Improved Materials Testing

Leaching Tests on Ready-Mixed

Concrete

Report to the Department of the Environment, Transport

and the Regions

DETR/DWI No 4551 /1

APRIL 1998
IMPROVED MATERIALS TESTING

LEACHING TESTS ON READY-MIXED CONCRETE

Report to the Department of the Environment, Transport and the Regions

Report No: DETR/DWI No 4551/1

APRIL 1998

Authors: M W Norris, S Blake and K Moore

Contract Manager: I M Wilson

Contract No: 10780-0

DoE Reference No: DWI 70/2/72

Contract Duration: 20/05/97-30/03/2000

This report has the following distribution :

DWI Nominated Officer - 8 copies, Authors and Contract Manager

Any enquiries relating to this report should be referred to the Contract Manager at the

following address :

WRc plc, Henley Road, Medmenham, Marlow, Buckinghamshire SL7 21=iD .

Telephone: 01491 571 531
IMPROVED MATERIALS TESTING

LEACHING TESTS ON READY MIXED CONCRETE

The objective of this study was to establish `benchmark' levels for the leaching of metals

listed in BS 6920 from generic ready-mixed concretes and assess these against current

maximum admissible concentrations (MAC).

The aqueous leaching of metals was performed using the methods in BS 6920,

`Suitability of non-metallic products for use in contact with water intended for human

consumption with regard to their effect on the quality of the water' . The metals content

of the selected ready-mixed concretes was also determined to establish if there was a

correlation between the aqueous leaching and the total metal content. Two sample

preparation procedures were used for the analysis of solid samples, to give results for

acid extractable and total metals.

Quarry Products Association (QPA) arranged for the preparation and curing of concrete

test cubes using six different ready-mixed concrete mix compositions each with two

types of aggregate, gravel and granite . The concrete test cubes were cured for a period of

28 days. Standard curing conditions were used for 14 of the test cubes, ie total immersion

in water, cured at a temperature of 20 °C . In addition two test cubes were air cured at a

temperature of 20 °C for comparison.

The type of cement and additions used for the test specimens is given below ;

Cement

Portland (UK)

Portland (Imported)

Portland (UK)

_ Portland (UK)

Portland (UK)

Sulfate-resisting Portland cement

In addition one test sample was prepared using

supplementary fuel.

EXECUTIVE SUMMARY

Additions

none

none

Pulverised fuel ash

Ground granulated blastfumace slag

Microsilica

none

Portland cement manufactured at a works using Cemfuel as a

Results for the aqueous leachates showed only four of the thirteen listed metals to be

present above the limit of detection of the methods used. Aluminium was detected in all

the leachate samples, barium, chromium and iron were detected in some of the aqueous

leachate samples. Of these metals only aluminium was detected leaching above the MAC

of 200 gg 1 -t for drinking water in the majority of the aqueous leachate samples.

The highest concentration in the aqueous leachates appeared to occur with test specimens

prepared using gravel as aggregate. Greater leaching of aluminium and iron was observed

in test specimens prepared containing ground granulated blastfumace slag regardless of

the other constituents .

Results for the analysis of total metals in the solid samples showed that the ready-mixed

cement mixtures . did not contain silver, cadmium, mercury or selenium. Of the metals
IMPROVED MATERIALS TESTING

LEACHING TESTS ON READY MIXED CONCRETE

found, aluminium and iron were found in the greatest concentration, followed by barium

and manganese.

When digested in concentrated acid the metals arsenic, chromium, manganese, nickel and

lead were readily extracted from the solid test specimens . However none of these metals

were detected in the aqueous leachates, except chromium which was found at low

concentrations . 4&ar-ninitrm, barium and -iron wvm also --readily extracted by the acid

digestion process at the high concentrations of acid used.
CONTENTS

EXECUTIVE SUMMARY

LIST OF TABLES

1 . INTRODUCTION

2. OBJECTIVES

3 . METHODOLOGY

3 .1 Test Specimens

3 .2 Preparation of aqueous leachates

3 .3 Preparation of solid samples

3.4 Analysis

4. RESULTS

5. DISCUSSION

5 .1 Aqueous leachates

5 .2 Metals in solid samples

6. CONCLUSIONS

7 . REFERENCES
LIST OF TABLES

Table 3.1 Composition and curing conditions of Test Specimens

Table 3.2 List of specified metals as given in BS 6920 Part 1 (Specification)

and Methods of Analysis for -the Metals Determined.

