Effects of Loading Rate on Flexural-tension Properties and Uniaxial Compressive Strength of Micro-surfacing Mixture

The major objective of this research was to discuss the effects of loading rate on the flexural-tension properties and uniaxial compressive strength of micro-surfacing mixture using three-point bending test and uniaxial compressive test respectively. As a preventive maintenance surface treatment on asphalt pavement, micro-surfacing was formed on the basis of the ISSA recommendation of an optimum micro-surfacing design. Tests were conducted over a wide range of temperature to investigate the difference of properties from low loading rate to a relatively high loading rate. Three-point bending test was used to study the flexural strength, strain and modulus of micro-surfacing mixture, and uniaxial compressive test was carried out to obtain the relationship between strength and the loading rate as well as temperature. The experimental results showed that flexural strength at high loading rate was larger than that at low loading rate. The flexural strength difference between low and high loading rate enlarged when the temperature rose. The flexural strain at high loading rate increased compared with results of the low loading rate. Results of the flexural modulus revealed that micro-surfacing mixture exhibited better anti-cracking characteristic at low temperature when given a relatively low loading rate. Results of uniaxial compressive test revealed that the strength difference of micro-surfacing among different loading rates increased with the increase of temperature. The logarithm relationship between the strength and loading rate over a wide range of temperature was obtained to compare the experimental and predicted values, which resulting in a reasonable consistency.

Rutting Resistance of HMA Rehabilitated with Micro-Surfacing

The work presented here is a study on the measurement and prediction of the rutting resistance of previously rutted asphalt mixes rehabilitated with a layer of micro-surfacing manufactured with virgin and recycled aggregates at different stages of aging. The experimental procedure consisted of rutting tests on hot mix asphalt slabs already degraded and repaired with virgin and recycled micro-surfacing. Then, the evolution of the behavior of micro-surfacing cast on the hot mix asphalt slabs is observed according to loading cycles of the pavement rutting tester MLPC. Before rutting tests, slabs are subjected to 24 hours at 50&degC and aged for 2 days and 5 days at 85&degC in the oven. The results showed rutting percentages of 6.3% for hot mix asphalt slabs aged for 2 days and 7.2% for 5 days. These hot mix slabs repaired with virgin micro-surfacing have rutting percentage of about 9.2 % for 2 days of aging and 6.5% for 5 days of aging. While, the HMA slabs repaired with recycled micro-surfacing have rutting percentage of about 8.1% for 2 days of aging and 5.9% for 5 days of aging. These results allowed the development of a prediction model based essentially on three predictor variables including cycle number, rutting state and percentage of water in the micro-surfacing material. The developed model shows a strong correlation between the predicted rutting values and the rutting values measured with the MLPC rut tester. Thermal aging in oven has a positive impact on the resistance to permanent deformation of new asphalt mixes and those rehabilitated with micro-surfacing. The parameters of rutting state and contribution water are significant in the rutting prediction model, while the cycle number remains a non-significant parameter in the model but determinant.

A Protocol to Develop Phenolic Emulsifiers Used in Micro-surface by Control Technology

The phenolic emulsifiers used in emulsified asphalt of micro-surfacing, which was the most important tools in the road maintenance, were investigated by control technology. Many factors influencing this reaction were studied and three kinds of phenolic emulsifiers were prepared without catalyst in ethanol. The performance was researched that 2-（{2-[2-（2-Amino-ethylamino）-ethylamino]-ethyl-amino}-methyl）-4- nonyl-phenol （abbreviated as TETA） could be used in micro-surface. With addition of 0.5 % demulsifier, the mixing time was extended to 120 seconds obviously, and the cohesion torque （60 min） was 2.8 N＊m, which satisfied the opening traffic time shorter than 1 h. The wet track abrasion （6 d） was lower than 807 g/m2, with interracial modifier added, but the load wheel was increased with interfacial modifier increasing. When the TETA： demulsifier： interracial modifier =3：1：3, excellent performance was obtained and the experimental results met the International Slurry Surfacing Association （ISSA） standard. The synthesis process of this emulsifier is simple and the performance used in micro-surface was excellent, so this kind of emulsifier could have a better application future.