| At present,basalt is usually recommended for the anti slip surface of highway asphalt pavement in our country.However,the distribution of basalt and other hard stones is uneven in China.The emphasis on the use of basalt will lead to a substantial increase in the cost of construction and unsustainable resources.Compared with hard rock such as basalt,the distribution of limestone is relatively uniform and the price is low.Therefore,the key technology of limestone aggregates used in anti slide surface of asphalt pavement was systematically studied in this paper.The main research contents include the development of asphalt pavement skid resistance tester,the study on the testing method and technical indexes of anti sliding performance of coarse aggregates,the study on influence factors and evaluation indexes of asphalt mixture anti sliding performance and the technical scheme of high quality limestone aggregates used in asphalt pavement anti slide surface.Based on the investigation of the measurement method of the anti slip performance of aggregates and asphalt mixture,the paper developed a testing instrument for the friction characteristics of aggregates and asphalt mixture.This tester is a miniature straight test system,which simulates the friction force of dynamic driving in the case of slippage rate 100% and automatically measures the dynamic friction coefficient in the process of road surface material friction.Meanwhile,the variation law of anti sliding performance with time is real-time displayed and the service life of asphalt pavement based on skid resistance is predicted.According to the tester,the comprehensive index of anti slide resistant N(t),D?,the skid resistance attenuation rate,anti sliding wear life and other indicators were put forward and its applicability was studied by bivariate correlation analysis.Research showed that: 1)the polishing value of aggregates,anti slide resistant N(t)index,D? and the anti sliding wear life were significantly correlation.These indicators were consistent to evaluate the anti sliding wear resistance of aggregates,so these indicators can be used to evaluate and select the anti slip performance of aggregates.2)The dynamic friction coefficient D?(time=4h)of the asphalt mixture and the anti sliding life(D? =0.4)had significant linear correlation with all kinds of the anti-sliding and wear-resistant index of the aggregates,which can be used as the evaluation indexes of asphalt mixture anti-sliding and wear-resistance performance.3)it was determined that the critical slip resistance screening value of the aggregates,D? was 0.46.More than twenty kinds of aggregates,sucn as limestone,basalt in Yunnan and basalt,granite and diabase in other areas,were tested.It was studied that the correlation between the performance index of coarse aggregates and its anti-sliding and wear-resistance performance was studied.The correlation between mineral composition of limestone and aggregate characteristics was also studied.The research showed that: 1)there was a good linear correlation between the crushing value,abrasion value,polishing value and the mixed proportion.Under the condition that the crushing value,wear value and polished value of a single aggregate are known,the crushing value,the wear value and the polished value of the mixed aggregate with different ratios can be predicted;2)The principle of selecting limestone by mineral composition was identified.First,select the aggregate which contains much dolomite and quartz,followed by the selection of relatively small amount of calcite.And clay mineral content should be less,even for 0.Based on the "aggregate / asphalt mixture friction tester",this paper systematically studies the influence of aggregate characteristics,aggregate mix proportion,mixture type and gradation,load,temperature and other factors on the performance of asphalt pavement.The results showed that: 1)the anti sliding performance of the optimal limestone is much higher than that of the common limestone.The anti sliding life of epitaxial limestone which has the best anti sliding performance is about 2 times that of ordinary limestone,and it can reach about 59% of basalt.2)For SMA-13,only add S10 or S12 basalt coarse aggregates into the limestone,its long-term anti sliding performance would be greatly improved,and the anti sliding life can be increased by about 50%;It can basically reach the sliding life of pure basalt by mixing 2 kinds of basalt coarse aggregate;3)For AC-13,the long-term anti sliding performance can be also greatly improved by mixing coarse and fine basalt aggregates with limestone,and anti sliding life can be increased by more than 50%;If the two basalt coarse aggregates are added,the sliding life of pure basalt can be basically achieved;It is worth noting that,for SMA-13,only the S10 or S12 kinds of basalt coarse aggregates are mixed with the limestone,which can reach the sliding life of pure basalt of AC-13;4)The coarser the gradation,the better the anti sliding performance.By adjusting the gradation,the anti sliding life of SMA-13 can be increased by 48%,and the anti sliding life of AC-13 can be increased by 18%.Under the same blending scheme,the anti sliding life of SMA-13 is longer than that of AC-13,and the anti sliding life of SMA-13 can be increased by 50%~200%.In this paper,the equivalent relation between the loading time of the friction characteristic tester and the actual traffic was studied by sampling in the actual operating highway.The prediction method of asphalt pavement anti sliding life was put forward,and the dynamic friction coefficient D? of the tester was 0.42.These were estimated that the anti sliding life of the fifteen standard limestone test road is about 5.4 years and the anti sliding life of the basalt mixed test road is about 9.0 years according to the plan B.The paper selected fifteen standard and epitaxial limestone aggregates to pave the limestone test road and the basalt mixed test road.The test road was divided into 4 technical programs,total 6km.The structure depth of test road TD(mm)was more than 0.80,and the lateral force coefficient SFC60 was greater than 54,which meet the requirements of the design documents and specifications.It was estimated that the economic benefit of the test road with high quality limestone paving was remarkable.On this basis,these were put forward that the limestone optimization and the technical process and design method of its application in anti slide surface of asphalt pavement,and a full set of technologies for high quality limestone used on the anti slip surface of expressway asphalt pavement were formed. |
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