Table 4.1 Concentration of metals in aqueous leachates prepared from

duplicate Granite Aggregate test cubes (gg 1" 1 )

Table 4.2 Concentration of metals in aqueous leachates prepared from

duplicate Gravel Aggregate test cubes (p,g 1'')

Table 4.3 Concentration of metals extracted by acid digestion from

pulverised samples (mg kg"' dried material)

Table 4.4 Concentration of total metals in pulverised samples (in- k-- 'dried

material)

Table 5.1 Mean concentrations of aluminium, barium, chromium and iron in

the aqueous leachates prepared from duplicate test cubes (gg 1" ' )
1. INTRODUCTION

Ready-mixed concrete has traditionally been used in contact with water for public supply

under the provision of Regulation 25 (1) (c) of the Water Supply (Water Quality)

Regulations 1989. The Drinking Water Inspectorate (DWn has recently issued notice that

exemption of traditional materials, such as cementitious materials, from approval is to be

removed. Consequently water undertakers will be required to use only products which

are approved under Regulation 25 (1) (a) in application to water supply pipes, service

reservoirs and water towers.

A protocol is required for `benchmarking/generic' type-testing of ready-mixed concretes

to enable an approval of generic types of ready-mixed concrete to be given. To determine

if the use of traditional ready-mixed concretes based on a range of Portland Cement types

could present a health hazard with respect to the leaching of metals, a study was

commissioned to determine the aqueous leachability and the total concentration of

selected metals.

In order to establish a data-base the DWI requested WRc to undertake a survey of

leaching of metals from ready-mixed concrete as a part of the DWI contract Improved

Methods for Materials Testing (70/2/72).

Quarry Products Association (QPA) arranged for the preparation and curing (standard

and non-standard) of moulded test specimens. These were prepared from a range of

"water-retaining quality" concretes, which included many of the cement types and two of

the aggregate types, currently supplied to the water industry. The metals chosen for study

were those listed in BS 6920.

Triplicate test cubes were prepared using six different ready-mixed concrete mix

compositions each with two types of aggregate, gravel and granite . The concrete test

cubes were cured totally immersed in water at a temperature of 20 °C for a period of 28

days. In addition two test cubes were air cured at a temperature of 20 °C for comparison .
OBJECTIVES

The objectives of this project were to :

a) to identify aqueous leaching of metals from ready-mixed concrete using the method

of test in-BS 6920.

b) to determine if there is any correlation between the aqueous leaching of metals and

the total metal content of ready-mixed concrete.
3. METHODOLOGY

3.1 Test Specimens

The test specimens of ready-mixed concrete mixtures were prepared and cured at the

quality control laboratories of ARC Southern - Premix (granite aggregates) and Tarmac

Topmix (gavel aggregates) .

The test specimens (100 mm cubes) are typically used, by industry, for the determination

of compressive strength. The test specimens were prepared using six different readymixed concrete mix compositions each with two types of aggregate, gravel and granite .

The test specimens were prepared using Portland cement, manufactured in either the UK

or imported from Europe. The additions used were pulverised fuel ash, ground granulated

blastfurnace slag or microsilica. Test specimens were also prepared using sulfate

resisting Portland cement using both aggregates types, but without any additions .

At the request of QPA an additional test sample using UK Portland cement,

manufactured at a cement works using Cemfuel as a supplementary fuel source, with no

additions and gravel as aggregate, was also included in the test .

