High temperatures performance investigation of

Bearing Capacity of Roads, Railways and Airfields – Loizos et al. (Eds) © 2017 Taylor & Francis Group, London, ISBN 978-1-138-29595-7

High temperatures performance investigation of geopolymer modified bitumen binders S.I.A. Ali

Near East University, Lefkoşa, North Cyprus

H.A.M. Yahia

Middle East College, Knowledge Oasis Muscat, Oman

A.N.H. Ibrahim & R.A. Al Mansob

Universiti Kebangsaan Malaysia, Bangi, Malaysia

ABSTRACT:  Bitumen binder mixing techniques attempt to balance the composition of bitumen and the modifier to achieve the long-lasting performance of modified bitumen binder, which led to enhance the pavement performance in roads construction. The main purpose of modification of bitumen binder is to produce mixtures with high resistance to deformation and cracking. The properties of the produced blends are depending on the physical and chemical properties of the used materials. The concentrations that used to produce modified bitumen binders were 0, 3, 5 and 7%.wt from the weight of bitumen, and various tests were used to evaluate the performance of base and modified asphalt binders including softening point, viscosity and Dynamic Shear Rheometer (DSR). The results of the best performance of modified bitumen binders 5% GPMB shows that the stiffness at high temperatures was improved as observed from the softening point and the viscosity, the enhancement was up to 20.21 and 31.33%, respectively. Also, the permanent deformation reduced nearly 3 times compared the base asphalt binder. 1  INTRODUCTION The bitumen binder and mixture need to be improved to reduce and prevent pavement distresses. As a result, polymers became a part of the materials used in the large quantity of applications than any other categories of materials available. Therefore to improve the properties of asphalt binder in the present, the polymers were used as additives to improve bitumen binder and mixture properties because of their excellent physical and chemical properties. Polymers can be defined as large molecules composed of a large number of correlations of small molecules with each other and this small molecule is called monomers (Saoula et al. 2008). Polymer modified bitumen binder shows significant improvement of mechanical and rheological properties at low, intermediate and high temperatures (Airey 2003). The combination of polymers provides an opportunity to be reused and recycled at the same time allows the possibility of maintaining sources as well as reduce the costs. On the other side, the combination of polymers successfully improved the performance and properties of bitumen (Liu et al. 2009). The effectiveness of polymer concentration on the microstructure, thermal and rheological properties using recycled polyethylene modified bitumen

come out with a significant modification of the theological reaction (Fuentes-Audén et al. 2008; Peralta 2010). Geopolymer Modified Bitumen (GPMB) is a new method to capitalize waste materials and use those materials in road paving. According to Ibrahim et al 2016, the geopolymer has constituents two main components namely; the alkaline liquid and the source of materials. The alkaline liquids ordinarily used in geo-polymerization are blends of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) or potassium silicate (K2SiO3) and potassium hydroxide (KOH), while the source of materials is based on aluminum and silicon (Ibrahim, Ahmad, et al. 2016). In this study, the rheological properties of geopolymer modified bitumen binders with the concentrations of 3, 5 and 7% at elevated temperatures were instigated using several testings.

2  EXPERIMENTAL METHODS 2.1  Materials The base bitumen used was 60/70 penetration grade, and the geopolymer was the combination of fly ash and the alkali liquid. The fly ash class F with a specific gravity of 2.26 was obtained from local

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company in Malaysia, while the alkali liquid was sodium silicate solution (Na2SiO3) and sodium hydroxide (NaOH) pallet diluted in water to produce 8 Molar (8M) NaOH solution. A combination of sodium silicate solution and sodium hydroxide solution was prepared to activate the alumino-silicate precursors in fly ash through a series of dissolutionhydrolysis-polycondensation (Ibrahim, Yusoff, et al. 2016). The physical properties of the base bitumen are shown in Table 1, while the chemical oxide compositions of the fly ash are listed in Table 2. 2.2  Preparation of Geopolymer Modified Bitumen (GPMB) The base bitumen was heated until it becomes fluid, then the geopolymer gel was added into the base asphalt blend with different concentrations namely; 3, 5 and 7% by weight of the bitumen and the blends was mixed using mechanical shear mixer for 90 minutes under a speed of 1000 rpm with a temperature of 150 C°±5 to produce a homogenous blends. The softening point test was used to estimate the homogeneity of the blends. A sample from each test was taken every 30 minutes during the 2 hours mixing period until the value for the softening point was stabilized. Moreover, the melt blending method was used to prepare the GPMB, and each concentration of the geopolymer in bitumen blends was coded in this study such as 3% = 3% GPMB. Table 1.  Physical properties of the base binder. Material

