Laboratory investigation of indirect tensile strength using roofing polyester waste fibers in hot mix asphalt

The vast quantity of waste materials (such as roofing polyester waste fibers) accumulating throughout the world is creating costly disposal problem. The use of these materials was proved to be economical, environmentally sound and effective in increasing the performance properties of the asphalt mixture in recent years. The primary objective of this research was to determine whether homogeneously dispersed roofing waste polyester fibers improve the indirect tensile strength (ITS) and moisture susceptibility properties of asphalt concrete mixtures containing various lengths and percentages of the fiber in various aggregate sources. The experimental design included the use of three aggregate sources, two lengths (0.635 cm (1/4 in.) and 1.270 cm (1/2 in.)) of this fiber, and two fiber contents (0.35% and 0.50% by weight of total mixture). The results of the experiments found that, in general, the addition of the polyester fiber was beneficial in improving the wet tensile strength and tensile strength ratio (TSR) of the modified mixture, increasing the toughness value in both dry and wet conditions, and increasing the void content, the asphalt content, the unit weight, and the Marshall stability.     

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.     

Effect of polyester resin additive on the properties of asphalt binders and mixtures

The properties of AC-5 control asphalt binder, mixture containing the same asphalt were compared with the properties of AC-10 asphalt binder modified by 0.75%, 1%, 2%, and 3% of polyester resin (PR), mixture containing pure AC-10 and AC-10 modified by 0.75% of PR, respectively.Initial research was done to determine the physical properties of unmodified and PR modified asphalt binders. The AC-10 asphalt binder modified by 0.75% of PR had good results compared to AC-5 control asphalt binder and all other modified binders, and hence this modified binder as well as unmodified binders were used to prepare Marshall samples for Marshall stability and flow, indirect tensile stiffness modulus (ITSM), indirect tensile strength (ITS) and creep stiffness tests.The results of investigation indicate that AC-10 + 0.75% PR binder has better physical properties than AC-5 control asphalt binder and, at the same time, PR improves mechanical properties of asphalt mixture.     

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.     

Determination of the optimum conditions for tire rubber in asphalt concrete

The Taguchi method was used to determine optimum conditions for tire rubber in asphalt concrete with Marshall Test. The tire rubber in asphalt concrete was explored under different experimental parameters including tire rubber gradation (sieve #10–40), mixing temperature (155–175 °C), aggregate gradation (grad. 1–3), tire rubber ratio (0–10% by weight of asphalt), binder ratio (4–7% by weight of asphalt), compaction temperature (110–135 °C), and mixing time (5–30 min). The optimum conditions were obtained for tire rubber gradation (sieve #40), mixing temperature (155 °C), aggregate gradation (grad. 1), tire rubber ratio (10%), binder ratio (5.5%), compaction temperature (135 °C), mixing time (15 min).     

Flexural response of hybrid carbon fiber thin cement composites

It is evident that the carbon-fiber-reinforced cementitious composites are being used in the structural and construction works owing to the synergetic action from two components viz. fiber and mortar matrix. Incorporation of a very nominal percentage of carbon fibers into a mortar mixture produces a strong and durable composite that leads the product of smart material properties. Flexural behavior of cement-based matrices carrying carbon fibers reinforcement of different percentage and size is studied in this paper. Influence of fiber content and length of the fiber is quantified using load–deflection curves. Specimens containing fiber of 0.0, 0.5, 1.0 and 1.5% with 3 mm (0.12 in.), 6 mm (0.36 in.), and their combination are prepared and tested. It is demonstrated that combination of 3 mm (0.12 in.) and 6 mm (0.36 in.) fibers enhances the bearing capacity to crack- and ultimate-stresses as well as the Young’s modulus of the fiber reinforced cement composites. The paper emphasizes the desired performances after the initiation of cracks and discusses the pre- and post-cracking load–deflection characteristics of the composites.     

Correlations among mechanical properties of steel fiber reinforced concrete

In this paper, applicability of previously published empirical relations among compressive strength, splitting tensile strength and flexural strength of normal concrete, polypropylene fiber reinforced concrete (PFRC) and glass fiber reinforced concrete (GFRC) to steel fiber reinforced concrete (SFRC) was evaluated; moreover, correlations among these mechanical properties of SFRC were analyzed. For the investigation, a large number of experimental data were collected from published literature, where water/binder ratio (w/b), steel fiber aspect ratio and volume fraction were reported in the general range of 0.25–0.5, 55–80 and 0.5–2.0%, respectively, and specimens were cylinders with size of Φ 150 × 300 mm and prisms with size of 150 × 150 × 500 mm. Results of evaluation on these published empirical relations indicate the inapplicability to SFRC, also confirm the necessity of determination on correlations among mechanical properties of SFRC. Through the regression analysis on the experimental data collected, power relations with coefficients of determination of 0.94 and 0.90 are obtained for SFRC between compressive strength and splitting tensile strength, and between splitting tensile strength and flexural strength, respectively.     