The test specimens were cured in water (deionised water for granite aggregate and tap

water for gravel aggregate) for a period of 28 days at 20 :t 2 °C (standard cure conditions

for physical testing). In addition two test specimens, prepared from each of the

aggregates and UK Portland cement, were air cured.

In total 16 mix compositions (triplicate test specimens) of ready-mixed concrete were

submitted to WRc for testing. The test specimens were sealed in plastic bags to retain

moisture. The ready-mixed concrete samples identified for testing, the aggregate used

and the curing conditions are listed in Table 3 .1 .
*Cement prepared at a works using Cemfuel as a supplementary fuel source

Table 3.1 Composition and

Cement Type

curing conditions of Test Specimens

Source Code Aggregate Curing conditions

(28 days at 20'°C)

QPA Mix

No

WRc Ref

Portland Southam (UK) PC/UK/GLJTW Gravel Tap water la 046C

Portland Southam (UK) PC/UK/GL/AC Gravel Air lb 047C

Portland Southam (UK) PC/UK/GUDI Gravel DI water Ic 048C

Portland Rochester (UK) PC/UK/GE/AC Granite Air 2a 022C

Portland Rochester (UK) PC/UK/GE/DI Granite DI water 26 023C

Portland Seament Tilbury (Imported) PC/IM/GL/DI Gravel Tap water 3 051C

Portland Seament Tilbury (Imported) PC/IM/GE/DI Granite DI water 4 025C

Sulfate-resisting Portland Blue Circle, Weardale SRPC/GL/fW Gravel Tap water 5 053C

Portland /Pulverised fuel ash, Southam (UK)/Ash Resources PC/PFA/GL/TW Gravel Tap water 6 049C

Portland /Ground granulated Southam (UK)/Civil & Marine, PC/GGBS/GUTW Gravel Tap water 7 050C

blastfurnace slag Llanwern

Portland /Microsilica Southam (UK)/Elkem, Norway PC/MS/GIJTW Gravel Tap water 8 054C

Sulfate-resisting Portland Blue Circle, Masons SRPC/GE/DI Granite DI water 9 024C

Portland /Pulverised fuel ash, Rochester (UK)/Ash Resources PC/PFA/GE/DI Granite DI water 10 026C

Portland /Ground granulated Rochester (UK)/Civil & Marine PC/GGBS/GE/DI Granite DI water 11 027C

blastfurnace slag Purfleet

Portland /Microsilica Rochester (UK)/Carbon PC/MS/GE/DI Granite DI water 12 028C

Enterprises/Iceland

Portland Ribblesdale* PCR/GL/TW Gravel Tap water 13 052C
3.2 Preparation of aqueous leachates

The method used to prepare the aqueous leachates was according to the method in BS

6920

The test cubes were 100 mm square, total surface area 60,000-mm2 . To ensure that the

required surface to volume ratio of 0.15 cm2 ml' I was achieved the volume of test water

was increased to 4 litres .

Duplicate test cubes of each concrete mix were pre-conditioned in Medmenham tap

water, aggresivity index 12.1 (aggresivity index = pH + log (total alkalinity x calcium

hardness)), for 24-hour periods until the pH of the water was less than 9 on two

consecutive occasions.

The pre-conditioning water for the test cubes prepared using granite as aggregate and

cured in deionised water initially had a . pH greater than 9 after the first 24 hours.

However the pH was less than 9 for the second and third 24 hour period. The test cubes

prepared using gravel as aggregate and cured in tap water initially had a pH less than or

near to 9 after the initial 24 hour period.

The test cubes were then transferred to clean containers (5 litre borosilicate beakers) and

leached in test water (4 litres, deionised water) according to BS 6920.

The test specimens were leached for 24 hours after which time the leachate was

discarded. The test specimens were then leached for a further six sequential periods, five

24-hour and one 72-hour period and concluding with a 24-hour period. Samples of the

final leachates were taken for the determination of metals.

