Materials and Design 66 (2015) 5159Contents lists available at ScienceDirect
Materials and Design
journal homepage: www.elsevier .com/locate /matdesLaboratory evaluation on performance of diatomite and glass fibercompound modified asphalt mixturehttp://dx.doi.org/10.1016/j.matdes.2014.10.0330261-3069/ 2014 Elsevier Ltd. All rights reserved.
Corresponding author at: No. 199, South Guangming Street, City of Handan,Hebei Province, China. Tel.: +86 15383202570.
E-mail addresses: email@example.com, firstname.lastname@example.org (L. Li).Qinglin Guo a, Lili Li b,, Yongchun Cheng c, Yubo Jiao c, Chun Xu ca School of Civil Engineering, Hebei University of Engineering, Handan, Hebei 056038, ChinabDepartment of Students Affairs, Hebei University of Engineering, Handan, Hebei 056038, ChinacCollege of Transportation, Jilin University, Changchun, Jilin 130025, China
a r t i c l e i n f oArticle history:Received 3 August 2014Accepted 14 October 2014Available online 23 October 2014
Keywords:DiatomiteGlass fiberStatistical regression analysisAsphalt mixturea b s t r a c t
The purpose of this paper is to investigate the compound effects of diatomite and glass fiber on asphaltmixture. The diatomite and glass fiber compound modified asphalt mixture (DGFMAM) was prepared inlaboratory. Performances of DGFMAM were investigated by experimental method. Wheel tracking test,low temperature indirect tensile test, indirect tensile fatigue test (ITFT) and indirect tensile stiffness mod-ulus test (ITSM) were carried out. The statistical analysis of variance (ANOVA) method and statisticalregression method were used to evaluate the effects of diatomite and glass fiber on properties of asphaltmixture. Results indicate that diatomite and glass fiber improve the rutting resistance and fatigue prop-erties of control asphalt mixture. Diatomite has a significant effect on the stiffness modulus of asphaltmixture. Disadvantage of diatomite on low temperature deformation property of asphalt mixture issolved by glass fiber. DGFMAM has better travelling performances than the control mixture. It will pro-vide a reference for the design of compound modified asphalt mixture.
2014 Elsevier Ltd. All rights reserved.1. Introduction
Asphalt pavement has been widely used in the world due to itsgood performance. It is constructed using hot asphalt mixture. Hotasphalt mixture is a typical viscoelastic material. This will result inrutting deformation at high temperature in summer and pavementcracking at low temperature in winter. And then the rutting defor-mation and cracks in pavement will affect the travelling perfor-mance of vehicles seriously [1,2]. Thereby, researchers in manycountries have been trying to modify the asphalt mixture in orderto solve these problems as much as possible.
Diatomite is a material which has light weight, high porosityand good insulation property, its reserve is huge and the cost islow. It has been used to modify asphalt mixture as a result of thesecharacteristics in recent years. And the properties of asphalt binderand mixture modified by diatomite were studied. Bao  and Xu investigated the basic properties of diatomite modified asphaltbinder. The results suggest that the penetration and ductilitydecrease with the increase of diatomite, and the softening temper-ature of asphalt binder is increased by diatomite. Cong et al. evaluated the effect of diatomite on the viscosity of asphalt, theresults indicate that the viscosity of modified binder increases withthe increase of diatomite, the diatomite modified asphalt mixtureis susceptible to low temperature cracking. Zhu et al.  evaluatedthe insulation property and pavement performances of diatomitemodified asphalt mixture in laboratory. The results show that diat-omite not only improves the rutting resistance significantly butalso reduces the thermal conductivity coefficient of asphalt mix-ture. And the bending stiffness modulus of diatomite modifiedasphalt binder is less than that of the control binder at low temper-ature. Tan et al.  studied the interaction between diatomite andasphalt, the fracture property of modified asphalt mixture at lowtemperature. The results indicate that there is no chemical reactionoccurred between diatomite and asphalt, the fracture temperatureof modified mixture is lower than that of the control mixture. Chenet al.  also studied the insulation performance of asphalt mix-ture modified by diatomite, the results suggest that the thermalconductivity of mixture is reduced by diatomite. Diatomite is help-ful for the surface temperature reducing of roadbed in permafrostregion. Li et al.  also suggested that the bending strength andbending tensile strain of diatomite modified asphalt mixture areless than that of the control mixture at low temperature. Therefore,it can be seen that the high temperature stability and thermalphysical property of asphalt mixture are improved by diatomite,but the low temperature deformation ability of diatomite modifiedasphalt mixture is declined. The pavement which is constructed
Table 2Properties of diatomite.