国产环氧沥青混合料在混凝土桥面中的应用研究

测试了国产环氧沥青混合料的水稳定性能、高温稳定性能、低温抗裂性能以及抗疲劳性能指标。在混凝土桥面铺装时,对国产多组分环氧沥青混合料高温、低温稳定性和水稳定性指标的检验,应在环氧沥青基本固化后进行,固化温度及固化时间采用120℃,12h（或125℃,4h）。混合料的各项技术指标控制为：车辙试验动稳定度DS≥25000次／mm（60℃）,或DS≥15000次／mm（70℃）;浸水马歇尔残留稳定度≥85％;冻融劈裂残留强度比TSR≥85％;-10℃低温弯曲应变εB≥3．0×10^-3。     

A laboratory study on stone matrix asphalt using ground tire rubber

This research investigated the feasibility using asphalt rubber (AR), produced by blending ground tire rubber (GTR) with an asphalt, as a binder for stone matrix asphalt (SMA). Two different sizes of GTR produced in Taiwan were used. The potential performance of AR–SMA mixtures was also evaluated. The results of this study showed that it was not feasible to produce a suitable SMA mixture using an asphalt rubber made by blending an AC-20 with 30% coarse GTR with a maximum size of 0.85 mm. However, SMA mixtures meeting typical volumetric requirements for SMA could be produced using an asphalt rubber containing 20% of a fine GTR with a maximum size of 0.6 mm. No fiber was needed to prevent drain-down when this asphalt rubber was used. The AR–SMA mixtures were not significantly different from the conventional SMA mixtures in terms of moisture susceptibility from the results of AASHTO T283 tests. The results of the wheel tracking tests at 60 °C show that rutting resistance of AR–SMA mixtures was better than that of the conventional SMA mixtures.     

Rutting evaluation of hydrated lime and SBS modified asphalt mixtures for laboratory and field compacted samples

The purpose of this study is to evaluate permanent deformation for hydrated lime and SBS modified asphalt mixtures. Control (C), 2% hydrated lime (2L), 5% SBS polymer mixtures and 2%hydrated lime–5%SBS (2L5SBS) mixtures were prepared. The Laboratoire Central des Ponts et Chaussées (LCPC) wheel tracker, also known as French Rutting Tester were realized with two different stages. Same LCPC slabs were produced. Original LCPC compactors and also field cylinder were used separately. LCPC rutting values were determined with left and right wheel loadings. Also averages were obtained with calculation. Repeated creep tests were used for these mixtures and permanent deformations were plotted for two different moisture conditioning that water immersion and freeze and thaw cycles. Diameter samples (100 mm and 150 mm) were studied in repeated creep tests. In the result that LCPC tracking values were compared with repeated creep tests in terms of sample diameters. LCPC wheel-tracking test results show that 2L5SBS mixtures reveal utmost performance according to the other mixtures types. Polymer modification increased rutting resistance of lime modified ones. Both original LCPC compactor and field cylinder compaction showed resemble results. 150 mm samples showed highest correlation (higher than R² = 0.80) between LCPC test and repeated creep test for different compaction types and different moisture conditionings.     

Effects of using asphaltite as filler on mechanical properties of hot mix asphalt

This study focuses on determining the engineering characteristics of hot mix asphalt using mineral filler with asphaltite. Since asphaltite which consists of high amount of sulfur leads to air pollution when used as a heating material and also being hydrocarbon sourced, it seems better to use asphaltite in the hot mix asphalts. The hot mix asphalts in this study were prepared by using 25%, 50%, 75%, and 100% mixing ratios based on the mineral filler ratio to analyze the possibility of using asphaltite. The results reveal that using asphaltite as a whole filler significantly increased the retained Marshall stability by 27% and increased the stiffness modulus by 91% at 15 °C. As for the tensile strength test, it was determined that the control mixtures lost 35% of its tensile strength ratio after one freeze–thaw cycle, however the mixtures containing completely asphaltite as filler lost only 13%. A remarkable increase was found at fatigue test. The cycle number leading to failure of the mixtures containing 25%, 50%, 75% and 100% asphaltite by weight of filler were 2.9, 3.6, 5.4 and 7.9 times greater than those of the control mixtures respectively at 300 kPa stress level. Using asphaltite as filler exhibited high performance by improving especially the resistance to moisture damage and fatigue life.     

