materials Article
Influence of Water Solute Exposure on the Chemical Evolution and Rheological Properties of Asphalt Ling Pang, Xuemei Zhang, Shaopeng Wu, Yong Ye * and Yuanyuan Li State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China;
[email protected] (L.P.);
[email protected] (X.Z.);
[email protected] (S.W.);
[email protected] (Y.L.) * Correspondence:
[email protected] Received: 19 April 2018; Accepted: 28 May 2018; Published: 11 June 2018
Abstract: The properties of asphalt pavement are damaged under the effects of moisture. The pH value and salt concentration of water are the key factors that affect the chemical and rheological properties of asphalt during moisture damage. Four kinds of water solutions, including distilled water, an acidic solution, alkaline solution and saline solution were used to investigate the effects of aqueous solute compositions on the chemical and rheological properties of asphalt. Thin-layer chromatography with flame ionization detection (TLC-FID), Fourier transform infrared (FTIR) spectroscopy and dynamic shear rheometer (DSR) were applied to investigate the components, chemistry and rheology characteristics of asphalt specimens before and after water solute exposure. The experimental results show that moisture damage of asphalt is not only associated with an oxidation process between asphalt with oxygen, but it is also highly dependent on some compounds of asphalt dissolving and being removed in the water solutions. In detail, after immersion in water solute, the fraction of saturates, aromatics and resins in asphalt binders decreased, while asphaltenes increased; an increase in the carbonyl and sulphoxide indices, and a decrease in the butadiene index were also found from the FTIR analyzer test. The rheological properties of asphalt are sensitive to water solute immersing. The addition of aqueous solutes causes more serious moisture damage on asphalt binders, with the pH11 solution presenting as the most destructive during water solute exposure. Keywords: asphalt; water solute exposure; aqueous solute compositions; chemical evolutions; rheological properties
1. Introduction Asphalt pavement, for its excellent driving performance and low noise advantages, is widely applied in the world [1]. During the service phase of asphalt pavement, moisture from the natural environment can diffuse into the asphalt binder, which results in the attenuation of the pavement performance of the asphalt mixture [2,3]. Recent studies suggest that the interaction between water oxygen molecules and asphalt can cause oxidation and aging of asphalt and increase its stiffness and viscosity [4,5]. Also the water may dissolve part of the components of asphalt, which softens the asphalt, reduces the adhesion between the asphalt binder and aggregate, and reduces the cohesion capability inside the asphalt binder. As a result, the mechanical properties of asphalt concrete and the binder are degraded [6–9]. Moisture damage is considered one of the most important factors affecting asphalt mixture durability [10–13]. Water is closely related to the moisture damage of asphalt pavement during its service phase, and the different aqueous solute compositions of water, such as in areas of acid rain, seaboards, or saline and alkaline land, may cause different moisture damage effects on an asphalt binder [14,15]. In salty and humid environments, the strength of asphalt mixture deteriorates easily Materials 2018, 11, 983; doi:10.3390/ma11060983
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because of moisture damage from water infiltration and salt chemical corrosion [16,17]. Following immersion in acid rain solutions, the pavement performance of the asphalt mixtures decreased with the decrease in the solution pH value [18]. In an acid rain area, where rainfall with pH < 3 occurs [19], and in saline and alkaline land areas where the pH value of soil may be over pH10 [20], the pavement is subjected to around 10% sodium chloride corrosion damage under snow melting [21]. The reduction in the properties of the asphalt mixture has been related to component changes under the effect of aqueous solute in the water solution. An important consideration for understanding the asphalt moisture damage process in different water solutions is that the chemical composition and rheological properties of asphalt may not be the same as at the asphalt-water surface where environmental factors have the greatest impact. Thus, understanding the process of moisture damage in asphalt under environmental exposure, especially the role and effect of the aqueous solute component in this process, is very important to the research and prevention of moisture damage to asphalt pavement. However, there is little research on the effects of aqueous solute composition on the chemical and rheological properties of asphalt. Besides, due to the test conditions and material differences, the degree of influence of different aqueous solute composition factors on the chemical and rheological properties of asphalt is unclear. The main objective of this paper is to analyze the evolution of the chemical and rheological properties of asphalt at different pH values of water solution and saline solution conditions, hence, four kinds of water solution, including distilled water, acidic, alkaline and saline solution, were used to immerse the asphalt. The effects of water solute exposure on asphalt chemical composition, construction and rheology were investigated using four compositions which were analyzed using thin-layer chromatography with flame ionization detection (TLC-FID), Fourier transform infrared spectroscopy (FTIR) and dynamic shear rheometer (DSR). 2. Materials and Experimental Methods 2.1. Materials The 70# asphalt and SBS modified asphalt were obtained from Hubei Guochuang Hi-tech Material Co., Ltd., Wuhan, China. Their basic properties are exhibited in Table 1. The ductility test temperatures of 70# asphalt and SBS modified asphalt were 10 ◦ C and 5 ◦ C, respectively. Table 1. Basic properties of 70# asphalt and SBS modified asphalt. Properties ◦ C,
Penetration (25 10 g, 5 s) Softening point Ductility
Units
70# Asphalt
SBS Modified Asphalt
Test Specification
0.1 mm ◦C cm
68 47.2 63.2
56 74.0 68.0
ASTM D5-61 ASTM D36-26 ASTM D113
2.2. Preparation of Solutions In different regions, the aqueous solute composition of water solutions are different in nature. For example, the pH value of rainfall may be around 3 in acid rain areas, the pavement is subjected to around 10% sodium chloride corrosion damage under snow melting, or the pH value of the solution may be over pH10 in saline and alkaline land. So, pH3 acid solution, 10% NaCl salt solution and pH11 alkali solution were selected in this paper. The preparation methods of these are described below. Artificial acid solution was prepared to simulate the natural ingredients in acid rain, such as the SO4 2− and NO3 − anions. It was prepared with excellent pure sulfuric acid and nitric acid by the serial dilution method [22], the molar ratio of sulfuric acid and nitric acid was 9:1, the pH value was 3. Alkaline solution was prepared with sodium hydroxide, and the pH value was 11. The water solute immersing tests of asphalt binders were conducted at 25 ◦ C and normal pressure, the pH of the solution was measured with a precise pH test paper. Sodium chloride was diluted with distilled water, the concentration of which was 10%.
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solution was measured with a precise pH test paper. Sodium chloride was diluted with distilled water, the concentration of which was 10%. Materials 2018, 11, 983
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2.3. Water Solute Immersing Tests
First, a circular glass dish, with a diameter of 100 mm and height of 18 mm, was washed with 2.3. Water Solute Immersing Tests 6 g of each asphalt binder was poured onto the glass dish and put deionized (DI) water. The selected into First, an oven at a constant temperature of 120 of °C100 for mm 10 min formofa 18 smooth asphalt film;with the a circular glass dish, with a diameter and to height mm, was washed thickness of asphalt was about 60.76 that,binder the samples were taken outglass and cooled to deionized (DI) water.film The selected g ofmm. eachAfter asphalt was poured onto the dish and ◦ room temperature. put into an oven at a constant temperature of 120 C for 10 min to form a smooth asphalt film; Then, 40 of mL of the solutions were poured into the that, dish the andsamples immersed thetaken asphalt the glass the thickness asphalt film was about 0.76 mm. After were outfilms, and cooled to dish was capped. The temperature of the immersing water solute was 25 °C, the test times for 70# room temperature. asphalt were as 7 dayswere and 14 days,into and the 14 days days forthe theasphalt SBS modified asphalt. Then, 40designated mL of the solutions poured dish and 28 immersed films, the glass ◦ During water The solute immersion the solutions were replaced because the# dish wasthe capped. temperature of test, the immersing water solute was 25 every C, theweek test times for 70 carboxylic acid of asphalt be dissolved andand reduce theand pH 28 value thethe solution [23]. After the asphalt were designated ascan 7 days and 14 days, 14 days daysoffor SBS modified asphalt. water solute immersion test, in order to make sure the water was fully evaporated from the surface During the water solute immersion test, the solutions were replaced every week because the carboxylic of theofasphalt all the asphalt specimens were putof into oven at[23]. a constant temperature of acid asphaltsamples, can be dissolved and reduce the pH value thean solution After the water solute 150 °C for 30 min. Subsequently, the asphalt specimens were separated from the glass dish with a immersion test, in order to make sure the water was fully evaporated from the surface of the asphalt ◦ spatula. all the asphalt specimens were put into an oven at a constant temperature of 150 C for samples, 30 min. Subsequently, the asphalt specimens were separated from the glass dish with a spatula. 2.4. Characterization Methods 2.4. Characterization Methods 2.4.1. Experimental Program Plan 2.4.1. Experimental Program Plan The experimental program plan is shown in Figure 1. At the first, two kinds of asphalt (70# # asphalt The experimental program plan iswere shown in Figureto 1. be At the first, twoinkinds of asphalt (70solutions asphalt and SBS modified asphalt) prepared immersed different water and SBS modified asphalt) werealkaline prepared to be immersed in different solutions (distilled (distilled water, acid solution, solution and sodium chloridewater solution). Secondly, the water, TLCacid solution, solution andwere sodium solution). Secondly, the TLC-FID tests,solute FTIR FID tests, FTIRalkaline tests and DSR tests usedchloride to characterize the effect of immersion in water tests and DSR tests were used to characterize the effect of immersion in water solute on the chemical on the chemical evolution and rheological properties of asphalt. To increase the accuracy, two times evolution and rheological properties of asphalt. To increase of theasphalt accuracy, two times replicate tests were replicate tests were carried out. Lastly, the mechanism during moisture damage was carried out. Lastly, the mechanism of asphalt during moisture damage was summarized. summarized.