Property Color PH Specific gravity (g/cm3) Bulk density (g/cm3)
Value Orange 78 2.12.3 0.350.42
Table 3Particles size distribution of diatomite.
Particle size (lm) 40
Value (%) 62 27 4.4 2.1 1.4
52 Q. Guo et al. /Materials and Design 66 (2015) 5159using asphalt mixture modified by diatomite is more susceptible tolow temperature cracking than the common pavement. However,the asphalt pavement in seasonal frozen regions such as Jilin prov-ince of China has a severe need on low temperature property ofasphalt mixture. The asphalt pavement in these regions must havegood high temperature stability and anti-crack performance at lowtemperature simultaneously. Therefore, it is needed to improve thelow temperature deformation property of diatomite modifiedasphalt mixture.
Glass fiber is a kind of inorganic fiber with high tensile strength.In the previous studies, glass fiber has been used to modify asphaltmixture successfully in order to improve the deformation ability.Aysar et al.  investigated the fracture behavior of asphalt con-crete with glass fiber. It shows that the glass fiber modified mix-ture has a potential resistance to against crack initiation. Thiswill be beneficial to preventing pavement cracks at low tempera-ture. Abtahi et al.  thought that glass fiber improves thestrength, fatigue property and ductility of asphalt mixture. Fu investigated the properties of asphalt mixture modified byglass fiber. The result suggests that glass fiber has no significantinfluence on the bending strength, but the bending failure strainincreases with the increase of glass fiber. Glass fiber improvesthe property of rutting resistance significantly. Besides, Mahrezet al.  indicated that the use of glass fiber in pavement mayincrease the cost of construction, but this will reduce the cost ofmaintenance. It can be found that glass fiber not only improvesthe ductility, anti-cracking property and fatigue property of asphaltmixture but also seems to be economic for the modification of mix-ture. In summary, some effects of diatomite and glass fiber onasphalt mixture are similar, and the others are different. The down-side of one modifier on the mixture can be changed by anothermodifier. Effects of diatomite and glass fiber on asphalt mixturehave been investigated in previous researches separately. The com-pound modified effects of diatomite and glass fiber are unknown. Ifdiatomite and glass fiber are used to modify asphalt mixture simul-taneously, a new kind of asphalt mixture which has good ruttingresistance and low temperature performance may be obtained.Furthermore, it will provide a technology reference for the designof mixture.
In this paper, a preparation process of diatomite and glass fibercompound modified asphalt mixture (DGFMAM) was discussed.The control asphalt was modified by diatomite. Then the modifiedasphalt and glass fiber were used to prepare DGFMAM. The speci-mens of DGFMAM for experiments were prepared in laboratory.Effects of diatomite and glass fiber on the performances of asphaltmixture were tested and evaluated.
2. Materials and preparation method
In this study, the heavy traffic asphalt AH-90 was used forexperiments. Its basic properties are listed in Table 1. Diatomiteis the calcined product, and its physical properties are presentedin Table 2. As shown in Table 3, the particle size distribution ofdiatomite was investigated according to the Standard ASTMD4464-10. Glass fiber is the short fiber from Taishan FiberglassTable 1Properties of the control asphalt.
Property Value Standard
Penetration (25 C, 0.1 mm) 86 ASTM-D5Ductility (15 C, cm) 168.5 ASTM-D113Softening point (C) 44.5 ASTM-D36Penetration index 1.416 Inc., Shandong Province, China. And its properties are presentedin Table 4. Silane coupling agent was used to process the glass fiberin order to improve the bonding property of interface. The aggre-gates are limestone. As presented in Table 5, apparent specificgravities of aggregate were tested according to the StandardsASTM:C127 and ASTM:C128. The selected gradation of asphaltmixture is shown in Fig. 1.
2.2. Preparation method of DGFMAM
The control asphalt was modified by diatomite at first. The pro-cessing method has significant impact on the properties of modi-fied asphalt. A low mixing speed is difficult to ensure uniformdistribution of diatomite in asphalt. Therefore, the equipment witha speed of 600 r/min was used to blend. The specific processes ofasphalt modification are as follows.
First, diatomite and the control asphalt were weighed with therequired quality, and they were placed in the oven at 135 C for 4 h.Second, diatomite and the control asphalt were taken out from theoven. Diatomite was added into the control asphalt. The diatomiteand asphalt were mixed by the blending equipment with a speed of600 r/min.
Based on the results of repeated test, it was found that theblending time should be set for 15 min. Besides, diatomite particleswill sink in asphalt as a result of the weight of particle when themodified asphalt is placed for a long time. So a second blendingshould be conducted when the modified asphalt was used forexperiment again.
