Automated Chloride Determination in Concrete

Transcription

1 ETTLER TOLEDO Automated Chloride Determination in Concrete Application 729 High chloride content in concrete may cause degradation and therefore the content needs to be checked on a regular basis. This method is based on SN EN 14629:2007 and determines the chloride content of previously ground concrete samples in a fully automated procedure including sample preparation (digestion, heating, cooling and neutraliation). ETTLER TOLEDO Page 1 of 10 Titration Application 729

2 Sample 3 g ground concrete sample (concrete powder, particle sie < 1.18 mm) Compound Chloride, Cl -, =35.45 g/mol, =1 Chemicals Nitric acid HNO 3, ~33 % and ~1 % Ammonia NH 3, ~1 % Titrants Silver nitrate AgNO 3, c(agno 3 ) = 0.02 mol/l Ammonia NH 3, c(nh 3 ) 14.7 mol/l (~25 %) and c(nh 3 ) mol/l (~0.25 %) Standard Indication Chemistry Sodium chloride solution, NaCl c(nacl) = mol/l (~0.1 % Cl - ), 4 ml DGi112-Pro (inner electrolyte: KCl 3 mol/l, bridge electrolyte: KNO 3 1 mol/l) Di148-SC Cl - + Ag + = AgCl (s) Calculation R5: Chloride content (%), expressed as w/w R5 = Q[3]*C/m C = /(10*) R6: Chloride content (ppm), expressed as w/w Preparation and Procedures ing and special beakers on Inotion: ing beaker: Deion. water (for Tower A) Special beaker 1: Deion. water (for Tower B) Special beaker 2: HNO 3 ~1 % (for Tower A) Special beaker 3: NH 3 ~1 % (for Tower B) DH100: The target temperature is set to 95 C. Thermostating bath (LAUDA): The bath is filled with a special heat transfer liquid (e.g. "Kryo 30" from LAUDA or monoethylene glycol/water mixtures) for temperatures between 0 C and 90 C. Sample preparation: 3 g (accurately weighted) of sample is added into a titration beaker, placed on the Inotion and the method is started. ethod procedure (fully automated): Tower A: 1) Add 20 ml of HNO 3 ~33 % and 40 ml water to the sample 2) for 10 min 3) Add 60 ml of water 4) Heat up to 85 C 5) Cool down to 25 C 6) Neutraliation (EP) to 2.5 using NH 3 ~ 25 % 7) Neutraliation (EP) to 4.0 using NH 3 ~ 0.25 % 8) Cool down to 25 C 9) Rinse with water and dip rinsing in HNO 3 ~1 % and water Tower B: 10) Titration (EQP) of chloride with AgNO 3 c = 0.02 mol/l 11) Drain and rinse with water 12) Dip rinsing in NH 3 ~1 % and water Waste disposal Author, Version R5 = Q[3]*C/m C = 1000*/ Filtration of the liquid waste. The precipitate (AgCl) has to be classified as special waste. The liquid phase has to be neutralied to 7 before final disposal. Fabian Hobi, SG AnaChem, Version 1.0 Remarks 1) The method is based on SN EN 14629:2007 but it does not replace this standard. 2) The procedure of the standard was adapted to fit this automated system. ore information on the adaptions and more detailed information on the setup and procedure can be found in the "Comments" section below. 3) The method parameters have been developed and optimied for the above mentioned sample. It may be that some adaptions are needed for other samples. ETTLER TOLEDO Page 2 of 10 Titration Application 729

3 Instruments Accessories Titration Excellence T7/T9 Inotion Flex with two towers and 180 ml rack (other possibilities for higher sample throughput: Inotion Pro 23 x 180 ml or Inotion ax 43 x 180 ml) Lauda ECO Silver RE 420 with RS232/485 interface module 2x additional dosing unit DH100 3x SD660 membrane pump 1x SP280 peristaltic pump 2x burette 10 ml Burette 20 ml Heat exchanger (cooling finger, 23834) Y cable stirrer/pump, 6-pin ( ) 2x extension cable for stirrer/pump LabX 2017 Results Results for concrete with higher Cl content: Sample Concrete, high Cl (1/5) R % Sample Concrete, high Cl (2/5) R % Sample Concrete, high Cl (3/5) R % Sample Concrete, high Cl (4/5) R % Sample Concrete, high Cl (5/5) R % Statistics: R5 ean % s % srel % Results for concrete with lower Cl content: Sample Concrete, low Cl (1/5) R % Sample Concrete, low Cl (2/5) R % Sample Concrete, low Cl (3/5) R % Sample Concrete, low Cl (4/5) R % Sample Concrete, low Cl (5/5) R % Statistics: R5 ean % s % srel % ETTLER TOLEDO Page 3 of 10 Titration Application 729

4 Titration curves Neutraliation 1 (with NH 3 25 %): Neutraliation 2 (with NH %): Chloride titration: ETTLER TOLEDO Page 4 of 10 Titration Application 729

