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The European Union – Brite EuRam III

Mechanical properties of

lightweight aggregate concrete

EuroLightCon

Economic Design and Construction with

Light Weight Aggregate Concrete

Document BE96-3942/R23, June 2000

Contract BRPR-CT97-0381, Project BE96-3942



Although the project consortium does its best to ensure that any information given is accurate, no liability or responsibil-

ity of any kind (including liability for negligence) is accepted in this respect by the project consortium, the authors/editors

and those who contributed to the report.

Acknowledgements

This report is a deliverable of Task 4: Light Weight Aggregate Concrete Properties.

This report was prepared by Marie-Louise Peters (Smals R&D).

The research within this activity is combined with the research of Activity 3.2.1: ”Grading and composition of the aggre-

gate”, Report BE3942/R7, March 2000. Both reports can be read together.

InformationInformation regarding the report

Marie-Louise Peters, Smals R&D, De Nieuwe Erven 12, NL-5431 NT Cuijk, The Netherlands

Tel: +31 0485 322 445, e-mail: [email protected]

Information regarding the project in general:

Jan P.G. Mijnsbergen, CUR, PO Box 420, NL-2800 AK Gouda, the Netherlands

Tel: +31 182 540620, e-mail: [email protected]

Information on the project and the partners on the Internet: http://www.sintef.no/bygg/sement/elcon

ISBN 90 376 0198 7



The European Union – Brite EuRam III

Mechanical properties of

lightweight aggregate concrete

EuroLightCon

Economic Design and Construction with

Light Weight Aggregate Concrete

Document BE96-3942/R23, June 2000Contract BRPR-CT97-0381, Project BE96-3942

Selmer ASA, NO

SINTEF, The Foundation of Scientific and Industrial Research at the

Norwegian Institute of Technology, NO

NTNU, The Norwegian University of Science and Technology, NO

ExClay International, NO

Beton Son B.V., NL

B.V. VASIM, NL

CUR, Centre for Civil Engineering Research and Codes, NL

Smals B.V., NL

Delft University of Technology, NL

IceConsult, Línuhönnun hf., IS

The Icelandic Building Research Institute, IS

Taywood Engineering Limited, GB

Lias-Franken Leichtbaustoffe GmbH & Co KG, DE

Dragados y Construcciones S.A., ES

Eindhoven University of Technology, NLSpanbeton B.V., NL





Mechanical properties of lightweight aggregate concrete

BE96-3942 EuroLightCon 5

Table of Contents

PREFACE 7

SUMMARY 10

1 INTRODUCTION 11

1.1 General 11

1.2 Objective 11

1.3 Framework of the research 11

1.4 Technical content 12

1.5 Content report 12

2 REFERENCE MIXTURES 13

2.1 General 13

2.2 Matrix 13 2.3 Aggregate 14

2.3.1 General 14

2.3.2 Summary properties LWA 15

2.3.3 Particle size distribution of reference mixtures 17

2.4 Characteristics of mixtures 18

3 MECHANICAL PROPERTIES 19

3.1 General 19

3.2 Water absorption 19

3.3 Particle and bulk density 21

3.4 Crushing resistance 23 3.5 Particle shape and surface zone 23

3.6 Estimation of strength 24

4 RESULTS AND DISCUSSION 25

4.1 General 25

4.2 Density after demoulding 25

4.3 Cube compressive strength 26

4.4 Strength/density ratio 29

4.5 Ratio between flexural and compressive strength 31

4.6 Ratio between tensile splitting strength and cube

compressive strength 32 4.7 Ratio between E-value and cube compressive strength 33

5 CONCLUSIONS AND COMMENTS 35

5.1 Conclusions 35

5.2 Comments 36

6 REFERENCES 37

7 NOMENCLATURE 38

8 APPENDIX 1:

LABORATORY PROCEDURES AND TEST METHODS 40

8.1 Mixing procedure 40

8.2 Vibrating of the mixtures 40




6 BE96-3942 EuroLightCon

8.3 Casting and curing specimen 40

8.4 Used standards 41

9 APPENDIX 2: INFORMATION NEW MATERIALS VASIM (NL) 42

9.1 Material sources 42

10 APPENDIX 3: PARTICLE SIZE DISTRIBUTION 43





PREFACEThe lower density and higher insulating capacity are the most obvious characteristics of Light-

Weight Aggregate Concrete (LWAC) by which it distinguishes itself from ‘ordinary’ Normal

Weight Concrete (NWC). However, these are by no means the only characteristics, which jus-

tify the increasing attention for this (construction) material. If that were the case most of the de-

sign, production and execution rules would apply for LWAC as for normal weight concrete,

without any amendments.

LightWeight Aggregate (LWA) and LightWeight Aggregate Concrete are not new materials.

LWAC has been known since the early days of the Roman Empire: both the Colosseum and the

Pantheon were partly constructed with materials that can be characterised as lightweight aggre-gate concrete (aggregates of crushed lava, crushed brick and pumice). In the United States, over

100 World War II ships were built in LWAC, ranging in capacity from 3000 to 140000 tons and

their successful performance led, at that time, to an extended use of structural LWAC in build-

ings and bridges.

It is the objective of the EuroLightCon-project to develop a reliable and cost effective design

and construction methodology for structural concrete with LWA. The project addresses LWA

manufactured from geological sources (clay, pumice etc.) as well as from waste/secondary ma-

terials (fly-ash etc.). The methodology shall enable the European concrete and construction in-

dustry to enhance its capabilities in terms of cost-effective and environmentally friendly con-

struction, combining the building of lightweight structures with the utilisation of secondary ag-gregate sources.

The major research tasks are:

Lightweight aggregates : The identification and evaluation of new and unexploited sources spe-

cifically addressing the environmental issue by utilising alternative materials from waste. Fur-

ther the development of more generally applicable classification and quality assurance systems

for aggregates and aggregate production.

Lightweight aggregate concrete production : The development of a mix design methodology to

account for all relevant materials and concrete production and in-use properties. This will in-

clude assessment of test methods and quality assurance for production.

L ightweight aggregate concrete properties : The establishing of basic materials relations, the

influence of materials characteristics on mechanical properties and durability.

Lightweight aggregate concrete structur es : The development of design criteria and -rules with

special emphasis on high performance structures. The identification of new areas for applica-

tion.

The project is being carried out in five technical tasks and a task for co-ordination/management

and dissemination and exploitation. The objectives of all technical tasks are summarised below.

Starting point of the project, the project baseline, are the results of international research work

combined with the experience of the partners in the project whilst using LWAC. This subject is

dealt with in the first task.





Tasks 2-5 address the respective research tasks as mentioned above: the LWA itself, production

of LWAC, properties of LWAC and LWAC structures.

Sixteen partners from six European countries, representing aggregate manufacturers and suppli-

ers, contractors, consultants research organisations and universities are involved in the Eu-roLightCon-project. In addition, the project established co-operation with national clusters and

European working groups on guidelines and standards to increase the benefit, dissemination and

exploitation.

At the time the project is being performed, a Working Group under the international concrete

association f ib (the former CEB and FIP) is preparing an addendum to the CEB-FIP Model Code

1990, to make the Model Code applicable for LWAC. Basis for this work is a state -of-the-art

report referring mainly to European and North-American Standards and Codes. Partners in the

project are also active in the f ib Working Group.

