Study on properties of recycled tire rubber modified asphalt mixtures using dry process

To minimize waste tires pollution and improve properties of asphalt mixtures, properties of recycled tire rubber modified asphalt mixtures using dry process are studied in laboratory. Tests of three types asphalt mixtures containing different rubber content (1%, 2% and 3% by weight of total mix) and a control mixture without rubber were conducted. Based on results of rutting tests (60 °C), indirect tensile tests (−10 °C) and variance analysis, the addition of recycled tire rubber in asphalt mixtures using dry process could improve engineering properties of asphalt mixtures, and the rubber content has a significant effect on the performance of resistance to permanent deformation at high temperature and cracking at low temperature.     

Laboratory evaluation of WMA mixture for use in airport pavement rehabilitation

The concept of warm mix asphalt (WMA) gives a promise for rehabilitating airport pavement to realize quick turnover to traffic after construction, however, laboratory and field data in terms of the performance-related properties are significantly lacking for using WMA in airfield in Japan. To fill this gap, three WMA mixtures (different gradations) were systematically investigated compared with the conventional airfield used hot mix asphalt (HMA) through a series of laboratory tests in terms of wheel tracking test, submerged wheel tracking test, raveling test, static bending and fatigue bending test. These WMA mixtures were made at two production temperatures (30 and 50 °С lower than the normal, respectively) by incorporating a commercially sold additive. Results showed that overall, the WMA mixture with a coarse gradation produced at the temperature 30 °С lower than the normal exhibited a comparable performance compared with the control HMA mixture, and it was further recommended for use in airport pavement rehabilitation.     

The effects of using lime and styrene–butadiene–styrene on moisture sensitivity resistance of hot mix asphalt

This study focuses on determining the effects of styrene–butadiene–styrene (SBS) and using mineral filler with lime on various properties of hot mix asphalt especially moisture damage resistance. The asphalt cement was modified with 2%, 4% and 6% SBS. The lime treated mixtures containing 2% lime by weight of the total aggregate as filler. The physical and mechanical properties of polymer modified binder and binder–aggregate mixes were evaluated through their fundamental engineering properties such as dynamic shear rheometer (DSR), rotational viscosimeter (RV) for binders, Marshall stability, stiffness modulus, indirect tensile strength and moisture susceptibility for mixes. The retained Marshall stability (RMS) and tensile strength ratio (TSR) values were calculated to determine the resistance of mixtures to moisture damage. To investigate clearly the effective of SBS and lime seven freeze–thaw cycle was applied to specimens at TSR test. The results indicate that application of SBS modified binders and lime as mineral filler one by one improves the stability, stiffness and strength characteristic of hot mix asphalt. According to retained Marshall stability it is concluded that addition of only 2% lime have approximately same effect with addition of 6% SBS. Using lime together within the SBS modified mixes exhibit high accordance and exacerbates the improvement of properties. Specimens containing both 2% lime and 6% SBS, have the highest stiffness modulus which is 2.3 times higher than those of the control mixture and showed the least reduction in tensile strength ratio while maintaining 0.70 tensile strength ratio after seven freeze–thaw cycle.     

Laboratory evaluation of the effects of short-term oven aging on asphalt binders in asphalt mixtures using HP-GPC

Both the RTFO (rolling-thin film oven) aging of asphalt binders and the STOA (short-term oven aging) of asphalt mixtures are designed to simulate aging during the construction of hot mix asphalt (HMA) pavements. Many studies have been conducted evaluating the aging effects on asphalt binders since their properties can be easily measured using many conventional tests, such as rotational viscometer, DSR (dynamic shear rheometer), and BBR (bending beam rheometer). However, studies on asphalt mixture aging have been limited to mechanical properties such as strength and fatigue characteristics because considerable effort is required to identify the aging of the asphalt binder in a mixture. This study evaluated the effects of short-term oven aging on asphalt mixtures using the GPC (gel-permeation chromatography) procedure. Nine asphalt mixtures, using three different binder sources, were prepared and five short-term aging methods were used to evaluate these mixes. For comparison, the RTFO aging was also conducted for nine asphalt binders. The aging of a binder within asphalt mixtures, including polymer-modified mixtures, could be identified under various short-term aging conditions. Statistical analysis of the GPC test results indicated that two commonly used short-term aging methods in the laboratory, a 154 °C oven aging for 2 h and a 135 °C oven aging for 4 h, are not significantly different, based on the increase in the large molecular size (LMS) ratios. The RTFO aging method was found to have less effect on binder aging than the short-term oven aging methods of asphalt mixtures.     