3.3 Preparation of solid samples

The third test cube of each concrete mix was analysed for the total content of the same

metals as above. Two methods of sample analysis were used, to give information on the

total and acid extractable metal concentrations in the concretes.

The damp test cube, as received, was weighed and the weight recorded. The test cube

was pulverised and milled to <50 gm and the powdered material dried at 105 °C.

3.4 Analysis

The final aqueous extracts and the dried pulverised material were analysed using the

analytical methods given in Table 3.2. The choice of analytical method was made in

relation to the required limit of detection (normally 1/10 of the maximum admissible

concentration (MAC)) and as appropriate to the determinand to be analysed. WRc has

NAMAS accreditation (Lab No 1550) for the analytical techniques in Table 3.2 .
Table 3.2 List of specified metals as given in BS 6920 Part 1 (Specification) and

Methods of Analysis for the Metals Determined.

MAC - Maximum admissible concentration

A: Digestion with hydrofluoric/perchloric acid

B: Acid digestion/dry ashing with magnesium nitrate

C: Acid digestion with vanadium pentoxide

D: Aqua-Regis digestion

E: Inductively coupled plasma atomic emission

spectrometry

F: Hydride generation atomic absorption spectrometry

G: Graphite furnace atomic absorption spectrometry

H: Flame atomic absorption spectrometry

1 : Cold vapour atomic absorption spectrometry

Metal MAC (ltg i") Solid

Total metals

samples

Acid extractable

metals

Aqueous leachates

Aluminium (Al) 200 A, E D, E E

Antimony (Sb) 10 B, F D, F F

Arsenic (As) 50 B, F D, F F

Barium (Ba) 1000 A, E D, E E

Cadmium (Cd) 5 A, E D, H G

Chromium (Cr) 50 A, E D, G G

Iron (Fe) 200 A, E D, E E

Lead (Pb) 50 A, E D, H G

Manganese (Mn) 50 A, E D, E E

Mercury (Hg) 1 C, I D, I I

Nickel (Ni) 50 A, E D, H G

Selenium (Se) 10 B, F D, F F

Silver (Ag) 10 A, E D, E G
4. RESULTS

The tables of results are given below. Results in bold italics are those metals whose

concentration exceeds the MAC.

The duplicate results for the concentration of metals in aqueous leachates prepared from

granite aggregate test cubes and gravel aggregate test cubes are given in Tables 4.1 and

4.2 respectively.

The concentration of acid extractable metals in pulverised samples are given in Table

4.3 .

The concentration of total metals in pulverised samples are given in Table 4.4

No metals of interest were found in the procedural blank aqueous leachate samples.

(There were no procedural blanks for the extract of the solid samples).

The following codes are used in the Tables;

Code Definition

AC Air cured

DI Deionised water cured

GE Granite

GGBS Ground granulated blastfumace slag

GL Gravel

IM Imported

MS Microsilica

PC Portland cement

PFA Pulverised fuel ash

SRPC Sulfate-resisting Portland cement

TW Tap water cured
Table 4.1 Concentration

Test Sample Ag

of metals

AI

in aqueous leachates prepared from

As Ba Cd Cr

duplicate Granite Aggregate

Fe Hg Mn Ni

test cubes

Pb

(Ng 1" I )

Sb Se

PC Rochester/GE/AC <0.20 60 <0.5 13 <0.10 <0.50 <4 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Rochester/GE/AC <0.20 120 <0.5 13 <0.10 <0.50 <4 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Rochester/GE/DI <0.20 100 <0.5 8 <0.10 <0.50 <4 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Rochester/GE/DI <0.20 120 <0.5 8 <0.10 0.60 <4 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Seament/GE/DI <0.20 160 <0.5 5 <0.10 1 .15 <4 <0.1 <2 <1.0 <2.0 <1 .0 <0.5

