As the raw material of concrete, sand is a natural resource formed in the long-term process of nature, and the more it is used, the less it is used. Although we have been used to the application of river sand, it will soon become history, and the application of machine-made sand will soon come. But now, it is in a stage of green and yellow, the variety of sand is miscellaneous, the index is not reasonable and fluctuates greatly, which affects the quality of concrete.

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砂子質(zhì)量波動，主要是顆粒形狀與級配不合理導(dǎo)致的比表面積、孔隙率、流變性的變化。混凝土中的水，一是用于膠材水化產(chǎn)生強度、二是對固體材料表面潤濕并填充其空隙使之產(chǎn)生流變方便施工。水在混凝土中的存在方式有三種：結(jié)合水、吸附水、自由水。

The fluctuation of sand quality is mainly caused by the change of specific surface area, porosity and rheological property caused by unreasonable particle shape and gradation. The water in concrete is used to produce strength by hydration of glue material, and to wet the surface of solid material and fill its gap to make it rheological, which is convenient for construction. There are three existing ways of water in concrete: combined water, adsorbed water and free water.

自由水受體系的電性吸附力小，若混凝土拌合物的密實度差則空隙通道粘滯阻力小而使自由水容易泌出。通常的辦法，一是增加細砂用量、二是增加摻合料用量。現(xiàn)在的問題就是細砂緊缺、需水量少的粉煤灰同樣緊缺。

If the compactness of the concrete mixture is poor, the viscosity resistance of the gap channel is small and the free water is easy to secrete. The common solution is to increase the amount of fine sand and admixture. Now the problem is that fine sand is in short supply, so is fly ash, which needs less water.

離析，不僅影響施工、更影響了混凝土的勻質(zhì)性。混凝土的離析，是漿骨分離導(dǎo)致的。漿骨分離，一是漏漿就如同泌水是因為骨料的孔隙率太大，二是因為漿骨之間不黏連導(dǎo)致漿體泌出。

Segregation not only affects the construction, but also affects the homogeneity of concrete. The segregation of concrete is caused by the separation of mortar and bone. There are two reasons for the separation of pulp and bone. One is that the leakage of pulp is like bleeding because the porosity of aggregate is too large; the other is that the non adhesion between pulp and bone leads to the bleeding of pulp.

泌漿現(xiàn)象通常是因為聚羧酸鹽系外加劑過摻造成的。聚羧酸鹽系外加劑是一個系列，不同的分子結(jié)構(gòu)性能差距會很大，也包括減水率差距很大，可能在20%—35%之間波動。

The bleeding phenomenon is usually caused by the over mixing of polycarboxylate additives. Polycarboxylate series admixtures are a series, and different molecular structures and properties will vary greatly, including water reduction rate, which may fluctuate between 20% and 35%.

我們在配合比設(shè)，希望隨著外加劑摻量的提高減水率線性增大，但忽略了其飽和摻量。一旦超過飽和摻量，混凝土拌合物中的部分水會被排出漿體，漿體與骨料分離，漿體本身又板結(jié)黏底造成泌漿現(xiàn)象。

In the design of mix proportion, we hope that the water reducing rate will increase linearly with the increase of admixture content, but we ignore its saturated content. Once the saturated content is exceeded, part of the water in the concrete mixture will be discharged from the slurry, and the slurry will be separated from the aggregate, and the slurry itself will harden and stick to the bottom, resulting in bleeding.

所以，如何把適當(dāng)?shù)淖杂伤粼跐{體以及拌合物體系中，是克服現(xiàn)階段砂子質(zhì)量以及聚羧酸鹽系外加劑質(zhì)量對混凝土勻質(zhì)性影響的重要因素。

Therefore, how to keep proper free water in the slurry and mixture system is an important factor to overcome the influence of sand quality and polycarboxylate admixture quality on concrete homogeneity.