Narrow Results

It is required to develop new paving materials for pavements, such as footpaths, car parks, etc., in parks, having good landscape. Such paving materials have been already developed, but these do not have sufficient strength, abrasion resistance and frost resistance.

In this study, a new paving was examined material using cement, sand and granite soil. The mix proportion of this material tested was 2:4:4 of cement, sand and granite soil by mass. The maximum flexural and compressive strength were both obtained at a water content of 14% of the total mass, and the strength were several times larger than that of paving material on the market consisting of 10% of cement and 90% granite soil. The abrasion resistance was tested according to ASTM C 779, and this resistance was about four times greater than that of the paving material on the market.

The frost resistance was obtained high value compared with the concrete of 72% in water cement ratio by a new simple resisting test method for freezing and thawing using liquid nitrogen and warm water. It is considered that this new paving material is applicable to pavement for footpath, car park, etc.

Face slab concrete suffers from serious frost damage in the cold regions in China. How to improve the frost resistance of face slab concrete in cold regions is one of the important issues in concrete-faced rockfill dam (CFRD) design and construction. The results in this paper indicate that the frost resistance of concrete can be improved by adding fly ash, fiber, MgO and shrinkage-reducing admixtures (SRAs), and their efficiencies are in the following sequence: (fly ash $+$ fiber) $>$ fiber $>$ fly ash $>$ MgO $>$ SRA. The incorporation of 0.8kg/m³ polyvinyl alcohol (PVA) fiber and 20wt.% fly ash together enhances the compressive strength and tensile capacity of concrete by 6–7% at the late age, whereas the addition of 6wt.% MgO or 1wt.% SRA reduces the compressive strength and tensile capacity by about 4–10% at various ages. The $D_s$ of concrete added with fly ash, fiber, MgO and SRA is within the range of 2.619–2.796. The frost resistance of concrete correlates linearly with the air void parameters, pore structures and $D_s$. The utilization of fly ash and/or PVA fiber refines and optimizes the pore structure, thus increasing $D_s$ and improving the frost resistance. On the contrary, MgO and SRA in this study are less effective in refining the pores than PVA fiber and fly ash, thereby producing smaller $D_s$ and relatively weaker frost resistance.

This paper focuses on the hydraulic structure concrete of Songtun Reservoir in Jilin and its vulnerability to freeze-thaw damage that leads to a decline in structural durability. Through field sampling and testing, a relationship is established between freeze-thaw cycles of the hydraulic concrete in an actual environment and in the laboratory. The test results facilitate the prediction of the number of freeze-thaw cycles that the concrete will be exposed to in an actual environment, through laboratory tests of freeze-thaw cycle parameters.

This understanding would enable people to predict the number of cycles of concrete in actual engineering environment through laboratory test freeze-thaw cycle parameters and propose reasonable management operation plan.

Towards Tongtianhe Bridge located in high altitude alpine permafrost, the absence of the concrete mix data and other special circumstances, we do plenty of relevant research: concrete mix preliminary design, comparative study of the strength and frost resistance of putting two water reducer in concrete under standard conservation and outdoor conservation, and the pore structure of the incorporation of two water reducer paste are analyzed. The results shows that: the early strength type of polycarboxylic water reducer possesses good effect of low temperature, and it can better improve the internal pore structure of sample, increase frost resistance of concrete. In addition, under the special circumstances, we discuss the construction and maintenance technology of concrete in order to better serve the construction site.