Study On Strength Effect Of Cement System Based On Different Blending Materials

With the development of society,the construction industry has higher requirements on the strength of concrete and it also has stricter control over costs.Therefore,the concrete industry needs to increase the strength and reduce the production cost at the same time.To achieve this goal,it is common practice to reduce the water-binder ratio and add mineral admixtures such as mineral powder and fly ash.In general,the strength of concrete is inversely proportional to the water-binder ratio,and the strength of paste and mortar made by cement-based materials and water-binder ratio also obey this law.However,in this law,the limiting condition for water-binder ratio is not specified.If the water-binder ratio continues to decrease,whether the strength of the water-binder ratio will continue to increase is unknown.Based on this,this paper study strength of the paste and the strength of the concrete under different water-binder ratios,and the experimental study on resistivity and microscopic properties,and explore the law between strength and water-binder ratio by study Ordinary Portland Cement System(C System for short),Cement-Slag System(C-S System for short),Cement-Fly Ash System(C-F System for short)and Cement-Slag-Fly Ash System(C-S-F system for short).(1)The standard consistency of different cementitious material systems is as follows: C system> C-F system> C-S-F system> C-S system.The C system has a standard consistency of 26%,the C-S system has a standard consistency of 22%,the C-F system has a standard consistency of 24%,and the C-S-F system has a standard consistency of 23%.(2)The compressive strength of slurry and concrete of four kinds of slurry systems at different consistencies for 3d and 28 d are studied.The results show that the compressive strength of the four kinds of slurry system is the highest at 3d and 28 d when four kinds of slurry system is keeped in the standard consistency water-binder ratio.The intensity of 3d is in order: C system> C-S system> C-S-F system> C-Fsystem,and the strengths of 28 d is in order: C-S system> C-S-F system> C system>C-F system.While the intensity of the hardened slurry below and above the standard consistency water-binder ratio is lower than the standard consistency water-binder ratio.(3)Through testing the pastes' resistivity of different cementitious material system under different consistency condition,it shows that the changing law of the paste'resistivity and strength is consistent.The resistivity curve rises the fastest and comes at peak at 72 h when it is in the standard consistency water-binder ratio.The peak value of the 72 h resistivity follow this order: C-S system> C system> C-S-F system> C-F system.When the water-binder ratio is lower or higher than the standard consistency,the rise rate of the resistivity curve decreases and the peak value of the resistivity at 72 hours decreases.(4)Through XRD and SEM microanalysis of the 3d and 28 d hydration products of the different cementitious material system slurries and concrete at different consistency,it shows that: when the water-binder ratio is the standard consistency water-binder ratio,the diffraction peaks intensity and the compaction degree of different cement systems' hydration product are consistent with the intensity changing rules.When the water-binder ratio is lower than the standard consistency,the hydration product is less than the one that is in the standard consistency water-binder ratio.When the water-binder ratio is higher than the standard consistency water-binder ratio,pore structure is more than the one that is in the standard consistency water-binder ratio.