The preparation procedures of DGFMAM are as follows.
1. Aggregates were mixed in the mixing oven at 170 C. And thenthe diatomite modified asphalt was added, they were mixedabout 90s in order to make aggregate surface uniformly coatedby asphalt mastic, then the diatomite modified asphalt mixturewas obtained.
2. Glass fiber was added into the diatomite modified asphalt mix-ture which had been obtained in previous step. They weremixed about 90s, and then the mineral filler was added. Thediatomite and glass fiber compound modified asphalt mixturewere obtained after a second mix within 90s. Distributionstatus of glass fiber in asphalt mixture has a direct impact onproperties. So the mixing time should be increasedTable 4Physical properties of glass fiber.
Property Value Standard
Length (mm) 12 GB/T 14336 Specific gravity (g/cm3) 2.5 GB/T 14335 Color White Melting temperature (C) >1500 ASTM-D7138Tensile strength (MPa) 31003400 ASTM-D5035Ultimate tensile strain (%) 3.33.6 ASTM-D5035
Table 5Apparent specific gravities of aggregate.
Sieve size (mm) 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075
Apparent specific gravity (g/cm3) 2.817 2.704 2.821 2.655 2.689 2.645 2.652 2.710 2.682
Fig. 1. Selected gradation in experiment.
Q. Guo et al. /Materials and Design 66 (2015) 5159 53appropriately if the dispersion of fiber is not good. And all theprocessing time should not exceed 6 min in order to preventasphalt aging.
The diatomite and glass fiber content are percentages by thetotal weight of control asphalt mixture in this paper. From thecost-effective viewpoint of modification on mixture, three contents(0.1%, 0.2% and 0.3%) of diatomite and glass fiber were selected forexperiments. Specimens were made in laboratory. According to theStandard JTG E20-2011 , the Marshall specimens were double-side struck for 75 times. And then the optimum asphalt contentwas determined on the basis of Marshall results, it is 4.8% for theunmodified mixture. The physical properties of Marshall specimenwere tested according to the Standard T0706 of JTG E20-2011, andthe average values are listed in Table 6.3. Experimental procedures
3.1. Wheel tracking test
Wheel tracking test is considered an effective method for theevaluation of high-temperature rutting resistance. It has been usedin previous studies frequently . So this method wasemployed to evaluate the rutting resistance property of DGFMAMTable 6Physical properties of Marshall specimen.
Modifiers content (%) Apparent specific gravity (g/cm3) Voids content (%)
(0, 0) 2.48 3.8(0.1, 0.1) 2.48 3.2(0.1, 0.2)a 2.47 3.4(0.1, 0.3) 2.46 3.1(0.2, 0.1) 2.47 3.6(0.2, 0.2) 2.46 2.9(0.2, 0.3) 2.47 4.0(0.3, 0.1) 2.45 4.1(0.3, 0.2) 2.45 4.1(0.3, 0.3) 2.46 3.7
a Note: the content (0.1, 0.2) means that the content of glass fiber is 0.1% and thecontent of diatomite is 0.2%.in this paper. The slab specimens were compacted by rollingcompactor for 24 times, its size is 300 mm 300 mm 50 mm.The test was conducted at 60 C. Stroke of test wheel is 23 cm.The wheel running speed is 42 times/min. The load is appliedon the slab through a rubber wheel 50 mm in width, its value is0.7 MPa. Specimens were placed in the oven at 60 C for 6 h beforetest. Rutting depth was recorded during the test. Dynamic stability(DS) and permanent deformation were used to evaluate the hightemperature stability of DGFMAM. DS is calculated by the follow-ing equation.
DS t2 t1 Nd2 d1
C1 C2 1
where DS is Dynamic stability, times /mm; d2 is the deformation attime t2 (t2 is 60 min), mm, it is the permanent deformation gener-ally; d1 is the deformation at time t1 (t1 is 45 min), mm; C1 is thecorrection factor of equipment, it is 1.0 for this equipment; C2 isthe correction factor of specimen, it is 1.0 for the specimen in thistest; N is the running speed of test wheel, it is 42 times/min.
3.2. Low temperature indirect tensile test
The low temperature tensile property of asphalt mixture is animportant indicator for the evaluation of pavement anti-crackingability. There are three methods which are often used to investi-gate the low temperature performance of asphalt mixture. Theyare three-point bending method, indirect tensile method andfour-point bending method . In general, diatomite andglass fiber distribute uniformly in mixture. For bending test, thetensile strain and fracture strength of mid-span are investigated,but there are few diatomite and...