PC Seament/GE/DI <0.20 220 <0.5 5 <0.10 1 .87 <4 <0.1 <2 <1.0 <2.0 <1 .0 <0.5

SRPC/GE/DI <0.20 90 <0.5 4 <0.10 <0.50 <4 <0.1 <2 <1.0 <2.0 <1 .0 <0.5

SRPC/GE/DI <0.20 170 <0.5 4 <0.10 <0.50 <4 <0.1 <2 <1 .0 <2.0 <1.0 <0.5

PC/PFA/GE/DI <0.20 170 <0.5 72 <0. 10 <0.50 <4 <0.1 <2 < 1 .0 <2.0 <1 .0 <0.5

PC/PFA/GE/DI <0.20 230 <0.5 67 <0.10 <0.50 5 <0.1 <2 < 1 .0 <2.0 <1 .0 <0.5

PC/GGBS/GE/DI <0.20 310 <0.5 9 <0.10 1 .80 6 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC/GGBS/GE/DI <0.20 470 <0.5 9 <0.10 0.53 7 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC/MS/GE/DI <0.20 70 <0.5 4 <0.10 0.88 7 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC/MS/GE/DI <0.20 90 <0.5 3 <0.10 0.81 12 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

MAC 10 200 50 1000 5 50 200 1 50 50 50 10 10
Table 4.2 Concentration of

Test Sample Ag

metals

Al

in aqueous

As

leachates prepared from

Ba Cd Cr

duplicate Gravel Aggregate test

Fe Hg Mn Ni

cubes

Pb

(ILg I' t )

Sb Se

PC Southam/GLJTW <0.20 300 <0.5 5 <0.10 6.29 <4 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Southam/GLITW <0.20 290 <0.5 4 <0.10 <0.50 <4 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Southam/GUAC <0.20 290 <0.5 <2 <0.10 2.32 <4 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Southam/GUAC <0.20 350 <0.5 <2 . <0.10 1 .78 <4 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Southam/GUDI 0.27 60 <0.5 <2 <0.10 <0.50 <4 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Southam/GUDI <0.20 <40 <0.5 <2 <0.10 <0.50 <4 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Seament/GL/TW <0.20 250 <0.5 8 <0.10 0.58 24 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Seament/GUTW <0.20 290 <0.5 12 <0.10 0.78 18 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

SRPC/GL/TW <0.20 200 <0.5 15 <0.10 <0.50 7 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

SRPC/GL/TW <0.20 200 <0.5 17 <0.10 <0.50 15 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC/PFA/GL/TW <0.20 360 <0.5 <2 <0.10 2.22 <4 <0.1 <2 < 1 .0 <2.0 < 1 .0 <0.5

PC/PFA/GUTW <0.20 380 <0.5 <2 <0.10 0.67 <4 <0.1 <2 <1.0 <2.0 <1 .0 <0.5

PC/GGBS/GL/TW <0.20 110 <0.5 10 <0.10 <0.50 15 <0.1 4 <1 .0 <2.0 <1 .0 <0.5

PC/GGBS/GL/TW <0.20 280 <0.5 8 <0.10 <0.50 6 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC/MS/GL/TW <0.20 160 <0.5 5 <0.10 <0.50 <4 <0.1 <2 < 1 .0 <2.0 < 1 .0 <0.5

PC/MS/GL/TW <0.20 140 <0.5 3 <0.10 <0.50 <4 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Ribblesdale/GUTW <0.20 260 <0.5 12 <0.10 <0.50 13 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

PC Ribblesdale/GUTW <0.20 260 <0.5 11 <0.10 <0.50 12 <0.1 <2 <1 .0 <2.0 <1 .0 <0.5

MAC 10 200 50 1000 5 50 200 1 50 50 50 10 10
Table 4.3 Concentration

Test Sample Ag

of metals

AI

extracted

As

by acid

Ba

digestion

Cd

from

Cr

pulverised

Fe

samples

Hg

(mg

Mn

kg" dried

Ni

material)

