenator offered similar fatigue lifecycle as conventional mix. However, at high stresses, conventional SMA mix offered better fatigue lifecycle. Increase in failure stresses resulted in decrease of number of fatigue cycles and increased in initial tensile strain of the mix. Thus, with the use of RAP substantial decrease in cost can be achieved without compromising the fatigue characteristic of the SMA mix.

POTENTIAL USE OF 'ENSET' FIBER ASH AS PARTIAL REPLACEMENT OF CONVENTIONAL FILLER MATERIAL IN HOT MIX ASPHALT

The main problems in road construction and maintance work in Ethiopia availability of a large amount of appropriate quality materials in road construction sites, aggregates in different size fractions are not readily obtainable, necessitating their procurement from long distances, thereby causing an exorbitant increase in construction costs. One of the main problems in constructing the asphalt paving mixture is obtaining a sufficient amount of filler material from crushing fine rock material and low percent using ordinary Portland cement (OPC), hydrated lime (HL) and marble dust. To overcome this problem, it is important to come across alternative filler material to address this gap using naturally available material. Currently, renewed attention has been given to the use of ‘waste’ materials instead of conventional aggregates in pavement construction. This research study investigates the potential use of ‘Enset’ fiber ash as a partial replacement of conventional filler material in hot mix asphalt supported by experimental laboratory investigation. In order to achieve this study, purposive sampling techniques were adopted to select the sample size and location. The study evaluated the potential of ‘Enset’ fiber ash as filler for the design of dense-graded hot mix asphalt by referencing traditional filler control mix procedures based on standard specifications, and a crush rock filler was utilized as a conventional filler material as a control for comparison. The Marshal Stability and Rutting Test (RT) was conducted to determine the HMA specimen's performance. Several HMA specimens were prepared using aggregate blend according to ASTM D 1559 with four different percentages of ‘Enset’ fiber ash (EFA) of 15%, 25%, 35% and 45% filler replacement the total filler weight used in the control mix. Specimens were prepared and tests performed according to EN 12697-22 procedure-B for rutting test. All HMA properties were taken at 4% air void and determined their optimum bitumen content (OBC). Almost the same result with the control mix was observed in the study at 15% and 25% of the ‘Enset’ fiber ash (EFA) replacement. However, higher Marshall Stability, a lower void filled with asphalt, better flow, a good void in mineral were observed at 25% ‘Enset’ fiber ash (EFA) replacement. At this rate, the rutting performance is less than that of the control mix but is within the specifications of 2.78mm and 2.9 mm of rutting depth less than 6mm that satisfies the EN 13108 requirement. As a result, Enset fiber ash filler can replace traditional filler material up to 25% of the total filler weight used in this study. It was recommended to use ‘Enset' fiber ash (EFA) as a filler material as a partial replacement in a bituminous paving mixture up to the specificed percentage by weight replacement.

Correction to: Laboratory Study on the use of Reclaimed Asphalt Pavement and Copper Slag in Warm Mix Asphalt Pavements using Waste Engine Oil as a Rejuvenator

This study aims to evaluate the effect of waste engine oil (WEO) on warm asphalt mixes incorporated with waste materials. Copper slag (CS) and reclaimed asphalt pavement (RAP), both considered waste materials were used in asphalt mixes. Seven types of mixes were prepared with different proportions of copper slag (0–15%) and RAP (0–30%) at 5%, 7.5%, and 10% WEO dosages. Marshall stability test, indirect tensile test, resilient modulus, and flow number test was carried to check the performance of these mixes. Also, a cracking test was used for evaluating the fracture energy of asphalt mixtures. It was found that asphalt mixes incorporated with CS (15%) and RAP (30%) performed similar to control mixes up to 7.5% rejuvenator dosages. The incorporation of copper slag (5%) improved the Marshall stability and tensile strength due to more angularity (multi-faced) and frictional angle (53°) of CS, resulting in excellent stability and load capacity. The resilient modulus in Mix 6 (30%RAP-5% CS) was observed to be maximum (3310.3 MPa). The use of waste engine oil softened the aged RAP bitumen, which leads to a decrease in stability, resilient modulus, rutting resistance, and increase in fracture energy. The RAP incorporated mixes showed lesser fracture energy due to the presence of stiff RAP bitumen. However, with the addition of WEO, the fracture energy increased which indicates that the cracking resistance of these mixes improved due softening action of WEO. Marshall quotient, which represents stiffness, decreased with an increase in CS content at all rejuvenator dosages.

