Fine sand, particle size distribution

Although it is entirely possible for erosion-corrosion to occur in the absence of entrained particulate, it is common to find erosion-corrosion accelerated by a dilute dispersion of fine particulate matter (sand, silt, gas bubbles) entrained in the fluid. The character of the particulate, and even the fluid itself, substantially influences the effect. Eight major characteristics are influential particle shape, particle size, particle density, particle hardness, particle size distribution, angle of impact, impact velocity, and fluid viscosity. 

Spent foundry sand is thought of as a beneficial substitute for fine sand for use in portland cement concrete. Prior to acceptance of inclusion, test standards applied on conventional fine sand shall be referred to as the standards for spent foundry sand to compare the physical properties of conventional sand and spent foundry sand. The most important parameters are particle size distribution, fineness modulus, dust content, density, organics content, deleterious materials content, and grain shape. Although no spent foundry sand satisfies all of the specifications, foundry sand can be blended with conventional sand to be incorporated into the concrete matrix. The replacing ratio normally starts at one-third. 

The sand should preferably be of a rounded shape and should have a suitable particle size distribution (typically less than 4 mm and with a limited amount of fines) which gives 30 to 40 % of voids. The characteristics of the sand can markedly affect both the soft and hard properties of the mortar. Sands suitable for building are designated in the UK as either Type S (BS 1199), or Type G (BS 1200) [26.31]. As the specified sands have a voidage in the above range, it is standard practice to design mortars with three volumes of sand to one volume of binder plus void-filling material. 

Particle-size distribution was determined before and after dissolution of organic cements (Lavkulich and Wiens, 1970) coarse (2.00-0.50 mm), medium (0.50-0.25) and fine (0.25-0.05 mm) sands were retrieved by sieving, while silt was separated from clay by sedimentation. The pH was determined potentiometri-cally in water and 1 M KCl solution (solid/liquid ratio, 1 2.5). Total exchangeable... 

Asphalts are characterised by the particle size distribution of the aggregate mixture. Theoretically, there are unlimited types of asphalts, namely, from asphalts consisting only of almost single-sized coarse aggregates to mixtures consisting only of fine aggregates (sand). All types of asphalts used range between these two extreme cases. 

The physical properties of soils important in corrosion are mainly those that determine the permeability of the soil to oxygen or air and to water. The particle size distribution of the soil is an important factor with respect to aeration and moisture content. In coarse texture soils such as sands and gravel, where there is free circulation of air, corrosion approaches the atmospheric type. Clay and silty soils are characterized in general by fine texture, high water-holding capacity, and by poor aeration and poor drainage. Variations in these characteristics within the same soil environment lead to higher corrosion rates comptired to that experienced by atmospherically exposed materials. 

Most importantly, the effect of using sand with an appropriate particle size distribution was properly appreciated. Sands that combine acceptable proportions of fine, medium, and coarser particles will achieve a higher density than sands of uniform particle size, and higher density leads directly to higher strength and better resistance to water infiltration. 

The grain size distribution of spent foundry sand is very uniform, with approximately 85 to 95% of the material between 0.6mm and 0.15mm (No. 30 and No. 100) sieve sizes. Five to twelve percent of foundry sand can be expected to be smaller than 0.075 mm (No. 200 sieve). The particle shape is typically subangular to round. Spent foundry sand gradations are too fine to satisfy the fine aggregate standard specified in specification ASTM C33 Standard Specification for Concrete Aggregates. 

Mineral Fine Particle Stabilization. Experiments were performed using test columns packed with a well blended mixture of 85% (by weight) 70-170 U.S. mesh sand and 15% mineral fine particles, The size distributions of the mineral fine particles are summarized below ... 

Next in importance for a proper understanding of size-distribution and particle-measurement is the manner in which fine material packs. It is well known that a column filled with sand may be shaken so that it will occupy less space. Similarly, certain soils may be pressed or tamped to become denser. Compaction is achieved at the expense of the void space, which may vary from a theoretical minimum of 26 percent to as high as 48 percent for spheres. Unfortunately there is no adequate method of describing a packing in terms of partide-orientation. We can only deal with it in terms of the free space present or the ease with which a liquid flows through it. Except in a statistical sense it is never possible to make two packings precisely identical unless we make a systematic arrangement of spheres. 

Figure 10. Weight percent bitumen and water (grade) weight percent coarse, fine, and clay-size particles (particle distribution) and weight percent clay (clay content), for the oil sand, overburden, clay layers, and the MFT suspension (21).

---