Ottawa Sand #12-20

Ottawa sand #12-20 is a naturally occurring, mechanically sorted, siliceous sand, mined from deposits near Ottawa, IL (Fig 4.1). It is commonly used as a stand-ard sand in the United States. The denotation 12-20 refers to the passing and re-taining sieve sizes. The specimens tested were purchased from AGSCO corpora-tion.

The material is classified as SP according to ASTM D2487 Unified Soil Classifications System (USCS). Particles of Ottawa Sand are rounded as shown in Fig. 4.1. Selected DIA images of Ottawa #12-20 are also presented in Fig. 4.2.

Grain size distributions of Ottawa #12-20 are presented using several size descriptors in Fig. 4.3. Variation between number and volume distribution is also depicted in Fig. 4.4. The size of number distribution is dominated by the finer particles while volume distribution is dominated by the larger particles. The grain size D₅₀ of Ottawa #12-20 is 1513 µm, by volume.

Typical particle size diameters in µm corresponding to several particle size descriptors are presented in Table 4.2. Comparison between EQPC sizes corresponding to various particle size diameters by weight and volume and number distributions are also presented in Table 4.3. Although commercially sourced Otta-wa sands are pre-sorted, dust was observed in DIA measurement of all Ottawa sands. Tiny amounts of dust can dominate number distributions. Consequently, particle diameter D₁, by volume, is also recorded in Table 4.3.

Fig. 4.1. Photo of Ottawa #12-20 sand with a 19 mm diameter US Penny for scale.

The density distribution for several commonly used shape descriptors is presented in Fig. 4.5 and summarized in Table 4.4. The distribution is clearly non gaussian and are thus fit with Johnson’s parameters. The fitting parameters are summarized in Table 4.5, and the goodness of fit is depicted in Fig. 4.6.

Fig. 4.2. Images of Ottawa #12-20 acquired using 2D DIA.

Table 4.2 Typical particle size diameters in µm corresponding to several particle size descriptors (by weight/volume distribution).

Ottawa #12-20	D1	D5	D10	D30	D50	D60	D90	D99
Feret-max	971	1089	1197	1487	1868	2299	3589	3976
EQPC	824	973	1040	1304	1513	1602	3205	3938
Feret-min	740	842	922	1161	1326	1411	2029	3820

Table 4.3 EQPC corresponding to various particle size diameters by weight/volume and number distributions

Ottawa #12-20	D1	D5	D10	D30	D50	D60	D90	D99
Volume	824	973	1040	1304	1513	1602	3205	3938
Number	3	3	4	5	7	8	21	70

Fig. 4.3. Particle size distributions of various size descriptors.

Fig. 4.4. Particle size by volume and number distributions.

Table 4.4 Statistics of particle shape descriptors for Ottawa #12-20 by number and volume distributions.

Ottawa #12-20	AR	S	Cx	Rwaddell
Number
Mean	0.78	0.69	0.96	0.72
Median	0.79	0.68	0.96	0.74
Standard Deviation	0.10	0.10	0.02	0.12
Volume
Mean	0.79	0.69	0.96	0.73
Median	0.80	0.68	0.96	0.75
Standard Deviation	0.10	0.10	0.02	0.11

Table 4.5 Johnson fitting parameters for Ottawa #12-20

Parameter	γ	δ	ξ	λ
AR	-2.48	2.14	-0.13	1.21
S	-0.65	2.91	0.02	1.20
Cx	-5.16	1.59	0.30	0.69
Rwadell	-1.72	1.53	-0.01	0.99

Fig. 4.5. Particle shape density distributions (based on volume) for Ottawa #12-20.

The Ottawa sands explored in this chapter consist of 99.8% Silicon Dioxide. The balance of the constituents consists of trace amounts of Aluminum, Titanium, Magnesium, Calcium, and Iron oxides. Their specific gravity is reported as 2.65 g/cm³.

Fig. 4.6. Johnson fitting of shape descriptors for Ottawa #12-20.