High Powder Content Research Articles

Effects of steel fiber reinforcement on surface wear resistance of self-compacting repair mortars

Abstract Self-compacting repair mortars (SCRM), as new technology products, are especially preferred for the rehabilitation and repair of reinforced concrete structures. The self-compactability of repair mortars may bring considerable advantages at narrow mould systems. However, due to the high powder content and absence of coarse aggregate, plain SCRMs are susceptible to surface abrasion, especially in case of repair of surfaces under high rates of abrasion (floors, slabs). Steel fiber reinforcement can be an excellent solution for the abrasion resistance problem of SCRMs. However, the optimum amount of fiber reinforcement to sustain self-compactability should be pre-determined. In this study, the optimum superplasticizer dosage and the maximum possible amount of fiber addition, which maintain the self-compactability and stability, was determined for mortars incorporating steel fibers. In addition, the mechanical performance and abrasion resistance of SCRMs prepared by using these fibers were determined. It was concluded that steel fibers can have rheological and mechanical synergistic effects, and that optimised fiber – superplasticizer dosage combinations can better improve the wear resistance while maintaining adequate flow properties for FR-SCRM.

Effect of variations from the recommended powder/liquid ratio on some properties of resin-modified cements

Objectives. The powder and liquid contents of cements are mixed in accordance with the recommended mixing ratio, but discrepancies occur despite the use of proportioning scoops. Little is known about powder/liquid ratio variations on certain properties of resin-modified cements. Methods. Two resin-modified glass ionomer cements (RMGIC) were mixed using various powder/liquid ratios: (a) Recommended ratio: Fuji Plus: powder/liquid 2:1; ProTecCEM p/l 2.25:1. (b) Maximal variation arising using proportioning aids (17% liquid surplus): Fuji Plus 1.66:1, ProTecCEM 1.875:1. Limits of mixing and specimen construction: either (c) both groups with more liquid (1.5:1) or (d) more powder (3:1). Flexural strength was determined using a 3-point bending test (after 24 h) and wear using a 3-body abrasion device. The extent of cure reaction was characterized using differential thermal analysis (DTA). Results. While higher powder content did not significantly affect the flexural strength of Fuji Plus and ProTecCEM, it considerably reduced wear of Fuji Plus. Increasing liquid content reduced flexural strength. A substantial increase in wear for Fuji Plus 1.5:1, and ProTecCEM 1.875:1 and 1.5:1 mixtures was observed. DTA demonstrated that a higher liquid content resulted in incomplete setting reactions, which could be detected even after 24 h of cure. Conclusions. If RMGICs are mixed with powder/liquid variations, given the inaccuracy of proportioning aids the properties of RMGIC will change slightly and may be disregarded. If set with higher powder/liquid variations, a surplus of powder has less influence on the properties than a surplus of liquid.

A feasibility study on the utilization of r-FA in SCC

Self-compacting concrete requires a high powder content or a viscosity agent (VA) to increase its segregation resistance. This paper presents the results of a preliminary study on the utilization of rejected fly ash (r-FA) as part of the powder content. r-FA is unsuitable in the production of blended cements simply due to its coarseness. Preliminary results suggested that r-FA could be used to replace VAs in the production of self-compacting concrete (SCC) and, possibly, with additional benefits. A detailed research project is under development based on results of this study.

混和剤を後添加した高流動コンクリートの諸性状

The purpose of this paper is to investigate the propeties of Super Workable Concrete that was added chemical admixture after mixing. Super Workable Concrete which has the property of selfcompacting is being widely used for various structure, but often causes a decrease of slumpflow and a incease of funnel flowing time with passage of time or fluctuation in surface moisture content of fine aggregate.In this paper, it considered about two methods of adding after mixing for the resoration of self-compacting. One was the addition a suitable amount of superplasticizer to the concrete of high powder content type decreased of slumpflow. The other was the method for viscous agent type that poured the mixture dissolved viscous agent in part of water and superplasticizer into concrete by mixing and excluding them. Both methods was clearly to be able to resore the properties of self-compacting and pumpability.