General information on the EuroLightCon-project, including links to the individual project part-ners, is available through the web site of the project: http://www.sintef.no/bygg/sement/elcon/

At the time of publication of this report, following EuroLightCon-reports have been published:

R1 Definitions and International Consensus Report. April 1998

R1a LightWeight Aggregates – Datasheets. Update September 1998

R2 LWAC Material Properties State-of-the-Art. December 1998

R3 Chloride penetration into concrete with lightweight aggregates. March 1999

R4 Methods for testing fresh lightweight aggregate concrete, December 1999

R5 A rational mix design method for lightweight aggregate concrete using typical UK ma-

terials, January 2000

R6 Properties of Lytag-based concrete mixtures strength class B15-B55, January 2000

R7 Grading and composition of the aggregate, March 2000

R8 Properties of lightweight concretes containing Lytag and Liapor, March 2000

R9 Technical and economic mixture optimisation of high strength lightweight aggregate

concrete, March 2000

R10 Paste optimisation based on flow properties and compressive strength, March 2000

R11 Pumping of LWAC based on expanded clay in Europe, March 2000

R12 Applicability of the particle-matrix model to LWAC, March 2000

R13 Large-scale chloride penetration test on LWAC-beams exposed to thermal and hygral

cycles, March 2000

R14 Structural LWAC. Specification and guideline for materials and production, June 200R15 Light Weight Aggregates, June 200

R16 In-situ tests on existing lightweight aggregate concrete structures, June 200

R17 Properties of LWAC made with natural lightweight aggregates, June 2000

R18 Durability of LWAC made with natural lightweight aggregates, June 2000

R19 Evaluation of the early age cracking of lightweight aggregate concrete, June 2000

R20 The effect of the moisture history on the water absorption of lightweight aggregates,

June 2000

R21 Stability and pumpability of lightweight aggregate concrete. Test methods, June 2000

R22 The economic potential of lightweight aggregate concrete in c.i.p. concrete bridges,

June 2000

R23 Mechanical properties of lightweight aggregate concrete, June 2000





R24 Prefabricated bridges, June 2000

R25 Chemical stability, wear resistance and freeze-thaw resistance of lightweight aggregate

concrete, June 2000

R26 Recycling lightweight aggregate concrete, June 2000

R27 Mechanical properties of LWAC compared with both NWC and HSC, June 2000R28 Prestressed beams loaded with shear force and/or torsional moment, June 2000

R29 A prestressed steel-LWAconcrete bridge system under fatigue loading

R30 Creep properties of LWAC, June 2000

R31 Long-term effects in LWAC: Strength under sustained loading; Shrinkage of High

Strength LWAC, June 2000

R32 Tensile strength as design parameter, June 2000

R33 Structural and economical comparison of bridges made of inverted T-beams with top-

ping, June 2000

R34 Fatigue of normal weight concrete and lightweight concrete, June 2000

R35 Composite models for short- and long-term strength and deformation properties of

LWAC, June 2000R36 High strength LWAC in construction elements, June 2000

R37 Comparison of bridges made of NWC and LWAC. Part 1: Steel concrete composite

bridges, June 2000

R38 Comparing high strength LWAC and HSC with the aid of a computer model, June 2000

R39 Proposal for a Recommendation on design rules for high strength LWAC, June 2000

R40 Comparison of bridges made of NWC and LWAC. Part 2: Bridges made of box beams

post-tensioned in transversal direction, June 2000

R41 LWA concrete under fatigue loading. A literature survey and a number of conducted

fatigue tests, June 2000

R42 The shear capacity of prestressed beams, June 2000

R43 A prestressed steel-LWA concrete bridge system under fatigue loading, June 2000





SUMMARYThe objective of the research described in this report is to examine the influence of replacing

normal weight aggregate (NWA) by lightweight aggregate (LWA) .

To achieve this objective two reference mixtures have been made (REF I and REF II). Both

mixtures are ready-mixed-concrete. REF II is the same as REF I with the exception of using

pumice sand, size 0-1mm and pumice, size 0-3mm in stead of sand 250µm-500µm and sand

125µm-250µm. Also the water/cement ratio (w/c) and the water/binder ratio (w/b) is different.

REF I has a nominal w/c-ratio of 0.60 and a nominal w/b-ratio of 0.4.

In these two reference mixtures NWA has been replaced by LWA in steps of 20% per volume.

The used LWA are: Leca 670 and Leca 800 (Norway), Liapor 3 and Liapor 8 (Germany), Lytag

(The Netherlands), Pumice (Iceland) and six new materials from BV Vasim (The Netherlands).The grading of the aggregate has always been the same, because the NWA, size 4-8mm and 8-

12mm, was replaced by LWA in the sizes 4-8mm and 8-12mm.

Of each mixture two samples of 40 litre concrete is made and the following properties have

been determined: cube compressive strength development, flexural strength, modulus of elastic-

ity (E-value) and the tensile splitting strength.

The following conclusions can be drawn (considering this type of reference mixture with the

mentioned nominal w/c of 0.60):

− The higher the density of the LWAC mixture, the higher the strength

− With the exception of Liapor 3 and Pumice, the compressive strength increases with the

amount of replacement of NWA by LWA. This increase is probably due to the water ab-

sorption of the LWA. The effective w/c is lower and the strength will be higher.

− To determine if there really is a linear trend more research is needed. The steps of replace-

ment should be smaller, the LWA should be sealed (if it were possible), segregation of the

LWA and the effective water content of the LWAC mixtures should be controlled.

− The strength development will continue after 28 days due to the internal water tank of the

LWA. Tests with prism compressive strength showed an increase of 10 N/mm2

between 28

days and 92 days.

− The best density/strength ratio is achieved in the case of this particular reference mixture,

when 100% Liapor 8, 80% Lytag and 80% Leca 800 is used.

− The ratio between the tensile splitting strength and the cube compressive strength is linear.The higher the strength the higher the tensile splitting strength.

The biggest problem that emerged during this research was the water absorption of the different

LWA. In all the mixtures the amount of water that was added to the mixture is kept constant. As

a consequence of this the effective water content will decrease with increasing replacement per-

centage of NWA by LWA. More research is needed to determine the effective water absorption

by LWA in a concrete mixture.

In the Dutch Code, VBC 1990, a relation is given for the cube compressive strength and the ten-

sile splitting strength in the case of NWC. This curve lies lower than the results found in this

study, but the angle of inclination is the same. More research is needed to give an indication of

this relation in the case of LWAC.





1 INTRODUCTION

1.1 GeneralThis report describes the research within Activity 4.2.3: “Mechanical properties of Lightweight

Aggregate Concrete”. The mechanical properties will be determined on concrete mixtures with

different kind of lightweight aggregate (LWA) such as Lytag from The Netherlands, Liapor

from Germany, Leca from Norway, Pumice from Iceland and new developed materials from

Vasim BV from The Netherlands.

This research is combined with the research of Activity 3.1.2: “Grading and composition of the

aggregate”. A report of this research is available (DocumentBE96-3942/TG3/4, April 1999).

The mixtures of this activity have been used to further examine the mechanical properties of these mixtures.

In this chapter the objectives of Activity 4.2.3 will be presented in section 1.2. Section 1.3 and 1.4

will describe the framework and the technical content of the research, respectively. Finally, section

1.5 will give a short introduction of this report.

1.2 ObjectiveThe main research task of Task 4 is to establish basic materials relations and the influence of

materials characteristics on mechanical properties and durability.

This research establishes a part of this task regarding the materials relations and the influence

of materials characteristics on mechanical properties.

The main objective of this research is to examine the influence of replacing normal weight ag-

gregate (NWA) by different kinds of lightweight aggregate (LWA) on hardened concrete.

Within this objective the combination of LWA and NWA will be determined with the best com-

bination of results regarding compressive strength, flexural strength, tensile splitting strength,

workability and demoulding density of the LWAC.

1.3 Framework of the researchTo determine the influence of replacing NWA by LWA two reference mixtures have been

made:

• REF I: a ready-mixed concrete mixture, often used in practice in the Netherlands, a nominal

water/cement ratio (w/c) of 0.60.

• REF II: a ready-mixed concrete mixture, same mixture as REF I but with the use of pumice

sand size 0-1 mm and pumice size 0-3mm. Nominal w/c of 0.40.

The components and the properties of these mixtures are presented in chapter 2 of this report.

In these reference mixtures the particle size distribution is kept constant.

In this particle size distribution, the NWA, size 4-12mm, has been replaced by LWA in steps of

20% per volume (20%, 40%, 60%, 80% and 100%). The LWA used are: Liapor 3 and Liapor 8

(Germany), Leca 670 and Leca 800 (Norway), Lytag (The Netherlands), Pumice (Iceland) and





six new materials from Vasim BV (The Netherlands).

The LWA is used oven dry (24 hours in a oven with a temperature of 105°C) or surface dry (af-

ter 24 hours saturated, with removed absorbed surface water).

1.4 Technical contentOf every mixture two samples have been made:

Sample 1: 12 cubes (100x100x100mm3) and 6 cubes (150x150x150mm

3);

Sample 2: 3 cylinders (Ø150x300mm3) and 6 beams (100x100x500mm

3).

From these samples specimen were made to determine the workability and the mechanical

properties of LWAC. This report describes mainly the mechanical properties of LWAC.

The technical content of the research within Activity 4.2.3 contains determination of:

• Compressive strength development (f cm,cube):

on cubes 150x150x150mm3

after: 28 days;


after: 1 day, 3 days, 7 days and 28 days;• Flexural strength (f ct,fl):

on prisms 100x100x500mm3after 28 days;

• Modulus of elasticity (E-value);

on cylinders Ø150x300mm3

after 28 days;

• Tensile splitting strength (f ctm,sp):


after 28 days.