Use of basalt in asphalt concrete mixes

One of the main reasons behind the appearance of early distresses in Jordan roads and the low surface skid resistance is the use of marginal quality limestone aggregate. Large quantities of good quality basalt are available in the Northeastern parts of Jordan. In this research, the possibility of improving the properties of local asphalt concrete mixes by replacing different portions of the normally used limestone aggregate by basalt was investigated. The replacement included total replacement of the limestone by basalt, replacing the coarse aggregate, and replacing the fine aggregate. Results showed that the optimal mix was the mix that had basalt coarse aggregate and limestone fine aggregate. In order to overcome the stripping potential of the optimal mix, 20% of the filler portion of the aggregate, material smaller than 0.075 mm, was replaced by lime. The optimal mix showed superiority, over the tested mixes, in all the evaluated properties, which were Marshall Stability, indirect tensile strength, stripping resistance, resilient modulus, dynamic creep, fatigue, and rutting.     

Prediction of bituminous mixture fatigue life based on accumulated strain

This research was aimed to predict the number of cycles that cause fracture of hot-mix asphalt (HMA) based on the number of cycles at which the slope of accumulated strain switched from decreasing to increasing mode. In addition, the effect of aggregate gradation and temperature on fatigue behaviors of HMA were evaluated.HMA specimens were prepared at optimum asphalt content using the Marshall mix design procedure. The specimens were prepared using crushed limestone aggregate, 60/70 penetration asphalt, and three different aggregate gradations with maximum nominal aggregate size of 12.5, 19.0, and 25.0 mm. Five magnitudes of load (1.5, 2.0, 2.5, 3.0, and 3.5 kN) were evaluated for their effect on fatigue behavior.Constant stress fatigue tests were performed using the Universal Testing Machine (UTM) at 25 °C. Other temperatures (10, 45, and 60 °C) were evaluated at a load of 3.5 kN.The tests results indicated that the slope of accumulated strain continued to decrease until the number of loading cycles approached 44% of the number of cycles that caused fracture of the HMA. Also, the initial stiffness of asphalt mixtures was found to increase as the magnitude of the load applied increased and as the aggregate gradation maximum nominal size decreased.     

CDW recycled aggregate renderings: Part II – Analysis of the effect of materials finer than 75 μm under accelerated aging performance

Quality control of the performance of renderings made up of construction and demolition waste (CDW) recycled aggregates needs to be improved as CDW recycling can prove to be an alternative to waste disposal in developing countries. This experimental work focuses the effectiveness of a mix design method to control and analyze the recycled aggregate composition influence on the performance of mortars and renderings. Leveling time in the placement of renderings was also studied. The mix design method of mortars takes into account two parameters: the “aggregates and plasticizing materials to cement ratio” and “the total materials finer than 75 μm” in the dry mortar. In Part I of this study [Construction and Building Materials, submitted to publishing] the basic properties of mortars of several mixes were analyzed for a constant cement content around 155 ± 10 kg/m³. The performance of renderings is the scope of Part II of this paper. The initial bond strength and visible drying cracks under laboratory conditions were first analyzed for renderings applied on masonry panels with two times of leveling during placement. After five months, accelerated aging of renderings was carried out. Ten wetting–drying cycles upon thermal shock, from 80 °C to laboratory room temperature, were applied to the masonry panels, and cracks were assessed for each cycle. Bond tensile strength was not affected by the thermal shock, but additional cracks were seen on the renderings. The mix design parameters of the mortars and their hardened state properties were related to the cracking of the renderings. The results show that the parameters “total materials finer than 75 μm” and “aggregate to cement ratio” can be used for the mix design of mortars with recycled CDW aggregates. The increase in tensile strength and the reduction in the content of total fines smaller than 75 μm have proved efficient parameters to control cracking of renderings under thermal shock. Leveling time during rendering placement was a secondary parameter for cracking behavior.     