Pb Sb Se

PC Southam/GL/TW <10 7100 3.80 124 <0.2 19.2 6825 <0.1 129 6.74 3 .98 0.81 <0.25

PC Southam/GL/AC <10 6445 2.40 135 <0.2 22.0 6295 <0.1 140 7 .05 3.74 0.74 <0.25

PC Southam/GL/DI <10 6760 2.79 153 <0.2 22.7 6485 <0.1 150 6.69 3.96 0.88 <0.25

PC Rochester/GE/AC <10 7585 3.33 65 .0 <0.2 19.5 8415 <0.1 188 8.54 5.74 <0.25 <0.25

PC Rochester/GE/DI <10 8040 3.72 52.0 <0.2 . 23 .5 9730 <0.1 201 10.1 109 <0.25 <0.25

PC Seament/GL/TW <10 6150 4.27 117 <0.2 66.5 7480 <0.1 118 30.1 5.22 0.87 <0.25

PC Seament/GE/DI <10 7555 9.20 44.0 <0.2 57.3 9770 <0.1 170 30.8 15.9 0.73 <0.25

SRPC/GL/TW <10 6675 3.77 170 <0.2 21 .3 9385 <0.1 264 9.83 45.2 1 .16 <0.25

PC/PFA/GL/TW <10 7515 7.33 162 <0.2 24.8 7490 <0.1 122 9.04 9.44 1 .41 <0.25

PC/GGBS/GL/TW <10 8315 2.69 226 <0.2 20.2 6405 <0.1 285 5.58 3 .47 0.92 <0.25

PC/MS/GL/TW <10 5915 3.42 154 <0.2 20.5 6290 <0.1 145 6.86 6.73 1 .8 <0.25

SRPC/GE/DI <10 7910 3 .24 67.0 <0.2 16.0 11505 <0.1 240 10.4 13.1 0.44 <0.25

PC/PFA/GE/DI <10 9500 9.01 228 <0.2 18.3 11075 <0.1 220 11.2 9.99 0.53 <0.25

PC/GGBS/GE/DI <10 10100 3.55 80.0 <0.2 20.4 9650 <0.1 297 10.2 6.22 <0.25 <0.25

PC/MS/GE/DI <10 7995 4.04 67.0 <0.2 19.3 9610 <0.1 189 10.2 12.5 0.31 <0.25

PC Ribblesdale/GL/TW <10 7540 4.75 167 <0.2 20.2 7490 <0.1 107 7.70 9.25 1 .02 <0.25
Table 4.4 Concentration

Test Sample Ag

of total metals in

AI As

pulverised

Ba

samples

Cd

(mg

Cr

kg" dried

Fe

material)

fig Mn Ni Pb Sb Se

PC Southam/GL/TW <0.5 10350 3.26 229 <0.2 20.0 4556 <0.1 91.0 8.34 6.40 1 .61 <1 .0

PC Southam/GL/AC <0.5 12885 3.41 277 <0.2 28.0 5931 <0.1 128 9.20 5.86 2.29 < 1 .0

PC Southam/GL/DI <0.5 11946 3.50 261 <0.2 25.6 5344 <0.1 120 9.26 6.25 2.03 < 1 .0

PC Rochester/GE/AC <0.5 48009 3.26 548 <0.2 23.6 8993 <0.1 200 11 .9 18.9 0.271 < 1 .0

PC Rochester/GE/DI <0.5 35807 3.53 412 <0.2 19.4 7013 <0.1 154 12.2 121 0.244 < 1 .0

PC Seament/GL/TW <0.5 13464 5.04 261 <0.2 75.8 7087 <0.1 106 36.8 7.72 1 .72 <1 .0

PC Seament/GE/DI <0.5 34341 9.29 405 <0.2 48.4 7022 <0.1 133 35.8 28.0 0.948 < 1 .0