5 Table of measured values Chloride titration: Volume ml Potential mv dv/dt ml/s 1st deriv. mv/ml Time s EQP ETTLER TOLEDO Page 5 of 10 Titration Application 729

6 Comments Details about the system: - Pumps: SD660 for water (PowerShower tower A), connected to Inotion* SD660 for water (PowerShower tower B), connected to titrator analog board (extension cable needed) 1x SD660 for HNO 3 ~33 %, connected to the titrator mainboard (extension cable needed) 1x SP280 as waste pump, connected to the titrator mainboard - rer: Compact stirrer (tower A), connected to Inotion* Compact stirrer (tower B), connected to Inotion - Tubes, sensors and accessories mounted on tower A: PowerShower, rer, DGi112-Pro, NH 3 ~25 % (20 ml burette), NH 3 ~0.25 % (10 ml burette), HNO 3 ~33 %, immersion heater (DH100), Dual Pt1000 (DH100), heat exchanger (cooling finger) - Tubes, sensors and accessories mounted on tower B: PowerShower, rer, Di148-SC, AgNO mol/l (10 ml burette), waste tube * One stirrer and one SD660 pump are connected to the same stirrer/pump output of the Inotion using a Y cable 6-pin ( ) Tower A (side view) Tower A Tower B Heat exchanger HNO 3 ~33 % Immersion heater Immersion heater NH 3 ~0.25 % Dual Pt1000 DGi112-Pro NH 3 ~25 % Di148-SC AgNO mol/l Waste ETTLER TOLEDO Page 6 of 10 Titration Application 729

7 Changes to the standard SN EN 14629:2007: - After the addition of 20 ml HNO 3 ~33 % to the sample 40 ml water (in the standard: 0 ml) are added to have enough solution to stir it. - After the 10 min stirring 60 ml of cold water (standard: 40 ml of hot water) are added to have enough solution to immerse the immersion heater. - The solution is neutralied with two titrants (NH 3 ~25 % and NH 3 ~0.25 %) to 4.0 to avoid any overshooting of the target (standard: neutraliation with NH 3 ~25 % to 3 5). - To get steeper titration curves the solution is again cooled down to 25 C after the neutraliation (standard: no cooling after neutraliation). - Due to the difficult automatiation of a filtration process, the solution isn't filtrated before the chloride titration (standard: filtration is applied). effect on the results is expected. - blank value was measured (standard: blank compensation). Further comments: - The results from this method were comparable to XRF measurements of the same samples measured in a concrete testing laboratory. - The method procedure with two towers was chosen to avoid any contact of the silver ring sensor with highly acidic solutions, which may lead to corrosion. - Di148-SC electrode was chosen, because it has no junction which can be blocked by the fine concrete powder. - For the titer determination the same method procedure without the 10 min stirring, heating and the first cooling can be used. - Analysis of one sample takes about 40 min (thereof 20 min are used for heating and cooling before the neutraliation and 3 min of cooling after the neutraliation). For multiple samples this process can be speed up by dividing the method into two loops. The first loop will include the sample preparation on tower A and the second loop the titration on tower B. In this way the samples can cool down while the others are prepared. - One of the crucial steps to get precise results is the rinsing of the titration head. It is therefore very important that the dip rinsing solutions (HNO 3 1 % and NH 3 1 %) are fresh and changed from time to time. The frequency of the solution change depends on the samples. For the samples measured in this application a change after 5 10 samples was needed. Automatic exchange of those solutions could be realied with two additional pumps for those solutions (mounted on tower B). - The neutraliation of the solution to between 3 5 can be achieved with NH 3 ~25 % only, but due to the very steep titration curve in this region an overshoot of the target will occur. To make sure that the solution is still in the range the target should be set to 3. For more accurate neutraliation the second titrant NH 3 ~0.25 % is needed as described in this application. - The set temperature at the DH100 is set to 95 C to achieve a fast heating. The heating is stopped by the titrator as soon as the sample solution is at 85 C. - Any RS232 controllable thermostating bath can be used for the heat exchanger if it can reach temperatures down to 5 C. The RS232 commands need to be changed to fit the commands of this bath. ETTLER TOLEDO Page 7 of 10 Titration Application 729