Asphalt
Immersing in different water solutions
Chemical structure and compositiin
Appearance
Morphology characterization
TLC-FID tests
Rheological properties
FTIR tests
DSR tests
Chemical Evolutions and Rheological Properties of Asphalt During Water Solute Exposure
Figure 1. Experimental plan. Figure 1. Experimental program program plan.
2.4.2. Four Compositions Analysis Asphalt consists of various molecular weights of hydrocarbons and its derivatives and based on the relative molecular size and polarity of asphalt, it can be divided into four components, namely
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saturates, aromatics, resins and asphaltenes [24,25]. In order to test the impact of aqueous solute composition on these four components of asphalt, TLC-FID (Iatron Laboratories Inc., Tokyo, Japan) was used to analyze the four components of asphalt before and after water solute exposure. Two percent (w/v) solutions of asphalt binders were prepared in dichloromethane, and 1 µL sample solution was spotted on chromarods. There was a three-stage process for the separation of asphalt fractions. The first stage was in n-heptane (70 mL) and expanded to 100 mm of the chromarods, the second stage in toluene/n-heptane (70 mL, 4/1 by volume) was developed to 50 mm of the chromarods, and the last development was in toluene/ethanol (70 mL, 11/9 by volume) and expanded to 25 mm of the chromarods. The solvent was dried in an oven at 80 ◦ C after each stage. Then, the chromarods were scanned in the TLC-FID analyzer. Four chromarods were tested for each sample, and finally the average values were used as the results. 2.4.3. Fourier Transform Infrared (FTIR) A Thermo Nicolet Nexus FTIR spectrophotometer (Thermo Fisher Scientific, Waltham, MA, USA) was used to test the chemical structure of asphalt binders before and after water solute exposure. The asphalt carbon disulfide solutions were prepared with a concentration of 5 wt % asphalt binders. All samples were obtained using a 0.1 mm path length KBr cell. Spectra were recorded using the following settings: number of scans 64; gain 1; apodization weak; and resolution 4. The change in chemical structure due to asphalt oxidation aging could be obtained by the calculation of functional and structural indices of some groups from the FTIR spectra. The oxidation aging of asphalt increases the area of carbonyl and the sulphoxide absorption peak, while greatly decreasing the area of butadiene double bonds absorption peak, the area of these absorption peaks are closely related with the degree of aging of asphalt, thus, carbonyl group C=O (centered around 1700 cm−1 ), sulphoxide group S=O (centered around 1030 cm−1 ) and chain segments of butadiene C=C (centered around 968 cm−1 ) could be used to characterize the degree of aging of the asphalt [26–28]. The carbonyl index (IC=O ), sulphoxide index (IS=O ) and butadiene index (ISBS ) can be calculated according to Equations (1)–(3). IC=O =
Area of the carbonyl band centered around 1700 cm−1 ∑ Area of the spectral bands between 2000 and 600 cm−1
(1)
IS=O =
Area of the sulphoxide band centered around 1030 cm−1 ∑ Area of the spectral bands between 2000 and 600 cm−1
(2)
ISBS =
Area of the butadine band centered around 968 cm−1 ∑ Area of the spectral bands between 2000 and 600 cm−1
(3)
2.4.4. Dynamic Shear Rheometer (DSR) Test The dynamic rheological properties of asphalt were investigated with a dynamic shear rheometer (MCR101, Anton Paar company, Graz, Austria) under a parallel plate configuration. A temperature sweep test from −10 ◦ C to 30 ◦ C with an increment of 2 ◦ C/min was performed under a strain-controlled mode, the constant frequency was 10 rad/s. The specifications followed AASHTO T 315. The strain sweep test was carried out at −10 ◦ C to determine whether 0.1% strain lies within the linear viscoelastic range of the aged binder in advance. The strain was maintained at 0.1% so that all testing would lie within the linear viscoelastic range. Moreover, the diameter of the plate was 8 mm, and the gap between the plates was 2 mm. 3. Results and Discussion 3.1. Water Solutions’ Effect on the Appearance of Asphalt Figure 2 displays the appearance of 70# asphalt after 7 days of the water solute immersion test. As can be seen, the surface exhibits obvious differences after immersion in different water solutions.
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3. Results and Discussion 3.1. Water Solutions’ Effect on the Appearance of Asphalt
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Figure 2 displays the appearance of 70# asphalt after 7 days of the water solute immersion test. As can be seen, the surface exhibits obvious differences after immersion in different water solutions. # Before Before water water solute solute immersion, immersion, the the surface surface of of 70 70# asphalt asphalt is is fairly fairly even, even, however, however, after after immersion immersion in in the four types of water solutions, the asphalt surface tends to be rougher and some micro the four types of water solutions, the asphalt surface tends to be rougher and some micro bumps bumps or or pits roughness increases pits can can be be observed. observed. In In detail, detail, the the roughness increases in in the the following following order, order, pH11 pH11 alkaline alkaline solution solution >> pH3 acidic solution > 10% NaCl saline solution > distilled water. The uneven surfaces pH3 acidic solution > 10% NaCl saline solution > distilled water. The uneven surfaces may may be be caused caused by by etching etching of of the the water water solutions, solutions, that that is, is, they they are are the the results results of of moisture moisture damage, damage, also, also, the the moisture moisture damage damage effect effect of of the thepH11 pH11alkaline alkalinesolution solutionimmersion immersionwas wasthe themost mostserious. serious. Figure 3 shows the water solutions after 7 days of the water Figure 3 shows the water solutions after 7 days of the water solute solute immersion immersion test. test. It It can can be be found found from from Figure Figure 33 that that some some light-yellow light-yellow oil oil patches patches exist exist on on the the surfaces surfaces of of the the four four water water solutions solutions (marked (marked with with aa white white dashed dashed line). line). The The oil oil patches patches may may derive derive from from insoluble insoluble compounds compounds of of asphalt asphalt under the action of hydrostatic pressure, which are pushed off the asphalt surface and float under the action of hydrostatic pressure, which are pushed off the asphalt surface and float onon toptop of of the water solutions. The changes in the features of the water solutions are consistent with the the water solutions. The changes in the features of the water solutions are consistent with the surface surface roughness of after asphalt after being immersed waterwhich solute, which indicates that the water roughness of asphalt being immersed in water in solute, indicates that the water solutions solutions can dissolve and remove some compounds of asphalt and result in the damage of asphalt. can dissolve and remove some compounds of asphalt and result in the damage of asphalt. In addition, In of thesize oil patch sizealkaline is pH11 solution alkaline solution > pH3solution acidic solution 10% saline NaCl theaddition, order ofthe theorder oil patch is pH11 > pH3 acidic > 10% > NaCl saline solution > distilled water; therefore, the degree of damage caused by the pH11 alkaline solution, solution > distilled water; therefore, the degree of damage caused by the pH11 alkaline solution, pH3 pH3 acidic solution and NaCl 10% NaCl solution are higher that of distilled the same acidic solution and 10% salinesaline solution are higher than than that of distilled water.water. At theAtsame time, time, the change in pH value of the alkaline solution after immersion for 7 days is shown in Figure 4, the change in pH value of the alkaline solution after immersion for 7 days is shown in Figure 4, the the pH value of the alkaline solution is about 11 before immersing the asphalt, however, the pH value pH value of the alkaline solution is about 11 before immersing the asphalt, however, the pH value is is about 9 afterimmersing immersingthe theasphalt, asphalt,which whichmeans meansthe thealkaline alkalinesolution solution is is neutralized neutralized by by some some acidic about 9 after acidic composition of the asphalt, or that acid from the asphalt can be dissolved in the solution and reduce composition of the asphalt, or that acid from the asphalt can be dissolved in the solution and reduce the the pH pH value value of of alkaline alkaline solution. solution.