SRPC/GL/TW <0.5 13399 4.03 317 <0.2 27.2 8157 <0.1 226 12.8 51 .2 1 .60 <1 .0

PC/PFA/GL/TW <0.5 16742 7.88 342 <0.2 31 .8 7193 <0.1 114 13.7 14.2 2.56 < 1 .0

PC/GGBS/GL/TW <0.5 14544 3.24 387 <0.2 28.6 5587 <0.1 248 8.45 6.86 1 .81 <1 .0

PC/MS/GL/TW <0.5 13426 3.98 321 <0.2 22.3 6201 <0.1 134 8 .95 9.91 4 .38 <1 .0

SRPC/GE/DI <0.5 46014 3.08 535 <0.2 18.4 10347 <0.1 224 13.1 26.0 0.587 <1 .0

PC/PFA/GE/DI <0.5 48265 3.45 716 <0.2 25 .2 10190 <0.1 203 15 .2 24.7 0.758 < 1 .0

PC/GGBS/GE/DI <0.5 38732 3.90 430 <0.2 24.0 7242 <0.1 232 12.9 18 .5 0.241 <1 .0

PC/MS/GE/DI <0.5 42789 4.73 529 <0.2 21 .8 8637 <0.1 177 12.9 24.1 0.435 < 1 .0

PC Ribblesdale/GL/TW <0.5 13304 5.06 320 <0.2 22.0 5992 <0.1 88.8 9.25 11 .6 1 .55 <1 .0
5. DISCUSSION

5.1 Aqueous leachates

Only four of the thirteen metals measured were detected at concentrations above the limit

of detection . Aluminium was detected in all the leachates and in some of the leachates

above the MAC (200 pg 1" 1 ) . Barium was detected in 13 of the 16 concrete mixtures

tested, however the concentration of barium never exceeded 10% of the MAC

(1000 gg 1" 1 ). Iron was detected in 7 of the 16 concrete mixtures tested, however only one

of the duplicate test specimens (PC Seament/GLITW) gave a result greater than 10% of

the MAC (200 gg 1" 1 ) . Chromium was detected in 8 of the 16 concrete mixtures tested,

only one of the duplicate test specimens (PC Southam/GLfTW) gave a result greater than

10% of the MAC (50 p,g 1' 1 ) . There was however a large discrepancy for chromium

concentration between the duplicate samples, this may be due to non-homogeneity in the

solid samples.

The highest concentration in the aqueous leachates appeared to occur with test specimens

prepared using gravel as aggregate (eg PC/UK/GIJTW aluminium = 295 ±5 gg 1' 1

compared with PC/UK/GE/DI aluminium = 110 ±10 leg 1" 1 ) . Greater leaching of

aluminium was also observed in the test specimens containing ground granulated

blastfurnace slag, regardless of the aggregate used (PC/GGBS/GE/DI aluminium = 390

±80 p.g 1" 1 , PC/GGBS/GLIDI aluminium = 345 ±65 gg 1" 1 ) compared with the other test

specimens.

The curing conditions (deionised or tap water) did not appear to significantly affect the

concentration of metals detected in the aqueous leachates . The leaching patterns from the

air-cured samples were similar to those of the corresponding samples cured either in

deionised or tap water.

Also there was no significant difference in the results for the test sample prepared using

Portland cement manufactured at a works using Cemfuel as a supplementary fuel or the

test sample prepared using Portland cement manufactured using conventional fuel.

Mean concentrations of aluminium, barium, chromium, and iron in aqueous leachates

prepared from duplicate test cubes are given in Table 5.1 .

5.2 Metals in solid samples

Results for the analysis of total metals in the solid samples showed that the ready-mixed

concretes did not contain silver, cadmium, mercury or selenium. Of the metals found,

aluminium and iron were found in the greatest concentration, followed by barium and

manganese.
Some metals, namely arsenic, chromium, manganese, nickel and lead, were readily

extracted from the solid samples when digested in concentrated acid. However none of

these metals were detected in the aqueous leachates, except chromium which was found

at low concentrations . Aluminium, barium and iron were also readily extracted in

concentrated acid.

The type of the aggregate did not appear to affect the total concentration of metals found

in the solid samples.

