Research On Design, Preparation, And Properties Of Organic-inorganic Multiple Concrete Internal Curing Materials

Internal curing is a method of inner concrete curing relying on the high water absorptionmaterial to release water when the humidity inside the concrete goes down. It has a greatadvantage on preventing concrete’s early shrinkage induced by non-saturated humidity andpromoting continuous hydration of unhydrated cementitious materials. The paper is fundedjointly by the National Natural Science Foundation of China (No.51202039). Designed andsynthesized new polymer internal curing materials of high absorbency in pore fluid solution,stability storage and controlled water-releasing internal curing agent. Its composition, structure,and properties were studied. The achieving conclusions as follows:In this paper, aiming to solve workability loss, strength reduction, and weak internal curingresulting from present polymerizational internal curing agents,we proposed and designed a kindof high water absorpency, stable water retaining, and controlled water releaseanionic/nonionic-type internal curing agents. By using cassava starch, AM, AMPS as the mainraw material and by solution polymerization, AN-ICA was systhesised. Its distilling waterabsorpency up to210~287and water-retention ratio in synthesized pore solution above80%and negetive pressure water releasing ratio is above75%. The The use of FT-IR, EDS,13CNMR and optical microscopy characterized the composition, morphology and structurecharacteristics of AN-ICA, proved the rule among the composition, network structure andabsorbent-storage stability. Studies have shown that AN-ICA characterizes moderately crosslinked continuous, porous three-dimensional strip network structures which provide enoughspace with water absorbency and water storage. Moreover, the weak sensitivity on alkali of-SO3H、-CONH2and functionally hydrophilic group facilitate water-absorbing and waterstorage performance in an alkaline environment.By compositing the rigid inorganic silicon-oxygen network in the AN-ICA network,improved the AN-ICA polymer network structure’s anti-shrinkage ability, released the technicalideas of internal curing materials to control water release, designed and prepared organic-inorganic composite internal curing materials(termed as OIM-ICA). Using EDS, SEM tocharacterize the composite cross-linked network structure and morphology and studies itsperformance of water-absorbing-water releasing in synthetic pore solution, building up theOIM-ICA absorbing-storing-releasing process evolution model. Its distilling water absorpencyup to188~270and water-retention ratio in synthesized pore solution above85%and negetivepressure water releasing ratio is above80%. Studies show that OIM-ICA having a cross linkednetwork structure of the composite strip,81%moisture in the structure exists mainly to the low binding force of the free water and bound water. Water absorpency, stable water retaining, andwater release of OIM-ICA were systematically investigated and it optimization and technologyparameters.Bring out the microgel internal curing technical ideas and polymer internal curing materialconsumption calculation method, the OIM-ICA dosage, fineness, adding way early shrinkage ofconcrete were investigated. It has been concluded that the concrete’s autogenous shrinkage atearly age has a positive correlation with the amount of the OIM-ICA, the degree of watersaturation and other parameters. And it related negatively with the fineness, water-cement ratioand other parameters. The results show that, due to the OIM-ICA internal curing function, thenumber of9to50nm pores were reduced and the number of its below the size of9nm isincreased. The autogenous shrinkage of concrete can be reduced by35%to85%, the internalrelative humidity maintained at above80%. OIM-ICA replenishment role induced by capillarypressure and humidity difference and gel surface film-forming effect suppression inlow-intensity plastic shrinkage are the two key factors.Mechanism and microstructure of the addition of OIM-ICA concrete were systematicallystudied. Research reveals that the improvement mechanism of its excellent properties,mechanical properties and durability are as follows: the gel space is relatively bigger in theprevious7days because of it occupied space has not been fully filled, and the early strength ofconcrete is relatively weak. With the effect of the OIM-ICA released water internal curing,unhydrated cementitious materials continued to hydrate, the increaseing of9to50nm pores innumber, the degree of hydration continued to rise and hydration products gradually filled pores.Finally forms “shell structure” which has an independent, regular, nearly round and dense layer.The structure is similar to the pores induced by the air-entraining agent to form the porestructure and improving the frost resistance of concrete. The shell structure dispersed the stress,improved the later strength. The improvement of the resistance to chloride ion permeability,carbonation resistance and resistance to sulfate attack lies in containing dense layer arch shellstructure to prevent the mitigation of Cl-、CO32-and SO42-ions.Designed20kilo tons per year product line, and prepared industrially product OIM-ICA.The indicators of the internal curing materials have reached the class one level of standardproduction requirements. The application of cast-in-place concrete roofing project shows thatconcrete surface has no cracks, no deformation, and with good crack resistance.