Key Engineering Materials Vols. 405-406

Abstract: Using slag and metakaoline as raw materials , different modules of water glass as activator ,a new type of cementitious material—slag-based geopolymer was prepared. The fluidity of slag-based geopolymer paste and optimum content of superplasticizer in slag-based geopolymer mortar being as evaluation standard, adaptablities of slag-based geopolymer to naphthalene superplasticizer and melamine superplasticizer were studied. The results have shown that both naphthalene superplasticizer and melamine superplasticizer with slag-based geopolymer were adaptable well, obvious saturated points and optimum contents to two kinds of superplasticizers were performed.

Abstract: According to design theory of molecular structure, a new poly-acrylic series superplasticizer PC-C with MPEG as graft side chain was designed, and was synthesized in water. The molecular structure of PC-C was shown by IR, the property of Poly-acrylic Superplasticzer was studied through methods of surface stress，dispersing property, slump maintenance and strength development. Experimental results showed that PC-C exerted low dosage，high dispersing property and dispersing retention property which improving with the increasing of dosage, and that PC-C has good adaptability with cement and strengthen efficiency to concrete.

Abstract: Naphthalene sulfate based superplasticizer and poly carboxylate superplasticizer (characterized by different polymerization of graft chain and backbone chain, different reaction temperature and different carboxyl/graft chain ratio) were applied to investigate their influences on fluidity of mineral admixtures (fly ash, granulated ground iron blast furnace slag, silica fume) -Portland cement-water system.

Abstract: By means of orthogonal experimental design, the composition (including Calcium formate, Ferric sulfate and Crystal-embryo) of Na+ & K+-free concrete hardening accelerator is designed, and the hardening accelerative effect of the concrete hardening accelerator is studied. The experimental result indicate that there are the interactions between compositions each other, the optimal combination of the factors is 4:5:3 (Calcium formate: Crystal-embryo: Ferric sulfate).By this combination, the concrete hardening accelerator is prepared. The early strength of the concrete which mixed with the concrete hardening accelerator can be enhanced 43%(1-daystrength), 47% (3-day strength), 39%(7-day strength), and 31%(28-day strength) compared with the controlled concrete. By altering the strength grade and the breed of the cement, the adaptability of the concrete hardening accelerator is studied too.

Abstract: The strength and shrinkage properties of mortars with different superplasticizer were studied. The results indicated that the saturation point was the best dosage of superplasticizer, at which it not only helped to reach highest paste fluidity with minimum superplasticizer dosage, but also reach the highest mortar strength and comparatively lower shrinkage rate.

Abstract: A series of water-soluble polycarboxylate-type superplasticizer (PCA) were synthesized by free-radical copolymerization of methyl acrylic acid and methoxy poly(ethylene glyco1) monoacrylate macromonomers in water solutions．Micelles were formed from the resultant PCA with predetermined hydrophobic and hydrophilic blocks in water. The hydrodynamic diameter and size distribution of micelles were determined by dynamic light scattering. The change of the concentration of the electrolyte results directly in the variation of the dispersing force of PCA in cement paste. The dispersing force degrades with increasing electrolyte concentration.

Abstract: The influence of superplasticizer (SP) and shrinkage-reducing admixtures (SRA) on the early age shrinkage of concrete with a controlled slump of 80±10 mm was investigated using a measuring apparatus developed specially. In addition, the influence of early age curing methods on the early age shrinkage of concrete was also studied. The early age shrinkage was increased sharply by the addition of SP when the concrete was exposed to the drying environment after initial setting. While under the same conditions the addition of SRA could reduce the early age shrinkage effectively. However, under sealed curing conditions at the early age, concretes with or without chemical admixtures all exhibited low early age shrinkage, which implies if a good method for curing could available then the addition of SRA will be unnecessary and the adverse effect of SP in enlarging shrinkage could also be eliminated.

Abstract: A slow-release type carboxylic polymer(SLPC) is synthesized with the monomer mixture at a certain Molecule ratio of methacrylic acid, methoxy polyethylene glycol methacrylate and polyethylene glycol di-methacrylate. Test results of the fluidity, Zeta potential and adsorption in cement paste show that the polymer SLPC has the remarkable anti-adsorbing and high fluid-retaining ability for enhancing fluidity of cement paste as time elapsed, concrete experimental results indicated that it could be used to substitute 30～50% polycarboxylic type water-reducer in the same quality for preparing high workability concrete and controlling its slump loss.

Abstract: Absorption and d esorption of super plasticizer by zeoltie were investigated, and zeolite superplasticizer with zeolite as carrier was produced. The addition of zeolite superplasticizer in cement and concrete increases the paste fluidity and concrete slump, while the loss of fluidity and slump are effectively controlled.

Abstract: Some long-term properties such as anti-carbonation properties, shrinkage, penetrability of chloride ion of fly ash concrete with nano-CaCO3 middle slurry were studied. Test results showed that the properties of anti-carbonation and impenetrability for chloride of fly ash concrete increased by adding nano-CaCO3 middle slurry because the tiny hole was filled by nano-CaCO3 and the density of concrete increased. But at the same time, the shrinkage of fly ash concrete with and without nano-CaCO3 was the same. Results of SEM also implied the hydration degree of fly ash could be increased by nano-CaCO3.