• Relation between density and compressive strength:

density after demoulding and compressive strength after 28 days;

• Relation between compressive strength and flexural strength:

after 28 days;• Relation between compressive strength and tensile splitting strength:after 28 days;

• Relation between compressive strength and modulus of elasticity:after 28 days.

1.5 Content reportIn chapter 2 the characteristics of the reference mixtures are presented. Chapter 3 describes the

mechanical properties, which includes the influence of the properties of the LWA, such as water

absorption, particle and bulk density, crushing resistance and particle shape and surface area, on

the mechanical properties. An estimation of the strength is also given at the end of this chapter.Chapter 4 describes and discusses the results, including density after demoulding, cube com-

pressive strength, tensile splitting strength, flexural strength and modulus of elasticity.

In chapter 5 the conclusions of this research are drawn.

And finally, in chapter 6, the quality assurance is written. This includes all the “highlights” of the

experimental research as well as a number of remarks.





2 REFERENCE MIXTURES

2.1 GeneralThe research within Activity 3.1.2 and Activity 4.2.3 is combined.

Within Activity 3.1.2 reference mixtures are designed, using the computer model Europack,

version 1.1, copyright 1995. This computer model determines a grading of the aggregate with an

optimum in packing density. Chapter 2 of this report will only give a summary of the character-

istics of these reference mixtures. More details and the selection of the reference mixtures will

be found in the report of Activity 3.1.2 (document BE96-3942/TG3/4, April 1999).

2.2 Matrix

A ready-mixed concrete mixture has been selected as reference mixture (REF I). This mixture

has often been used in practice in The Netherlands. To reduce the density and the w/c ratio, an-

other reference mixture has been made (REF II). In this mixture pumice sand, size 0-1 mm, and

pumice sand, size 0-3mm, has been used. The components of the matrix are the same as in REF

I. The characteristics of these components are given in Table 1.

Table 1: Characteristics of components of the matrix of reference mixtures REF I and REF II

Chemical analysis [m/m %] ρ

Material Origin SiO2 Al2O3 CaO MgO SO3 Cl [kg/m3]

Cement Cem I; 42,5R Buderus (NL) 17.7 5.9 62.9 0,9 2.9 0.01 3150

Additive Fly-ash Geertruidenberg

(NL)

55.6 23.3 5.3 1.9 - 0.01 2280

Water *** Cuijk (NL) 1000

Admixture Betomix 240

(plasticizer)

Masterbuilders

(NL)

Melamine/sulphonate 1140

Data about the matrix composition of the two mixtures are given in Table 2. REF I has a nomi-

nal water/cement ratio (w/c) of 0.60 and a nominal water/binder ratio (w/b) of 0.54 (in confor-

mity with prEN 206: k=0.4). REF II has a nominal w/c of 0.40 and a nominal w/b of 0.36.

Table 2: Matrix composition of references mixtures REF I and REF II

REF I REF II

[kg/m3] [kg/m3]

Water 165 172

Cem I;42,5R 276 429

Fly-ash 69 107

Betomix 240 0,9% 0,9%





2.3 Aggregate

2.3.1 GeneralSmals can deliver sand and gravel with a specific particle size distribution. Eight different sand

and gravel grain sizes can be used to compose such a specific particle size distribution. In this

research these grain sizes are used to compose a grading with an optimum in packing. This op-

timum is calculated with the computer program “Europack”.

The used sand and gravel grainsizes are:

• fine aggregate:

sand, size 0.125-0.250mm

sand, size 0.250-0.500mm

sand, size 0-2mm (SZ 1794)

• coarse aggregate:

gravel, size 2-5mm

gravel, size 2-4mmgravel, size 4-8mm

gravel, size 8-12mm

gravel, size 12-16mm

To design mixtures of LWAC, different LWA had to be selected. LWA used in this research

are:

• Expanded clay:

Leca 670 (Norsk Leca)

Leca 800 (Norsk Leca)

Liapor 3 (Lias-Franken: Liapor-Plant Pautzfeld)

Liapor 8 (Lias-Franken: Liapor-Plant Pautzveld)

• Based on fly-ash:

Lytag (Vasim)

• Natural:

Pumice (Iceland: Hekla)

• New materials of Vasim (Appendix 1):

Material-source number: 1A à this report refers to this material as Vasim 1.

Material-source number: 5/7B à this report refers to this material as Vasim 5/7b.

Material-source number: 3 à this report refers to this material as Vasim 3.


Material-source number: 7à

this report refers to this material as Vasim 7.Material-source number: 8 à this report refers to this material as Vasim 8.


The particle size distributions of the NWA and LWA are given in Appendix 3.

Comparing NWA and LWA, a lot of properties differ. The properties that differ the most are:

water absorption, bulk and particle density, void volume and crushing resistance.

In section 2.3.2 a summary of these properties for each LWA is given. As already mentioned,

more details can be found in the report of Activity 3.1.2 (document BE96-3942/TG3/4, April

1999).

Section 2.3.3 describes the grading of the reference mixtures.





2.3.2 Summary properties LWAIn Table 3 the properties of the different LWA, used in this research, are summarised. The stan-

dards which are used are listed in Appendix 1.

Looking at the characteristics, there is a relationship between particle density and bulk density,and between particle density and crushing resistance. These relationships are discussed in the

report of Activity 3.1.2 (Document BE96-3942/TG3/4, April 1999). In this report only the

groups with similar properties are given:

Group 1: Liapor 3 and Pumice;

Group 2: Leca 670 and Vasim 5/7b;

Group 3: Liapor 8, Lytag and Leca 800;

Group 4: Vasim 1.

When LWA of one group is used in a concrete mixture, there should be conformity in results

concerning workability and mechanical properties of the concrete. For example, the compres-

sive strength of concrete with Liapor 3 and concrete with Pumice (both are LWA of group 1)should be more or less the same.



Table 3: Properties LWA.

Material Grainsize Water absorption [%] Density [kg/m3] Void volume Crushing resistance

15 min. 30 min. 60 min. 24 hours 7 days Particle Bulk Uncompacted Compacted [N/mm2]

Leca 670 4-8mm 8.8 *** 9.7 13.9 19.6 1149 701 39.0 34.4 6.3

8-12mm 7.3 *** 8.6 11.1 18.0 1123 670 40.4 36.7 ***

Leca 800 4-8mm 6.4 6.5 13.5 *** 16.9 1386 810 41.6 36.6 10.3

Liapor 3 4-8mm 19.0 19.3 22.1 27.5 28.0 622 374 39.9 36.4 1.8

8-12mm 18.9 *** 24.8 34.1 36.4 541 300 44.6 41.7 ***

12-16mm 22.3 *** 24.5 31.0 *** *** *** *** ***

Liapor 8 4-8mm 7.4 *** 8.4 13.1 19.4 1309 803 38.7 34.6 ***

8-12mm 5.6 *** 7.6 12.3 *** 1502 805 46.4 42.4 ***

12-16mm 5.6 *** 7.0 11.7 *** *** *** *** 38,3 ***

Lytag 4-8mm *** 15.0 15.5 18.0 21.0 1386 790 43.0 36.8 4.5

8-12mm *** *** *** *** *** 1386 802 42.1 36.3 ***

Pumice 4-8mm *** *** *** *** *** 464 311 32.9 24.1 1.4

8-12mm 36.3 36.3 66.0 *** 190,0* 577 383 50.1 43.9 ***

12-16mm 39.0 39.0 *** *** 76.1 655 299 54.4 48.2 ***

Vasim 1 4-8mm *** *** 29.6 *** *** 1531 956 37.6 31.2 5.2

8-12mm *** *** 33.0 *** *** 1595 940 41.1 34.9 ***

Vasim 3 4-8mm 15.6 19.6 22.0 22.0 *** 1225 712 41.9 34.7 ***

6-12mm 17.0 17.0 17.2 17.2 *** 1337 720 46.1 40.7 ***

Vasim 5/7b 4-8mm *** *** 32.0 *** *** 1213 855 29.5 32.7 7.0

8-12mm *** *** 31.5 *** *** 1242 805 35.2 29.9 ***

Vasim 7 4-12mm 16.0 16.0 16.4 16.8 *** 1404 805 43.0 35.0 ***

Vasim 8 4-12mm 16.0 16.4 16.4 16.4 *** 1337 769 42.5 38.9 ***

Vasim 9 4-12mm 16.0 16.4 16.4 16.4 *** 1351 760 43.8 37.8 ***

*** These values are not determined.

* The water absorption of pumice, size 8-12mm, is more than 100%, which means that there is more mass of water absorbed than dry mass.