Figure 2.2.70 70# #asphalt asphaltappearance appearance before 7 days solution immersion (A) original Figure before andand afterafter 7 days waterwater solution immersion (A) original sample; sample; (B) distilled water; 10% NaCl salt solution; pH3 acid solution; (E)alkali pH11solution. alkali solution. (B) distilled water; (C) 10% (C) NaCl salt solution; (D) pH3(D) acid solution; (E) pH11
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Figure 3. Water solutions’ appearance after 7 days immersion (A) distilled water; (B) 10% NaCl salt Figure 3. Water solutions’ appearanceafter after77days days immersion immersion (A) water; (B) (B) 10%10% NaClNaCl salt salt Figure 3. Water solutions’ appearance (A)distilled distilled water; solution; (C) pH3 acid solution; (D) pH11 alkali solution. solution; (C) pH3 acid solution; (D) pH11 alkali solution. solution; (C) pH3 acid solution; (D) pH11 alkali solution.
Figure The pH value change of alkaline alkaline solution. (b) pH paper swatches after 7 days immersing Figure 4. 4. (a) The pH value change of solution. (b)The The pH paper color swatches after 7 days immersing Figure 4. (a) (a) The pH value change of alkaline solution. (b) The pHcolor paper color swatches after 7 days asphalt. asphalt. immersing asphalt.
3.2. Four ComponentFractions FractionsAnalysis Analysis Four Component 3.2.3.2. Four Component Fractions Analysis The effectofofthe theaqueous aqueoussolute solute compositions compositions on ofof asphalt was studied The effect onthe thecomponent componentfractions fractions asphalt was studied The effect of the aqueous solute compositions onof the component fractions of asphalt was studied # asphalt before with TLC-FID, the fractions of the four components 70 and after the water solute # with TLC-FID, the fractions of the four components of 70# asphalt before and after the water solute with TLC-FID, the fractions of the four components of 70 asphalt before and after the water solute immersion test are shown in Table 2. immersion test are shown in Table 2. immersion test Table are shown Tableof 2. asphaltenes increases, while the fractions of saturates, aromatics From 2, the in fraction From Table 2, the fraction of asphaltenes increases, while the fractions of saturates, aromatics and resins to decline. afterincreases, 14 days moisture aging, the fraction of asphaltenes From Tabletend 2, the fractionFor of example, asphaltenes while the fractions of saturates, aromatics and resins tend to decline. For example, after 14 days moisture aging, the fraction of asphaltenes increases to 13.01% in distilled water, 14.68% in 10% NaCl saline solution, 18.89% in pH3 acidic andincreases resins tend to decline. For example, after 14 moisture aging, the fraction of pH3 asphaltenes to 13.01% in distilled water, 14.68% in days 10% NaCl saline solution, 18.89% in acidic solution, and 19.68% in pH11 alkaline solution, compared with 11.31% of original sample; the fraction increases to 13.01% in distilled water, 14.68% in 10% NaCl saline solution, 18.89% in pH3 acidic solution, solution, and 19.68% in pH11 alkaline solution, compared with 11.31% of original sample; the fraction of resins fluctuates in distilled water, and decreases observably from 34.46% to 32.70% in 10% NaCl andof19.68% in pH11 alkaline solution, compared with observably 11.31% of original sample; the fraction resins resinssolution, fluctuates distilled water, and decreases tosolution. 32.70% in 10%ofNaCl saline to in 30.49% in pH3 acidic solution, and to 28.11% infrom pH1134.46% alkaline Similarly, fluctuates in distilled water,inand decreases observably 34.46% to 32.70% solution. in 10% NaCl saline saline solution, to 30.49% pH3 andwater, to from 28.11% in pH11 Similarly, saturates decline from 15.35% to acidic 15.02%solution, in distilled to 13.86 in 10%alkaline NaCl saline solution, to solution, to 30.49% in pH3 acidic solution, and to 28.11% in pH11 alkaline solution. Similarly, saturates saturates decline from 15.35% 15.02% in distilled water, to 13.86 in 10% NaClas saline 12.29% in pH3 acidic solution,toand slightly to 13.57% in pH11 alkaline solution well;solution, and the to decline from to 15.02% in adistilled water, 13.86 NaCl saline solution, 12.29% pH3 12.29% in 15.35% pH3 acidic solution, and slightly toto13.57% in10% pH11 alkaline solution well; andinthe fraction of aromatics vary in relatively narrow rangein from 38.64% to 37.56%. Afterasto water solute acidic solution, and slightly toin13.57% in pH11 solution as well; and the fraction of saline aromatics fraction of aromatics vary athe relatively narrow from 38.64% 37.56%. Afterand water solute immersion, especially with addition ofalkaline the range aqueous solute of to acidic, alkaline immersion, especially with thewith addition of low the37.56%. aqueous solute of solute acidic,saturates alkalineand and saline vary in a relatively narrow range from 38.64% to After water immersion, especially compositions, the components relatively molecular weight, including resins decrease while the asphaltene component increases. compositions, the components with relatively low molecular weight, including saturates and resins with the addition of the aqueous solute of acidic, alkaline and saline compositions, the components The component changesweight, of asphalt binders are caused and by the absorption of oxygen, and asphaltene by the decrease while themolecular asphaltene component increases. with relatively low including saturates resins decrease while the dissolution of some hydrophilic groups and water-soluble substances of asphalt, these two actions The increases. component changes of asphalt binders are caused by the absorption of oxygen, and by the component occur simultaneously during immersion in water solute. Thesubstances oxidation can be derived fromtwo theactions airdissolution of somechanges hydrophilic groupsbinders and water-soluble of asphalt, these The component of asphalt are caused by the absorption of oxygen, and by the occur simultaneously during immersion in water solute. The oxidation of canasphalt, be derived from airdissolution of some hydrophilic groups and water-soluble substances these twothe actions
occur simultaneously during immersion in water solute. The oxidation can be derived from the air-water-asphalt interaction and the oxygen in the water solutions [4]. Compared to the saturates and