Fatigue behavior of rubberized asphalt concrete mixtures containing warm asphalt additives

The long-term performance of pavement is associated with various factors such as pavement structure, materials, traffic loading, and environmental conditions. Improving the understanding of the fatigue behavior of the specific rubberized warm mix asphalt (WMA) is helpful in recycling the scrap tires and saving energy. This study explores the utilization of the conventional fatigue analysis approach in investigating the fatigue life of rubberized asphalt concrete mixtures containing the WMA additive. The fatigue beams were made with one rubber type (?40 mesh ambient crumb rubber), two aggregate sources, two WMA additives (Asphamin^® and Sasobit^®), and tested at 20 °C. A total of eight mixtures were performed and 29 fatigue beams were tested in this study. The test results indicated that the addition of crumb rubber and WMA additive not only reduced the mixing and compaction temperatures of rubberized asphalt mixtures offset by crumb rubber but also effectively extended the long-term performance of pavement when compared with conventional asphalt pavement. In addition, the exponential function forms are efficient in achieving the correlations between the dissipated energy and load cycle as well as mixture stiffness and load cycle.     

The properties of concrete made with fine dune sand

This paper presents the results of a study that investigated the properties of concrete made with dune sand. Different control concrete mixtures using ordinary Portland cement (OPC) with a minimum design compressive strength of 40 N/mm² were prepared. The amount of fine aggregates constituted about 36% by weight of all the aggregates. The workability ranged from low of 16 mm to a high of 122 mm. For each control mix, other mixtures were prepared in which the fine aggregates were replaced by different percentages of dune sand ranging from 10% to 100%. The effect of dune sand on the workability, compressive strength, tensile strength, modulus of elasticity and initial surface absorption test (ISAT) was studied. Experimental results show an improvement in the workability of concrete when fine aggregates were partially replaced by dune sand. An increase in slump was measured with increase in dune sand content. However, at high dune sand contents (above 50%); the slump starts to decrease with an increase in dune sand. Generally, the strength values decrease with increase in dune sand replacement. The strength loss was not found considerable as the maximum reduction was less than 25% when fine aggregates were fully replaced by dune sand. The absorption characteristics of concrete made with OPC as measured by the (ISAT) generally increased with higher dune sand contents.     

Experimental study of recycled asphalt mixtures with high percentages of reclaimed asphalt pavement (RAP)

This paper presents an experimental study to characterize the mechanical behaviour of bituminous mixtures containing high rates of reclaimed asphalt pavement (RAP). Two semi-dense mixtures of 12 and 20 mm maximum aggregate size and containing 40% and 60% RAP, respectively (S-12 and S-20, in accordance with Spanish specifications), which were used for rehabilitation of a highway section, were evaluated. First, the effect of RAP variability on the recycled mixtures was analyzed. Their mechanical properties were then studied by determining the stiffness modulus and indirect tensile strength and cracking and fatigue behaviour. Results show that high rates of recycled material can generally be incorporated into bituminous mixes by proper characterization and handling of RAP stockpiles.     

Effect of mineral admixtures and curing periods on shrinkage and cracking age under restrained condition

This paper presents the test results on cracking behavior at medium age of uniaxially restrained specimens containing different types of mineral admixture, namely fly ash and limestone powder. In this study, the uniaxially restrained shrinkage, free shrinkage and strength tests were conducted to study the potential of cracking of concrete under restrained shrinkage condition. The influences of water to binder ratio, mineral admixtures and curing period of concrete on cracking behavior were investigated in this study. The investigation showed that cracking age and cracking strain of restrained specimens vary with mix proportion, mineral admixture and curing period. The potential of shrinkage cracking is not influenced only by cracking strain and amount of shrinkage but also on shrinkage rate and tensile creep. Mixture with lower water to binder ratio (w/b = 0.35) shows shorter cracking age than the mixture with higher water to binder ratio (w/b = 0.55). Fly ash and limestone powder significantly increase cracking age of concrete. The cracking age increases with the increase of the replacement ratio of fly ash. The higher shrinkage rate, when exposed to drying, of mixture with longer curing period leads to shorter cracking age.     

Mechanistic-empirical mixture design for hot mix asphalt pavement recycling

Mixture design of six asphalt mixtures containing Reclaimed Asphalt Pavement (RAP) were evaluated by using a mechanistic-empirical approach. The testing methodology involved determination of the key mechanical properties and durability of wearing course and base course materials containing RAP at three different levels of addition (i.e. 10%, 30% and 50%), manufactured to a supplied specification, and the rheological properties of binder used in, and recovered from, these materials. In order to optimise both rutting and fatigue resistance, the recycled mixtures were manufactured by using 80/100 pen virgin bitumen (which is one grade softer than the 60/70 pen bitumen conventionally used for the respective parent asphalt materials), with or without added rejuvenating oil. This paper demonstrates that the asphalt mixtures containing RAP performed at least similar to, or better than, that of conventional asphalt materials.     