Influence of the Performance of Reclaimed Asphalt Pavement (RAP) Material on Bituminous Mix

The utilization of reclaimed asphalt pavement (RAP) material to prepare a durable bituminous concrete (BC) mixture, used for flexible pavement surface courses is a challenging task in this investigation. RAP material is one of the latest substitutes for virgin aggregate and virgin binder of the bituminous mix. Using RAP material in flexible pavements can improve the engineering properties of bituminous mix and is also beneficial for economic and environmental. To execute such study, virgin aggregate (VA) has been replaced by 0, 10, 20, 30, 40, 50, 60, 75, and 100% of RAP material, respectively, in the cited mix with 2% Ordinary Portland Cement (OPC) as mineral filler. To characterize the RAP material, several laboratory tests such as specific gravity test, water absorption test, shape test, impact test, Los-Angeles abrasion test and, advanced tests as X-RF, X-RD, and GPC test, etc. have been employed. However, to assess the durability and strength of RAP enriched BC mix, Marshall stability test, modified Marshall immersion test, indirect tensile strength (ITS) test and, Cantabro abrasion test has been conducted. Marshall stability test, modified Marshall immersion test, ITS test, and Cantabro abrasion test is explored that 50% RAP modified bituminous mix has the capability to best perform than the other studied mix in terms of durability and strength. Because the molecular bonding of carbonyl compound between aged and virgin binder is suspected in the mix improvement factor that leads to the longer span life of the RAP modified flexible pavement.

A laboratory study of the effect of fiberglass additive on the behavioural properties of RAP asphalt mixtures

The increase in the amount of reclaimed asphalt pavement (RAP) and environmental concerns for bitumen production have contributed to the use of RAP in road construction and maintenance. The use of higher than 15% of RAP adversely affects the physical and rheological properties of the asphalt binder and the mechanical properties of mixtures. Therefore, the use of bitumen and asphalt mixture improver were necessary to reduce the negative effects generated with the use of RAP. This paper aims to study the effect of fiberglass (FG) (0.5%, 1.0%, 1.5%, and 2%) on the mechanical properties of asphalt concrete containing 25%, 50% RAP and 9% waste engine oil. The performance of RAP asphalt mixtures incorporated with FG was evaluated using the Marshall stability test, moisture susceptibility test, and immersion wheel rutting test. The results indicated that the use of FG and RAP materials to rejuvenated asphalt mixtures resulted in an increase in the values of Marshall stability and rutting resistance. Moreover, the study revealed that increasing the content of RAP material and FG results in increased resistance of asphalt to moisture damage. This paper concluded that using 0.15% of FG and 50% RAP materials gives the best results.

Performance of Fly Ash as Replacement for Non-Renewable Constituent in Asphaltic Concrete for Road Development

The non-renewable constituent used in asphalt concrete consumed large amount of materials resulting an increase in the price of asphalt mixture and consequently the cost of road development. On the other hand, huge industrial waste being generated daily from human activities causes environmental degradations. Thus, the study evaluates the performance of fly ash (FA) in asphalt concrete development targeted for road application. The aggregate, bitumen, and fly ash were characterized before being used. The stone dust in asphalt mixture was replaced with FA in predetermined proportions of 2, 4, 6, and 8% to produce a cylindrical specimen of asphalt mixture concrete. Marshal stability test, flow test, X-ray diffraction (XRD), X-ray Fluorescence (XRF) and Scanning Electron Microscope (SEM) was conducted on the composite samples. From the results, stability values of 7.39, 7.70, 7.90 and 8.22 KN was obtained at 2, 4, 6 and 8% replacements, respectively. Hence, the optimum value of 8.22 KN obtained from 8% partial replacement with FA is adequate for heavy traffic while other partial replacement from 2- 6% with stability within the range of 7.39-7.90 KN is suitable for medium traffic in accordance with the criteria for the marshal mix design method provided by Asphalt institute (1997). Corresponding values of 3.7, 3.5, 3.3 and 3.0 mm was obtained for the flow. The flow, air void, void in mineral aggregates and void filled with bitumen results all satisfied Nigeria general specification for road and bridges (1997). Therefore, fly ash can be used as partial replacement in asphaltic concrete to enhance the performance of the mix with a reduced cost for pavement construction.

