To solve the initial damage,poor durability,and other problems of concrete caused by steam curing,the nano-hydrated calcium silicate polycarboxylate ether composite(n-C-S-H-PCE)was used to prepare high-strength non-steam-cured concrete.The effects of n-C-S-H-PCE on the compressive strength,hydration rate,pore size distri-bution,autogenous shrinkage and durability of concrete were studied using hydration heat,low-field nuclear mag-netic resonance and other methods.Results show that the crystal nucleus of nano-C-S-H provides nucleation sites for the hydration products of cement,reducing the critical ion concentration Ksp of nucleation.And the induction and acceleration periods are advanced significantly.Also,the early compressive strength of concrete is improved considerably.The compressive strength of concrete increases by 64%after 1 day of curing,and the strength of con-crete has no regression after 28 days of curing.The addition of the n-C-S-H-PCE refines the pore size of concrete matrix and increases the proportion of gel pores and capillary pores.As a result,the negative capillary pressure in-creases during the auto-drying process of concrete.Thus,the autogenous shrinkage of concrete increases.However,the most probable pore size of the concrete matrix and the cumulative volume of pores with a diameter of 50-100 nm decrease.This improves the resistance to chloride migration into concrete.The content of pores with a pore diameter larger than 14 nm(the critical pore diameter)decreases(from 0.0287 mL/g to 0.0156 mL/g).As a result,the freeze-thaw resistance of concrete is improved.The addition of n-C-S-H-PCE can reduce the porosity of con-crete.In addition,with the increase of slag content,the concentration of calcium aluminate phase and Ca2+ de-creases.In this way,the resistance to sulfate attack of concrete increases.The results provide a theoretical basis for the preparation of non-steam-cured,low shrinkage,high durability and high-strength concrete.
nano early strength agentnon-steam-cured concretepore structureautogenous shrinkagedurab-ilityC-S-H-PCE
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维普
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