الفهرس 
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Abstract
The aim of the current research is to apply the petrographic studies as new and successful technique to investigate the interaction between the aggregate and the asphalt binder in both unmodified and modified asphalt mixes. Also improving the performance of asphalt mixes through improving the asphalt binder by adding polyethylene either individually or combined with crumb rubber using different types of coarse aggregate (dolomitic limestone and basaltic), different types of fine aggregate (natural siliceous sand and crushed dolomitic limestone or basaltic sand) and limestone filler.
The previous researches from 1974 to 2011 studied the influence of petrography of rock on aggregate properties, influence of aggregate type on the interaction between the aggregate and the asphalt binder, influence of the aggregate type on properties of asphalt mixes, effect of modifier types on the asphalt binders properties, effect of asphalt binder type on asphalt mix properties and aggregate-asphalt binder interaction, were displayed.
Two types of aggregate rocks; sedimentary (dolomitic limestone from Ataqa quarry) and igneous (basaltic from Aswan quarry) and natural siliceous sand from Ismailia governorate and limestone filler, asphalt 60/70 penetration grade from El –Nasr refiner in Suez governorate, two types of polyethylene (high density polyethylene, HDPE and low density polyethylene, LDPE) and grinded crumb rubber (CR) from factories at 10th of Ramadan city were applied.
Geological setting of the two quarries was displayed. Petrographical investigation, geochemical, X-ray diffraction and differential thermal analyses of the different varieties of the rocks and the physical and mechanical studies of the aggregates were carried out. Geological and petrographical studies of the aggregate rocks indicated that the dolomitic limestone of Ataqa quarry is represented by three microfacies associations (Dolomitized micrite, sandy micrite and micrite), while the basaltic aggregate represented by metabasalts of fine grained massive and greenish grey to dark grey in color with porphyritic textures. The xencrysts of the porphyritic varieties are plagioclases and sometimes pyroxenes, hornblende, rare olivine and tremolite. Some alteration represented as pyroxene and hornblende are transformed into pale green fibrous actinolite / tremolite and chlorite.
Chemical analysis was carried out through the wet method analysis according to (Shapiro and Brannock, 1962). Physical and mechanical tests of the aggregates included: gradation, absorption, specific gravity, plasticity, flakiness and elongation index, abrasion, soundness and angularity number according to AASHTO and ASTM standard test methods.
Chemical analysis and X-Ray diffraction analysis of the dolomitic limestone aggregate indicated that the dolomitic limestone aggregate are differentiated into three different varieties (white variety of about 37 % with major constituent is calcite and the trace ones is quartz, grey variety of about 50 % with constituent is mainly dolomite and brownish variety of about 13 % with major constituent is dolomite and trace of calcite, quartz and hematite) by weight of head sample. While chemical analysis of studied basaltic samples showed presence of altered aggregate with minor amount and exhibits no significant variations in the average silica content, SiO2 (for fresh basalt equal to 50.8 % and altered basalt equal to 51.2 %). They are nearly similar in Al2O3 with values 17.7 and 18 % respectively. The Fe2O3 are 9 % and 8 % and the Na2O are 1.66 % and 2.55 % for fresh basalt and altered basalt respectively.
Differential thermal analysis of the two major varieties of these aggregates (white limestone and grey dolomitic limestone) indicated endothermic reaction by heat may be due to loss of some impurities such as argillaceous materials, some gypsum impurities or due to loss of CO2 at temperature range from 40 °C to 90 °C and loss of water of some clay minerals at temperature range from 90 °C to 110 °C. Fresh and altered basaltic aggregate indicated endothermic reaction by heat may be due to the loss of water of some impurities in the rock, loss of water in some clay minerals which were caused by alteration of the rock.
Physical and mechanical results of the two types of aggregates showed that the dolomitic limestone coarse aggregate exhibited greater values of absorption, high porosity and low disintegration values than those of basaltic aggregate. The basaltic aggregate has good cubical shape where the flakiness and the elongation indices values were zero and angularity number higher with value of 9 compared to dolomitic limestone aggregate value of 8.5. The specific gravity of basaltic aggregate was higher than that of dolomitic limestone Abrasion values of both types of aggregates indicated that the mechanical properties of the basaltic aggregate were stronger (16.8 and 14.7 %) than those of dolomitic limestone aggregate (22.7 and 24.2 %) for both size1 and size2, respectively.
Five modified asphalt binders were prepared by blending the base asphalt binder (control) with 3, 4, 5 and 6 % HDPE combined with 0, 1 or 2 % crumb rubber by weight of asphalt using. These binders were: (control + 3% HDPE + 0% CR, control+ 3% HDPE + 1% CR, control + 4% HDPE + 1 % CR, control + 5% HDPE + 2 % CR and control + 6 % HDPE + 0 % CR). These binders were used to prepare five modified asphalt mixes. Nine modified asphalt binders were also prepared using LDPE (4, 5 and 6 % with 0, 1 or 2 % crumb rubber) by weight of the asphalt by blending with the base asphalt binder (control). These binders were applied to prepare fifteen modified asphalt mixes. More than 180 asphalt mix specimens with different types and percents of asphalt binders were prepared according to Marshall test method (ASTM, D 1559).