Used standards:

Water absorption prEN 1097-6

Density prEN 1097-6

Void volume prEN 1097-3

Crushing resistance prEN 13055-1

M e c h ani c al pr o p er t i e s of l i gh t w e

i gh t a g gr e g a t e c on c r e t e

1 6

B E 9 6 - 3 9 4 2 E ur oL i h t C on





2.3.3 Particle size distribution of reference mixtures

A particle size distribution with an optimum in packing density is composed with the computer

program Europack (version 1.1, copyright 1995). In the report of Activity 3.1.2 (Document

BE96-3942/TG3/4, April 1999) this composition is described. In this report only the calculated particle size distribution is given.

• fine aggregate: sand, size 0.125-0.250mm 5.2%

sand, size 0.250-0.500mm 5.3%

sand, size 0-2mm (SZ 1794) 25.0%

• coarse aggregate: gravel, size 2-5mm 15.8%

gravel, size 2-4mm 5.8%




The particle size distribution curve is given in figure 1. This particle size distribution is in con-

formity with the Dutch standard NEN 5950. This particle size distribution is also, when using

these particular grain sizes of sand and gravel, the partic le size distribution with an optimum

packing density (packing degree is 0.763).

The NWA, size 4-8mm and 8-12mm, was replaced by all the different LWA, mentioned in

paragraph 4.3.1, per volume in increments of 20% (20, 40, 60, 80, 100%). The grading will be

more or less the same. It will always be between the A-curve and the B-curve of figure 1.

Curves conform NEN 5950

0,5

19,4

30,8

42

51,6

64,269,1

80,1

93,8

99,7

5

26

40

54,464

79

8892,5

97

24

36

44

58

68

80

92

12

20,426

38

51

66,5

82

0

20

40

60

80

100

120

1611,285,64210,5000,2500,125

Sieve [mm]

S i e v e r e s i

d u e

[ % ]

Reference

Curve A

Curve B

Curve C

Figure 1: Particle size distribution with an optimum packing density of mixtures.





2.4 Characteristics of mixturesIn Table 4 the characteristics of the two mixtures REF I and REF II are given.

Only the gravel in size 4-8mm and 8-12mm will be replaced by Leca 670, Leca 800, Liapor 3,

Liapor 8, Lytag, Pumice and six new materials, developed by Vasim BV (NL) in steps of 20%

per volume (20%, 40%, 60%, 80% and 100%).

Table 4: Composition of reference mixtures.

Materials REF I REF II

Fine and coarse aggregate

0-2mm 25.0% ***

0.250-0.500mm 5.3% ***

0.125-0.250mm 5.2% 5.2%

Pumice 0-1mm *** 25.0 %

Pumice 0-3mm *** 5.3%

2-5mm 15.8% 15.8%2-4 mm 5.8% 5.8%

4-8 mm 11.5% 11.5%

8-12 mm 8.8% 8.8%

12-16 mm 22.6% 22.6%

Total aggregate: 100% 100%

Void volume 24.0% 32.7%

Particles < 125 µm 0.3% 4.3%

Vsa 48.3% 44.3%

Vst 51.4% 51.4%FMsa 3.1% 3.1%

FMst 1.6% 1.6%

MATRIX

Water 165 kg 172 kg

Cem I; 42,5R 276 kg 429 kg

Fly-ash 69 kg 107 kg

Betomix 240 2.5 kg 3.9 kg

Volume percentage matrix 28% 35%

λ-value 0.51 ***

W/c (nominal) 0.60 0.40

W/b (nominal, k=0.4) 0.54 0.36

Vsa volume % of particles size 0.125-4mm

Vst volume % of particles size > 4mm

FMsa Fineness modulus of particles size 0.125mm-4mm

FMst Fineness modulus of particles size > 4mm

λ-value Flow-resistance-value

*** These values are not determined.





3 MECHANICAL PROPERTIES

3.1 GeneralLWA has properties that differ from NWA. This has an effect on the mechanical properties of

the concrete. Some of these factors are:

• water absorption;

• particle and bulk density;

• crushing resistance;

• particle shape and surface zone.

In the following sections these factors will be described in relation to the mechanical properties

of LWAC.

3.2 Water absorptionThe most important factor mentioned above is water absorption. Because of this water absorp-

tion the effective w/c ratio will decrease and inside the LWA a “water tank” will be found. This

water absorption makes it possible that hydration continues relatively long, namely when at later

ages initially absorbed water is transported to the hydrating paste.

It is not clear how much water in the mixture will be absorbed by the LWA. Water absorption in

a completely water environment or in a concrete mixture is totally different.

There is also a difference in water absorption in a water tank or in a rotating pan-mixer. Sometests have been made with different LWA to determine the difference in water absorption in a

water tank and in a rotating pan-mixer, filled with water. Liapor 3 and Pumice, i.e. both LWA

with a lot of pores, had a water absorption after 15 minutes in a “water tank” of 18.6% and

36.3%, respectively. But in a rotating pan-mixer filled with water these values were 26.1% and

27.5%, respectively. Tests with dense LWA, for instance Liapor 8 and Leca 800, showed that

this difference was about 0%.

When mixing LWAC, there should be a correction of the mixing water because of this water

absorption by LWA. An approximate estimation of this correction can be made on the basis of

the 30 minutes water absorption value. Research at the Norwegian University of Science and

Technology showed that this correction should be based on the 1 hour water absorption value in

the case Leca is used.

In this research, no correction of the water content has been made for water absorption by the

LWA. In all mixtures the same amount of mixing water was added, viz. 165 kg/m3. Since dif-

ferent types of LWA were used, each type having characteristic water absorption, the effective

water/cement ratios of the mixtures was different. This, of coarse, complicates the interpretation

of the test results. Since all the aggregates used in this research were oven-dried before mixing

and the absorption characteristics of the different aggregates are known (see data sheets), it is

possible to estimate the effective water/cement ratio as a function of the replacement percentage

of the NWA by LWA (see later in this paragraph).

In all the mixtures the NWA, size 4-8mm and 8-12mm, will be replaced by the different LWA.

A mixture consists of 280 litre matrix and 720 litre aggregate. This 720 litre aggregate weighs,





in the case of NWA, 720x2.645kg/l=1904.4 kg. The volume of the fractions 4-8mm and 8-

12mm is: (11.5%+17.3?%) x 720 litres = 207.36 litres. The NWA fractions 4-8mm and 8-12mm

are replaced by LWA in steps of 20%. In Table 5 the amount of LWA is presented for each re-

placement percentage in kg per m3.

Table 5: Amount of LWA in kg per 1 m3

concrete

m/m Leca 670 Leca 800 Liapor 3 Liapor 8 Lytag Pumice Vasim 1 Vasim 5/7b

20% 33.207 40.515 17.013 41.100 40.515 16.516 44.695 36.043

40% 66.400 81.031 34.026 82.201 81.031 33.032 89.391 72.086

60% 99.600 121.546 51.039 123.300 121.546 49.548 134.087 108.129

80% 132.800 162.063 68.052 164.400 162.063 66.065 178.783 144.172

100% 166.038 202.578 85.066 205.501 202.578 82.580 223.478 180.215

Looking at the water absorption after different periods of time (15 min, 30 min, 60 min and

7days), an effective w/c ratio in the different mixtures would hold as presented in figures 2 and

3. For each type of LWA the effective w/c-ratio decreases when more NWA is replaced byLWA. Hypothetically the lower the w/c -ratio, the dryer the mixture and the higher the com-

pressive strength. But if the mixture is too dry it will be difficult to compact it and thus the

strength will decrease.

Figure 2: Effective w/c-ratio due to water absorption after 15 min and 30 min.

Figure 3: Effective w/c-ratio due to water absorption after 60 min and 7 days.

As mentioned earlier already it is not clear how much water the LWA will absorb in a mixture.

Because of water absorption of the LWA, the effective w/c-ratio will decrease and the strength

of the hardened concrete will be higher. This should be considered when analysing the data. It

seems reasonable to assume that the water absorption after 60 min. gives the best approximation

of the w/c ratio at the time of setting and is closest to the effective w/c ratio.

