| The damages of airport pavements always occur in the joints of concrete pavement slabs,which is the main reason affecting their service life and restrict the development of aviation industry and national defense construction.At home and abroad,how to reduce the cutting of the pavement slab is a problem that has not been effectively solved.Crumb Rubber Concrete(CRC)has good resistance to cracking,impact and low elastic modulus,therefore,CRC is an ideal material for airport pavement.This paper proposes to use CRC to enlarge the size of the airport pavement slab,decrease the number of the cutting,extend the service life of the pavement,and reduce the maintenance cost during the service life.Thereby,this thesis has important engineering value and economic significance.Based on the existing theory of cement concrete airport pavement design,the calculation formula of the length of CRC airport pavement slab was deduced theoretically,improving the existing way for determining the length of concrete pavement slabs by empirical method.What's more,the thermal expansion properties of CRC was studied by CTE test,and thermal expansion coefficient was measured,determining the important parameters in the length design of CRC pavement slab.For the first time,the advantage of slab length of CRC airport pavement was analyzed qualitatively and quantitatively,and a breakthrough was realized that CRC large-size airport pavement slabs are applied to practical projects.The main research results were:(1)The allowable value of temperature stress(ft)was introduced into the slab design theory.The temperature stress coefficient(Bx),one of the key parameters,was analyzed,and the curve of the maximum value(Bx,max)with the slab thickness(h)was obtained,which laid the foundation for deriving the formula of the maximum slab length.After analysis and derivation,the formula Lmax=(2ft-E?hTgBx,max)/4rf for calculating the maximum slab length of the airport pavement was obtained,which was suitable for CRC.It could also be concluded that the maximum slab length was related to the properties of the concrete and the airport parameters.(2)As for the property of thermal expansion of CRC,the results are obtained by the CET test which is improved by multi-temperature linear fitting method.First,at natural temperature,the thermal expansion rate is proportional to temperature.Second,the rubber is a king of material with large thermal deformation,however,the addition of rubber does not increase the thermal expansion coefficient of the concrete.In spite of changing the particle size and the content of rubber,the measured values of CRC thermal expansion coefficient(9.77×10-6?14.07×10-6(/?))are in the range of the cement concrete(8×10-6?14×10-6(/?)).Third,the content and the particle size of rubber have a certain influence on the thermal expansion property of CRC.The thermal expansion coefficient of CRC of 60 mesh rubber is smaller than that of CRC of 20 mesh rubber by 7.0%?10.7%.While in the case of the same particle size,the thermal expansion coefficient of the CRC which the rubber content is 15%is smaller than that of the concrete without rubber and the CRC of 30%rubber content by 7.2%?13.6%and 22.2%?25.3%,respectively.(3)Based on the material properties of CRC and qualitative and quantitative analysis,the conclusion can be drawn that the maximum slab length of the CRC airport pavement can be expanded to 4?5 times of the ordinary concrete pavement slab(5?6m),which has great engineering significance.The theoretical analysis results were validated through the 200-meter CRC runway test at a southwest airport and the engineering practice of the CRC large-size pavement slab at a northwest airport.A program for slab length calculation is developed to design the CRC airport pavement,which is convenient for engineering applications and has practical promotion value. |
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