Endress+Hauser Solitrend MMP20, Руководство по эксплуатации

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Solitrend MMP20 (Option D) SWZ probe
Hauser 31
2. The concrete sample with a normal-distribution grading curve and a water target
value of 170 l/m³ was measured with the SWZ probe and 170 l/m³ was displayed as
the reading.
3. After that, a 5 kg concrete sample was kiln-dried. A kiln-dried value of 149 l/m
3 was
determined, i.e. there was a difference of –21 l/m 3 .
 As the concrete was mixed in the twin-shaft mixer without being continuously
mixed again in the truck mixer, the kiln-dried sample during the first sampling
contained a lot of large gravel pieces. These large gravel pieces resulted in a
considerable error during sampling: there were simply too many large pieces of
gravel in the sample which "drove down" the kiln-dried value to 149 l/m³ (gravel
pieces have no water content). The cement paste, which was very high as a
result, caused the SWZ reading to deviate from the (actually incorrect) kiln-dried
value.
Influence of large gravel pieces when sampling:
• Kiln-dried sample of 1.5 kg (3.31 lb): ± 2 large gravel pieces produce an error of
±9 l/m³
• Formulation A with a relatively high fines content and low 16/32mm gravel content:
approx. 5 pieces of 16/32mm gravel
• Formulation B with gap-grading, i.e. low 4/8mm gravel content and high 16/32mm
gravel content: approx. 15 pieces of 16/32mm gravel
• Kiln-dried sample of 5 kg (11 lb): ± 2 large gravel pieces produce an error of ±3 l/m³
• Formulation A with a relatively high fines content and low 16/32mm gravel content:
approx. 16 pieces of 16/32mm gravel
• Formulation B with gap-grading, i.e. low 4/8mm gravel content and high 16/32mm
gravel content: approx. 100 pieces of 16/32mm gravel
A single piece of 16/32mm gravel weighs 10 to 50 g (0.35 to 1.76 oz). Therefore,
correct sampling has an important impact on accuracy