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Concrete with Low Permeability

Harald Justnes

PhD, Chief Scientist at SINTEF, Adjunct Professor at NTNU

E-mail: harald.justnes@sintef.noSINTEF Building and Infrastructure

Richard Birkelandsvei 3, NO-7465 Trondheim, Norway

Key words:Admixture, concrete, hydrophobicity, permeability

1. INTRODUCTION

Concrete with low porosity/permeability is one of the activities within project 1 Advanced

cementing materials and admixtures in the Norwegian centre for research driven innovation

COIN (Concrete Innovation). The objective is to make concrete with low porosity and

permeability, but focused on matrix.

Two state-of-the-art reports (STARs) were scheduled for 2007 on different approaches to

achieve the objective; 1) low porosity through particle packing dealing with obvious systems

like adding fine particles (e.g. silica fume) to more advanced systems focusing on avoidance of

initial Ettringite formation functioning as spacers hampering packing of cement grains in the

fresh state and 2) Low permeability through hydrophobicity dealing with hydrophobizing

agents intermixed in the concrete and not applied on the surface of hardened concrete.

However, only the second report is finalized at present and reviewed in the next chapter.

2. LOW PERMEABILITY THROUGH HYDROPHICITY

The durability and aesthetic appearance of concrete may be improved by the addition of

hydrophobizing agents as a consequence of reduced water permeability.

Hydrophobizing agents lead to less water absorption at the same time as they let water vapour

out. This may lead to a dryer interior over time and thereby reduced rate of detrimental

reactions needing liquid water as reaction medium. The ingress of water born aggressives like

chlorides will be reduced (in particular in marine splash zones), but also corrosion rates may be

decreased. Carbonation rates may, however, be somewhat increased.

Vegetable oils seem to be the most cost-effective hydrophobizing agents as good effects may

be achieved by additions of only 0.5 % of the cement mass. Furthermore, the cheapest and

most available vegetable oil based on rapeseed is among the most effective tested as

examplified by capillary suction in Fig. 1 [1, 2].

It is recommended to continue research on the effect of rapeseed oil as a concrete admixture,

also at dosages above 1.5 %. The research should focus on rapeseed oil as hydrophobizing

agent, but also on its effect on other interesting concrete properties for COIN; like hardening

retarder, shrinkage reducing agents, electrical resistivity and pH reduction.

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Sawn mortar discs with vegetable oils

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0.10

0.20

0.30

0.40

0 100 200 300 400 500 600

Time, sqrt(s)

Waterabsorption(kg/m

2)

REF. I

0.5%RAPE

1%RAPE

1.5%RAPE

Fig. 1 Water absorption of sawn mortar discs with 0.0, 0.5, 1.0 and 1.5 % rapeseed oil added.

3. PROJECT DATA

COIN - Concrete Innovation Centre - is one of 14 Norwegian Centres for Research based

Innovation (CRI), which is an initiative by the Research Council of Norway. The main

objective for the CRIs is to enhance the capability of the business sector to innovate by

focusing on long-term research based on forging close alliances between research-intensive

enterprises and prominent research groups.

About 25 researchers from SINTEF (host), the Norwegian University of Science and

Technology (NTNU) and industry partners work in the COIN projects (presently 5 projects).

COIN involves moreover 15 - 20 PhD-students, 10 - 20 M.Sc.-students and international guest

researchers. The research covers a wide range of research topics.

COIN has a budget of NOK 200 mill over 8 years (from 2007), and is financed by the Research

Council of Norway ( 40 %), industrial partners ( 45 %) and by SINTEF Building and

Infrastructure and, NTNU (in all approx 15 %). The present COIN partners are the Research

Council of Norway, SINTEF, NTNU, Norcem, Unicon, maxit Group, Borregaard, Spenncon,

Rescon Mapei, The Norwegian Public Roads Administration, Veidekke and Aker Kvrner.

For more information, log on to www.sintef.no/coin

4. REFERENCES

1. H. Justnes, T.A. stnor and N. Barnils Vila: Vegetable Oils as Water Repellents for

Mortars, Proceedings of the 1st International Conference of Asian Concrete Federation,

Chiang Mai, 28-29 October 2004, Thailand, Vol. 2, pp. 689-698.

2. H. Vikan and H. Justnes: Influence of Vegetable Oils on Durability and Pore Structure of

Mortars, Proceedings of the Seventh CANMET/ACI International Conference onDurability of Concrete, May 28 June 3, 2006, ACI SP-234-25, pp. 417-430.

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