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Construction of cold winter in northern China , is usually added early strength agent and antifreeze to prevent concrete frost damage , the main component of these early strength agent and antifreeze is chloride, sulfate , nitrate inorganic salts and organic salts , the most commonly used as NaCl, CaCl2, Ca (NO3) 2, Na2SO4 , etc. . Experience has shown that the mixing of concrete early strength agent and antifreeze is easy to crack than other concrete early . The concrete cracks generated in the non-load under the action of more than 80% is because of the contraction of the concrete , while affecting the larger is the dry shrinkage and cracking of concrete at early autogenous shrinkage . In this paper, two kinds of water-cement ratio ( 0.50 and 0.32 ) of concrete mixed with NaCl , CaCl2, Ca (NO3) 2 , of Na2SO4 four kinds of inorganic salts , ash 0.5% , 1.0% , 1.5% , 2.0% , 2.5 % early autogenous shrinkage and drying shrinkage study found that adding concrete at early ages in addition to the a Na2SO4 other three salt since the contraction will be reduced , and decreases with the increase in dosage , which changes in NaCl and CaCl2 , Ca ( NO3) 2 small changes . Incorporation of the Na2SO4 concrete early autogenous shrinkage has been micro-expansion phenomenon , until forming 15h ( water-cement ratio 0.50 ) and 22h ( water-cement ratio 0.32 ) was a slight contraction . Early drying shrinkage after mixing four kinds of salt increases , the where CaCl2 affect the largest , Na2SO4 Secondly , Ca (NO3) 2 and NaCl smaller . CaCl2, Ca (NO3) 2 and NaCl with content increase drying shrinkage increases , Na2SO4 opposite . Overall , CaCl2 early concrete shrinkage greatest impact , and Cl- corrosion of steel should be used with caution in practical engineering . Na2SO4 and the other three salts varied , cause it may appear in early autogenous shrinkage micro - expansion phenomenon shrinkage of concrete early in the actual project with minimal impact .
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