Rehabilitating destructed reinforced concrete T connections by steel straps

The aim of this paper is to present results of testing a full scale reinforced concrete T connection by static loading. The connection represents a beam–column connection. The beam and column had a square cross section with a 300 mm dimension. The height of the column was 2.9 m and the clear beam length was 1.4 m. The connection was initially tested to failure. Galvanised steel straps were used to rehabilitate the connection. Epoxy resin was used to fix the steel straps to the concrete surface. The connection was tested after the rehabilitation. Results of testing the rehabilitated connection show that the yield and ultimate loads were 65 kN and 95 kN, respectively, compared with the original test results of 75 kN and 84 kN, respectively. Based on results of the tests, it can be concluded that the rehabilitating method used in this study was effective in increasing the ultimate strength of the T connection.     

Mechanical properties of natural fibers reinforced sustainable masonry

This research evaluates the physical and mechanical properties of Portland cement masonry blocks reinforced with lechuguilla natural fibers, that were lightened with 2-l bottles of polyethylene terephthalate.A concrete mix was designed for a target compressive strength of 16 MPa at 28 days, and slump of 70 mm. Masonry concrete blocks with dimensions of 730 × 340 × 130 mm were produced for two different fiber lengths (25 and 50 mm) and with fiber contents of 0.25%, 0.50%, 0.75% and 1.0%.Based on the obtained results, it was found that as the aspect ratio decreases the compressive strength increases and that the use of natural fiber (Vf = 0.5–0.75%) improves masonry post-cracking features, showing a ductile behavior and generating a uniform cracking pattern in the longitudinal sides of the blocks.     

Improvement of residual compressive strength and spalling resistance of high-strength RC columns subjected to fire

This paper investigates the spalling properties of high-strength concrete in order to improve the residual compressive strength and spalling resistance in specimens subjected to 3 h of unloading fire conditions. This study consists of three series of experiments with eighteen different specimens varying in fiber type and content, finishing material and simultaneous fiber content and lateral confinement. They were fabricated to a 300 × 300 × 600 mm mock-up size. Results of the fire test showed that the control concrete was explosive, while the specimens that contained more than 0.1 vol% of polypropylene (PP) and polyvinylalcohol (PVA) fibers were prevented from spalling. One specimen, finished by a fire endurance spray, exhibited even more severe spalling than the control concrete. The specimen containing 0.1 vol% of PP fiber and using a confining metal fabric at the same time, showed the most effective spalling resistance; in particular, the residual compressive strength ratio was even higher than that of the control concrete before the fire test. It was demonstrated that adding fibers in concrete prevented the spalling occurrence and confining metal fabric around the main bars of concrete specimens can secure the strength of structures during the conditions of elevated temperature.     

Performance of deteriorated corrugated steel culverts rehabilitated with sprayed-on cementitious liners subjected to surface loads

A variety of alternatives to rehabilitate culverts have been developed over the past decades given their advantages over conventional open-cut culvert replacement. However, the performance of many of these systems has not yet been examined through laboratory testing. The objective of the present paper is to examine the performance of deteriorated steel culverts rehabilitated with spray-on liners when subjected to surface loads. Two 1200 mm diameter corrugated steel pipelines with similar levels of deterioration in the invert-haunch area were buried to a depth of 1200 mm and tested under service load employing a load frame simulating a single axle of a Canadian design truck. The pipelines were then rehabilitated with spray on-cementitious liners (each with a different target thickness). Once rehabilitated, the pipelines were examined again under the service load employing the single axle load frame at 1200 mm of soil cover, and then tested employing a tandem axle load frame at 2100 and 1200 mm of soil cover. During all tests, changes in diameter, curvature and liner strains were monitored. The data obtained indicates that the flexible pipelines responded like semi-rigid structures after rehabilitation. It was also observed that the difference in liner thickness of 30% did influence the response of the pipelines, and that extreme fiber tensions during service loading were 7% and 13% of the tensile strength of the liner materials for the 76 mm and 51 mm liner thicknesses that were specified.     