Table 5.1 Mean concentrations of aluminium, barium, chromium and iron in

the aqueous leachates prepared from duplicate test cubes (gg 1'1 )

Test Sample Al Ba Cr Fe

PC/GGBS/GE/DI 390 t80 9 1 .2 ±0.6 6.5 ±0.5

PC/PFA/GLTW 370 :00 <2 1 .4 t0.8 <4

PC/GGBS/GLTW 345 :t65 9 ±1 <0.50 11 ±5

PC Southam/GIJAC 320 ±30 <2 2.1 ±0.3 <4

PC Southam/GLTW 295 t5 5 6.29 <4

PC Seament/GLTW 270 :t-20 10 :t2 0.7 ±0.1 21 ±3

PC Ribblesdale/GLTW 260 12 <0.50 13

PC/PFA/GEIDI 200 :00 70 <0.50 4.5 ±0.5

SRPC/GLTW 200 16 ±1 <0.50 11±4

PC Seament/GE/DI 190 ±30 5 1 .5±0.4 <4

PC/MS/GLTW 150±10 4±1 <0.50 <4

PC/SRPC/GE/DI 130 ±40 4 <0.50 <4

PC Rochester /GE/DI 110 ±10 8 0.6 ±0.1 <4

PC Rochester/GE/AC 90 ±30 13 <0.50 <4

PCIMS/GE/DI 80 ±10 4 0.9 10±3

PC Southam/GLDI 50±10 <2 <0.50 <4

MAC 200 1000 50 200
6. CONCLUSIONS

Results for the aqueous leachates showed only four of the thirteen listed metals to be

present above the limit of detection of the methods used. Aluminium was detected in all

the leachate sazn~plese barium. chromium and iron were detected in some of the aqueous

leachate samples. Of these metals only aluminium was detected leaching above the MAC

of 200 Rg 1' 1 for drinking water in the majority of the aqueous leachate samples. The

concentration of the other metals was mostly below 10% of the MAC.

The highest concentration of aluminium in the aqueous leachates appeared to occur with

test specimens prepared using gravel as aggregate. There was also more aqueous leaching

of aluminium and iron in test specimens prepared containing ground granulated

blastfurnace slag, regardless of the other constituents . This may be due to the type of

addition or the ratio of the addition to cement and aggregate.

The curing conditions (deionised water, tap water or air cured) did not significantly affect

the concentration of metals detected in the aqueous leachates .

There was no significant difference in the results for the test sample prepared using

Portland cement manufactured at a works using Cemfuel as a supplementary fuel or the

test samples prepared using Portland cements manufactured using conventional fuel .

Results for the analysis of total metals in the solid samples showed that the ready-mixed

concretes did not contain silver, cadmium, mercury or selenium. Of the metals found,

aluminium and iron were found in the greatest concentration, followed by barium and

manganese. Some metals, namely arsenic, chromium, manganese, nickel and lead, were

readily extracted from the solid samples when digested under concentrated acid

conditions. However none of these metals were detected in the aqueous leachates, except

chromium which was found at low concentrations . Aluminium, barium and iron were

also readily acid extracted at the high concentrations used.

A meeting with representatives of QPA and the DWI was arranged at WRc Medmenham

to discuss the results of this study. At the meeting DWI stated that the concentration of

the specified metals found in the aqueous leachates was not of concern and that actual

testing of 'admixture-free' concretes was unlikely to be required to obtain an

authorisation for use for water supply pipes, service reservoirs and water towers after 1st

April 2000. The methods used for this study could be used to `benchmark' ready-mixed

concretes.
7. REFERENCES

BS 6920 Suitability of non-metallic products for use in contact with water intended for

human consumption with regard to their effect on the quality of water;

BS 6920 1996 Part 1 Specification

BS 6920 1996 Part 2 Methods of test, Section 2.1 Samples for test

BS 6920 1996 Part 2 Methods of test, Section 2.6 The extraction of metals