Effects of maltene on the attributes of reclaimed asphalt pavement: Performance optimisation

The asphalt mixtures using elevated percentages of the reclaimed asphalt pavement (RAP) are of significant interest due to its ability to address environmental issues and reduce cost of asphalt. However, utilising elevated RAP content is associated with several disadvantages. Hence, this study explores the potential application of maltene as a rejuvenator to improve the output of asphalt mixtures incorporating RAP binder. The contents of maltene were optimised according to several parameters, namely penetration, softening point, ductility, and viscosity tests. Thereafter, the specimens containing an optimum maltene percentage were assessed using maltene-to-asphaltene ratio, storage stability, Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), Fourier Transform Infrared (FTIR) spectroscopy and Thermogravimetric Analysis (TGA) measurements. Subsequently, the mechanical characteristics of asphalt mixtures were analysed using Marshall Stability, moisture damage, resilient modulus (MR), and Cantabro loss tests. The results demonstrated that 8% and 16% of maltene restored the physical properties of 30% and 50% of RAP binder, respectively. In addition, the workability was improved due to the reduction of viscosity, while maltene-rejuvenator managed to compensate the light components of RAP binder that were lost during the lifespan. As a result, the high- and low-temperature performance of RAP binder were restored approximately to that of virgin asphalt (VA). The oxygenated indices of RAP binder were effectively abated by blending with maltene. The TGA exhibited that the thermal stability of rejuvenated asphalts was close to VA. Accordingly, the mechanical characteristics of rejuvenated mixtures were improved compared to the VA mixture. Therefore, the maltene with a suitable dose is recommended to rejuvenate the RAP binder, and reuse it in the pavement construction.

Effects of Polyethylene Terephthalate and Crumb Rubber on Selected Properties of Asphaltic Concrete

This study investigated the combined effects of polyethylene terephthalate (PET) and crumb rubber (CR) as modifiers on some properties of asphaltic concrete. Asphaltic concrete materials were obtained from a construction site. CR of 9.5 mm size was obtained by sieving, while PET bottles were collected, sorted, washed, dried and shredded by mechanical means. The physical properties of these materials were determined following standard procedure. Bitumen was modified by wet process with PET and characterised. Asphaltic concrete samples with partial replacement of coarse aggregate in the mix with CR were prepared. Samples without modifiers were also prepared as control. These were subjected to Marshall Stability test. The percentage variation for stability and flow between the control and the modified mixes, were 27 % and 0.29 % respectively, while those of the volumetric properties of bulk density, voids filled bitumen (VFB), air voids (VA) and voids in mineral aggregate (VMA) were 0 %, - 0.13 %, 0 % and 0 % respectively. It was concluded that, there was no difference between the flow and volumetric properties of the control and modified mixes.
 Keywords: Polyethylene terephthalate, crumb rubber, asphaltic concrete, stability, flow, volumetric parameters

Performance Evaluation of Stone Matrix Asphalt (SMA) Mixes Using Different Types of Fibers as Additives. (Dept. c)

