Applied Mechanics and Materials Vols. 405-408

Abstract: This article presents the recent advances in cold-recycled waste pavement materials with cement. It introduces various factors of influence on pavement performance, including cement content, gradation, reclaimed asphalt pavement (RAP), optimum moisture content (OMC), compaction density and curing conditions; explores main pavement performance, such as mechanical properties, shrinkage properties, fatigue properties and water stability properties of the cement cold-recycled mixture; summarizes the application experience of the cement cold-recycled mixture; pointes out the research topic of cement cold-recycled base at present, which includes properties of old pavement materials, the application of additives, the establishment of pavement performance evaluation indexes and systems, etc.

Abstract: In order to achieve a scientific selection of fly ash used in concrete, the influences of fly ash level on cementitious system rheological parameters, hydration degree and capillary adsorption properties were quantitative analyzed. The results show that Class I fly ash reduces the yield stress and plastic viscosity of cementitious system. The yield stress of system increases dramatically and the plastic viscosity of system reduces when Class III fly ash added. Rheological parameters of cementitious system change little when Class II fly ash added. The higher level fly ash uses the more CSH gel generates and the less Ca(OH)₂ crystals generates in cementitious system at early age (3d to 7d). High level fly ash increases the cement paste initial capillary adsorption amount but reduces the capillary absorption rate.

Abstract: Concrete cracks often appear in construction period and operation period of the canal lining. For analyzing the cause of these cracks, the factors which will cause cracks are classified based on the data collected. Also sensitivity analysis on these factors is carried out with 3D contact nonlinear finite element method. The result shows that, the factors which resulting in concrete cracks are temperature variation, humidity, uneven settlement of foundation, expansion deformation of foundation soil, external loads etc.; Joint-cutting should be done as soon as possible, expansive property of the foundation soil and construction quality of canal lining should be strictly controlled.

Abstract: For recognizing the characteristics of sandstone and mudstone which are the representative materials of soft rock, the site rolling test are conducted in Yutan reservoir as example. In this paper, the influence factors on the dry density are discussed such as: filling thickness, rolling frequency, and exciting force and so on. Surface settlement also is analyzed. According to the research, dam rolling parameters are advised. The results can provide the basis for dam design and construction and also can provide reference for similar material site rolling test research.

Abstract: The early age drying shrinkage of cement-based materials with same the same workability staring from the initial setting time was studied. Superplasticizers (SP) were used to get the same workability. The drying shrinkage of paste was measured by clock gauge, and CABR-NES deformation instrument was used to measure the shrinkage of concrete. Temperature probes were buried into both paste and concrete specimen cores to measure the temperature curve, and temperature deformation was considered into the early shrinkage. Results show the addition of SP increases much more shrinkage than the control group, and polycarboxylate SP increases more shrinkage than naphthalene SP. The different temperature peak time of different mixtures show that the addition of SP changes the hydration process of cement, and the shrinkage of cement-based materials after temperature compensation is bigger than the measured value in the first 6 hours, but the gap is not big.

Abstract: The chloride diffusion coefficients of different water-binder ratio high performance concrete (HPC) subjected to different one-way loads，freeze-thaw cycles and different standard curing ages were measured by electro-migration (RCM) tests and the results were analyzed. The test results indicate that with the increase of one-way load, its influence on the chloride permeability of different water-binder ratio HPC rises in the same proportion. The influence of the curing age on the chloride permeability of HPC will decrease with the reduction of the water-binder ratio of HPC. Under the same freeze-thaw cycle conditions, the relationships between chloride diffusion coefficients of different water-binder ratio HPC and curing ages are nearly suitable to power function.

Abstract: There is a wide range of saline soil distributied in China , 4.88% of the country's land can be used for salinization land.The salinization of soil in Tianjin area is 6614200 acres among them.The saline soil characteristics of collapsibillity, expansion, corrosion resistance are easy to make the roads salt cause expansion deformation, melting trap net crack and potholes, falling off and any other diseases, thus it is currently an urgent need to solve the problem of saline soil improved road in the salinization area of rural highway construction.Research group in the Green Meadow Depression saline soil application, applies the power plant fly ash resources based on the technology support analysis, obtains feasible technology application results.

Abstract: Silane impregnation effects on concrete sulfate attack resistance ability are systemic researched, through forming different cementitious material system and different water cement ratio mortar specimens, treating with silane impregnation and then curing to 14d age naturally, and doing sulfate solution wetting-drying test. Results shows that silane impregnation effect is poor when fly ash amount is large or water gel is relatively low. Through XRD microscopic, the improving sulfate attack resistance ability mechanisms are analyzed from aspect of cementations material hydration product; water-binder ratio effect on silane impregnation is explained by water absorption test.

Abstract: Abstract: Efficient water reducer plays a key role in the allocation of high performance concrete. The experiment uses four grades concrete of C15, C20, C25 and C30 by setting the different water-cement ratio. Each grade is divided into adding water reducing agent and not adding.To test the concrete strength of eight groups by testing compressive strength gains the relationship between the concrete strength added water reducer and water-cement ratio. Through processing experimental data, to get the role water reducer played in conditions of different water cement ratio. What’s more, to gain the corresponding quantitative calculation formula by exerting the regression analysis.

Abstract: Slag powder can improve concrete compression strength and durability owing to the activity of volcano ash and powder filling effect when replacing cement as active mineral admixture. Test results show that the 28-day strength can reach to 74MPa if slag powder with the fineness 810 m²/kg is used to replace 60% cement when making C40 concrete. And at 4.0MPa water pressure, the seepage height can be only 12mm, the electric flux in 6 hours can drop by 72% than that didn't use slag powder, the ability of freeze-thaw cycle can reach F350. But attention should be paid to the grinding process impact on the economy of the massive practical application process.