Relation of mechanical properties of recycled aged CRM mixtures with binder molecular size distribution

This paper presents an experimental analysis of the relationship between molecular sizes of mixed rubberized binders (aged rubberized binders + virgin rubberized binders) and the engineering properties of recycled aged rubberized mixtures. Gel permeation chromatography (GPC) was utilized to characterize the molecular size change of rubberized binders depending on three aging levels and four long-term aged (LTA) binder percentages. Rubberized mixtures were artificially long-term aged in the laboratory, and the aged rubberized mixtures were recycled at 0%, 15%, 25%, and 35% (by weight of total mixture) using typical recycling guildelines. Samples of laboratory-prepared recycled aged rubberized mixtures were tested for indirect tensile strength (ITS) in dry and wet states, rutting resistance, resilient modulus, and ITS after long-term aging in the laboratory. In general, the results indicated that the compositional changes of mixed rubberized binders have good correlations with the engineering properties of recycled aged rubberized mixtures, except for the resilient modulus.     

Effects of rejuvenator on performance-based properties of rejuvenated asphalt binder and mixtures

Firstly, the performance-based properties of rejuvenated aged asphalt binders, i.e., the blends of aged binders containing a rejuvenator at various percentages, were investigated under high, intermediate and low temperatures. The tests were conducted on the blends at three stages as follows: no aging, rolling thin film oven (RTFO) residuals and as well RTFO + pressure aging vessel (PAV) residuals through dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. Optimum concentrations of the rejuvenator needed for the blends to reach a target PG grade were obtained from the blending charts of the rejuvenated aged binders in terms of performance properties. The rejuvenator is a soft binder containing a low asphaltene content of 2 wt%. Secondly, selected performance-based properties were conducted on hot mix asphalt (HMA) using the rejuvenated aged binder and a virgin HMA as a control mixture. Results showed that the rejuvenator affected significantly the performance-based properties of both the rejuvenated aged binders and the mixtures containing the rejuvenated aged binders. It was possible to get optimum concentrations of the rejuvenator using the blending charts so that the rejuvenated binders reach a target PG grade. The mean value of the concentrations was proved to be more reliable through the performance-based properties of the mixtures if it is used for a design value for recycling. The properties of the asphalt paving mixtures with the rejuvenated binders were even improved or in the same level as the properties of the virgin mixtures.     

Mechanical characterization of a bituminous mix under quasi-static and high-strain rate loading

There are various methods to determine the compressive and tensile strength of asphalt concrete under static loading conditions and most studies on asphalt strength and fracture have been conducted under such loading conditions. However, pavement materials also have to withstand a wide variety of loading and temperature conditions which may vary from quasi-static to high-strain rate impact, and pavement breakdown may occur due to fracture and/or fatigue failure. In the present study, a bituminous mix with 30% RAP has been characterized under quasi-static (10^?3–10^?4 strain/s) and high-strain rate (200–700 strain/s) regimes. The experimental studies have been performed to better understand the compressive, tensile and fracture response of bituminous mixes. Split Hopkinson pressure bar (SHPB) and its modifications were used for high-strain rate characterization of this bituminous mixture. It was observed that the mechanical properties of the hot mix asphalt (HMA) changed significantly under high-strain rate testing. Also, the failure mechanisms observed under the high-strain rate loading were found to be considerably different from those obtained in static testing, where failure of binder was a predominant mechanism. It was observed that high-strain rate loading caused trans-aggregate failures in the specimens; in addition to failure of the binder.     

Permeability of high-performance concrete subjected to elevated temperature (600 °C)

Permeability is one of the most important parameters to quantify the durability of high-performance concrete. Permeability is closely related with the spalling phenomenon in concrete at elevated temperature. This parameter is commonly measured on non-thermally damaged specimens. This paper presents the results of an experimental investigation carried out to study the effect of elevated temperature on the permeability of high-performance concrete. For this purpose, three types of concrete mixtures were prepared: (i) control high-performance concrete; (ii) high-performance concrete incorporating polypropylene fibres; and (iii) high-performance concrete made with lightweight aggregates. A heating–cooling cycle was applied on 160 × 320 mm, 110 × 220 mm, and 150 × 300 mm cylindrical specimens. The maximum test temperature was kept as either 200 or 600 °C. After the thermal treatment, 65 mm thick slices were cut from each cylinder and dried prior to being subjected to permeability test. Results of thermal gradients in the concrete specimens during the heating–cooling cycles, compressive strength, and splitting tensile strength of concrete mixtures are also presented here. A relationship between the thermal damage indicators and permeability is presented.     

