The Research On GTM Mix Design Method

Currently, the asphalt pavement was adopted extensively with the advantage of itsoneself, which was eighty percent of the high-grade highway that have been open to trafficalready. Along with the development of the national economy, in recent years, lots ofdilapidation forms such as rutting become more acute because of the increasing of traffic'svolume and loading capacity of vehicle, the application of the super-single tire, theoverloading seriously and channeling running. Shortcomings of the current Marshall MixDesign Method appeared rapidly. However, the procedure of gyratory compacting is near to thefield condition of compaction. Taking the causes of deformation into account, you mustimprove mix's shear strength if you want to remove rutting. GTM is the mix test and designmethod that can improve mix's shear strength.GTM Mix Design Method is being introduced into China now. However, it is difficult topopularize in most design and construction unit in short date because the GTM is moreexpensive. Therefore, the research carried on mix design method is necessary by which we canbuild up the relations between GTM Mix Design Method and Marshall Mix Design Methodand put forward criterion when the asphalt pavement is constructing in order to make theadvantage of GTM Mix Design Method spread. The asphalt pavement's dilapidation isdecreased and performance is improved consumedly using GTM Mix Design Method. Thiskind of design method has important realistic and economic meaning because it can prolongpavement's life and reduce the cost of project.Aimed at analyzing the limitations of the Marshall Mix Design Method in the high-gradehighway in China, the text put forward the GTM Mix Design Method and analyze therelations between strength and composition such as asphalt, mineral stone and gradation, pointout performances for the mixture which was constructed. This text mainly emphasizes on thegradation design for the four types of gradation using GTM and Marshall Mix Design Methodand examination the performances of mixture. Gradation B with good performances is the bestand is applied to actual construction. This topic draws several conclusions by experimentalanalysis and comparison.(1) The GTM mix design method that apply sciences reason logically and adoptprinciple of stress and strain to carry on the design. The specimen was compacted by rollingand revolving under the certain pressure while experiment through which the function stressedon the specimen is similar to the function stressed on the surface of pavement by theautomobile tire. GTM mix design method not only can be used for gradation constitute design,at the same time, but also can be carried on selecting the best gradation.(2) The contact is good close between GTM method and actual circumstance of highways.While making use of the GTM design bituminous concrete, the actual load condition affectedon the pavement is fully considered and different design's press is choosed according to thecircumstance of each highway, as a result, the bituminous concrete designed by GTM methodis more reasonable.(3) To verify the optimum bituminous fraction in the grading constitution design, theGTM Mix Design Method depends on the index GSI and GSF only, thus avoiding the deviationof void rate, stability and flowing etc, when they are selected more times with larger disperse inthe Marshall Mix Design Method.(4) The bituminous concrete using GTM Mix Design Method considered the factor whichwill create rutting. From the point of theories analysis, there are two major reasons, one isbecause the wheel load's repeated compaction make the bituminous pavement dense gradually;the other is the high temperature strength of the bituminous mixture can not resist the repeatedaction of the wheel load, the bituminous mixture under the wheel create shear deformation andis pressed to its two sides, the two sides of bituminous concrete surface swell out and appearlateral flow which produce rutting. The GTM Mix Design Method considered these problemswell. The adoptive perpendicularity pressure is the real pressure of the highway's automobiletire applying to the pavement, and the sample is compacted to a balance condition at thispressure, so can not produce the first deformation. At the same time, the design bituminousmixture using GTM method has the needed shear strength which is the wheel load required, socan not produce the lateral movement because of the shear strength shortage.(5) Marshall method while designing the bituminous mixture consider the volume indexsuch as the void rate, the saturation degree etc, while the GTM method did not use such volumeindex to verify the bituminous fraction. But from the index that the GTM method can assurethe bituminous quantity, it can see that the compaction stable value and the volume indexcontain certain relation. When bituminous mixture is compacted excessively or is filledmore bitumen, the compaction stable value become larger, and starting to appear plasticdeformation.(6) From the sample density of the two kinds of compaction method, the relationsbetween them are not a constant, needing to carry on test to the specific grading in order to putforward the engineering control index. In this topic for study the recommendation standarddensity of the construction adoption is" the equivalent density", that is 1.02 times of the densityof Marshall sample with the optimum bitumen and aggregate ratio ( relevant GTM sampledensity), and the compactness is 98% of the standard density.(7) To verify the constitution of bituminous concrete with the same grading using the twokinds of compactive methods, their road performance are quite different. The anti-permanentdeformation ability in high temperature, anti-water failure ability and anti-water infiltrationability of the bituminous concrete grading using GTM method are all higher than that usingMarshall method, and the anti-crack ability in low temperature and surface anti-slip ability ofthe bituminous concrete grading using GTM method are all lower than that using Marshallmethod. Investigate its reasons, the void rate of bituminous concrete grading using GTMmethod is smaller, whereas it is the main factor influencing the anti-water failure, anti-waterinfiltration and surface structure coefficient ability of bituminous mixture. The void rate is big,the anti-water failure, the anti-water infiltration ability of bituminous mixture will reduce,contrary, its anti-slip ability increase. The amount of bitumen affects the low-temperature andhigh-temperature performance of bituminous mixture greatly, usually bituminous mixture of alarger bituminous fraction has higher low-temperature performance and lower high-temperature performance.(8) The construction of test road show that the construction technology of therecommendation bituminous concrete grading with GTM method and Marshall method is same,if the compactive combination pattern is reasonable, they all can obtain the requirecompactness and on–site void rate. On the same time, using GTM density control theconstruction quality reduce the phenomenon that the compactness is larger than 100%, andavoid pursuing the levelness with insufficient real compactness.