| At present,premixed concrete has been widely used in construction engineering because of its excellent performance and high efficiency of mechanical production.Compared with conventional ordinary concrete,premix concrete improves its performance,strength and durability by adjusting the mix ratio and adding "the fifth component" and "the sixth component".However,ready-mixed concrete mixing proportion and composition adjustment on an adverse effect on its mechanical properties,especially in the cube compressive strength approximately the same(the so-called with intensity)under the condition of the traditional normal concrete with premixed concrete mechanics performance how much difference,concrete structure mechanics performance have much impact,there is no clear conclusion.This article is trying to keep the compressive strength of concrete cube approximately equal or the same conditions,considering the change of the working performance(slump),and the corresponding composition adjustment,to carry out the ready-mixed concrete mechanics performance contrast test research,special considerations compared with traditional 4 components of ordinary concrete,in order to gain performance(slump)change regularity of influence on the mechanical behavior of ready-mixed concrete as well as traditional modern ready-mixed concrete and ordinary concrete,the differences of mechanical properties or consistency,for the modern ready-mixed concrete in structure engineering design calculation consider differences in mechanical behavior to provide necessary evidence.In this paper,different mix ratios are designed to study the influence of composition adjustment on the performance and strength of ready-mixed concrete.On this basis,the basic mechanical properties of concrete specimens were tested by selecting 10 groups of mixture ratios with approximately equal(same)compressive strength of cubes and different components.A comparative study on the bending mechanical properties of 5experimental beams with different workability and similar compressive strength of cubes was completed.Research shows that:(1)in ready-mixed concrete,the incorporation of fly ash,ore powder and water-reducing agent has a certain improvement effect on its working performance.The slump and expansion degree both increase significantly with the increase of water-reducing agent.In addition,the adjustment of these three components has a great impact on the cube’s compressive strength.The increase of the amount of water reducer can improve the cube’s compressive strength for 28 days.The increase of the dosage of water reducer slows down after the addition of 1.5%.The increase of replacement rate of fly ash and ore powder is not conducive to the development of concrete strength,but the compressive strength at 60 d increases obviously.In terms of the effect of working performance and strength,the three components are coordinated.(2)Compared with the 4-component ordinary concrete,the tensile strength ratio and tensile strength ratio of the premixed concrete tend to decrease,and the flexural strength of some groups increases slightly;The ratio of axial compressive strength to cubic compressive strength is stable in the range of 0.79～0.81,slightly larger than 0.76 of ordinary concrete.The component changes in the premix concrete beam have a slight influence on load-deflection curve,cracking load,measured ultimate compressive strain,yield load and ultimate load.Meanwhile,compared with the four components of ordinary concrete,the load cracks in the test beam appear discretization,with prominent randomness and complex development of cracks.On the crack width of premixed concrete beam,compared with the concrete test beam corresponding to the mixture ratio of low dosage(0.5%,1.2%)and 1.6% of water-reducing agent,the crack width has a weak control ability,but it has a strong ability to limit the rise of the maximum crack width value.The mixing ratio corresponding to 40% fly ash replacement ratio can control the development of load crack width more than 25%. |
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