Physical and mechanical tests of modified asphalt binders with LDPE with or without CR included: softening point, penetration, penetration temperature susceptibility and kinematic viscosity. While, the tests were carried out on asphalt mixes included: Marshall test method ASTM, D1559 and Wheel Tracking test method TRRL, 1976. Thin sections for the selected asphalt binders and mixes and also, slabs for the selected asphalt mixes were prepared to petrographical investigation.
The research program of the asphalt binders and mixes was divided into two main stages as follows:
Stage I: This stage was concerned with the asphalt binders and additives. The main objective of this stage was to investigate the effect of PE either individually or combined with CR on the asphalt binder properties.
Stage II: This stage was concerned with the properties of asphalt mixes with different types of binders, types of coarse and fine aggregates and limestone filler. This stage was carried out though two main phases:
Phase 1: The properties of unmodified mixes were investigated through this stage. It is divided into three sub- phases:
Phase 1.a: Using natural siliceous sand only as fine aggregate with dolomitic limestone aggregate and limestone filler.
Phase 1.b: Using natural siliceous sand and crushed dolomitic limestone sand as fine aggregate with dolomitic limestone as coarse aggregate and limestone filler.
Phase 1.c: Using natural siliceous sand and crushed basaltic sand as fine aggregate with basaltic as coarse aggregate and limestone filler.
Phase 2: The properties of modified mixes with different types of modified binders. It is divided into three sub- phases:
Phase 2.a: Using HDPE either individually or combined with CR using dolomitic limestone as coarse aggregate, natural siliceous sand and crushed dolomitic limestone sand as fine aggregate and limestone filler.
Phase 2.b: Using LDPE either individually or combined with CR using dolomitic limestone as coarse aggregate, natural siliceous sand only as fine aggregate and limestone filler.
Phase 2.c: Using the best modified LDPE either individually or combined with CR using dolomitic limestone or basaltic as coarse aggregate and limestone filler, natural siliceous sand and crushed dolomite limestone or basaltic sand as fine aggregate. Asphalt binders results indicated that all modified asphalt binders showed higher softening temperature than the unmodified binder by approximately, from 6 to 21°C for the binders P4R0 and P5R2, respectively. The reduction percents of penetration of modified asphalt binders ranged from 22.2 to 50.8 % for the binders P6R0 and P5R2 respectively compared to unmodified binder. The best improvement in PTS was obtained with the modified binder P4R2 (0.030) compared to the control binder (0.044). The increase percent in kinematic viscosity at 135 °C for the modified binders ranged from 240.2 to 570.1 % and the increase percents in kinematic viscosity at 150 °C for modified asphalt binders ranged from 126.3 to 559 % for binders P4R0 and P6R2, respectively compared to unmodified binder. When the temperature reached to 170°C, the lowest viscosity value for modified binders was 234 cSt while the highest viscosity value was 561 cSt for the binders P4R0 and P6R2, respectively. The properties of HDPE modified binders were not examined because their particles were difficult to be dissolved into the base asphalt causing blockage of the viscometer tube resulting in highly variable results.
Unmodified asphalt mixes (phase1; a, b and c) revealed that basaltic mix (CB) exhibited the highest Marshall stability and the highest Marshall stiffness with values of 14.800 kN and 5692 N/mm, respectively.
Modified asphalt mixes (phase2.a) indicated that all modified mixes with high density polyethylene using coarse dolomitic limestone aggregates (size1, size2), crushed dolomitic limestone and siliceous sand fine aggregate and limestone filler exhibited high coefficient of variations while unmodified mix exhibits low coefficient of variations for the three specimens at the same binder content. So, high density polyethylene was excluded from the rest of the research.
Modified mixes (phase2.b) indicated that all modified mixes exhibited increase in stability compared to unmodified (control) mix. No significant increases in stability values between the modified mixes are observed. The mix with 4% polyethylene and 2 % crumb rubber showed the highest stability value 12.300 KN with increment 21.4 % higher than the control mix.
Modified mixes (phase2.c) indicated that basaltic mixes exhibited Marshall stability and Marshall stiffness higher than dolomitic limestone mixes. The highest Marshall stability value was belonged to the basaltic mix with 4 % polyethylene and 2 % crumb rubber with value 21.900 kN with increasing percent of 48.0 % compared the unmodified basaltic mix. Modified dolomitic limestone mix with 4 % polyethylene and 2 % crumb rubber exhibited Marshall stability value of 18.600 KN with increasing percent of 51.6 %, compared the unmodified dolomitic limestone mix. The highest Marshall stiffness was belonged to the modified basaltic mix with 4 % polyethylene and 0 % crumb rubber with value 6948 N/mm. While, the lowest Marshall stiffness was belonged to the modified dolomitic limestone mix with 4 % LDPE and 2 % CR with value 5026 N/mm.
Rut resistance increased in all dolomitic limestone mixes rather than basaltic mixes with the same binder type. The dolomitic limestone mix with 4% polyethylene and 2 % crumb rubber was the best mix for rut resistance (with rut depth 1.68 mm) with increasing than the unmodified mix (withrut depth of 4.56 mm) by 2.7 times. Modified basaltic mix with 4% LDPE and 2 % CR exhibited the highest resistance against rutting among the basaltic modified mixes (with rut depth value 4.12 mm) and increasing by 2.01 times more than the unmodified mix (with rut depth 8.29 mm).