Study on Performance Optimization of Composite Natural Asphalt Modified Gussasphalt Mix

In order to systematically study and develop a type of gussasphalt (GA) mix with superior performance, namely GA-10; the effect of Qingchuan Rock Asphalt (QRA) and Trinidad Lake asphalt (TLA) on the GA-10 mix was assessed based on the study of composite natural asphalt modified gussasphalt (CNAMGA) binder. Various analytical tests were used to evaluate the engineering properties, thermal stability and microstructure of CNAMGA mix. The results indicate that the stability of QRA modified binder and TLA modified binder in the normal temperature range and the high temperature range have been improved, and the temperature susceptibility is reduced. The optimal asphalt–aggregate ratio of the GA mix is determined to be 9.7%, which has good high-temperature stability, low-temperature crack resistance and construction workability. The QRA mix has better high-temperature stability than the TLA mix, whereas the low-temperature cracking resistance of the TLA mix is better than that of the QRA mix. The two kinds of GA-10 mix have similar construction workability. The fact that the abundant fine aggregates wrapped in binder fill the coarse aggregates surface contributes to the better adhesion of the GA asphalt concrete. The distribution of aggregate and binder is relatively uniform with fewer pores, and the overall proportion of the binder is greater than that of aggregate.

Multiple Stress Creep Recovery (MSCR) Test for Determination of Waste Engine Oil Modified Asphalt Binder as Pavement Material

Engineers have been using modified binders to improve the quality of flexible pavements. The use of waste material is one of the solutions taken in this direction. It is for this ground that the studies emphasis on the evaluation of waste engine oil as a modifier for asphalt binder as a pavement material. In the study uses four samples extracted from 80/100 penetration grade bitumen. From four sample first sample was checked for weather requirements of asphalt binder meet or not and the three were modified with different content of engine oil (3,6 and 9%). The behaviors of both unmodified and modified binder were checked for rheological properties. Dynamic shear rheometer (DSR) was used to determine high temperature performance grade (PG) and multiple stress creep recovery tests to determine rutting resistance properties of the binder. PG analysis indicates that both aged and un-aged 3% and 6% modified binder have similar higher PG grade with the unmodified one and 9% modified to have lower PG vale. Jnr3.2 value of modified asphalt binder is lower than unmodified binder indicating that modification had improved the rutting resistance and design traffic load (ESALS). The study shows that it is possible to use waste engine oil-modified binder as a pavement material.

Effect of Aggregate Gradation and Filler Content on the Rutting Resistance of Modified Colored Hot Mix Asphalt

Rutting is considered as the most generated distress in Iraqi roads as a result of the high temperature and excessive traffic load. So, it is essential to utilize polymer modified binder to increase the performance of pavements. The objective of this paper is to assess the effect of aggregate gradation and filler content on the rutting formation of Colored Hot Mix Asphalt CHMA. The HMA was colored by using iron oxide as filler to produce red HMA. Two blends were used: fine and coarse with two different types of filler iron oxide for CHMA and limestone for conventional HMA with two filler content 6% and 10%. Neat (AC 40-50) and modified asphalt (AC 40-50 + 4%SBS) were used. Tests are held on adding 4% Styrene Butadiene Styrene )SBS( by the weight of neat asphalt (AC 40-50) to raise the performance grade by two grades from PG (64-16) to PG (76-16) [1] and [2]. The wheel tracking test is used to assess the rut depth of the CHMA. The test results showed that the using iron oxide with neat asphalt increase the rut depth resistance by 200 and 400 failure load cycles than mixtures using limestone (cycles that mix reach 25 mm rut depth) for fine and coarse mix respectively. Also, the effect of gradation shows that the fine mixture fails at 4000 cycles while the coarse mixture fails at 1800 cycles for 6% limestone mixtures. Increasing the iron oxide content from 6% to 10% leads to increase the failure load cycles by 2200 and 1200 cycles for fine and coarse mixture respectively using modified asphalt. The fine mixture with 10% iron oxide using modified asphalt gives the best performance with 7000 cycles than the coarse mixture with 10% filler content and modified asphalt with 4000 cycles. irrespective the filler and type of binder, the dense mixtures using iron oxide as filler exhibit better resistance to rutting formation than coarse mixtures.

Laboratory Characterization of Asphalt Binders Modified with Styrene Butadiene Rubber (SBR)

The study describes the laboratory assessment (physical and rheological properties) of the binders (PG 64-22 and PG 76-22) modified with Styrene Butadiene Rubber (SBR), and a comprehensive comparison between these two modified binder types. PG 64-22 and PG 76-22 were used as base binders. Both of the base binders were blended with SBR at four different percentages of content (0%, 4%, 6%, and 8% by the weight of the binder). The base and modified binders were artificially short-term and long-term aged using a rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were conducted on the SBR modified binder using rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). In depth rutting performance was investigated using Multiple Stress Creep Recovery (MSCR). The results of this study indicated that (1) the addition of SBR into both binders increased the viscosity and polymer modified asphalt (PMA) binders observed to have more significant effect on its viscosity property; (2) the higher the SBR content, the better the rutting resistance of the binder and it is observed that the effect is prominent on the control binder; (3) MSCR test results showed that the SBR modified binders improved the binder percentage recovery and found to have a more significant effect on the PG 76-22 binder compared to PG 64-22; and (4) both the control PG 64-22 and PMA PG 76-22 binders resulted in similar trends on the cracking properties and were found to have insignificant effects due to the addition of an SBR modifier.

