the application of innovative silent joint systems   [6]。

APJs are successfully used in Switzerland even on heavy traffic motorways [5,20]。 New Swiss guidelines on APJ were released by the Swiss Guidelines of the Swiss Federal Road Office (ASTRA) in 2005 [26]。 In 1996 and 1997, 18 APJs were installed on seven dif- ferent test sites for in field performance observation using the four most commonly applied APJ systems in Switzerland。 Most of these APJ systems showed satisfactory performance。 Three joints were replaced in the 5-year monitoring period。 Cracking and debonding were the most common defects detected during visual inspections。 Lateral debonding in bridge parapet or footway zones happened in 70% of the investigated joints。 Recent researches done by EMPA showed that the performance of APJs could be improved signifi- cantly on the basis of material selection and on-site construction [27,28]。 APJs have been widely used in Germany since 1980s be- cause of the low cost of maintaining and cleaning as well as high travel comfort。 Federal Institute for Materials Research and Testing (BAM) has developed test criteria and methodologies for quality assurance as well as rules for the approval of   APJ。

A survey done by Umass Dartmouth showed that 25% of the Departments of transportation (DOTs) in USA used APJs。 Only  a few DOTs followed a specification or guideline for joint design pur- pose。 No DOT had any guidelines for evaluation of joint perfor- mance [11]。 Bramel and Dolan carried out a survey of 50 state departments of transportation in USA to assess the use and instal- lation guidelines [9,11]。 The survey data showed that APJs were used successfully in many states but not all。 Splitting in cold weather and track out in warm weather were the causes that leaded to a poor performance。 Chang and Lee reported a statistics of 7763 bridge joints in Indiana, USA [2]。 The percentage of APJ

108 L。 Mo et al。 / Construction and Building Materials 45 (2013)  106–114

was 3。8。 Field inspection indicated that APJ materials did not show satisfactory performance。 57。53% of the joints showed good perfor- mance, 21。23% for fair performance while 21。23% for a poor perfor- mance。 The main failure modes included shoving and rutting in hot weather and cracks in the shoulder areas in cold weather。 The cracks were related to large  bridge  movements  while  shoving and rutting was due to inferior quality of asphalt materials。 Chang and Lee also mentioned that polymer modified asphalt joints were the least favored joints to be used。 Suggestions for the improve- ment included increasing adhesion property, material testing be- fore installation, selection for the locations without heavy traffic and small bridge movements。 New Jersey Turnpike Authority re- ported good performance with APJs [12]。 The service life ranged from 7 to 10 years。 The advantages of the application of APJs in- cluded low cost, easy installation, low instance of snow plow dam- age and good watertightness。 The problems reported were that APJs did not have an effective method for sealing joints at curbs and parapets。 The joint material was softened in hot weather and cracked in cold weather。

The performance of APJs used at Sultan Ismail Bridge in Muar and Kota Bridge in Klang, Malaysia was reported to be unsatisfac- tory because the joint material cracked, flowed and rutted under wheel load。 The reasons for the unsatisfactory performance were attributed to the hot climate, steep gradient of the bridge and pres- ence of stationary and queuing traffic [29]。 In India, APJs are only used for bridge decks with asphalt concrete wearing courses。 The service life is expected to be about 10 years at an ambient temper- ature ranging from 5 °C to 50 °C [8]。 Yu and Li reported that asphalt bridge expansion joints when used in cold countries tended to crack within the first 2 years。 The use of polymer modified asphalt improved the joint performance。 Field application showed satisfac- tory performance after 7 years of trafficking at a lowest and highest monthly temperatures of —23 °C and 25 °C respectively [30]。 The application of APJs in Guihai freeway, Guangxi, China showed a satisfactory performance with the life span of 5–8 years。 The aging and deterioration of joint material resulted in frequent mainte- nance and repair [31]。