8 ethod 001 Title General titration Compatible with T7 / T9 ID 729 Title Chloride in concrete 002 Auxiliary instrument OUT_SP_00_005\ Auxiliary instrument OUT_SP_01_002\ ing Inotion T/1A Position ing beaker Time [s] Auxiliary instrument Output TTL (Single Pin) DH100 ON Fixed time Time [s] easure (normal) [1] Temperature Unit C Acquisition of measured values Acquisition Set value T > set value Set value [ C] 85 t(max) [s] 900 ean value 014 Auxiliary instrument Output TTL (Single Pin) DH100 OFF Fixed time Time [s] ing Inotion T/1B Position Special beaker 1 Time [s] Auxiliary instrument START\ Sample Number of IDs 1 ID 1 Concrete Entry type Weight Lower limit [g] 2.0 Upper limit [g] 4.0 Density [g/ml] 1.0 Correction factor 1.0 Temperature [ C] 25.0 Entry Arbitrary Inotion reader ne 007 Head position Inotion T/Tower A Inotion T/1A Sample 008 Pump Auxiliary reagent HNO % Volume [ml] 20 Pump property 1-way 009 Pump Auxiliary reagent Water-A Volume [ml] 40 Pump property 1-way 010 Duration [s] Pump Auxiliary reagent Water-A Volume [ml] 60 Pump property 1-way 016 easure (normal) [2] Temperature Unit C Acquisition of measured values Acquisition Set value T < set value Set value [ C] 25 t(max) [s] 1500 ean value 017 Auxiliary instrument STOP\ Titration (EP) [1] Titrant Titrant NH3 25 % Concentration [mol/l] 14.7 DG112-Pro Unit Temperature sensor Temperature unit C Predispense ne Wait time [s] 0 ETTLER TOLEDO Page 8 of 10 Titration Application 729

9 Control Endpoint type Absolute Tendency Positive Endpoint value [] 2.5 Control band [] 2.5 Dosing rate (max) [ml/min] 10 Dosing rate (min) [µl/min] 1 Termination At EP Termination delay [s] 5 At Vmax [ml] 20.0 ax. time infinite ax. time [s] 8 Accompanying Stating Accompanying stating 019 Calculation R1 Result Neut. Consumption Step 1 Result unit ml R1=VEND Constant C= 1 [ne] [ne] Decimal places 3 ne 020 Titration (EP) [2] Titrant Titrant NH % Concentration [mol/l] DG112-Pro Unit Temperature sensor Temperature unit C Predispense ne Wait time [s] 0 Control Endpoint type Absolute Tendency Positive Endpoint value [] 4.0 Control band [] 3.0 Dosing rate (max) [ml/min] 10 Dosing rate (min) [µl/min] 1 Termination At EP Termination delay [s] 5 At Vmax [ml] 20.0 ax. time infinite ax. time [s] 8 Accompanying Stating Accompanying stating 021 Calculation R2 Result Neut. Consumption Step 2 Result unit ml R2=VEND[2] Constant C= 1 [ne] [ne] Decimal places 3 ne 022 Auxiliary instrument START\ easure (normal) [3] Temperature Unit C Acquisition of measured values Acquisition Set value T < set value Set value [ C] 25 t(max) [s] 600 ean value 024 Auxiliary instrument STOP\ easure (normal) [4] DG112-Pro Unit Temperature sensor Temperature unit C Acquisition of measured values Acquisition Equilibrium controlled de [mv] 0.5 dt [s] 1 t(min) [s] 5 t(max) [s] 30 ean value 026 Calculation R3 Result value Result unit R3=E[4] Constant C= 1 [ne] [ne] Decimal places 2 ne 027 Rinse Auxiliary reagent Water-A Rinse cycles 1 Vol. per cycle [ml] 10 Position Current position Drain 028 ing Interval 1 Position Special beaker 2 Time [s] 10 Speed [%] ing Interval 1 Position ing beaker Time [s] Head position Inotion T/Tower B Inotion T/1B Sample ETTLER TOLEDO Page 9 of 10 Titration Application 729

10 031 Duration [s] Titration (EQP) [3] Titrant Titrant AgNO3 Concentration [mol/l] 0.02 mv D148-SC Unit mv Predispense ne Wait time [s] 0 Control Control rmal Precipitation Show parameters Titrant addition Dynamic de (set value) [mv] 9.0 dv(min) [ml] dv(max) [ml] 0.4 Equilibrium controlled de [mv] 0.5 dt [s] 1 t(min) [s] 3 t(max) [s] 30 Evaluation and Recognition Procedure Standard Threshold [mv/ml] 10 Tendency Negative Ranges 0 Add. EQP criteria Termination At Vmax [ml] 10.0 At potential At slope After number of recognied EQPs Combined termination criteria Accompanying Stating Accompanying stating 036 Rinse Auxiliary reagent Water-B Rinse cycles 3 Vol. per cycle [ml] 10 Position Current position Drain Drain pump Waste 037 ing Interval 1 Position Special beaker 3 Time [s] 10 Speed [%] ing Interval 1 Position Special beaker 1 Time [s] End of Sample 040 Park 041 Park Position Inotion T/1A ing beaker Inotion T/1B Position Special beaker Calculation R4 Result Consumption Result unit ml R4=VEQ[3] Constant C= 1 [ne] [ne] Decimal places 4 ne 034 Calculation R5 Result Chloride content Result unit % R5=Q[3]*C/m Constant C= /(10*) [Chloride] [Chloride] Decimal places 4 ne 035 Calculation R6 Result Chloride content Result unit ppm R6=Q[3]*C/m Constant C= 1000*/ [Chloride] [Chloride] Decimal places 0 ne ETTLER TOLEDO Page 10 of 10 Titration Application 729