Effective w/c-ratio (waterabsorption after 15 min)

0,53

0,54

0,55

0,56

0,57

0,58

0,59

0,60

20% 40% 60% 80% 100%

Replaced NWA with LWA

E f f e c

t i v e w

/ c - r a

t i oLeca 670

Leca 800

Liapor 3

Liapor 8

Effective w/c-ratio (waterabsorption after 30 min)

0,48

0,50

0,52

0,54

0,56

0,58

0,60

20% 40% 60% 80% 100%


E f f e c t i v e w / c - r a t i o

Leca 800

Liapor 3

Pumice

Vasim I

Effective w/c-ratio (water absorption after 60 min)

0,48

0,50

0,52

0,54

0,56

0,58

0,60

20% 40% 60% 80% 100%

Replaced NDA by LWA

E f f e c t i v e w / c - r a t i o

Leca 670

Leca 800

Liapor 3

Liapor 8

Lytag

Pumice

Effective w/c-ratio (after 7 days)

0,35

0,40

0,45

0,50

0,55

0,60

20% 40% 60% 80% 100%


E f f e c

t i v e w

/ c - r a

t i

Leca 670

Leca 800

Liapor 3

Liapor 8

Lytag

Pumice

Vasim I

Vasim II





3.3 Particle and bulk densityLooking at the particle density of the different LWA, Liapor 3 and Pumice have the lowest

value. Because of this low density, the mixtures with these LWA will have problems when the

concrete will be compacted. Segregation will occur and the LWA will float on the surface of the

fresh concrete. Due to this segregation the strength will be lower. The particle and bulk densityare given in figure 4.

Figure 4: Particle and bulk density per LWA

Figure 5: Theoretical density of mixtures with different kind of LWA.

Particle and bulk density [kg/m3]

1136

1386

582

14061386

565

1563

1281

1228

1404

1337 1351

686

810

337

804 796

331

948

716

830805

769 760

0

20 0

40 0

60 0

80 0

1000

1200

1400

1600

1800

Leca 670 Leca 800 Liapor 3 Liapor 8 Lytag Pumice Vasim 1 Vasim 3 Vasim

5/7b

V as im 7 V as im 8 V as im 9

Lightweight aggregate

D e n s

i t y [ k g / m

3 ]

Particle

Bulk

Theoretical density

1950

2000

2050

2100

2150

2200

2250

2300

2350

2400

2450


5/7b

Vasim 7 Vasim 8 Vasim 9


T h e o r e

t i c

a l d e n s

i t y [ k g

/ m 3 ]

20%

40%

60%

80%

100%





The density of the particles also has an effect on the density of the different mixtures. The lower

the particle density, the lower the density of the mixture will be. The theoretical density of the

concrete mixtures with different LWA is given in figure 5. This decrease is strongly correlated

with the percentage of the NWA that is has been replaced.

In figure 6 the theoretical density of the concrete mixtures is given per percentage of replace-

ment. When replacing 20% of the NWA it doesn’t matter which LWA is used, the density will

be more or less the same and probably there will not be much difference in strength.

Figure 6: Theoretical density per replacement of the NWA

When more than 20% of the NWA is replaced, the difference between Liapor 3 and Pumice and

the other LWA is bigger.

With the exception of Liapor 3 and Pumice, the different LWA have, at a certain percentage of

replacement, the same density. The strength of the concrete with these materials should also be

more or less the same.

Theoretical density

1950

2000

2050

2100

2150

2200

2250

2300

2350

2400

2450

Leca 670 Leca 800 Liapor 3 Liapor 8 Lytag Pumice Vasim 1 Vasim 3 Vasim5/7b



T h e o r e

t i c a

l d e n s

i t y [ k g

/ m 3 ]

20%

40%

60%

80%

100%





3.4 Crushing resistanceStrength and stiffness of aggregate particles have an effect on the strength of the concrete.

Weaker particles require stronger mortars and thus higher cement contents. There is a differencein fracture path between NWA and LWA when they are used in concrete. Figure 7 shows this

difference.

Lightweight aggregate Normal weight aggregate

Figure 7 Fracture path of lightweight and normal weight aggregate

In the case of LWA the fracture path travels through the particle. In the case of NWA this frac-

ture path travels around the particle.

In LWAC, the matrix will be the stronger than the LWA. The LWAC will collapse through the

LWA-particles.

In NWC, the particles will be stronger than the matrix and the fracture path will go around the

NWA, i.e. through the matrix.

According to the standard prEN 13055-1:1997, there is no simple relationship between the

crushing resistance of LWA and the properties of the concrete. The test results of the crushing

resistance should be considered as an internal production control. Liapor 3 and Pumice have the

lowest strength (±1,5N/mm2). With the exception of Liapor 8 and Leca 8 (±10 N/mm

2), the

crushing resistance of the different LWA is ±5 N/mm2. Because of this difference it could be

expected that Pumice and Liapor 3 will not give high strengths.

More information about aggregate strength can be found in the report: “LWAC Material Proper-

ties, State-of-the-Art” (Document BE96-3942/R2, December 1998), section 2.3.3: Aggregate

strength.

3.5 Particle shape and surface zoneWhen the surface of the particle is porous, the matrix will penetrate into the pores of the parti-

cle. Because of this penetration into the surface of the particle, the matrix will be firmly attached

to the particle. This will result in a stronger bond between the aggregate and the matrix.

Research in Norway by Sintef showed that, in the case of Leca, only water was penetrated in the

LWA and not, for instance, cement or fly-ash.





Particles <125µm attached to the LWA-particles have an influence on the need of mixing water.

The more particles <125µm, the more water is needed. These particles <125 µm have also an

effect on the effectiveness of a plasticizer. The more particles <125µm, the better the effect of

plasticizer.

3.6 Estimation of strengthLooking at the properties of the different LWA mentioned in the sections above, it is possible to

give an estimation of the strength.

Because of the water absorption of the LWA, the w/c -ratio will increase the more NWA is re-

placed by LWA. The lower the w/c-ratio, the higher the strength.

The density decreases when more NWA is replaced by LWA. The lower the density, probably

the lower the strength.

The crushing resistance of LWA is very low compared to NWA. The more NWA is replaced the

lower the strength.For each property a trend curve can be made. It is not known how much the different curves

increase or decrease. It is only an indication what could happen depending on what kind of

LWA is used and which property will dominate.

Strength

W/c-ratio

Density

Crushing resistance

Segregation

Replaced NWA by LWA

Figure 8: Trend curves, indicating strength depending on material properties.

Depending on what kind of LWA is used the trend curve will increase or decrease.For each different LWA one of the factors will dominate. Density and segregation will probably

predominate in the case of Liapor 3 and Pumice and the strength will decrease the more NWA is

replaced by LWA.





4 RESULTS AND DISCUSSION

4.1 GeneralTwo reference mixtures have been made. In these reference mixtures the NWA has been re-

placed by LWA in steps of 20% per volume.

Of these mixtures the following properties are determined:

• Density after demoulding;

• Cube compressive strength on cubes 100x100x100mm3

and 150x150x150mm3;

• Tensile splitting strength on cubes 150x150x150mm3;

• Flexural strength on prisms 100x100x500mm3;

• Modulus of elasticity on cylinders ∅150x300mm3

.These properties will be presented and discussed in the following sections.

4.2 Density after demouldingConform prEN 206 the definition of LWAC is: Concrete having an oven-dry density of not less

than 800 kg/m3

and not more than 2100 kg/m3. It is produced using lightweight aggregate for all

or part of the total aggregate. In this research the density after demoulding is determined. For

Figure 9: Density after demoulding, Concrete with different LWA-percentages

some mixtures with different kind of LWA the oven-dry density was measured. The difference

between oven-dry density and demoulding density was about 100 to 150 kg/m3. All the values

in figure 9 can be subtracted with this value. In the graphs it can be seen that, if 20% of NWA

(fractions 4-8 mm and 8-12 mm) is replaced by LWA, the difference in density between REF I

Density after demoulding

2270

2250

2310

2230

2250

2170

2250

22702260

2280

2160

2220

2160

2220

22402230

2310

22502260

22402230

2140

2090

2170

2210

2170

2260

2280

2220 22202230

2190

2120

2180

2030

2180

2210

2140

22002190

2290

2290

2190

2280

2190

1850

1900

1950

2000

2050

2100

2150

2200

2250

2300

2350


5/7b



D

e n s

i t y a

f t e r

d e m o u

l d i n g

[ k g

/ m 3 ]

20%

40%

60%

80%

100%





and the mixtures with LWA is about 40 kg/m3. When 100% is replaced, the average difference

is about 170 kg/m3, depending on what kind of LWA is used.

Some mixtures appear to have a relatively high density and can not be considered as LWAC.

This should be borne in mind when looking at the results of the compressive strength tests.

4.3 Cube compressive strengthTwo sizes of cubes are made. Size 100x100x100mm

3and 150x150x1503mm

3. Cube compres-

sive strength after 28 days is determined on both sizes. Looking at the results the values of the

cube compressive strength determined on cubes 100x100x100mm3

are higher than on cubes

150x150x150mm3. This mean value of the conversion factor is: 0,981.