Stone matrix asphalt (SMA) is a gap graded hot mix asphalt (HMA) which gains its main strength from stone on stone contact. It provides a rut-resistant, durable surfacing material which is suitable for heavily trafficked roads. Typical SMA consists of 70-80 % coarse aggregate, 8-12 % mineral fillers, and 6-7 % binder. Due to this high binder content, stabilizing additives are needed to prevent draindown that might occur during transport and placement. According to SMA standards, cellulose and mineral fibers are the most suitable stabilizing additives to be used in SMA, but due to lack of those specific types of fibers in some countries, another types of fibers are being tested to replace them in the mix. The main objective of this study is to investigate the characteristics of SMA mixtures using fiberglass as a stabilizing additive. Another SMA mix of the best result was prepared using polypropylene fiber instead of fiberglass and tested for comparison purposes. Two different SMA gradations were tested, nominal maximum aggregate size (NMAS) 12.50 mm and NMAS 19.00 mm at four different fiber contents for each gradation 0.00 %, 0.30 %, 0.50 %, and 0.70 % by total weight of the mix. SMA samples were tested through series of performance tests selected to be Marshall stability test, moisture susceptibility test, indirect tensile strength test (ITS), and draindown test.

Study on the decay behavior of the stability of asphalt mixture under different dry-wet cycle conditions

Asphalt mixtures will inevitably be affected by rainwater and the effect the of dry-wet cycle during the process of use. To explore the decay of the stability of asphalt mixtures under different dry-wet cycle conditions, a dry-wet cycle laboratory test was carried out based on standard Marshall specimens. The asphalt mixture specimens were subjected to dry-wet cycle treatment for specified cycle durations and numbers of cycles at three temperatures, and Marshall stability tests were then carried out. In this way, the decay of the stability of the asphalt mixture under different dry-wet cycle conditions was evaluated. The results show that the number of dry-wet cycles exhibited good linear relationships with the stability and the stability decay rate, respectively. As the temperature of the dry-wet cycle increased, the stability of the asphalt mixture was found to decrease; the higher the temperature, the greater the stability decay rate. A power function relationship was found between the dry-wet cycle duration and the stability decay rate of the asphalt mixture, and exhibited a decreasing trend. Under the premise of a fixed total dry-wet cycle duration, the dry-wet cycle conditions of a short duration and many cycles were found to have the greatest influence on the stability decay rate of the asphalt mixture. Moreover, a BP neural network prediction model was established by MATLAB software. By comparing the predicted and true values, the established BP neural network prediction model was found to well predict the stability of the asphalt mixture under different dry-wet cycle conditions.

Recycled Polyethylene Terephthalate as Reinforcement Additive of Asphalt Mixture for Pavement Application

This study explores the effect of incorporating recycled polyethylene terephthalate (PET) into asphalt pavement mixtures. The performance characteristics were observed to determine if the mechanical properties of the resulting mixture had significantly improved. The PET-asphalt mixtures were prepared using the dry method and were then evaluated based on the Marshall flow and stability tests, as well as its volumetric properties – such as air voids, voids filled with asphalt (VFA), voids in mineral aggregates (VMA), bulk specific gravity (BSG), and maximum specific gravity (MSG). Results show that the optimum PET content in the mixture is 15% by weight of asphalt binder at 5% binder composition of the overall asphalt pavement mixture. The stability was observed to increase by 14.2% compared with the conventional mix and each sample passed the standards set by the Asphalt Institute. Based on the results, it can be concluded that at certain amounts, the addition of PET improves the Marshall properties of the pavement.

Effect of CENEX polymer on the performance of bituminous concrete and dense bituminous macadam of pavement

This paper focuses on the effect of centrifuged latex (CENEX) polymer on the performance of bituminous concrete (BC) and dense bituminous macadam (DBM) of pavement. In this study, VG30 binder is modified with CENEX polymer at different percentages such as 0%, 2%, 4%, 6% and 8% by the weight of the binder. Using storage stability test it is found that optimum content of CENEX polymer is 6%. Mixes using CENEX modified binder require slightly lesser optimum binder content (OBC) than the plain mixes. Retained marshal stability (RMS) test, tensile strength ratio (TSR) test, resilient modulus ratio (RMR) test, boiling water test (BWT), four-point bending beam test (FPBT) and wheel tracking test (WTT) are conducted on these mixes. The results show that the incorporation of CENEX polymer improves the moisture damage resistance, fatigue life and rut resistance. Furthermore, life-cycle cost analysis reveals that CENEX modified mixes are more economical compared to plain mixes over long-run, even though the initial cost of modified and unmodified mixes are almost the same. As a whole, better performance is obtained by using CENEX modified mixes resulting in higher pavement service life.

