Non-Dispersibility And Fluidity Synergistic Development Of Non-Dispersible Underwater Concrete

At present,the non-dispersible underwater concrete is mainly mixed with flocculant to improve the non-dispersibility of concrete,but the flocculant will cause the poor fluidity of concrete,which leads to concrete plugging pipe and cofferdam leakage and other problems during cofferdam construction.Therefore,there is an urgent need for a kind of concrete with both non-dispersibility and fluidity.This paper explores the influence of shortening of underwater concrete initial setting time,waterproofing agent and flocculant on the non-dispersibility and fluidity of non-dispersible underwater concrete,and combined with micro-analysis,the nondispersibility and fluidity synergistic development of non-dispersible underwater concrete is studied and the following conclusions are drawn:(1)Compared with direct pouring molding,cube molding can significantly improve the underwater strength of cement paste,mortar and concrete materials.(2)The addition of calcium formate and triethanolamine can greatly shorten the initial setting time of the underwater non-dispersible concrete,and then shorten the underwater rest time of the concrete after pouring.Shortening the rest time of concrete is beneficial to the non-dispersibility of non-dispersible underwater concrete,but has an adverse effect on the fluidity of concrete.With the shortening of the rest time,the p H and turbidity of the water sample increased,but the strength of underwater concrete increases,indicating that using the evaluation of water sample p H and turbidity to shorten the rest time of concrete under water is not reasonable.The microscopic test shows that shortening the underwater rest time of the nondispersible underwater concrete can improve the concrete pore structure,and avoiding the long-time invasion of the external water to the concrete after pouring,thus increasing the underwater strength of the concrete.(3)The addition of silicone waterproofing agent is beneficial to the nondispersibility and fluidity of non-dispersible underwater concrete.With the increase of silicone water-proofing agent content,the fluidity of concrete increases,and the ratio of underwater strength and water-land strength increases.For C30 and C25 concrete,when 0.6% silicone waterproof agent is added,the underwater strength value of concrete is the highest,and the water resistance is the best,so it is recommended to add 0.6% silicone waterproof agent.The microscopic test shows that silicone water-proofing agent and hydration product of concrete generate waterproofing reactant,fill concrete hole structure,improve water-proofing and underwater strength of concrete.(4)The effects of different amount of flocculant on the non-dispersibility and fluidity of concrete were investigated.The results show that the flocculant has a great adverse effect on the fluidity of concrete,but it is beneficial to the anti-washout of non-dispersible underwater concrete.It can significantly improve the underwater strength and water-land strength ratio of concrete,and reduce the p H value and turbidity value of water samples.The microscopic test shows that the adsorption of flocculant and the action of bridge connect the hydration products of concrete,so as to improve the underwater strength of concrete.(5)Under the condition of 1.0% flocculant content,3% calcium formate,0.5%triethanolamine and 0.6% silicone water-proofing agent are added,the underwater strength and water-land strength ratio of C30 and C25 underwater non-dispersed concrete is close to that of the concrete with 2.0% flocculant content,and it also has good fluidity.The microscopic test shows that although there are some gaps between the two strength grades of concrete,the hydration products are closely overlapped to improve the underwater strength of the non-dispersed concrete.The results show that the non-dispersibility and fluidity synergistic development of non-dispersible underwater concrete can be realized when the addition of low flocculant is supplemented by shortening the rest time and silicone water-proofing agent.