CALIBRATION OF RAPID MOISTURE METER (RMM)

 

CALIBRATION OF RAPID MOISTURE METER (RMM)

REF. CODE- IS:2720 Part-2

·         Rapid moisture meter (RMM) is most popular equipment for quick determine the moisture content of soil and fine aggregate in construction fields.

·         The RMM can be determine moisture content very quick within 5 minutes, up to 50% or 25% as per capacity of RMM.

·         But there are different between actual moisture content & RMM value most of the cases, that’s why we need to be compare RMM reading with actual moisture.

 

Working Principal

Calcium Carbide (CaC2) reacted with Water (Moister in test sample) and produce gas. This gas developed a pressure in RMM chamber which show on RMM meter.

CaC2 + 2H2O → C2H2(gas) + Ca(OH)2

Calibration Procedure

Step-1

At first take 1000 gm completely dry sand and divide it equally 10 nos. of sample, each sample weight = 100 gm.

During this process it should be noted that the weight balance can be measured weight by 0.01 gm accuracy for good result.

 

Sample-1	100 gm
Sample-2	100 gm
Sample-3	100 gm
Sample-4	100 gm
Sample-5	100 gm
Sample-6	100 gm
Sample-7	100 gm
Sample-8	100 gm
Sample-9	100 gm
Sample-10	100 gm
Total=	1000 gm

 

Step-2 

Take sample-1 than add 2% of water by weight and mixed with sample properly to make homogeneous mix.

Step-3  

Now take 6 gm sample from sample -1 (water mixed sample) and test by RMM, then note the RMM reading.

Step-4

After test of sample-1 in RMM take the remaining sample for find out moisture content by Oven dry method

Step-5

Now repeat🔁 the step- 2,3 & 4 for sample-2, sample-3 , ......... Sample-10 .

But added water shall be increase 2% for every sample by this manner 👇

Sl No	Wt. of dry Sample	Added % of Water	Wt. of Water Added
Sample-1	100 gm	2%	2 gm
Sample-2	100 gm	4%	4 gm
Sample-3	100 gm	6%	6 gm
Sample-4	100 gm	8%	8 gm
Sample-5	100 gm	10%	10 gm
Sample-6	100 gm	12%	12 gm
Sample-7	100 gm	14%	14 gm
Sample-8	100 gm	16%	16 gm
Sample-9	100 gm	18%	18 gm
Sample-10	100 gm	20%	20 gm

 

 Step-6

Now test all remaining individual sample by oven dry method and find out moisture content of each samples.

Step-7

After find out moisture content of each Sample, Draw a X-Y graph 📈 

Because RMM Reading directly proportional to Actual moisture content

Then RMM is function of Actual moisture.  

like 

Y= f(x) or Y= mX + C

Step-8

Make the graph

Sample No	RMM Reading	Oven dry Moisture (%)
Sample-1	2	1.84
Sample-2	5	4.08
Sample-3	6	6.12
Sample-4	8	8.1
Sample-5	10	10.2
Sample-6	12	11.9
Sample-7	13	13.87
Sample-8	15	15.77
Sample-9	17	18.2
Sample-10	18	19.68

Step-9

Now apply the Liner Equation and find out actual moisture content,

In during field test use this chart and find out the result

y = 1.1211x - 0.9075
RMM Value	Test Moisture (%)
1	0.21
2	1.33
3	2.46
4	3.58
5	4.70
6	5.82
7	6.94
8	8.06
9	9.18
10	10.30
11	11.42
12	12.55
13	13.67
14	14.79
15	15.91
16	17.03
17	18.15
18	19.27
19	20.39
20	21.51
21	22.64
22	23.76
23	24.88
24	26.00
25	27.12
26	28.24
27	29.36
28	30.48
29	31.60
30	32.73
31	33.85
32	34.97
33	36.09
34	37.21
35	38.33
36	39.45
37	40.57
38	41.69
39	42.82
40	43.94
41	45.06
42	46.18
43	47.30
44	48.42
45	49.54
46	50.66
47	51.78
48	52.91
49	54.03
50	55.15

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