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asphaltenes, aromatics and resins are more susceptible to oxidation and the polar or ionic chemical groups in the resins can also be solvated by water [23,29–31], therefore, there are more asphaltenes and less aromatics and resins after being immersed in water solute. With the water-soluble substances Materials 2018, 4, x of 17 of asphalt solvated and displaced by water, some saturates presumably were seeped up, and 7pushed by hydrostatic pressure up to the surface of water and constitute a part of oil patch because it is water-asphalt interaction and the oxygen in the water solutions [4]. Compared to the saturates and water insoluble and less dense resulting in a to reduction saturates. decrease in the asphaltenes, aromatics andthan resinswater, are more susceptible oxidationofand the polarThe or ionic chemical saturates of asphalt exposed to water solute was a little different compared to common oxidized aging groups in the resins can also be solvated by water [23,29–31], therefore, there are more asphaltenes in heat-oxidized and UV-oxidized aging. Thus, the oxidation asphalt and effect of dissolution and less aromatics and resins after being immersed in waterofsolute. With thethe water-soluble substancesand and of displaced saturates presumably were seeped up,which and pushed removalofofasphalt some solvated compounds asphaltby in water, water some solutions seems to occur simultaneously, changes by hydrostatic pressure to the surface of water and constitute a partwith of oilan patch because it is water the content and proportion ofup each component in asphalt. In addition, increase of water solute insoluble and less dense than water, resulting in a reduction of saturates. The decrease in the saturates immersion time, the change in amplitude of the components of asphalt binders increases. of asphalt exposed to water solute was a little different compared to common oxidized aging in heatoxidized and UV-oxidized aging.ofThus, the oxidation of asphalt andsolute the effect of dissolution and Table 2. Component fractions 70# asphalt before and after water immersion test. removal of some compounds of asphalt in water solutions seems to occur simultaneously, which changes Sample the content and proportion of each(%) component in asphalt. InResins addition, an increase of Saturates Aromatics (%) (%) with Asphaltenes (%) water solute immersion time, the change in amplitude of the components of asphalt binders increases. Original sample
15.35
38.88
34.44
11.33
7 days fractions of15.11 34.15 Table 2. Component 70 asphalt before38.77 and after water solute immersion test. 11.97 Distilled water 14 days 15.02 37.79 34.68 12.51 Sample Saturates (%) Aromatics (%) Resins (%) Asphaltenes (%) 7 days 15.57 39.04 32.83 Original sample 15.35 38.88 34.44 11.33 12.56 10% NaCl salt solution 14 days 15.36 37.56 33.02 14.06 7 days 15.11 38.77 34.15 11.97 Distilled water 7 days14 days 11.00 39.28 31.78 15.02 37.79 34.68 12.51 17.94 pH3 acid solution 14 days7 days 12.29 38.32 30.49 15.57 39.04 32.83 12.56 18.89 10%NaCl salt solution 14 days 15.36 37.56 33.02 14.06 16.54 7 days 16.73 39.03 27.70 pH11 alkali solution 7 days 11.00 39.28 31.78 17.94 19.68 14 days 13.57 38.64 28.11 pH3 acid solution 14 days 12.29 38.32 30.49 18.89 7 days 16.73 39.03 27.70 16.54 pH11alkali solution The colloidal structure of asphalt represented by the Gaestel index (Ic), and the Ic value is 14 dayscan be13.57 38.64 28.11 19.68 #
calculated according to the Equation (4) [28]. The increase in Ic is used to be characteristic of asphalt Theand colloidal structure of asphalt can betherefore represented Gaestel index (Ic), to andinvestigate the Ic valuethe heat-oxidized UV-oxidized aging usually, thebyIcthe value is also used is calculated according to the Equation (4) [28]. The increase in Ic is used to be characteristic of asphalt colloidal structure change of asphalt before and after moisture aging. heat-oxidized and UV-oxidized aging usually, therefore the Ic value is also used to investigate the colloidal structure change of asphalt before and after+moisture aromatics resins aging.
IC =
aromatics + resins saturates + asphaltenes
𝐼𝐶 =
(4)
(4)
saturates + asphaltenes
70#
The results are shown in Figure 5. As shown in Figure 5, the Gaestel index values of # asphalt The results are shown in Figure 5. As shown in Figure 5, the Gaestel index values of 70 asphalt increase over 7over days7 days and 14 water solute immersing, moregel-like gel-like asphalt increase anddays 14 days water solute immersing,which which means means more asphalt hashas formedformed after water solutesolute exposure, especially after immersion solution. after water exposure, especially after immersionin inpH11 pH11 alkaline alkaline solution.
5. Gaestel of 70 the# 70 asphalt beforeand andafter after water water solute FigureFigure 5. Gaestel indexindex of the asphalt before soluteimmersion. immersion. #
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Chemical Structure Analysis 3.3.3.3. Chemical Structure Analysis 3.3. Chemical Structure Analysis The chemical structures asphalt binders were tested FTIR. The results FTIR The chemical structures of of asphalt binders were tested byby thethe FTIR. The results of of thethe FTIR The chemical structures of asphalt binders were tested by the FTIR. The results of the FTIR #70asphalts # asphalts spectrums of and SBS modified asphalt are shown in Figures 6 and 7, respectively. spectrums of 70 and SBS modified asphalt are shown in Figures 6 and 7, respectively. spectrums of 70# asphalts and SBS modified asphalt are shown in Figures 6 and 7, respectively. Compared spectra origin asphalt, after immersing water solute, carbonyl and Compared to to thethe spectra of of the origin asphalt, after immersing in in water solute, thethe carbonyl and Compared to the spectra of thethe origin asphalt, after immersing in water solute, the carbonyl and sulphoxide absorption peaks tend to be more obvious, while the butadiene absorption bands sulphoxide absorption peaks tend to be more obvious, while the butadiene absorption bands decrease sulphoxide absorption peaks tend to be more obvious, while the butadiene absorption bands decrease obviously, which shows that more carbonyl and sulphoxide groups were generated, and obviously, which shows that more carbonyl and sulphoxide groups were generated, and the chain decrease obviously, which shows that more carbonyl and sulphoxide groups were generated, and the chain butadiene decomposed due in distilled water. segments of segments butadiene decomposed due to immersing inimmersing distilledinwater. the chain segments of of butadiene decomposed due to to immersing distilled water.
# asphalt before and after distilled water aging. Figure 6. FTIR spectra of the Figure 6. FTIR spectra of the the 70##70 asphalt before and and after after distilled distilled water water aging. aging. Figure 6. FTIR spectra of 70 asphalt before
Figure 7. FTIR spectra of the SBS modified asphalt before and after distilled water aging. Figure 7. FTIR spectra of the SBS modified asphalt before and after distilled water aging. Figure 7. FTIR spectra of the SBS modified asphalt before and after distilled water aging.