Mathematical modeling of improving the characteristics of bitumen for asphalt concrete by modifying

A significant increase in traffic intensity and increased axle loads of vehicles on the roads led to the fact that asphalt concrete is not able to provide the required durability of road surfaces. The durability of asphalt concrete pavements is directly related to the quality of the materials used, primarily bitumen. Bitumen is most susceptible to changes under the influence of traffic loads and weather conditions. At the same time, bitumen largely determines the condition of the road surface. The behavior of bitumen can be changed by modifying it with additives. The novelty of bitumen modification lies in the fact that the addition of polymer to bitumen makes it possible to obtain a road surface that is resistant to cracking at low temperatures and to provide fatigue strength at high temperatures. Rutting resistance is also achieved. An important role in the choice of the modifier is played by economic issues related to the rise in the cost of coating, as well as the need to use additional equipment, the stability of the modified binder during storage and transportation, etc. Carbon nanotubes (CNTs) were used as a modifier for asphalt concrete mixtures. During the experiment, a significant improvement in the main indicators of asphalt concrete mixtures was revealed, as well as the maximum permissible deviations for the amount of binder in the asphalt concrete mixture and for the main indicators were observed. Moreover, the most important thing that has been achieved is a significant increase in rutting resistance by rolling a loaded wheel.

Development of Plywood Binder by Partial Replacement of Phenol-Formaldehyde Resins with Birch Outer Bark Components

The apparent shift in climate has resulted in the pursuit of environmentally friendly bio-based products to reduce the carbon footprint. In the scientific literature, there are many attempts to make phenol-formaldehyde resins (PFR) more sustainable by using bio-based phenolics in the synthesis instead of petroleum-based phenol. However, it is also important to reduce the content of formaldehyde in the binder, the vapours of which are toxic and even carcinogenic to the human body. One of the technologically simplest solutions could be the incorporation of another bio-based wood composite binder into the completed industrial PFR. In turn, birch outer bark suberinic acids are an effective, ecological, thermosetting binder to produce mechanically durable and moisture-resistant wood composites. The aim of the study was to adapt the components of birch outer bark (suberinic acids and betulin-based extractives) for their incorporation into industrial PFR and to find the optimal degree of resins replacement in practical experiments. At the same time, to keep a similar level of the bending strength and moisture resistance (shear strength) of the plywood bonded with the modified binder compared to pure industrial PFR. As a result, it was found that it was possible to replace up to 30 wt% (dry basis) of the industrial PFR with birch outer bark components to obtain birch plywood without significant loss of the bending strength and moisture resistance. In this way, it would be possible to significantly reduce the carbon footprint of the synthetic PFR binder in the birch plywood industry by using birch processing residues.

Influence of Additives on the Fatigue Life and Stiffness of Asphalt Concrete

Implementation of additives to the asphalt binder can enhance the overall physical properties of the modified asphalt concrete. In the present assessment, an attempt has been made to use 2 % of silica fumes and 4 % of fly ash class F for modification of asphalt binder in wet process. Asphalt concrete wearing course mixtures have been prepared and compacted by roller in the laboratory. The beam specimens of 400 mm length and 50 mm height and 63 mm width were extracted from the slab samples. The specimens were subjected to the four-point repeated flexural bending beam test. The flexural stiffness was calculated under three constant micro strain levels of (250, 400, and 750). The fatigue life was monitored in terms the number of load repetitions to reach the required reduction in stiffness. It was concluded that the flexural stiffness increases by (11, and 15) %, (17.7, and 63.6) %, (57.2, and 65) % when 2% of silica fumes or 4 % of fly ash are implemented and the specimen’s practices 750, 400, and 250 microstrain levels respectively. However, the fatigue life of asphalt concrete beam specimens increases by (40, and 72.8) %, (115, and 220.6) %, (46, and 94.6) % when 2% of silica fumes or 4 % of fly ash are implemented and the specimen’s practices 750, 400, and 250 microstrain levels respectively. It is recommended to use modified binder with fly ash and silica fumes in asphalt concrete to enhance the fatigue life and stiffness.

The Use of SBS-Modified Binder to Eliminate the Aggregate Gradation Deviation Effects in Asphalt Mixtures

Asphalt Hot Mix (HMA) is mainly applied in highway construction in Iraq because of its economic advantage and easy maintenance. Various factors impact the performance of HMA in the field. It is one of the significant impacts on aggregate gradation. The Universal Specification for Roads and Bridges in Iraq (SCRB) limits the different types of asphalt layers and allows for designed tolerance aggregate gradation. It is quite hard for contractors in the present asphalt industries to achieve the required job mix because of sieves' control problems. This study focuses on the effects on the required specification performance of aggregate deviations by using original and modified asphalt binder with AC(40-50) and 4% SBS, respectively. A mid gradation of the base asphalt mixture was selected as a reference mix, and more than 24 deviated mixtures were then prepared. Typical Marshall routine studies on prepared compounds were performed to assess the properties of the mixture. Bailey's theory (CA, Fac ratios) was also employed for understanding the impact of these deviations on the arrangement of particles and blending performance. Results show that the mixture performance is not affected greatly by minor aggregate deviations. However, a significant deviation in coarse aggregates leads to a decrease in Marshall properties. Results showed that a good tool for understanding mixing performance is the Bailey performance assessment method. This paper aims to study the effects of using 4% Styrene Butadiene Styrene (SBS) and eliminating the effect of aggregate gradation deviations on the mixture performance.