Surface Properties Of Aggregates Research Articles

Effect of Silane Coupling Agent Treatment of Aggregates on Mortar Workability, Strength and Interfacial Microscopic Properties

In this study, 3-aminopropyltriethoxysilane (KH550) and vinyltrimethoxysilane (KH171) were used to modify aggregates and prepare aggregates with different surface wettability. The effect of silane coupling agents on aggregate surface properties was characterized through FT-IR, XPS, contact angles and aggregate water absorption. The influence of the aggregate’s surface wettability on the interface properties was discussed using MIP, SEM, BSE and nanoindentation, and then the influence mechanism of the interface microscopic properties on the macro-properties of mortar was revealed. The results showed that the type of silane has an intense impact on the surface properties of aggregates. KH550-modified aggregates increased the contact angle from 23.6° to 59°, while KH171-modified aggregates increased it from 23.6° to 91.6°. Silane-modified aggregates reduced the surface hydrophilicity, thereby reducing the water absorption and improving the mortar’s workability. However, KH550-modified aggregates exhibited a more effective enhancement of the mortar’s mechanical properties. Specifically, KH550-modified aggregates reduced the aggregate’s surface hydrophilicity, consequently alleviating the interfacial edge effect. This led to a 10% increase in the compressive strength of the mortar, an 11.6% reduction in the porosity, an 8.4% decrease in the interfacial porosity, and a 42.3% increase in the elastic modulus of the ITZ. Meanwhile, the cement matrix obtained a greater amount of water for cement hydration, resulting in an increased degree of hydration and an 18.5% increase in the elastic modulus of the cement matrix. The improvement in the ITZ between the modified aggregates and the cement matrix is considered to be one of the fundamental reasons for the enhancement of the mortar’s performance.

Stability and structure of protein-polysaccharide coacervates in the presence of protein aggregates.

We have studied at pH 4.2 and three protein (Pr):polysaccharide (Pol) weight ratios (8:1, 2:1 and 1:1) the structure and stability of beta-lactoglobulin/acacia gum/water dispersions containing protein aggregates (BLG/AG/W) or free from aggregates (AF-BLG/AG/W). Phase diagrams were characteristic of complex coacervation. BLG/AG/W dispersions displayed a larger biphasic area than AF-BLG/AG/W dispersions, that moved towards the protein axis. It was concluded that protein aggregates affected complex coacervation both by entropic (size and molecular masses of aggregates) and enthalpic (surface properties of aggregates) effects. Laser light scattering measurements revealed that the particles diameter (d(43)) induced by demixing was controlled by protein aggregates in AF-BLG/AG/W dispersions. At 1 wt.% biopolymer concentration, particles were 15-20 times larger in AF-BLG/AG/W dispersions than in BLG/AG/W dispersions at (Pr:Pol) ratios of 2:1 or 1:1. Confocal scanning laser microscopy showed that AF-BLG/AG/W dispersions only contained spherical coacervates. BLG/AG/W dispersions contained both coacervates and aggregates coated with AG or/and BLG/AG coacervates. At a (Pr:Pol) ratio of 2:1 and 1:1, coacervates were vesicular or multivesicular. Coacervates were smaller in BLG/AG/W dispersions than in AF-BLG/AG/W dispersions. It was concluded that protein aggregates have the intrinsic ability to stabilize complex coacervates and could be used to design multifunctional delivery systems. This study showed that composite dispersions containing both protein aggregates embedded in protein-polysaccharide coacervates and free coacervates may be performed. In this respect, the design of protein aggregates with controlled size distribution and surface properties could open new possibilities both in the non-chemical control of coacervates stability and in the development of multifunctional delivery systems.

Electric surface properties of fractal aggregates—rotational and translational electrokinetics

Fractal aggregates from γ-Al 2O 3 obtained by flame hydrolysis with different hydrodynamic radius are studied by electric light scattering (rotational) and electrophoresis (translational) electrokinetics. The nonequilibrium, electric surface properties of the aggregates characterized by their electric polarizability are studied. The electric polarizability depends linearly on the aggregates dimensions and decreases with indifferent electrolyte concentration increase tending to a constant value. The aggregate structure (the existence of “inner” counterions in the pore space) could be supposed as responsible for an “internal” electric polarizability, relaxing in the kHz region. The electrophoretic mobilities do not depend on the κa-parameter ( κ −1=thickness of diffuse double layer, a=radius of initial spherical γ-Al 2O 3 particles).