Preparation And Application Of Silane-Modified Polycarboxylate Superplasticizer In Concrete Viscosity Reduction

Modern buildings exhibit the trend of being high-rise,lightweight,and long-span due to advancements in construction technology and economic status.High-performance concrete is frequently employed in these projects.High-performance concrete is typically made for high strength,necessitating a lot of cementitious materials and a low water-cement ratio.This can result in fresh concrete having a high viscosity and poor fluidity,which adds time and costs to the construction process,especially when using a pump to create ultra-high-strength concrete.A micro-crosslinked structure of silane-modified polycarboxylate superplasticizer was created by hydrolytic silane condensation in an aqueous solution to address the high viscosity of highgrade concrete.The interaction between polycarboxylic acid water-reducing agent and cementitious materials with various silane contents was also investigated.A series of silane-modified polycarboxylate superplasticizers(SPCEs)with micro crosslinking,low characteristic viscosity,and small hydrodynamic radius was created applying molecular design principles.This polymerization used isobutyl alcohol polyoxyethylene ether(HPEG),acrylic acid(AA),and 3-(trimethoxysilyl)propyl methacrylate(KH570)as synthetic monomers,ammonium persulfate(APS)and ascorbic acid(Vc)as redox initiating system and mercaptoethanol(ME)as chain transfer agent.Experimental results demonstrated that silane coupling agents can alter adsorption behavior of polycarboxylate superplasticizers(PCE)on cement particles.The addition of silane coupling agent increased PCE adsorption on cement particles and decreased the amount of PCE in pore solution.In addition,when compared with the control group,saturated adsorption capacity of SPCEs on cement increased significantly,while ZETA potential decreased.Excessive introduction of silane coupling agents during the polymerization process can reduce the water reduction of SPCEs.For the same fluidity of cement paste,SPCEs can significantly reduce plastic viscosity and yield stress of cement paste.T500 time and V-funnel outflow time of concrete prepared with SPCEs were reduced by 23.53%and 11.00%,respectively,and plastic viscosity was reduced by 19.43%compared with that of concrete prepared in the control group,indicating that SPCEs can significantly reduce viscosity of high-performance concrete and increase ease of construction.The tests on heat of hydration,SEM images,and concrete strength showed that SPCEs retarded hydration process of cement,which was detrimental to development of early strength of concrete.Compared with control group,1d and 3d strengths of concrete prepared by SPCEs were lowered by 15.66%and 6.53%,respectively.On the other hand,hydrolytic condensation of silanol promoted development of late strength of concrete,and 28-day strength can be increased by 8.79%compared with control group.Besides that promotion of late strength of concrete by SPCEs enhanced the durability performance of concrete,resistance to chloride ion and sulfate resistance can also be increased by 25.88%and 2.22%,respectively.In summary,SPCEs prepared in this thesis exhibit significant potential to be applied as a viscosity-reducing agent in concrete engineering.