Ratio between cubes 100x100x100mm3 and 150x150x150mm3

0,0

0,2

0,4

0,6

0,8

1,0

1,2

0,0 10,0 20,0 30,0 40,0 50,0 60,0

Compressive strength on cubes 100x100x100mm3 [N/mm2]

R a

t i o

Figure 10: Ratio between compressive strength measured on cubes 100x100x100mm3

and on cubes

150x150x150mm3

After multiplying the results of the cube compressive strength on cubes 100x100x100mm3

with

their own conversion factor, the strength development as presented in figure 10 is obtained. In

this graph all the results are presented.





The strength development of Liapor 3 and Pumice are the lowest. Lytag has the best results. The

difference between the lowest and the highest compressive strength is about 20N/mm2.

Due to the internal “water tank” of the LWA, the strength development after 28 days will con-

tinue. This strength gain might be limited, however, by the strength of the aggregate.

Tests showed that the compressive strength on prisms after 92 days was about 10 N/mm2

higher

than after 28 days. The more water is absorbed initially by the LWA, the longer the hydration

process may continue.

The hypothesis that the strength increases (due to water absorption in the initial stage of mixing)

the more NWA is replaced by LWA could be true. At least with the kind of concrete mixtures

and with the w/c ratios considered in this test series.



Strength development of mixtures REF I

0,0

10,0

20,0

30,0

40,0

50,0

60,0

0 5 10 15 20 25 30

Days

C u b e c o m p r e s s i v e s t r e n g t h [ N / m m

Leca 670

Leca 800

Liapor 3

Liapor 8

Lytag

Pumice

Vasim I

REF I

Figure 11: Strength development of lightweight aggregate concrete as function of time.

2 8

B E 9 6 - 3 9 4 2 E ur oL i h t C on







In figure 12 the cube compressive strength after 28 days on cubes 150x150x150mm3

is pre-

sented as function of the replacement percentage.

Graphic 12: Cube compressive strength after 28 days on cubes 150x150x150mm3

as function of

replacement percentage

Liapor 3 and Pumice give a decreasing trend. Probably due to the low particle density and seg-regation of these LWA when the concrete is compacted.

The trend of mixtures with Leca 670 seems to be almost horizontal.

Leca 800, Liapor 8, Lytag and Vasim 1 seems to have an increasing trend.

At each replacement percentage Lytag gives the best results concerning compressive strength.

To investigate if there really is a linear trend, more research is needed. In this additional re-

search the steps of replacement of NWA by LWA should be smaller, the LWA should be sealed

(if possible), and segregation and the effective water content in a mixture should be controlled.

4.4 Strength/density ratio

The relation between the density after demoulding and the cube compressive strength deter-mined on cubes 150x150x150mm

3after 28 days is presented in figure 13. The trend seems to be

linear, although the correlation is very low. The higher the density, the higher the strength.

In figure 14 the density/strength ratio is presented per LWA. The lower this value, the better it

is. All the mixtures, with exception of Liapor 3 and Pumice, have a better density/strength ratio

than REF I.

The best results were obtained by using 100% Liapor 8, 80% Leca 800 and 80% Lytag. The de-

crease in density compared to REF I is, in those cases, about 110 kg/m3.

0

10

20

30

40

50

60

0% 20% 40% 60% 80% 100% 120%

R e p l a c e d N W A b y L W A

C u

b e c o m p r e s s

i v e s

t r e n g

t h [ N / m m

2 ]

L e c a 6 7 0

L e c a 8 0 0

L i apo r 3

L i apo r 8

Ly t ag

P u m i c e

V as i m 1





Graphic 13: Ratio between cube compressive strength and density after demoulding.

0

10

20

30

40

50

60

70

80

0% 20% 40% 60% 80% 100%

Replaced NWA by LWA

R a t i o d e n s i t y a f t e r d e m o u l d i n g / f c ; 2 8

Leca 670

Leca 800

Liapor 3

Liapor 8

Lytag

Pumice

Vasim 1

Vasim 3

Vasim 5/7b

Ref I

Graphic 14: Ratio between density after demoulding and cube compressive strength after 28

days.

y = 0,0471x - 60,604

R2

= 0,1924

0,0

10,0

20,0

30,0

40,0

50,0

60,0

2000 2050 2100 2150 2200 2250 2300 2350

Density after demoulding [kg/m3]

C u b e c o m p r e s s i v e s t r e n g t h [ N / m m 2 ]





4.5 Ratio between flexural and compressive strengthThe flexural strength is determined on prisms 100x100x500mm

3conform prEN 12359; April

1996. A two-point loading is used. The results of the concrete mixtures with Leca 670, Liapor ,Liapor 8, Pumice and Vasim 1 are listed in Table 6.

Table 6: Flexural strength on prisms: 100x100x500mm3

[N/mm2 ]

Replacement of NWA Leca 670 Liapor 3 Liapor 8 Pumice Vasim 1

20% LWA 5.5 6.6 *** *** 4.5

40% LWA 6.0 5.4 4.1 4.1 4.1

60% LWA 6.2 4.3 *** 4.2 3.7

80% LWA 6.9 5.0 3.9 2.9 ***

100% LWA 5.9 5.2 *** 3.1 5.0

*** Values are not determined.

The ratio between flexural strength and cube compressive strength is given in figure 15. The

values are taken from concrete mixtures with increased replacement percentage of NWA by

LWA.

Graphic 15: Ratio between cube compressive strength and flexural strength.

Looking at the results, there seems to be no relation between flexural strength and cube com-

pressive strength. The flexural strength is 7.6%-19.0% of the compressive strength.

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

9,0

0,0 10,0 20,0 30,0 40,0 50,0 60,0

Cube compressive strength (150x150x150mm3) [N/mm2]

F l e x u r a l s t r e n g t h ( 1 0 0 x 1 0 0 x 5 0 0 m m 3 )

[ N / m m 2 ]

Leca 670

Liapor 3

Liapor 8

Pumice

Vasim 1





4.6 Ratio between tensile splitting strength and cubecompressive strength

The tensile splitting strength is determined on cubes 150x150x150mm3

after 28 days. The Dutch

code VBC 1990 gives equations by means of which the tensile splitting strength can be derived

from the cube compressive strength.

For NWC this equation is:

cubeck,spctm, 0.05f 1.05f += (4.1)

in which f ctm,sp is the mean splitting tensile strength. In Fig. 16 the measurement points are pre-

sented together with the curve representing equation (4.1). It appears that for LWAC equation

(4.1) underestimates the mean tensile splitting strength.

Table 7: Mean tensile splitting strength [N/mm2 ] at 28 days (cubes 150x150x150mm

3 )

Replacement % of NWA Leca 670 Leca 800 Liapor 3 Liapor 8 Lytag Pumice

20% LWA 3.60 *** 3.40 *** *** ***

40% LWA 3.30 3.75 3.80 4.20 *** 4.10

60% LWA 3.47 3.45 *** *** *** 3.10

80% LWA 4.00 3.70 3.15 3.90 4.60 2.95

100% LWA *** *** 3.15 *** 3.70 3.15*** Values are not determined.

Figure 16: Relation between characteristic cube compressive strength and mean tensile split-

ting strength at 28 days

0 , 00

0 , 50

1 , 00

1 , 50

2 , 00

2 , 50

3 , 00

3 , 50

4 , 00

4 , 50

5 , 00

0 , 0 10 , 0 20 , 0 30,0 4 0 , 0 50,0 60,0

C u b e c o m p r e s s i v e s t r e n g t h [ N / m m 2 ]

T e n s

i l e s p

l i t t i n g s

t r e n g

t h [ N / m m

2

L e c a 6 7 0

L e c a 8 0 0

L i a p o r 3

L i a p o r 8

L y t a g

P u m i c e

V a s i m I

f c t = 1 , 0 5 + 0 , 0 5 f ' c k





In CUR report 173, the relation between the tensile splitting strength and the characteristic cube

compressive strength is also determined for Lytag, Aardelite, Liapor and gravel. With the ex-

ception of Liapor, all the experimental results were below the curve given in CUR report 173. In

other words, CUR report 173 overestimates the tensile strength of LWAC. This difference is probably due to the shape of the specimen used in different experimental test series. In CUR

report 173, specimen are used with a rectangular shape. Specimens used in this research are

cubes.

