Synthesis And Performance Of Clay Inhibitor Based On Biological Materials

As the third-generation high-performance water reducer,polycarboxylate superplasticizer(PCE)is an important admixture of high-performance concrete.However,with the rapid development of the concrete industry,polycarboxylate superplasticize has gradually revealed some of its own problems,among them,polycarboxylate superplasticizer is very sensitive to clay,which is an important issue restricting its development and promotion.To enhance clay tolerance of PCE,four clay inhibitors based on biological materials were synthesized using different biological materials in this paper,and their clay tolerance properties were evaluated.The mechanism of interaction with clay was explored.Through nucleophilic substitution reaction,a small molecule clay inhibitor CT1was prepared with?-cyclodextrin(?-CD)and 3-chloro-2-hydroxypropyl trimethylammonium chloride(CHPTAC).Using the fluidity of cement paste containing1%sodium bentonite as the evaluation index,the effects of?-CD and CHPTAC molar ratio and reaction temperature on the dispersion properties of cement paste mixed with bentonite were discussed.The results show that the optimal molar ratio of?-CD and CHPTAC is 1:8,and the reaction temperature is 60?.FT-IR measurement results showed that CHPTAC has been successfully grafted onto?-CD.The ~1H NMR measurement results indicated that the grafting rate of CHPTAC on?-CD was 68%.Based on the obtained results,?-cyclodextrin was still used as the biological materials,together with 2-bromoisobutyryl bromide(Bi BB)undergoes an acylate reaction to prepare?-cyclodextrin-based macroinitiator(?-CD-Br).FT-IR measurement results show that 2-bromoisobutyryl bromide has been grafted onto the surface of?-CD.The results of ~1H NMR showed that the acyl bromide rate of the reaction was 30%.Through the principle of ARGET ATRP,using cuprous bromide as the catalyst and Vc as the reducing agent,the initiator?-CD-Br was used to initiate the cationic monomer methacryloxyethyltrimethyl ammonium chloride(DMC)and amphoteric monomer betaine(DMAPS)polymerized to obtain clay inhibitors CT2 and CT3.FT-IR results showed that CT2 and CT3 were successfully syntheized.Meanwhile,the influence of the molar ratio of initiator and monomer on the dispersion performance of cement paste with clay was discussed.The dispersion performances of CT2 and CT3 are the best while n(?-CD-Br):n(DMC)=1:10 and n(?-CD-Br):n(DMAPS)=1:10,respectively.Following the principle of free radical polymerization,the clay inhibitor based on dextrin(CT4)was prepared at 60?using ammonium cerium nitrate to initiate the polymerization of DMC.The infrared spectrometer was used to characterize and analyze the polymer.The results showed that the absorption peak of the characteristic functional group of the target product CT4 appeared,and the DMC grafting onto dextrin was obtained as was successful.The optimal molar ratio of dextrin molecular glucose unit(G)to DMC was obtained as 1:3 and the optimal amount of initiator ammonium cerium nitrate were discussed.The synthesized clay inhibitor CT4 exhibits the best dispersibility to the cement paste mixed with clay when the dosage of ammonium cerium nitrate is 2.5%of the mass of dextrin.The clay inhibition effects of four clay inhibitors on sodium bentonite were measured separately.The water to cement ratio is 0.29,the amount of polycarboxylate superplasticizers is 0.15%,the amount of clay inhibitor is 0.03%,and the fluidity test of cement paste mixed with 1%sodium bentonite shows that the clay inhibitor has a certain effect of inhibiting clay.The fluidity of the cement paste mixed with the four clay inhibitors CT1,CT2,CT3,and CT4 was higher than that of the polycarboxylate superplasticizers.The cement paste mixed with CT1,CT2,CT3,and CT4 can reach 257mm,282 mm,272 mm,and 250 mm in 15 min,respectively.After mixed with CT1,CT2,CT3 and CT4,the initial fluidity of cement mortar is 219 mm,232 mm,225 mm and 212 mm respectively,which is 5%,12%,8%and 2%higher than that of PCE alone.The fluidity of mortar was tested for 120 min,of which the fluidity of mortar was the largest at 30 min.The fluidity of mortar mixed with CT1,CT2,CT3 and CT4 was220 mm,235 mm,232 mm and 215 mm respectively.The fluidity result of cement mortar is consistent with the fluidity test result of cement paste.Cement mortar and concrete strength test results show that the addition of clay inhibitor can improve the strength.The flexural strength after 28 days of cement mortar can achieve about 9 MPa,the compressive strength after 28 days of cement mortar can achieve about 70 MPa,and the concrete cube compressive strength can achieve about 55 MPa.Using the method of measuring the content of total organic carbon,the amount of clay adsorbed to the clay inhibitor was calculated.Clay inhibitors have a certain amount of adsorption on clay,but the amount of adsorption was different.The concentration of clay inhibitor increased from 0.5 g/L to 2.5 g/L,and the adsorption capacity has been increasing.The general trend of the adsorption capacity of the four clay inhibitors on clay is CT2>CT3>CT4>CT1.At a concentration of 2.5 g/L,the adsorption capacities of CT1,CT2,CT3 and CT4 were 56.5 mg/g,67 mg/g,69 mg/g and 60 mg/g,respectively.The XRD test results show that the interlayer spacing of bentonite after mixed clay inhibitor is larger than that of untreated bentonite.It is speculated that the cationic side chain of clay inhibitor enters the interlayer of bentonite,which reduces the adsorption of bentonite to polycarboxylate superplasticizer and shows clay inhibition effect.