The results of group indices of 70# asphalt and SBS modified asphalt before and after immersion # asphalt and SBS modified asphalt before and after immersion The results of group indices of #70 The results group indices of 70 asphalt in different waterofsolutions are shown in Table and 3. SBS modified asphalt before and after immersion different water solutions shown Table in in different water areare shown in in Table 3. 3.sulphoxide index of asphalt increase continuously From Table 3,solutions both the carbonyl index and the From Table 3, both the carbonyl index and sulphoxide index of asphalt increase continuously Table 3, bothimmersion the carbonyl index andshows thethe sulphoxide index of asphalt continuously with From extended solution time, which the interaction between theincrease water and asphalt can with extended solution immersion time, which shows the interaction between the water and asphalt with solution immersion time,more which shows thecomponents. interaction between the water and asphalt causeextended the oxidation of asphalt and form asphaltene In addition, both the carbonyl can cause oxidation asphalt and form more asphaltene components. In addition, both the can cause thethe oxidation of of asphalt form more asphaltene components. addition, both the index and sulphoxide index are the and highest after immersion in pH11 alkaline In solution, followed by carbonyl index and sulphoxide index are the highest after immersion in pH11 alkaline solution, carbonyl index and sulphoxide the highest after immersion in pH11 alkaline solution, the pH3 acid solution, 10% NaClindex salineare solution and distilled water, therefore, saline, alkaline and followed by the pH3 acid solution, 10% NaCl saline solution and distilled water, therefore, saline, followed by the pH3 acid solution, 10% NaCl saline solution and distilled water, therefore, saline, acidic components can increase the damage rate of asphalt binders during water solute immersion. alkaline and acidic components can increase damage rate asphalt binders during water solute alkaline and acidic components increase thethe damage rate of of asphalt during water solute The increase of the carbonyl andcan sulphoxide index were relatively faster binders when the immersion time is immersion. The increase of the carbonyl and sulphoxide index were relatively faster when immersion. The increase the iscarbonyl andin sulphoxide indexthe were relatively faster when thethe less than 7 days, however,of there a decrease this trend when immersion time is from 7 days immersion time is less than 7 days, however, there a decrease this trend when immersion immersion time is less than 7 days, however, there is aisdecrease in in this trend when thethe immersion time is from 7 days to 14 days. It can be found from Table 4 that both the carbonyl index and time is from 7 days to 14 days. It can be found from Table 4 that both the carbonyl index and # asphalt. With sulphoxide index of SBS modified bitumen experience a similar change tendency as 70 sulphoxide index of SBS modified bitumen experience a similar change tendency as 70# asphalt. With
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to 14 days. It can be found from Table 4 that both the carbonyl index and sulphoxide index of SBS modified bitumen experience a similar change tendency as 70# asphalt. With respect to the butadiene index, it was found to reduce after moisture aging and decrease continuously with extended immersion Materials 2018, 4, x 9 of 17 time from 0 days to 28 days, which indicates that the chain segments of butadiene in SBS experience significant respect degradation. to the butadiene index, it was found to reduce after moisture aging and decrease continuously The extended results ofimmersion FTIR spectra of asphalt and of SBS modifier with timedemonstrate from 0 days that to 28oxidation days, which indicates thatdegradation the chain segments of occur simultaneously during water solute immersion. The aqueous solute in the solutions, that is, butadiene in SBS experience significant degradation. The results and of FTIR spectra demonstrate that oxidation of asphalt and degradation of SBS the saline, alkaline acidic components promote the oxidation of asphalt, and the pH11 alkaline modifier simultaneously during water solute immersion. The aqueous solute in the solutions, solution has occur the most severe effect during water solute immersion. that is, the saline, alkaline and acidic components promote the oxidation of asphalt, and the pH11 alkaline solution the most severe duringbefore waterand solute immersion. Tablehas 3. Group indices of effect 70# asphalt after water solute immersion. Table 3. Group indices of 70# asphalt before and Saline after water solute immersion. 10% NaCl Results
Original Sample
Distilled Water
Solution
pH3 Acid Solution
pH11 Alkaline Solution
10% NaCl pH3 Acid pH11 Alkaline Original 7Distilled days 14Water days 7 days 14 days 7 days 14 days 7 days 14 days Saline Solution Solution Solution Sample Carbonyl index 0.0003 0.0009 0.0012 0.0009 0.0051 0.0106 0.0121 0.0148 0.0151 7 days 14 days 7 days 14 days 7 days 14 days 7 days 14 days Sulphoxide index 0.0348 0.0387 0.0412 0.0567 0.0598 0.0651 0.0662 0.0717 0.0778 Carbonyl index 0.0003 0.0009 0.0012 0.0009 0.0051 0.0106 0.0121 0.0148 0.0151 Sulphoxide index 0.0348 0.0387 0.0412 0.0567 0.0598 0.0651 0.0662 0.0717 0.0778 Results
Table 4. Group indices of SBS modified asphalt before and after water solute immersion. Table 4. Group indices of SBS modified asphalt before and after water solute immersion.
Results Results
Original Original Sample Sample
Carbony1 index Carbony1 index Sulphoxide index Sulphoxide index Butadiene index Butadiene index
0.0108 0.0108 0.0198 0.0198 0.0252 0.0252
Saline Alkaline Distilled 10% 10% NaClNaCl Saline pH3 Acid pH11pH11 Alkaline pH3 Acid Solution Solution Solution Water Solution Solution Solution days 28 days 14 days28 days 28 days14 days 14 days 28 days 14 days 28 days 1414days 28 days 14 days 28 days 14 days 28 days 0.0109 0.0109 0.0135 0.01350.0110 0.0110 0.0135 0.0135 0.0117 0.01170.02010.02010.01290.01290.0216 0.0216 0.0202 0.0202 0.0218 0.02180.0220 0.0220 0.0259 0.0259 0.0223 0.02230.02570.02570.02330.02330.0265 0.0265 0.0245 0.0237 0.02370.0229 0.0229 0.0229 0.0229 0.0228 0.02280.02050.02050.02200.02200.0207 0.0207 0.0245 Distilled Water
3.4. Rheological Properties Analysis 3.4. Rheological Properties Analysis above tests show there are some changes in chemical composition and structure can be TheThe above tests show there are some changes in chemical composition and structure can be observed during water solute immersing; the newly-formed material structure may cause certain observed during water solute immersing; the newly-formed material structure may cause certain effects on the rheological properties of asphalt. In this paper, the DSR was used to investigate the effects on the rheological properties of asphalt. In this paper, the DSR was used to investigate the rheological properties of asphalt binders before and after being immersed in water solute. The rheological of asphalt binders and after being immersed in water (G*· solute. complex # complexproperties modulus, phase angle, ruttingbefore parameter (G*/sinδ) and fatigue parameter sinδ)The of 70 # asphalt modulus, phase angle, rutting parameter (G*/sinδ) and fatigue parameter (G* · sinδ) of 70 asphalt from −10 °C to 30 °C before and after 7 days of water solute immersion are shown in Figures from8–10. −10 ◦ C to 30 ◦ C before and after 7 days of water solute immersion are shown in Figures 8–10.
# asphalt before and after 7 days immersion. # asphalt Figure 8. Complex modulus angleofof7070 Figure 8. Complex modulusand andphase phase angle before and after 7 days immersion.
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From Figure Figure 8, 8, after after 77 days days immersion, immersion, the the complex complex modulus modulus and and phase phase angle angle of of 70 70## asphalt asphalt From # # binders changed changed significantly. significantly. The The complex complex modulus modulus of of 70 70 asphalt asphalt immersed immersed in distilled water water is is binders in distilled # asphalt, and the complex modulus of asphalt immersed in the # higher than that of the original 70 higher than that of the original 70 asphalt, and the complex modulus of asphalt immersed in the pH11 pH11 alkaline solution and 10%saline NaClsolution saline solution arewhile lower, while there isno almost no difference alkaline solution and 10% NaCl are lower, there is almost difference between between the complex asphaltimmersed binders immersed in the pH3 acidic solution and original the complex modulusmodulus of asphaltofbinders in the pH3 acidic solution and original asphalt. # asphalt immersed in distilled water is lower than that of the# original # asphalt. The phase angle of 70 The phase angle of 70 asphalt immersed in distilled water is lower than that of the original 70 asphalt, 70# asphalt, andangle the phase of immersed 70# asphalt in immersed the other kinds of waterare solutions and the phase of 70#angle asphalt the otherinthree kindsthree of water solutions higher. # # are higher. The G*/sinδ of 70 asphalt before and after 7 days immersion is shown in Figure 9, which The G*/sinδ of 70 asphalt before and after 7 days immersion is shown in Figure 9, which demonstrates demonstrates the permanent deformation resistance of asphalt under repeated loads. The rutting the permanent deformation resistance of asphalt under repeated loads. The rutting parameter of parameter of asphalt immersed in is distilled waterhigher is apparently than that of thehowever, original asphalt immersed in distilled water apparently than that higher of the original asphalt, asphalt, however, the rutting parameter of asphalt immersed in the pH11 alkaline solution and 10% the rutting parameter of asphalt immersed in the pH11 alkaline solution and 10% NaCl saline solution NaCl saline solution are lower, and the rutting parameter of asphalt binders immersed in the pH3 are lower, and the rutting parameter of asphalt binders immersed in the pH3 acidic solution is close to acidic solution is close to the original asphalt. From Figure 10,the after daysofimmersion, G*·sinδ in of the original asphalt. From Figure 10, after 7 days immersion, G*7·sinδ 70# asphaltthe immersed # asphalt immersed in distilled water and pH3 acidic solution is apparently higher than that of the 70 distilled water and pH3 acidic solution is apparently higher than that of the original asphalt, while the originalfactor asphalt, while the fatigue factor asphalt immersed in the pH11 solution and 10% fatigue of asphalt immersed in theofpH11 alkaline solution and 10%alkaline NaCl saline solution are NaCl saline solution are slightly lower. The lower the G*·sinδ is, the better the fatigue cracking slightly lower. The lower the G*·sinδ is, the better the fatigue cracking resistance of asphalt binder resistance of asphalt distilled water and pH3 acidic solution significantly is. Therefore, distilledbinder water is. andTherefore, pH3 acidic solution can significantly decrease the can resistant fatigue # # decrease the asphalt, resistantand fatigue ability 70 asphalt, and effects of 7ordays pH11 ability of 70 the effects of of 7 days immersion in the pH11 alkaline 10% immersion NaCl saline in solution # asphalt are not obvious. # alkaline or 10% NaCl saline solution on the resistant fatigue ability of 70 on the resistant fatigue ability of 70 asphalt are not obvious. The change change tendency tendency of of 70 70## asphalt Figures 8–10 8–10 show show that that the the addition addition of of aqueous aqueous solute solute The asphalt in in Figures changes the the variation variation trend rheological properties changes trend of of rheological properties of of asphalt asphalt in in the the early early phase phase of of immersion. immersion. Previous studies showed that some asphalt components forming cohesion capability inside the Previous studies showed that some asphalt components forming cohesion capability inside the asphalt asphalt are easily solvated and displaced by water [28]. This displacement should weaken the are easily solvated and displaced by water [28]. This displacement should weaken the asphalt’s asphalt’s inside andthe decrease themodulus, complex modulus, rutting parameter fatigue factor, while inside bond and bond decrease complex rutting parameter and fatigueand factor, while increasing increasing the phase angle. This process may be reinforced when the aqueous solute of acidic, alkaline the phase angle. This process may be reinforced when the aqueous solute of acidic, alkaline or salt or salt compositions exists in thesolutions. water solutions. compositions exists in the water
# asphalt before and after 7 days immersion. Figure Figure 9. 9. Rutting Rutting parameter parameter of of 70 70# asphalt before and after 7 days immersion.
