Dust grains particle size distribution

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. 

While there is considerable uncertainty in the size distribution and composition of circumstellar dust grains, much of the evidence points towards some sort of amorphous carbon with a range of sizes up to ca. 1 pm although it seems that the grains can be successfully modelled with particles of radius 0.05 pm (Martin Rogers 1987). Therefore, we anticipate that there are solid particles containing upwards of ca. 1011 atoms. 

Environmental airborne endotoxins are usually associated with dust particles or aqueous aerosol with a broad size distribution. Endotoxin exposure has been associated with a variety of pulmonary and systemic diseases in homes, office buildings and occupational environments. These diseases or conditions include chronic nose and throat irritation, humidifier fever, organic dust toxic syndrome, grain fever, byssinosis, asthma-like syndrome, exacerbation of asthma, and progressive irreversible airflow obstruction (Heederik et al., 1991 Michel et al., 1996 Muittari et al., 1980 Olenchock, 1990 Rylan-der, 1996 Rylander et al., 1978 Schenker et al., 1998 Schwartz et al., 1994 Schwartz et al., 1995). Recognition of the link between endotoxin exposures and these conditions has led to proposals to establish occupational health exposure limits. The Netherlands Health Council has recently published a criteria document for endotoxin that recommends a health-based occupational exposure limit of 50 EU/m for full shift, personal, inhalable dust sampling (Douwes and Heederik, 1998). 

The term particle (or grain) size refers to the structural make-up of such substances as granulates, powders, dusts, granular mixes, and suspensions. Knowledge of the particle size, in conjunction with the comminution process, determines such details as grinding efficiency and ultimate product fineness. To establish particle sizes and their distribution within powdered systems, the user can have recourse to a number of different measuring processes designed to indicate, with appropriate particle definition, details of the probable equivalent diameter of a particle. 

---