Effects of silicon fume and latex on properties and hydration of modified mortars
Polybutadiene-graft-polystyrene (PB-g-PS) latex with a weight ratio of 50/50 was used to modify cement mortar. This study examines the effects of silicon fume content and the polymer-cement ratios (P/C) on the flow, compressive and flexural strength and water absorption rate of PB-g-PS latex modified cement mortar. The experimental results show that the flow of modified mortar is increased with increasing polymer-cement ratios, and it is decreased with increasing silicon fume content, PB-g-PS latex and suitable silicon fume content can markedly reduce capillary water absorption rate. PB-g-PS latex can marked influences much on the mechanical properties of modified mortars. The compressive of the polymer modified mortar decreased, and the flexural strength of a portion of polymer modified mortar increased. The suitble silicon fume can improve mechanical properties of modified mortats. The effect of PB-g-PS latex and silicon fume content on cement hydration was explored by XRD, the analysis results showed that the cement hydration was influenced by silicon fume content and P/C.
Properties of plain and latex modified Portland cement pastes and concretes with and without superplasticizer
Abstract This paper deals with the effects of latex concentration on the workability and strength characteristics of Portland cement pastes with and without superplasticizer. Durability assessments are made by immersing these pastes in 5% Na2SO4 and 2.5% NaCl solutions. From the results obtained, it is found that the superplasticizer and superplasticizer–latex combinations may improve the workability of the Portland cement pastes. The Portland cement pastes with superplasticizer have much higher strengths than the latex modified Portland cement pastes with and without superplasticizer. In general, curing in lime-saturated water adversely affect the strength of the pastes containing latex from about 28 days onwards. In the durability test, the resistance of latex modified Portland cement pastes with and without superplasticizer to NaCl is decreased. Degradation mechanism depends on the characteristics of the corrosive medium as well as the resistance of the material itself to the resulting chemical action. The character of strain–stress data of latex modified concretes becomes more prominent as the latex concentration increases. These data are anomalous when compared with the data normally observed for concretes without admixture. The proposed equations are found adequate to describe the stress–strain behaviour of latex modified concretes in compression. These equations can also be applied in calculating the initial modulus of elasticity and proportional limit in the case of polymer modified concretes, which exhibit non-linear behaviour at high stress.
Adsorption of immunoglobulin Y in supermacroporous continuous cryogel with immobilized Cu(2+) ions.
The influence of temperature, pH and ionic strength on the adsorption of Immunoglobulin Y (IgY) in IDA-Cu(2+) cryogel system was studied by batch equilibrium measurements. The adsorptive equilibrium data were obtained at 17 and 27°C, pH 5.0 and 6.5, and at ionic strength of 50 and 200mmolL(-1) NaCl. Langmuir, Freundlich and Langmuir-Freundlich models were fitted to equilibrium data, while the enthalpy of adsorption of IgY in IDA-Cu(2+) cryogel system was calculated through Van't Hoff analysis. The binding of IgY on cryogel was stronger at 27°C and lowest pH and ionic strength values, with apparent maximum adsorption capacity of 27mgg(-1). The adsorption of protein in the resin was spontaneous in all analyzed cases. The results provide valuable information to enable the improvement of IgY purification processes.