Properties

Asphalt 60/70 Specific Gravity Penetration @ 25°C Softening point (°C) Viscosity @ 135°C (Pa.s)

Test method

Value

ASTM D70 ASTM D5

  1.03 82

ASTM D36

46.0

ASTM D4402   0.24

Table  2.  Chemical Composition (%) of Oxide Fly ash (Chien et al. 2012). Oxide

Fly ash

SiO2 Al2O3 Fe2O3 CaO MgO SO3 K2O Na2O LOI

52.50 22.82 5.34 7.16 2.56 0.20 0.99 0.48 3.35

3  EXPERIMENTAL TEST PROCEDURES 3.1  The physical properties tests The physical properties tests were used to investigate the physical properties of GBMB including the penetration, softening point, and the ductility (25°C) tests which were conducted based on ASTM specification namely; D5, ASTM D36, and ASTM D113 respectively. According to the research aims, the softening point test was only test performed on the modified bitumen binders, while the penetration and ductility were conducted for base bitumen binder to ensure that the bitumen was within the requirement of ASTM specification. 3.2  Viscosity The Brookfield rotational Viscometer was used for the assessment of the viscosity of base bitumen binder and GPMB samples. Three readings were noted for each test temperature, and the average was recognized as the test result. In addition, the test temperatures were 135°C and 165°C respectively. 3.3  The rheological properties test The Dynamic Shear Rheometer (DSR) is used to characterize the viscous and elastic behaviour of asphalt cement at intermediate and high in-service temperatures. Moreover, DSR measures the rheological properties factors such as complex shear modulus (G*) and the phase angle (δ) of bitumen binder at the desired temperature and frequency of loading, as per AASHTO T315. Frequency sweeps were conducted for all binders using a 25  mm diameter plate and a 1  mm gap for intermediate to high temperatures 25–75°C. The tests were performed at nine frequencies ranging from 1  rad/s (nearly 0.159 Hz) to 100 rad/s (nearly 15 Hz) while the test temperatures were from 46+6 to 82°C. The failure temperatures are considered for all bitumen blends according to the Superpave specification for G*/sin δ values of less than 1.0 kPa in the case of unaged bitumen. In addition, the results of the complex shear modulus G* and phase angle δ were used for the construction of master curves. The master curve of the asphalt cement characteristic at a reference temperature Tref is defined as the correlation between the stiffness and the reduced loading time or frequency (Walubita et al. 2011). 4  RESULTS AND DISCUSSION 4.1  The influences of GPMB on softening point The modifier effects on softening point test of base bitumen binder using geopolymer are shown

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in Figure 1. The consequences show that the modified binders have the highest softening point values compared with the base binder. This indicates that the addition increase of geopolymer in bitumen blends able to increase the hardness of modified binders. Moreover, the significant enhancement was observed with the concentration of 5% GPMB. It was noted that 7% GPMB for the softening point slightly decreased, but it’s better than the base binder in terms of performance. This is reduction it might be due to the ununiformed dispersion or agglomeration of GPMB. 4.2  Effects of GPMB on viscosity Figure 2 shows the results of the viscosity of base binder and GPMB binders. It can be seen that values were decreased instantaneously with increasing the temperature, regardless of the geopolymer concentration. Moreover, it was found that the base binder has the lowest viscosity, whereas the modified sample with 5% GPMB has the highest viscosity. This indicated that 5% GPMB has better performance in terms of rutting resistance. In addition, the viscosity test results of base binder and modified binders with geopolymer remains within the Superpave specifications at the temperature of 135°C, were the viscosity should be less than the maximum limit of 3 Pa.s. The results obtained, were similar to the results that found by Al-Mansob (2014) when Epoxidized Natural Rubber (ENR) polymer with concentrations of 3, 6, 9 and 12% used to modified bitumen binders. It noted that the addition of polymer increases the viscosity values (Al-Mansob et al. 2014).

Figure 1.  Softening point of base binder and GPMB.

Figures 2.  Viscosity of base binder and GPMB binders.