Conform CUR Recommendation 39, the value of f ctm,sp found with equation (4.1) should be

multiplied with:

k 0.4 0.623001 = +

ρ(4.2)

where ρ is the oven dry density. Unfortunately only the density after demoulding is determined

in this research. When using the density after demoulding in eq. (6.2), the value of k 1 hardly

deviates from 1.

From a large number of measurements it was found that the oven dry density is about 100 to

150 kg/m3

lower than the density after demoulding. Using this information for estimating the

oven-dry density, the value of k 1 could be determined with eq. (4.2). Only a small improvement

was obtained. More research is needed to determine the relationship between tensile strength

and compressive strength of LWAC.

4.7 Ratio between E-value and cube compressive strengthThe modulus of elasticity is determined on cylinders ∅150mmx300mm conform ASTM C 469-

94. According to the Dutch concrete code VBC 1990 the relationship between the modulus

Graph 17: Relation between compressive strength and modulus of elasticity.

0

5 0 0 0

1 0 0 0 0

1 5 0 0 0

2 0 0 0 0

2 5 0 0 0

3 0 0 0 0

3 5 0 0 0

4 0 0 0 0

0 , 0 5 , 0 1 0 , 0 1 5 , 0 2 0 , 0 2 5 , 0 3 0 , 0 3 5 , 0 4 0 , 0 4 5 , 0 5 0 , 0

C u b e c o m p r e s s i v e s t r e n g t h a f t e r 2 8 d a y s [ N / m m 2 ]

E - v a

l u e

[ N / m m

2 ]

L e c a 6 7 0

L i a p o r 3

L i a p o r 8

P u m i c e

E c = 2 2 2 5 0 + f c k





Table 8: E-modulus LWAC, measured on cylinders Ø150mmx300mm.

Replacement NWA Leca 670 Leca 800 Liapor 3 Liapor 8 Lytag Pumice

20% 20930 *** 22442 *** *** ***

40% 22634 *** 21796 22092 *** ***

60% 20425 *** 20728 *** *** 18759

80% 20485 *** 18946 *** *** ***

100% 19935 *** 17289 *** *** ***

*** Values are not determined.

of elasticity and the cube compressive strength is given by the equation:

Ec=22250+250f ck,cube (4.3)

This equation holds for NWC. In CUR report 173 a modification of this equation has been pro-

posed in order to make it applicable for LWAC made with Lytag, Liapor and Aardelite.

In CUR Recommendation 39, the modulus of elasticity for LWAC is determined by multiplyingthe values obtained with eq. (4.3) with the factor k 2. For this factor it was proposed:

k 23002

1,5

=

ρ(4.4)

By multiplying the values obtained with eq. (4.3) with appropriate k 2-values, theoretical values

for the modulus of elasticity are obtained between the function of Ec=22250+250f ck,cube and the

measured values, both presented in Fig. 17. The difference in results is probably due to the dif-

ference in compacting the concrete in the cube moulds and in the cylinder moulds. When com-

pacting the cylinders, segregation occurred. More research is needed to establish a reliable rela-tionship between the strength and modulus of elasticity of LWAC.





5 CONCLUSIONS and COMMENTSA number of experimental test series was performed with the aim to investigate the effect of

partial replacement of a part of the NWA by different types of LWA. Only the particle fractions

4-8 mm and 8-12 mm were replaced, and this in subsequent steps of 20%. In all the mixtures the

added water content was kept constant. In the experiments emphasis was on measuring the de-

moulding density, the cube compressive strength, the tensile splitting strength and the modulus

of elasticity. Results were compared with clauses given in the Dutch Concrete Code VBC 1990

and with ad-hoc recommendations especially dealing with LWAC, i.e. CUR Recommendation

39.

5.1 ConclusionsThe following tentative conclusions can be drawn (considering the used reference mixture with

this the indicated w/c):

Density-strength relationship

• The higher the density of the LWAC-mixture the higher the strength.

• The best density/strength ratio would occur, in the case of this particular reference mixture,

when 100% Liapor 8, 80% Lytag and 80% Leca 800 is used.

Ef fect of partial replacement of NWA (f ractions 4-8 mm and 8-12 mm) by LWA

• There seems to be, with the exception of Liapor 3 and Pumice, an increasing trend in cubecompressive strength if a higher percentage of the NWA (fractions 4-8 mm and 8-12 mm) is

replaced by LWA.

• With the exception of Liapor 3 and Pumice, the more NWA is replaced by LWA, the higher

the strength. This increase is probably due to the water absorption of the LWA in the initial

stage, resulting in a lower effective w/c ratio. At later ages the initially absorbed may be-

come available for continuing hydration.

To determine if there really is a linear trend between replacement percentage and strength, more

research is needed. Segregation of the LWA and the effective water content of the LWAC mix-

tures should be controlled

.

Late strength development

• The strength development will continue after 28 days due to the “internal water tank”, pro-

vided by the (partly saturated) LWA. Compressive strength tests performed on prisms re-

vealed an increase of 10 N/mm2

between 28 days and 92 days.

Splitting tensile strength versus compressive strength

• The ratio between the tensile splitting strength and the cube compressive strength is linear.

The higher the strength, the higher the tensile splitting strength.

• For NWC the Dutch code VBC 1990 gives a relation between the tensile strength and the

cube compressive strength. If applied to LWAC, this relationship appears to underestimate

the measured tensile strength.





• Like the Dutch code VBC 1990, also the CUR Recommendation 39 underestimates the

measured tensile strength, even though this recommendation deals especially with LWAC.

CUR Recommendation 39, however, is certainly an improvement compared with the VBC

1990.

More research is needed to give a more accurate indication of the relationship between tensilestrength and compressive strength when dealing with LWAC.

Modulus of elastici ty versus compressive strength

• The modulus of elasticity of LWAC was found to be less than predicted with the relation-

ship proposed in the Dutch code VBC 1990 (valid for NWC) and also less than predicted

with the CUR Recommendation 39 on LWAC.

More research is needed to give a reliable relationship between the modulus of elasticity and the

cube compressive strength of LWAC.

5.2 CommentsThe following comments highlight some of the experiences gained during this research project.

• The biggest problem, which occurred during this research, is the water absorption of the

different LWA. In all the mixtures the amount of mixing water is kept constant. Since dif-

ferent types of aggregate have different absorption characteristics, the effective wa-

ter/cement ratio must have been different in the tests considered in this research project.

More research is needed to determine the effective water absorption by LWA in a concrete mix-

ture.

• Tests with mixing LWA in a pan-mixer showed that none of LWA particles was crushed in

this mixer.

• Testing confirmed that there is a difference in water absorption by LWA in static a vessel

and in a pan-mixer. LWA with a higher porosity, like Liapor 3 and Pumice, had a water ab-

sorption in pure water after 15 minutes of 18.6% and 36.3%, respectively. But in the rotat-

ing mixer filled with water, the water absorption after 15 minutes was 26.1% and 27.5%, re-

spectively. The water absorption of Liapor 8, in this case, was about zero.

• The compaction of LWAC has a big influence on the strength of the concrete. Tests, with

increased vibrating time and increased frequency, showed that the best compressive strength

was yielded when the LWAC was vibrated at a frequency of 50Hz during 120 seconds if

plastic moulds (150x150x150mm3) were used. When steel moulds (100x100x500mm

3) were

used, the best compressive strength was obtained when the frequency was 65Hz and the vi-

brating time was 180 seconds.





6 REFERENCESLydon, F.W.

Concrete Mix Design, 2nd

edition, Applied science publishers, 1982

Nordic concrete research, proceedings nordic concrete research, Espoo, Finland 1996

A.M. NevilleProperties of concrete, fourth edition

Ernst Mørtsell

Modellering av del materialenes betydning for betongens konsistens, NTH 1996: 12, Trondheim

Ernst Mørtsell, Sverre Smeplass, Tor arne Hammer, Magne Maage

Flowcyl - How to determine the flow properties of the matrix phase of high performance con-

crete, Proc 4th

International Symposium on utilisation of High Strength / High Performance

concrete, May 1996, Paris

J.L. ClarkeStructural lightweight aggregate concrete, 1993, Blackie Academie & Professional

Ludmila Dolar-Mantuani, Ph.D., P.E., F.G.A.C.

Handbook of Concrete Aggregates, 1983, (ISBN:0-8155-0951-0)

Andrew Short, William Kinnniburgh

Lightweight Concrete, third edition, 1978, (ISBN: 0-85334-734-4)

Ken W. Day Concrete Mix Design, Quality Control and Specification. 1995

Rilem Technical Comittee 26-GM granular materials.