Laboratory investigation of the properties of asphalt concrete mixtures modified with TOP–SBS

Benefits of adding Tall oil pitch (TOP), Styrene-butadiene-styrene (SBS) and TOP + SBS to AC-10 in variant quantities to AC-10 were investigated. Initial research was done to determine the physical properties of asphalt cement and modifiers.Seven asphalt binder formulations were prepared with 8% of TOP; 8 + 3, 8 + 6 and 8 + 9% of TOP + SBS, respectively; 3, 6 and 9% of SBS by total weight of binder. After that, Marshall samples were prepared by using the modified and unmodified asphalt binders.Additionally, compression strength test were done in different conditions to determine water, heat and frost resistance of all Marshall samples.Fatigue life and plastic deformation tests for Marshall samples (for different asphalt mixtures: modified and unmodified) were carried out using PC controlled repeated load indirect tensile test equipment developed at Suleyman Demirel University by Tigdemir (SDU-Asphalt Tester).The results of investigation indicate that asphalt mixture modified by 8% TOP + 6% SBS gives the best results in the tests that were carried out in this study, so that, this modification increases physical and mechanical properties of asphalt binder.     

Use of mineral admixtures for enhanced resistance against sulfate attack

The effect of mineral admixtures such as nano silica, micro silica, fly ash and ground granulated blast furnace slag on the expansion of mortar bars caused by internal and external sulfate attack was investigated. According to data recorded through 12 months, all of the mineral additives, particularly slag, have significantly reduced the expansions caused by sulfate attack. It was shown that, the effectiveness of nano silica was also very significant. When used with sulfate contaminated sands, high sulfate resistant mixtures were produced with 4–6% nano silica replacement ratios. In the case of external sulfate attack, however, only 2% nano silica is most likely enough for keeping the expansions below 0.03% after 12 months.     

Performance of self-compacting concrete containing different mineral admixtures

This paper presents experimental study on the properties of self-compacting concrete (SCC). Portland cement (PC) was replaced with fly ash (FA), granulated blast furnace slag (GBFS), limestone powder (LP), basalt powder (BP) and marble powder (MP) in various proportioning rates. The influence of mineral admixtures on the workability, compressive strength, ultrasonic pulse velocity, density and sulphate resistance of SCC was investigated. Sulphate resistance tests involved immersion in 10% magnesium sulphate and 10% sodium sulphate solutions for a period of 400 days. The degree of sulphate attack was evaluated using visual examination and reduction in compressive strength. The test results showed that among the mineral admixtures used, FA and GBFS significantly increased the workability and compressive strength of SCC mixtures. Replacing 25% of PC with FA resulted in a strength of more than 105 MPa at 400 days. Moreover, the presence of mineral admixtures had a beneficial effect on the strength loss due to sodium and magnesium sulphate attack. On the other hand, the best resistance to sodium and magnesium sulphate attacks was obtained from a combination of 40% GBFS with 60% PC.     

Strengths and flexural strain of CRC specimens at low temperature

Crumb rubber concrete (CRC) is made by adding rubber crumbs into conventional concrete. This study undertakes an experimental study on the cubic compressive strength, axial compressive strength, flexural strength and splitting tensile strength of CRC specimens at both ambient temperature 20 °C and low temperature ?25 °C. The flexural stress–strain responses were also recorded. The averaged size of rubber crumbs used in the study is about 1.5 mm. Four levels of rubber contents are investigated, which are 0%, 5%, 10% and 15% by volume, respectively. The mix design aimed at 40 MPa of compressive strength and 100 mm of slump for all the CRC specimens. The results show that CRC increases its magnitude in strengths when temperature decreases, which is similar to the case of conventional concrete, but still exhibits ductility in low temperature. The conclusion from this study is that CRC may be more beneficial in its application in low temperature environments than in ambient temperature environments.