Experimental study and simulation analysis on design of stone mastic asphalt along Marshall mix methods using low-density polyethylene for eco-friendly nature

The extended traffic volume and backing require sufficient and solid pavements, which controls the black-top difficulty. A huge amount of assessment deal with the Stone Mastic Asphalt (SMA) gives a difficult surface course. Various down to earth tries are made to adjust SMA mixes with built strands and polymers. Directly a day's plastic waste is the key issue for an eco neighbourly legitimate condition. In this assessment work, plastic waste like Low-Density Polyethylene (LDPE) fundamental food thing sacks are used as an additional substance to diminish the leakage at high temperatures during limit, transportation, circumstance, and compaction to improve the interfacial security among sums and spread. Like this, the mix plan of SMA is executed with Marshall mix structure procedures. Marshall Stability Test finishes this testing research. The all out level of the SMA mix and the folio content was 5.5%, 6%, 6.5% by weight of genuine and plastic waste used was 5%, 10%, 15% by weight of bitumen. This current paper's objective is analyzing Objectives, advancement material piece, economy achieving by using waste materials and inclinations over the mixes. For sure, even in this work, we applied simulation investigation, as you can see in this paper.

Preparation and mechanical properties of asphalt mixtures reinforced by modified bamboo fibers

Cracking resistance and durability are the main concerns in asphalt mixture for pavement. The addition of fibers is an effective way for reinforcing asphalt mixture. Bamboo fibers (BFs) show unique characteristics such as high specific strength and modulus, renewability and low cost. Thus, BFs mechanically extracted from green bamboos were used to improve the mechanical properties of asphalt mixture and thus increase the service life of asphalt pavement. For improving the poor interfacial adhesion resulted from the hydrophobicity of asphalt and the hydrophilicity of BFs, a melamine–formaldehyde (MF) copolymer was synthesized and used to modify the BFs. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectronic spectroscopy (XPS), and nuclear magnetic resonance (NMR) analyses were conducted to reveal the surface chemistry of BFs. The results proved that the MF copolymer was grafted onto the surface of BFs via the formation of covalent bonding between hydroxyl groups of BFs and amino group of melamine. The mechanical properties of the asphalt mixture were evaluated by Marshall stability, direct tensile, and indirect tensile tests. Results showed that the addition of modified BFs increased the stability and the tensile strength of the asphalt mixture. SEM images of the fractured surface of asphalt mixture indicated that strong adhesion was formed between the modified BFs and asphalt matrices.

Determining Optimum Carbon Nanotubes Content for Asphalt Mixture in Road Pavements

Although small amount of binder in asphalt concrete mixture may commonly range from 3.5 to 5.5% of total mixture as per many international specifications, it has a significant impact on the total cost of pavement construction. Therefore, this paper investigated the effects of five carbon nanotubes contents of 0.05%, 0.1%, 0.15%, 0.2%, 0.25% by asphalt weight as an additive material for binder on performance characteristics of asphalt mixtures. Performance properties of CNTs modified asphalt mixtures were investigated through the Marshall stability (MS) test, indirect tensile (IDT) test, static modulus (SM) test, wheel tracking (WT) test. The results indicated that asphalt mixtures with CNT modified binder can improve both the rutting performance, IDT strength and marshall stability of tested asphalt mixtures significantly at higher percentages of carbon nanotubes. However, the issue that should be considered is the construction cost of asphalt pavement. Based on the asphalt pavement structural analysis and construction cost, it can be concluded that an optimum CNT content of 0.1% by asphalt weight may be used as additive for asphalt binder in asphalt mixtures.