P. Bartos

fresh concrete properties and tests, 1992. Elsevier science publishers BV

Yves Malier High performance concrete - from material to structure, 1992





7 NOMENCLATURELWA Lightweight aggregate

LWAC Lightweight aggregate concrete

NWA Normal weight aggregate

NWC Normal weight concrete

REF I Reference mixture I

REF II Reference mixture II

SZ 1794 Standard sand of Smals, the first two numbers refer to the amount of percentage on

sieve 1mm, the last two numbers refer to the amount of percentage on sieve 250µm

w/b water/binder ratiow/c water/cement ratio

f ct,sp tensile splitting strength

f ctm,sp mean tensile splitting strength

f ct,fl flexural strength

f ck,cube characteristic cube compressive strength

ρ density

CEB Comité Euro-international du Béton

CEN Comité Européen de Normalisation

CTR Cost Time Resources (form)

EN European Standard

FIB Féderation Internationale du Béton

FIP Féderation Internationale de la Précontrainte









8 APPENDIX 1:LABORATORY PROCEDURES AND TEST METHODS

8.1 Mixing procedureEvery mixture has been made with the same mixing procedure:

1. mix pan and mixer blades were dampened prior to the mixing;

2. coarse NWA was added to the mix pan;

3. coarse LWA was added to the mix pan;

4. fine NWA was added to the mix pan;

5. fine LWA was added to the mix pan;

6. mixture was mixed for 60 seconds;7. cement and fly ash was added to the mixture;

8. mixture was mixed for 60 seconds;

9. 2/3 of the water was added to the rotating mix pan;

10. plasticizer and 1/3 of the water was added to rotating mix pan;

11. mixture was mixed for 5 minutes.

Total mixing time: 7 minutes.

A forced action pan mixer was used for all the mixtures.

8.2 Vibrating of the mixturesThe vibration time and frequency is kept constant using a vibrating table:

• until the surface of the concrete is smooth and glassy and no air no air bubbles appeared to

the surface of the concrete in the mould;

• 3 plastic moulds (150x150x150mm3) with concrete were vibrated together on the vibrating

table during 120 seconds with a frequency of 50 Hz;

• 6 steel moulds (100x100x100mm3) with concrete were vibrated together on the vibrating


• 2 steel moulds (100x100x500mm3) with concrete were vibrated together on the vibrating


• 3 steel cylindrical moulds (ø150x300mm3) with concrete were vibrated together on the vi-

brating table during 180 seconds with a frequency of 65 Hz;

8.3 Casting and curing specimenAll moulds were oiled prior to use and were free from dust and dirt.

After filling the moulds with fresh concrete, the surfaces were finished with a trowel and cov-

ered with plastic.

After 24 hours, the specimens were demoulded and the density of the specimen was determined.

Finally the specimen were put in plastic bags and placed in a climate-room with a temperature

of 20ºC (±2ºC) and a humidity of 97%.





8.4 Used standardsThe following standards have been used:

NEN 3543; October 1982: Coarse lightweight aggregate for lightweight concrete.

NEN 5950; September 1995: Regulations for concrete. Technology (VBT 1995) Require-ments, productions and inspection.

NEN 5957; November 1988: Concrete – Determination of the consistency of fresh concrete –

Flow test.

NEN 6720; September 1995: TGB 1990. Regulations for concrete. Structural requirements and

calculation methods.

prEN September 1996: lightweight aggregates. Part 1: Lightweight aggregates for concrete

and mortar

prEN 206; April 1997: Concrete-Performance, production and conformity.

prEN 933-1; November 1992: Tests for geometrical properties of aggregates- Part 1: Determi-

nation of particle size distribution – Granulometric analysis (sieving method)

prEN 1097-6: February 1997: Tests for mechanical and physical properties of aggregates -

Part 6: Determination of particle density and waterabsorption

prEN 1097-8; April 1997: Tests for mechanical and physical properties of aggregates. Part 8:

determination of the polished stone value.

prEN 12350; March 1996: Testing concrete - Determination of consistency of fresh concrete-

Vebe test.

prEN 12357; April 1996: Testing concrete - Determination of consistency of fresh concrete -

Degree of compactability.

prEN 12359; April 1996: Testing concrete - Determination of flexural strength of test speci-

mens.

prEN 12362; April 1996: Testing concrete - Determination of tensile splitting strength of testspecimens.

prEN 12363; April 1996: Testing concrete -Determination of density of hardened concrete

prEN 12382; April 1996: Testing concrete - Determination of consistency of fresh concrete -

Slump test.

prEN 12394; April 1996: Testing concrete - Determination of compressive strength of test

specimens

prEN 12395; April 1996: Testing concrete - Determination of air content of fresh concrete -

Pressure methods





9 APPENDIX 2:INFORMATION NEW MATERIALS VASIM (NL)

(source: Vasim BV (NL))

9.1 Material sources Number 1A Mixture (dry-weight)

Fly-ash coal-fired power station 45%

Fly-ash Burned silt of sewage works 45%

Cement Portland 52,5 10%

Palletising-water 300 litres/ton

Production method B = Cold bounded

Status See workoutline

Number 5/7b Mixture (dry-weight)

Fly-ash coal-fired power station 21%

Fines Pumice 43%

Silt

- moisture

Quarries/seagravel

60% each

15%

Cement Portland 52,5 21%

Palletising-water --- litres/ton

Production method B = Cold bounded

Status See workoutline

Production method

Vasim 3 Fly-ash: coal-fired power station

Fly-ash: bio-mass conversion

Sintered


Silt: quarries/seagravel

Sintered


Silt: recycled concrete

Sintered / cold bounded


Silt: drinking water treatment works

Sintered / cold bounderd





10 APPENDIX 3:PARTICLE SIZE DISTRIBUTION



Figure 1: Particle size distribution of sand and gravel.

Particle size distribution of sand and gravel

0

10

20

30

40

50

60

70

80

90

100

Sieves

C u m u l a t i v e o n s i e v

e [ % ]

2-5mm 015292969696100100

SZ 1794 0005216092100100

0,250-0,500mm 00001218899100

0,125-0,250mm 0000034698100

2-4mm 001698100100100100100

4-8mm 079799100100100100100

2-8mm 046684100100100100100

8-12mm 085100100100100100100100

12-16mm 299100100100100100100100

C16C8C42mm1mm0,500mm0,250mm0,125mmresidue

4 4

B E 9 6 - 3 9 4 2 E ur oL i h t C on





Figure 2: Particle size distribution of Lytag, Leca 670, Leca 800, and Liapor 3.

Particle size distribution of LWA

0

10

20

30

40

50

60

70

80

90

100

Sieves

C u m u l a t i v e o n s i e v e [ % ]

Lytag, 4-8mm 01929999100100100100

Lytag 6-12mm 06596999999100100100

Leca 670, 4-8mm 00949797979899100

Leca 670, 8-12mm 0090100100100100100100

Leca 800, 3-6mm 0087100100100100100100

Leca 800, 6-12mm 068100100100100100100100

Liapor 8, 4-8mm 0094100100100100100100


M e c h ani c al pr o p er t i e s of l i gh t w ei gh t a g gr e g a t e c on c r e t e

B E 9 6 - 3 9 4 2 E ur oL i h t C on

4 5



Figure 3: Particle size distribution of Liapor 8 and Pumice.


0

10

20

30

40

50

60

70

80

90

100

Sieves

C u m u l a t i v e o n s i e v e [ % ]

Liapor 3, 4-8mm 0398100100100100100100

Liapor 3, 8-16mm 0100100100100100100100100

Pumice, 4-8mm 0094100100100100100100

Pumice, 8-12mm 097100100100100100100100

Pumice, 12-16mm 0100100100100100100100100

Pumice, 0-2mm 0031237618195100

Pumice, 0-1mm 000128658086100


4 6

B E 9 6 - 3 9 4 2 E ur oL i h t C on






0

10

20

30

40

50

60

70

80

90

100

Sieves

C u m u l a t i v e o n s i e v e [

% ]

Vasim 1 937737782869195100

Vasim 3 06959898989999100

Vasim 5/7b, 4-8mm 16569898100100100100100

Vasim 5/7b, 6-12mm 090989898989899100

Vasim 7 071989999999999100

Vasim 8 065979898989898100

Vasim 9 059989999999999100


Figure 4: Particle size distribution of new materials from BV Vasim (the Netherlands).

M e c h ani c al pr o p er t i e s of l i gh t w ei gh t a g gr e g a t e c on c r e t e

B E 9 6 - 3 9 4 2 E ur oL i h t C on

4 7




mechanical properties of light weight agg

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