The complex modulus, (G*·sinδ) modulus, phase phase angle, angle, rutting rutting parameter parameter (G*/sinδ) (G*/sinδ) and fatigue parameter (G*·sinδ) of 70 70## asphalt asphaltbefore beforeand andafter after 14 days of water solute immersion are shown in Figures 14 days of water solute immersion are shown in Figures 11–13.11–13. From From 11,complex the complex modulus increases phase angle clearly decreases days FigureFigure 11, the modulus increases and and phase angle clearly decreases afterafter 14 14 days of # immersion. From Figure 12, the G*/sinδ of 70 asphalt immersed in the pH11 alkaline solution, 10%
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# asphalt. # asphalt NaCl saline solution pH3 acidic solution are70 higher than thatthat of the original 70# 70 asphalt. In Figure NaCl saline solution and pH3 acidic solution are higher than of in the original In Figure of immersion. Fromand Figure 12, the G*/sinδ of immersed the pH11 alkaline solution, # # # 13, the G*·sinδ of solution 70 asphalt immersed in the pH11 alkaline solution andand NaCl saline 13, the G*·sinδ of 70 asphalt immersed in the pH11 alkaline solution 10% NaCl saline solution 10% NaCl saline and pH3 acidic solution are higher than that of10% the original 70 solution asphalt. # asphalt, # asphalt, # are similar to that of the original 70 and the G*·sinδ of asphalt immersed in the distilled are similar to that of the original 70 and the G*·sinδ of asphalt immersed in the distilled In Figure 13, the G*·sinδ of 70 asphalt immersed in the pH11 alkaline solution and 10% NaCl saline # asphalt. #that water andare pH3 acidic is higher than of the original 70·sinδ TheThe effects of distilled water and pH3 acidic solution is higher than that of and the original 70# asphalt. effects of in distilled solution similar tosolution that of the original 70 asphalt, the G* of asphalt immersed the # # # asphalt. water immersion thethe rheological performance of 70 asphalt is most significant after 14 14 days water immersion on rheological of 70 is most significant days distilled water andonpH3 acidic solution isperformance higher than that of asphalt the original 70 Theafter effects of # immersion, followed by the pH3 solution on the complex modulus, phase angle and G*·sinδ, and the immersion, followed by the pH3 solution on the complex modulus, phase angle and G*·sinδ, and distilled water immersion on the rheological performance of 70 asphalt is most significant after 14 daysthe pH11 alkaline solution G*/sinδ. Because ofthe the displacement effect of water solutions aqueous pH11 alkaline solution onpH3 G*/sinδ. Because of the displacement effect of water solutions with aqueous immersion, followed byonthe solution on complex modulus, phase angle and G*with ·sinδ, and the solute, more time is needed to observe the effect of the water solution, thus, the increase in the solute, more time is needed to observe the effect of the water solution, thus, the increase in pH11 alkaline solution on G*/sinδ. Because of the displacement effect of water solutions with aqueousthe complex modulus, G*/sinδ G*·sinδ, andand thethe decrease of of phase angle appear after 14 days complex modulus, G*/sinδ and G*·sinδ, the decrease phase angle appear after 14 days solute, more time is needed toand observe the effect of water solution, thus, the increase in the complex immersion. immersion. modulus, G*/sinδ and G*·sinδ, and the decrease of phase angle appear after 14 days immersion.
# asphalt # asphalt before andand after days immersion. Figure 10. 10. Fatigue factor of 70 asphalt before and after 77 days immersion. Figure Fatigue factor of# 70 before after 7 days immersion.
# asphalt before and after 14 days immersion. Figure 11. 11. Complex modulus andand phase angle of 70 70 # asphalt Figure 11. Complex modulus and phase angle of asphalt before andand after 14 days immersion. Figure Complex modulus phase angle of# 70 before after 14 days immersion.
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# asphalt # Figure 12. parameter of before and after days immersion. Figure 12. Rutting parameter of 70 before and after 1414 days immersion. Figure 12.Rutting Rutting parameter of70 70#asphalt asphalt before and after 14 days immersion.
# asphalt # Figure 13. Fatigue factor of 70 before and after 1414days immersion. Figure Figure13. 13.Fatigue Fatiguefactor factorof of70 70#asphalt asphaltbefore beforeand andafter after 14days daysimmersion. immersion.
Figures 14 15 modulus and phase angle SBS modified asphalt after Figures 14 and 15 the the complex modulus and phase angle ofof SBS Figures 14 and andpresent 15 present present the complex complex modulus and phase angle of SBSmodified modifiedasphalt asphaltafter after 14 days and 28 days immersion, respectively. From Figures 14 and 15, the effects of immersion in 14 days and 28 days immersion, respectively. From Figures and theeffects effectsofofimmersion immersion in in 14 days and 28 days immersion, respectively. From Figures 1414 and 15,15,the # asphalt. water solutions on the complex modulus of SBS modified asphalt are similar to that of 70 # # solutions oncomplex the complex modulus of SBS modified asphalt are similartotothat thatofof70 70 asphalt. asphalt. waterwater solutions on the modulus of SBS modified asphalt are similar However, there are differences in effects of phase angle between SBS modified asphalt However, are some some differences in the the effects of the the phase angle betweenSBS SBSmodified modifiedasphalt asphalt However, therethere are some differences in the effects of the phase angle between # asphalt; the phase angle of SBS modified asphalt after immersion is lower than the original and 70 # asphalt; the phase angle of SBS modified asphalt after immersion is lower than the original # and 70 and 70 asphalt; the phase angle of SBS modified asphalt after immersion is lower than the original # asphalt. It seems that the modification of asphalt, and the range isis lower than that of # asphalt. It seems that the modification of asphalt, anddescent the descent descent range lower of#70 70 asphalt, and the range is lower thanthan thatthat of 70 asphalt. It seems that the modification of bitumen by can to change in rheological properties when subjected to immersion in bitumen bySBS SBSlead canlead lead toless less change inthe the rheological properties when subjectedto toimmersion immersionin in bitumen by SBS can to less change in the rheological properties when subjected water solute. Additionally, among these different water solution immersion conditions, the effect of water solute. Additionally, among these different water solution immersion conditions, the effect of waterdistilled solute. Additionally, among these different water solution immersion conditions, the effect of distilledwater wateron onthe thecomplex complexmodulus modulusand andphase phaseangle angleisisthe themost mostremarkable. remarkable.The Theasphalt asphaltbecome become distilled water on the complex modulus and phase angle is the most remarkable. The asphalt become stiffer stifferafter afterbeing beingimmersed immersedin indistilled distilledwater, water,especially especiallyfor forthose thosesamples samplesimmersed immersedfor for28 28days. days.The The stifferresults after beingindicated immersed in to distilled water, especially for those samples immersed for 28 days. results also also indicated that that to aa certain certain extent, extent, the the rheological rheological properties properties show show aa corresponding corresponding The results also indicated that tochemical a certain extent, the rheological properties show a corresponding relationship relationship to to the the change change in in chemical components. components. Asphaltene Asphaltene isis the the main main component component that that affects affects relationship to the change in chemical components. Asphaltene is the main component that affects the rheological property of asphalt [32]. With the prolonged water solute immersion time, the relative
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the rheological property of asphalt [32]. With the prolonged water solute immersion time, the relative amount of of asphaltene inin the surface amount asphaltene the surfaceofofthe theasphalt asphaltincreases increasesgradually, gradually,which whichresults results in in the the increase increase in theincomplex modulus. the complex modulus.