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.     

Investigation of mixing ratio and restraint condition effects on alkali–silica gel pressure in mortar by using a uniaxial alkali–silica gel pressure measuring device (ASGPM-D)

A pressure of alkali silica gel which is the product of alkali–silica reaction causes pattern crack development and ultimately failure in cement based materials. This paper examines the measurement of alkali–silica gel pressure in cylindrical mortar specimen by a new test device (alkali–silica gel pressure measuring device, ASGPM-D) and investigates also the effects of the test medium on test results. Specimens of various sizes and geometries were tested to develop standard specimen size for ASGPM test method. The most suitable specimen with diameter of 35 mm and 250 mm in length was selected by optimizing the experimental results. Furthermore, the highest alkali–silica pressure value was recorded on a specimen which has 0.45 w/c and 74–150 μm grain size in an 80 °C 1 N NaOH solution. Also, swelling pressures of four reactive aggregates (opal, chert, basalt and chalcedony) were determined under two distinct restraint stages (1.5 kN and 3 kN).     

Preliminary experimental investigation of the fatigue bond behavior of CFRP confined RC beams

This paper presents the results of the first phase of a study on the effect of the confinement provided by transverse carbon fiber reinforced polymer (CFRP) sheets on the fatigue bond strength of steel reinforcing bars in concrete beams. Reinforced concrete bond-beams 150 × 250 × 2000 mm were tested. The variables examined were the area of the CFRP sheets (none or one U-wrap CFRP sheet), the reinforcing bar diameter (20 or 25 mm) and the load range applied to the specimens. The results showed that increasing the bar diameter increased the fatigue bond strength for the unwrapped beams. The CFRP sheets increased the bond strength of the bond-beams with 20 mm bars. However, for the beams with 25 mm steel bars the failure mode changed from a bond splitting failure for the unwrapped beams to a diagonal shear failure for the CFRP wrapped beams, and there was little increase in fatigue strength. Finally, the bond failure mechanism for repeated loading is described.     

Strength and toughness improvement of cement binders using expandable thermoplastic microspheres

The effect of Expandable Thermoplastic Microspheres (ETM) loading on the fracture resistance and indirect tensile strength of cement binders is studied. Portland white cement (PWC) was used as the matrix in the current study. Loadings of 0.1%, 0.35%, 0.5%, 0.75% and 1%, by weight, of ETM were added to the dry cement. Semi-circular bend specimens, 152 mm in diameter and 27 mm thickness with different notch depths were fabricated to study the crack resistance of the compounds, J_c. For the indirect tensile tests, circular specimens, 50 mm in diameter and 12.7 mm thickness were used. All specimens were left to cure under water for 7 days. A 2.5-fold increase in the indirect tensile strength was achieved at an ETM loading of 0.35% by weight. A nearly threefold increase in the fracture resistance occurred at the 0.1% ETM loading. The thermal resistivity of the compounds increased by 30% for a 1% Expancel loading. Fracture surface examination revealed that the ETM facilitated the permeation of water by creating pores. Thus, an optimum strength and fracture resistance was achieved between 0.1% and 0.4%.     

Nanostructured zonolite–cementitious surface compounds for thermal insulation

This paper investigates the effect of zonolite loadings on the thermal resistivity and indirect tensile strength of nanostructured cementitious compounds. The main objective of this research is to develop a structural lightweight compound that can be used on building skins and cores for pre fabricated structural insulated panels (SIPs). The application of this compound is intended to improve the thermal resistivity of the building envelope with suitable mechanical performances. The zonolite dosage was added to the cement-nano clay blend at different dosages up to 40% by weight. The nano clay reinforcement used is montmorillonite clay (Hydrated sodium calcium aluminum silicate). The mixes were prepared using water of consistence. The wet compounds were molded in PVC cylindrical molds, having 50 mm inside diameter and 27 mm height, and left for 24 h, then demolded and cured in humid air (20 ± 1 °C&100% RH) for 28 days. The samples were then dried at 105 ± 5 °C for 24 h before testing using a forced convection oven. The thermal resistivity and indirect tensile strength of the different compounds were evaluated. Results demonstrate that the thermal resistivity at 40% zonolite loading enhanced by about 2.9 folds compared to the control samples. An increase of more than 30% in the indirect tensile strength was also achieved when a 0.5% by weight of polycarboxylate superplasticizer was used.