4.3  Effects of GPMB on rheological properties 4.3.1  Isochronal plot Always The isochronal plots of the G* contrasted with temperature (°C) at the frequency of 10 rad (1.59 Hz) are presented in Figure 3. It was found that the G* increased with addition increase of modifier up to 5% then decreased slightly in 7%, but it’s still enhanced compared with the base bitumen in terms of performance. In addition, the most obvious improvement in G* was for 5% GPMB, thus leading to the most strongly improved of temperature susceptibility among all investigated modified binders. Several studies were conducted to evaluate the viscoelastic functions using different polymers such as Styrene–Butadiene–Styrene (SBS), Natural Rubber latex (NR), and Epoxidized Natural Rubber (ENR). All these polymers show similar an increase in G* values at high temperatures which represent an improvement in terms of the temperature susceptibility (Airey 2003). 4.3.2  Rheological master curves In The master curves reflect the time dependency of bitumens over a wide range of loading times a reference temperature was selected first, and then the data at all other temperatures are shifted horizontally to construct a single smooth curve. The master curves of the complex modulus and phase angle for base bitumen binder and modified binders with geopolymer are shown in Figures  4 and 5. It was observed that an increase in the complex modulus upon increasing the geopolymer

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The phase angle master curves for the base binder and modified binders which shown in Figure 5, indicate that a reduction in phase angle with increasing the modifier content at temperatures between 46–64°C, while it was increased above mentioned temperatures due to modifier reacted as filler as the modified binders reach the failure temperatures. Furthermore, it was shown that the 5% has a lower phase angle than the base binders and other modified binders, which means it has better viscoelastic recovery performance. 4.3.3  Effects of GPMB on failure temperature Figure  6 shows the results of failure temperature obtained from frequency sweep tests. As expected,

Figure 3.  Isochronal plots of the G* for base binder and GPMB binders.

Figure  5.  Phase angle master curves for base binder and modified GPMB binders.

Figure  4.  Complex modulus master curves for base binder and modified GPMB.

concentration in bitumen matrix. This is due to the increase in stiffness of modified binders which lead to mitigated and prevented the high-temperature pavement distresses such as rutting. On the other hand, the concentration of 7% shows a different behaviour, as the complex modulus reduced slightly. This reduction, it might be due to chemical reactions with addition increase of modifier content, also it could be due the agglomeration occurs among the geopolymer components.

Figure  6.  Failure temperature of base binder and GPMB binders.

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it was found that the base binder has the lowest failure temperature nearly 59°C, while the modified binders have better failure temperatures compared with base asphalt binder. This indicates that the modifier able to enhance the high-temperature properties of bitumen, the highest improvement of failure temperature as shown if Figure 5 was for 5% GPMB with an enhancement of 39.22% followed by 7% GPMB and 3% GPMB with an improvement of 35.19 and 31.37%, respectively. However, previous studies conducted on various types of polymers modified bitumen such as crumb rubber, polyphosphoric acid, and propylene maleic anhydride show similar performance that the modified binders have slightly higher fail temperatures than the base binder. 4.3.4  Examples effects of GPMB on rutting parameter Figure  7 shows the graphs of rutting for base binder and geopolymer modified binders using both techniques Superpave Specification (SPS) G*/sinδ and Aroon Shenoy suggested parameter G*/(1−(1/tanδ sinδ)) when δ>52 (Shenoy 2001). From Figure  7, it was observed that the similar improvement to resist the permanent deformation obtained from the previous testings, the lowest rutting resistance was for the base binder, while modified binders show an enhancement and the 5% GPMB has the highest rutting resistance among the modified binders, which performs much better than other modified binders. The results approve that the modifier capable to increases the hardiness

of bitumen at high temperatures. Nonetheless, the 7% display different behavior as the resistance to permanent deformation slightly declined. According to SPS and ASP parameter, the evaluation and comparison of rutting parameter of the base binder and modified binders using both SPS and the ASP methods revealed that there were no much differences between the both techniques, this indicates that both methods are able to use to estimate and determine the rutting parameters of base modified bitumens. 5  CONCLUSION Number In this paper, high-temperature rheological properties of bitumen modified with geopolymer were investigated using various tastings and techniques. The amounts of 3, 5, and 7% of the modifier were added to the base asphalt cement. Based on the test outcomes of this chapter, the softening point and viscosity were approved that the hardness of modified binders increased, thus resulting in improved temperature susceptibility for both modifiers. Moreover, the master curves results indicated an increase in elastic behavior compared with the base binder and from the failure temperature tests, it can be observed that all modified blends had slightly greater failure temperatures in comparison to the base binder. In addition, according to the results of the rutting parameters, it can be concluded that the uses geopolymer as bitumen modifier were able to improve the resistance against rutting at high temperatures. Generally, the best result noted when the addition of modifiers was the 5%. REFERENCES

Figure  7.  Rutting parameter for base binder and GPMB binders.

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