Figure Complexmodulus modulus phase SBS modified asphaltand before anddays after Figure14. 14. Complex andand phase angleangle of SBSofmodified asphalt before after 14 14 immersion. days immersion.
Figure Complexmodulus modulus phase SBS modified asphaltand before anddays after Figure15. 15. Complex andand phase angleangle of SBSofmodified asphalt before after 28 28 immersion. days immersion.
Figures and present rutting parameter SBS modified asphalt after days and Figures 1616 and 17 17 present thethe rutting parameter of of SBS modified asphalt after 14 14 days and 28 28 days days water solute immersion, respectively. The rutting parameter of asphalt immersed in distilled water solute immersion, respectively. The rutting parameter of asphalt immersed in distilled water water is distinctly higher than that of the original asphalt after 14 days, however, the rutting is distinctly higher than that of the original asphalt after 14 days, however, the rutting parameter of parameter of asphalt immersed in the water solution with the aqueous solute is close to the original asphalt immersed in the water solution with the aqueous solute is close to the original asphalt over asphalt over 14 days and are obviously higher than that of the original asphalt after 28 days. 14 days and are obviously higher than that of the original asphalt after 28 days. Figures 18 and 19 present the G*·sinδ of SBS modified asphalt after 14 days and 28 days water Figures 18 and 19 present the G*·sinδ of SBS modified asphalt after 14 days and 28 days water solute immersion, respectively. The fatigue factor of SBS modified asphalt immersed in distilled solute immersion, respectively. The fatigue factor of SBS modified asphalt immersed in distilled water and pH3 acidic solution is distinctly higher than that of original SBS modified asphalt over 14 water and pH3 acidic solution is of distinctly higher than that of original SBS modified asphalt over days, however, the fatigue factor asphalt immersed in pH11 alkaline solution and 10% NaCl saline 14 solution days, however, the fatigue factor of asphalt immersed in pH11 alkaline solution and 10% NaCl is lower than the original SBS modified asphalt and are slightly higher than that of the saline solution is lower than the original SBS modified asphalt and are slightly higher than that of the original asphalt after 28 days. original asphalt after 28 days.
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16. Rutting parameter of SBS modified asphalt beforeand andafter after 14 14 days days immersion. Figure Figure 16. Rutting parameter of SBS modified asphalt before immersion. Figure 16. Rutting parameter of SBS modified asphalt before and after 14 days immersion. Figure 16. Rutting parameter of SBS modified asphalt before and after 14 days immersion.
Figure 17. Rutting parameter of SBS modified asphalt before and after 28 days immersion.
Figure 17. Rutting parameter of SBS modified asphalt beforeand and after 28 28 days days immersion. Figure Figure 17. Rutting parameter of SBS modified asphalt immersion. 17. Rutting parameter of SBS modified asphaltbefore before and after after 28 days immersion.
Figure 18. Fatigue factor of SBS modified asphalt before and after 14 days immersion. Figure 18. Fatigue factor of SBS modified asphalt before and after 14 days immersion. Figure 18. Fatigue factor of SBS modified asphalt before and after 14 days immersion.
Figure 18. Fatigue factor of SBS modified asphalt before and after 14 days immersion.
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Figure 19.19. Fatigue factor of of SBS modified asphalt before and after 28 28 days immersion. Figure Fatigue factor SBS modified asphalt before and after days immersion.
results above demonstrate that these four kinds water solutions can change AllAll thethe results above demonstrate that allall of of these four kinds of of water solutions can change thethe rheological performance asphalt, aqueous solute composition plays important role rheological performance of of asphalt, thethe aqueous solute composition plays anan important role in in thethe properties asphalt after water solute exposure, and sum these chemical processes leads properties of of asphalt after water solute exposure, and thethe sum of of these chemical processes leads to to asphalt hardening and higher brittleness. The aging process, the dissolving and removal processes, asphalt hardening and higher brittleness. The aging process, the dissolving and removal processes, slow distilled water, however process is accelerated with addition aqueous solute is is slow in in distilled water, however thethe process is accelerated with thethe addition of of aqueous solute compositions such as those found in acid rain areas, the seaboard, and in areas with saline and compositions such as those found in acid rain areas, the seaboard, and in areas with saline and alkaline soil. alkaline soil. 4. 4. Conclusions Conclusions The effects of of water solute exposure onon asphalt chemistry and rheology were investigated byby The effects water solute exposure asphalt chemistry and rheology were investigated TLC-FID, FTIR spectra and and DSR.DSR. BasedBased on theon analysis above, above, the following conclusions can be drawn: TLC-FID, FTIR spectra the analysis the following conclusions can be (1) With the water-soluble substances of asphalt solvated and displaced by water, some drawn: water-insoluble component fractions also of canasphalt seep upsolvated and separate from the surface of the asphalt. (1) With light the water-soluble substances and displaced by water, some waterMoisture damage is associated with dissolution andup removes some polar compounds insoluble light component fractions also can seep and separate fromor thenonpolar surface of the asphalt. from the asphalt surface to water closely. Moisture damage is associated with dissolution and removes some polar or nonpolar compounds (2) the Unlike common oxidized in heat-oxidized and UV-oxidized aging, saturate fractions from asphalt surface to wateraging closely. may be(2) removed the surface of water and formand a light-yellow oil patch, reduces the Unlikeonto common oxidized agingsolutions in heat-oxidized UV-oxidized aging, that saturate fractions content of removed saturates onto in asphalt after water solute immersion. may be the surface of water solutions and form a light-yellow oil patch, that reduces Compared with distilled water, the addition ofimmersion. aqueous solute compositions can remarkably the(3) content of saturates in asphalt after water solute affect the properties of asphalt during water solute exposure, andcompositions it was clear that effects (3)chemical Compared with distilled water, the addition of aqueous solute canthe remarkably could bethe ordered as follows, pH11 alkalineduring solution > pH3 acidic solutionand > 10% NaCl saline affect chemical properties of asphalt water solute exposure, it was clear thatsolution. the effects It may the addition of the aqueous solute compositions accelerates the> dissolving and ionizing couldbebethat ordered as follows, pH11 alkaline solution > pH3 acidic solution 10% NaCl saline solution. of It some compounds from asphalt surface to water solutions and theand chemical maysoluble be that the addition of the the aqueous solute compositions accelerates thedegrade dissolving ionizing properties asphalt and the extent moisture of some of soluble compounds fromofthe asphaltdamage. surface to water solutions and degrade the chemical (4) Immersion in water solutions changes in the chemical composition and structure of properties of asphalt and the extent induced of moisture damage. asphalt.(4)As a result, the newly-formed material changes structureincaused certaincomposition effects on the rheological Immersion in water solutions induced the chemical and structure of properties While the complex modulus, parameter fatigue factor and asphalt. of Asasphalt. a result, the newly-formed materialrutting structure caused and certain effects onincreased the rheological theproperties phase angle decreased in distilled water, the adding of aqueous solute brought about the opposite of asphalt. While the complex modulus, rutting parameter and fatigue factor increased effects earlyangle phases of immersion. With water, the immersion timeofprolonged, the relative amount and in thethe phase decreased in distilled the adding aqueous solute brought aboutofthe asphaltene the surface asphalt increased gradually, which resulted in an increase in thethe complex opposite in effects in the of early phases of immersion. With the immersion time prolonged, relative modulus a decrease in the phase amountand of asphaltene surfaceangle. of asphalt increased gradually, which resulted in an increase in the complex modulus and a decrease in the phase angle. The changes in the chemical composition and rheological properties of asphalt binders during immersion in water solutions were investigated in this paper, however, the interactions between
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The changes in the chemical composition and rheological properties of asphalt binders during immersion in water solutions were investigated in this paper, however, the interactions between water solutions and asphalt and the influence on the micro-domains’ mechanical and conventional physical properties of asphalt binders are still not clear. Investigations of the effects of exposure to water solutions on the micro-domains’ mechanical properties and conventional physical properties such as penetration, softening point and ductility, will be carried out in our future research. Author Contributions: Conceived and designed the experiments: L.P., X.Z. and Y.Y.; Performed the experiments: X.Z.; Attributed reagents/materials/analysis tools: L.P., S.W. and Y.Y.; Wrote the paper: L.P., X.Z. and Y.L. Funding: This research was funded by the National Basic Research Program of China (973 Program No. 2014CB932104) and Technological Innovation Major Project of Hubei Province (2016AAA023). Conflicts of Interest: The authors declare no conflict of interest.
