Improvements On Effect Of Mud On Polycarboxylate Superplasticizer In Concrete

The inevitable mud in the concrete aggregates will reduce the water-reducing and dispersion of the polycarboxylate superplasticizer(PCE),thereby affecting the workability of the concrete.Studies have shown that the clay(especially montmorillonite)in the mud has the most significant negative effect on the PCE.Clays absorb the PCE and the mixing water,so that the effective PCE and the free water in the cement slurry that keeps the slurry fluid are reduced,which is the main reason that the mud affects the workability of concrete blended with PCE.From the aspects of "addition of anti-mud additives" and "over-doping PCE and water",the improvement measures and mechanisms of mud-mixed concrete blended with PCE were studied.According to the previous results of affiliated research group,5 improvements have been taken with sodium metasilicate(pentahydrate),polyethylene glycol-4000 and a novel quaternary ammonium salt as anti-mud additives,as well as super-doped water reducers and pre-absorbed super absorbent polymer(SAP).Mainly based on macroscopic experiments to study the improvements of the workability and mechanical properties of concrete,and mechanisms of improvements are analyzed.In order to provides a more reliable reference for the actual production and application of concrete blended with PCE.According to the experimental results of mortar and concrete,sodium metasilicate(pentahydrate),polyethylene glycol-4000 and the novel quaternary ammonium salt can effectively improve the negative effect of mud on concrete with PCE,and effectively improve the workability while ensuring the strength of concrete.Polyethylene glycol has the best improvement on compressive strength.The optimum content is between 0.4% and 1.0%,which increases with the increase of mud content.The novel quaternary ammonium salt has the best effect on the improvement of work performance,but it contains chloride ions,so the dosage should be controlled.The optimum dosage is 0.015%-0.03%.When the clay content is less than or equal to 5%,the super-admixed water-reducing agent can improve the flowability and strength.By introducing additional water consumption and internal maintenance,SAP can effectively improve the influence of mud on the water-reducing agent-mixed carboxylic acid,and the appropriate water consumption and pre-absorbing method can further improve its effect.Finally,by means of total organic carbon analysis and X-ray diffraction analysis,the mechanism of SAP negative effect on mud was explored from the perspective of microscopic adsorption amount and inter-layer expansion.It was found that SAP can reduce the adsorption of polycarboxylate superplasticizer by mud.