Wu Shaopeng

An improvement in electrical properties of asphalt concrete

Materials such as Koch AH—70, basalt aggregate, limestone powder and graphite particles were used to prepare conductive asphalt concrete, which is a new type of multifunctional concrete. The mix proportion by weight was shown as follows. Fine aggregates (2.36–4.75 mm): fine aggregates (<2.36mm): lime-stone powder: asphalt=120∶240∶14∶30. The content of added graphite particles ranged from 0% to 20% (by the weight of asphalt concrete). A conductive asphalt concrete with a resistivity around 10–103Ω·m was obtained. Special attention was paid to the effects of graphite content, graphite physical-chemical properties, asphalt content and temperature on the resistivity. Furthermore, an attempt was made to develop an electrically conductive model for asphalt concrete.

Effects of Fibre Additive on the High Temperature Property of Asphalt Binder

Polyester fibre and floc xylogen fibre were used to prepare fibre-asphalt binder. An SHRP’ s dynamic shear rheometer (DSR) was employed to investigate the rheology characteristics of fibre-asphalt binder, and the flow resistance of binder was revealed by combining the rutting parameter, G * / sinδ. The results indicate that both kinds of fibres remarkably improved the high temperature performance of asphalt binder. At the same time, the reinforcement mechanism of the fibres in the asphalt binder was also analyzed.

Optimization of blended mortars using steel slag sand

A new kind of mortar made of ground granulated blast-furnace slag (GGBFS), gypsum, clinker and steel slag sand (<4.75 mm) was developed. The ratio of steel slag sand to GGBFS was 1:1 and the amount of gypsum was 4% by weight while the dosage of clinker ranged from 0% to 24%. The optimization formulation of such mortar was studied. The content of steel slag sand should be less than 50% according to the volume stability of blended mortar, and the dosage of clinker is about 10% based on the strength development. Besides strength, the hydration heat, pore structure and micro pattern of blended mortar were also determined. The experimental results show the application of steel slag sand may reduce the dosage of cement clinker and increase the content of industrial waste product such as GGBFS, and the clinker is also a better admixture for blended mortar using steel slag sand.

Effects of conductive fillers on temperature distribution of asphalt pavements

The sun provides a cheap and abundant source of clean and renewable energy. Solar cells have been used to capture this energy and generate electricity. A more useful form of the solar cell would be asphalt pavements, which get heated up by solar radiation. Graphite powders are utilized as thermal conductive fillers to make an asphalt collector conductive so as to improve the efficiency of the asphalt collector. Accounting for the important application conditions and evaluating the effects of the heat conductive materials and the solar energy absorbability of the conductive asphalt collector, a finite element model has been developed to predict temperature distributions in the conductive asphalt solar collector. In this study, an experimental validation exercise was conducted using the measured data taken from full-depth asphalt slabs. Validation results showed that the model can satisfactorily predict the temperature distributions in asphalt concrete slabs. The optimal depth is 25–50 mm for placing pipes that serve as the heat exchanger. Meanwhile, the effect of the surroundings on the solar energy potential of the asphalt collector was noticeable.

Percolation Model of Graphite-modified Asphalt Concrete

The addition of graphite powder in conventional asphalt mixture can produced asphalt concrete with excellent electrical performance. Percolation theory was employed to discuss the relation between the conductivity and graphite content of graphite-modified asphalt concrete. It was found that the results of percolation model are consistent with experimental values. The percolation threshold of graphite-modified asphalt concrete is 10.94% graphite content account for the total volume of the binder phase consisting of asphalt and graphite. The critical exponent is 3.16, beyond the range of 1.6–2.1 for the standard lattice continuous percolation problem. Its reason is that the tunnel conduction mechanism originates near the critical percent content, which causes this system to be not universal. Tunnel mechanism is demonstrated by the nonlinear voltage-current characteristic near percolation threshold. The percolation model is able to well predict the formation and development of conductive network in graphite-modified asphalt concrete.

Design and preparation of steel slag SMA

On the basis of the characteristics of high rigidity and excellent friction resistance, a new kind of steel slag SMA (stone matrix asphalt) concrete was designed and prepared. The main processes include aggregate gradation, performance analysis of steel slag before and after aging, preparation methods and properties test of steel slag SMA. The experimental results indicate that the index of steel slags activation is less than 1 percent, the dynamic stability is 5699 times/mm, and both the residual stability and ratio of frozen splitting strength are more than 80 percent; the friction factor and structure depth are 67.1% and 0.7 mm respectively. These results show the steel slag SMA is superior to the common asphalt concrete and SMA that uses common aggregate.

Reducing the compaction segregation of hot mix asphalt

This paper presented the methods of reducing the compaction segregation of asphalt layer by improving the operating characteristics of roller and paver. The fit formula, which expresses the compaction rule of the paving layer after passing different rolling passes of the steel wheel roller, was also put forward. The measured results of test road show that when some technical methods are adopted, the compaction segregation can be controlled.

Rutting Resistance of Asphalt Overlay with Multilayer Wheel Tracking Test

The rutting resistance of multilayer asphalt overlay was researched by using laboratory wheel tracking test. The effects of loading level and test temperature on rutting resistance of asphalt overlay structure were evaluated by means of multilayer specimens. In comparison with multilayer tests, standard specimens of various layers were also conducted to evaluate the rutting resistance. Experimental results indicated that the test temperature and applied load have a significant effect on rutting resistance of asphalt concrete. Higher test temperature and heavier applied load resulted in higher rut depths. In addition, the mutilayer wheel tracking test has been demonstrated to be a more reasonable solution in evaluation on rutting resistance of asphatt pavement structure beasuse it reflects the cumulative permanent deformation in all of asphalt layers.

Microstructure of steel fiber reinforced polymer-cement-based composites

Mercury intrusion porosimetry was used to measure the pore structure of steel fiber reinforced polymer-cement-based composite. The results indicate that the large pore volume decreases by 57.8%–51.2% and by 87.1%–88% with the addition of steel fibers and polymers respectively. When both steel fibers and polymers are simultaneously added, the large pore volume decreases by 88.3%–90.1%. As a surface active material, polymer has a favorable water-reduced and forming-film effect, which is contributed to the decrease of the thickness of water film and the improvement of the conglutination between the fibers and the matrix. Polymers could form a microstructure network. This network structure and the bone structure of cement hydration products penetrate each other and thus the interpenetrating network with sticky aggregate and steel fiber inside forms.

The properties of road base course materials of granular soils stabilized by AGS granular soil stabilizing cement

The properties of road base course materials of granular soils stabilized by AGS granular soil stabilizing cement[1] were studied. The AGS cement has an expansibility to a certain degree, so the dry shrinkage of AGS cement paste and AGS stabilized granular is much lower than that of Portland slag cement. AGS has a good suitability to granular soils. Granular soils stabilized by AGS have a much higher strength than that of soils stabilized by P S cement. The same strength can be reached with 20% reduction of cement dosage for AGS cement. And their elastic and resilient modulus are similar, but the former has a much higher tensile splitting strength, so the AGS stabilized granular has a much better anti-cracking performance than that of the P S stabilized granular. The reduced value of the strength and the density with the retard time for the granular soils stabilized by AGS is lower than that for P S cement.