References 1. 2. 3. 4. 5. 6. 7. 8. 9.
10.
11.
12.
13. 14. 15. 16. 17.
National Asphalt Pavement Association. Black and Green: Sustainable Asphalt, Now and Tomorrow; Recycled Materials: Lanham, MD, USA, 2016. Hung, A.M.; Goodwin, A.; Fini, E.H. Effects of water exposure on bitumen surface microstructure. Constr. Build. Mater. 2017, 135, 682–688. [CrossRef] Behiry, E.M. Laboratory evaluation of resistance to moisture damage in asphalt mixtures. Ain Shams Eng. J. 2013, 4, 351–363. [CrossRef] Noguera, J.A.H.; Quintana, H.A.R.; Gómez, W.D.F. The influence of water on the oxidation of asphalt cements. Constr. Build. Mater. 2014, 71, 451–455. [CrossRef] Ma, T.; Huang, X.; Mahmoud, E.; Garibaldy, E. Effect of moisture on the aging behavior of asphalt binder. Int. J. Miner. Metall. Mater. 2011, 18, 460–466. [CrossRef] Kang, A.H.; Zhou, X.; Mei-Ping, W.U.; Sun, L.J. Aging of TOR asphalt rubber in combination of environmental factors. J. Nanjing Univ. Sci. Technol. 2012, 36, 724–728. Liu, K.; Deng, L.; Zheng, J. Nanoscale study on water damage for different warm mix asphalt binders. Int. J. Pavement Res. Technol. 2016, 9, 405–413. [CrossRef] López-Montero, T.; Miró, R. Differences in cracking resistance of asphalt mixtures due to ageing and moisture damage. Constr. Build. Mater. 2016, 112, 299–306. [CrossRef] Luo, Y.; Zhang, Z.; Cheng, G.; Zhang, K. The deterioration and performance improvement of long-term mechanical properties of warm-mix asphalt mixtures under special environmental conditions. Constr. Build. Mater. 2017, 135, 622–631. [CrossRef] Yao, H.; Dai, Q.; You, Z. Chemo-physical analysis and molecular dynamics (MD) simulation of moisture susceptibility of nano hydrated lime modified asphalt mixtures. Constr. Build. Mater. 2015, 101, 536–547. [CrossRef] Cheng, D.; Little, D.N.; Lytton, R.L.; Holste, J.C.; Davis, R.; Brown, S.; Hobson, K.; Dunning, M.; Mcdaniel, B.; Newman, K. Use of surface free energy properties of the asphalt-aggregate system to predict moisture damage potential. Asph. Paving Technol. Assoc. Asph. Paving Technol. Proc. Tech. Sess. 2002, 71, 59–88. Huang, S.C.; Turner, T.F.; Pauli, A.T.; Miknis, F.P.; Branthaver, J.F.; Robertson, R.E. Evaluation of different techniques for adhesive properties of asphalt-filler systems at interfacial region. J. ASTM Int. 2005, 2, 1–15. [CrossRef] Kakar, M.R.; Hamzah, M.O.; Valentin, J. A review on moisture damages of hot and warm mix asphalt and related investigations. J. Clean. Prod. 2015, 99, 39–58. [CrossRef] Feng, D.; Yi, J.; Wang, D.; Chen, L. Impact of salt and freeze–thaw cycles on performance of asphalt mixtures in coastal frozen region of China. Cold Reg. Sci. Technol. 2010, 62, 34–41. [CrossRef] Wang, Y.; Ye, J.; Liu, Y.; Qiang, X.; Feng, L. Influence of freeze–thaw cycles on properties of asphalt-modified epoxy repair materials. Constr. Build. Mater. 2013, 41, 580–585. [CrossRef] Zhao, Q.; Zhao, J. Influence of coastal area salinity on road surface resistance to permanent deformation performance. J. Dalian Jiaotong Univ. 2016, 37, 69–72. Ma, Q.; Wu, J.; Qin, K. Tests and analyses of the influence of chlorine salt on freezing-thawing splitting tensile strength of asphalt concrete. J. Glaciol. Geocryol. 2013, 35, 1202–1208.
Materials 2018, 11, 983
18. 19. 20.
21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32.
17 of 17
Feng, X.J.; Tang, X.; Xiong, X. Study on influence of acid rain on pavement performances of asphalt mixtures. J. Wuhan Univ. Technol. 2015, 37, 39–43. Zhang, Q.; Hu, J.R.; Peng, Y.H. Analysis of chemical mechanism for aggregates corroded by acid rain in asphalt mixtures. Highway 2004, 2, 104–106. Dendooven, L.; Alcántara-Hernández, R.J.; Valenzuela-Encinas, C.; Luna-Guido, M.; Perez-Guevara, F.; Marsch, R. Dynamics of carbon and nitrogen in an extreme alkaline saline soil: A review. Soil. Biol. Biochem. 2010, 42, 865–877. [CrossRef] Wang, Z.; Zhang, T.; Shao, M. Investigation on snow-melting performance of asphalt mixtures incorporating with salt-storage aggregates. Constr. Build. Mater. 2017, 142, 187–198. [CrossRef] Zhang, Q.; Jia, X.J.; Li, Y.L.; Tong, S.J. the simulation study on effect of acid rain on the strength and void rate of asphalt mixture. J. China Foreign Highw. 2005, 25, 78–80. Zhang, Q.; Meng, X.R.; Yan, W. Analysis of the chemical mechanism of influence of precipitation on components of asphalt binder. J. Xian Univ. Archit. Technol. 2010, 42, 669–673. Liu, X.; Wu, S.; Liu, G.; Li, L. Effect of ultraviolet aging on rheology and chemistry of LDH-modified bitumen. Materials 2015, 8, 5238–5249. [CrossRef] [PubMed] Huo, K.; Zhai, Y.; Liao, K.; Yang, P.; Yan, F.; Wei, Y. A study on change of family composition and properties of Liaoshu paving asphalt on aging. Petrol. Sci. Technol. 2001, 19, 651–660. Ouyang, C.; Wang, S.; Zhang, Y.; Zhang, Y. Improving the aging resistance of asphalt by addition of Zinc dialkyldithiophosphate. Fuel 2006, 85, 1060–1066. [CrossRef] Redelius, P.; Soenen, H. Relation between bitumen chemistry and performance. Fuel 2015, 140, 34–43. [CrossRef] Yao, H.; Dai, Q.; You, Z. Fourier transform infrared spectroscopy characterization of aging-related properties of original and nano-modified asphalt binders. Constr. Build. Mater. 2015, 101, 1078–1087. [CrossRef] Tarefder, R.A.; Arisa, I. Molecular dynamic simulations for determining change in thermodynamic properties of asphaltene and resin because of aging. Energy Fuels 2011, 25, 2211–2222. [CrossRef] Lu, X.; Isacsson, U. Effect of ageing on bitumen chemistry and rheology. Constr. Build. Mater. 2002, 16, 15–22. [CrossRef] Siddiqui, M.N.; Ali, M.F. Studies on the aging behavior of the arabian asphalts. Fuel 1999, 78, 1005–1015. [CrossRef] Caro, S.; Diaz, A.; Rojas, D.; Nuñez, H. A Micromechanical model to evaluate the impact of air void content and connectivity in the oxidation of asphalt mixtures. Constr. Build. Mater. 2014, 61, 181–190. [CrossRef] © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
