Research On The Preparation And Performance Of High-strength Permeable Concrete

Pervious concrete has a porous structure and is benificial to solve urban water-logging disaster,replenish groundwater resources,alleviate"heat-island effect",absorb sound and reduce noise,etc.In this paper,the relationship between the characteristics of coarse aggregate and mechanical properties of pervious concrete,the influence of cement slurry and admixture on the strength and the permeable rate of the pervious concrete are studied.Meanwhile,the pervious concrete is also prepared by alkali-activated blast furnace slag as cementitious materials,which is proved to have good mechanical properties.The main results are as follows:1.The aggregates size,shape,mud content,et al,which have great influences on the properties of the pervious concrete.The results show that the increase of aggregate size will reduce the packing density of aggregate and the strength of pervious concrete,and improve the pervious rate.The compressive strength 28 d of the pervious concrete prepared by ball milling for 2 hours and 4.75⁷.5 mm aggregate can reach 33.5 MPa,and the pervious rate can reach2.6 mm/s.The mud content of aggregate should be strictly controlled below 0.4%.The strength of pervious concrete will be greatly reduced as the mud content is more than 0.4%,and the pervious rate will decreased.2.The low water binder ratio or the small amount of cementitious materials will cause the poor bonding strength of the pervious concrete paste,while the high water binder ratio or the large amount of cementitious materials will cause the accumulation of the paste to block the pore channel of the pervious concrete.The results show that the optimal cement dosage is 400⁴75 kg/m3,the water binder ratio ranges between 0.28⁰.3 in cement pervious concrete,the blast furnace slag dosage falls in 425⁴75 kg/m3,and the water binder ratio is between 0.30⁰.34 in alkali-activated blast furnace slag pervious concrete.3.In the cement pervious concrete,0.5%of the water reducing agent improves the fluidity of cement slurry,and increases the compressive strength of the pervious concrete by24%.The mineral admixtures such as fly ash,blast furnace slag,silica fume can improve the hydration strength of cement slurry.As 10%fly ash,15%blast furnace slag and 4%silica fume are added to slurry,the compressive strength of the pervious concretes increase by 6%,31%and 21%respectively.Adding 4‰dispersible emulsion powder can improve the cohesiveness of cement slurry,which increase the compressive strength of the pervious concretes by 7%.Adding 1‰cellulose can improve the consistency of cement slurry and increase the compressive strength of the pervious concretes by 5%.4.In the alkali-activated blast furnace slag pervious concrete,the compressive strength can reach 35.7 MPa at 28 d and the permeable rate of water can reach 1.8 mm/s by using 20kg/m3NaOH and 180 kg/m3water glass as the alkali-activator.The main crystallization are C-S-H and albite(Na_2.12Al₂Si₂O_8.06)phase observed by SEM and XRD in the slurry of the alkali-activated blast furnace slag pervious concrete.