Assessment of the Engineering Properties of Modified Asphalt Using Aluminium Dross as a Filler

Aluminum dross waste creates environmental burden for manufacturers and hence the need for its re-use. This experimental research assessed the engineering properties of modified asphalt using aluminium dross as a filer material. The aluminium dross used was obtained from a steel manufacturing industry. Elemental composition of the oxides was done using XRF equipment. Sieve analysis of the aluminium dross and the coarse aggregate was also assessed. Additionally, ductility, penetration, ball and ring and Marshall stability test were used in achieving the aim of this research. The outcome of the research revealed that 10-20% addition of the aluminium dross improved the stability of the modified asphalt. Physical observation revealed that the utilization of the waste stiffened the modified asphalt. The result showed that the addition of aluminium dross reduced the VMA. This will also increase the asphalt mix flushing. Additionally, at higher percentage addition of the waste the stiffness of the asphalt mix increases especially at a higher temperature. The use of this material will help in the reduction of solid waste and reduce the cost of management while reducing the cost of pavement construction in track with the trash to treasure drive.

Performance evaluation of asphalt concrete mixture incorporating calcite powder as filler substitute for sustainable pavement construction

The increasing cost and paucity of conventional pavement construction materials has in recent times become very worrisome and a serious challenge in the road construction industry. This has spurred the search for a less expensive and environmentally friendly material, readily available and suitable for the purpose of constructing sustainable pavements both in the rural and urban areas of developing countries. In this research, the suitability of calcite powder in asphalt as filler in substituted proportions was investigated through tests on the modified samples for enhanced engineering properties. This was achieved by partially replacing conventional filler with calcite in proportion of “10%, 20%, 30%, 40% and 50%” respectively. After the production of the modified bituminous concrete at the various proportions, the samples produced were placed in a water bath for 30 minutes at a temperature of 60°C before conducting the Marshall stability test and flow. Marshall stability values of 37.7 kN, 37.9 kN, 34.0 kN, 35.0 kN, 28.9 kN and corresponding flow values of 12.0 mm, 11.3 mm, 10.5 mm, 9.60 mm, 10.3 mm, were obtained for the modification proportions respectively. The stability values were observed to be higher than the control mix and likewise satisfy the minimum requirement of 3.33 kN or 340 kg according to the Marshal mix design specification for wearing course surfacing. Similarly, the flow values obtained where found to be within the specified range of 8 – 17 mm at 0.25mm units. Percentage air voids (Vv) values of 3.7%, 5.2%, 4.7%, 3.0%, and 5.9% obtained where also found to satisfy the required range of 3-5% according to the specification. Voids filled with bitumen (VFB) values of 78.58%, 69.56%, 69.73%, 76.63%, and 58.93% derived where also within specified range 75 – 85 % of the specification. The X-Ray diffraction (XRD) micrograph showed the distinct presence of calcium and oxygen in the hot mix asphalt modified with calcite, while the scanning electron microscope (SEM) provided an in-depth perspective of the concrete grains in the hot mix matrix and the improved bonding of the aggregates, bitumen and calcite due the presence of calcium. The results have shown the possibility of calcite utilization in bituminous mixes, towards reducing cost of construction and best suitable for medium trafficked roads, parking lots and walkways.

Effects of Crumb Rubber at Different Sizes in Asphalt Mixtures on Mechanical Properties

High vehicles loads due to increasing the road users are one of the main issues affecting the asphalt pavement surface and its performance by resulting various problems such as fatigue cracking and other deformations due to road overloading caused by vehicles loads. The use of crumb rubber in asphalt pavements has attracted increasingly growing attention and become one of the factors that increase the strength of the pavement. Crumb rubber is used to improve asphalt binder properties and pavement performance since it contributes as an additive material in the structural applications and reducing the environmental problem. The main contribution and purpose of this research is to investigate the effectiveness of adding crumb rubber into the asphalt by using the wet method. There were two different amounts of crumb rubber content used in this study (2.5 % and 3.5 % of the overall asphalt mixture weight) and two different crumb rubber sizes (0.6 mm and 0.3 mm) that were examined in this study. In addition to this study, asphalt grade 60/70 penetration grade. The performance of the modified binder is comparatively evaluated with an unmodified binder to find the best modifier. The evaluation is done through conducting the comparison between results obtained from modified and unmodified asphalt samples using Marshall stability, flow and resilience modulus test. The results from this study shows crumb rubber is an efficient material to be used as an additive to asphalt binder since it contributes in better performance by increasing the strength and stiffness of pavement and can be used for future development.