Sulfate Attack on Concrete - Chapter 6 ppt

6 Prevention of sulfate attack

6.1 INTRODUCTION

Concrete in service is often exposed to aggressive environments. Although

severe exposure conditions may sometime be at the origin the premature

degradation of concrete, durability problems often originate from an improper

production and use of the material. As mentioned in the first chapter of this

monograph, man abuses concrete in various ways, most of them based on an

insufficient knowledge of the material.

It should however be emphasized that it is relatively simple and econom￾ical to produce durable concrete. We have numerous examples of durable

concrete structures that have performed as expected for decades while being

exposed to severe conditions. In all cases, concrete had been produced and

handled with care.

As discussed in Chapters 4 and 5, the widespread occurrence and destruc￾tiveness of sulfate attack led to many investigations over the years into the

mechanism of deterioration. Many of these studies have also allowed iden￾tification of practical solutions to protect concrete against sulfate attack.

These prevention methods are briefly reviewed in the following paragraphs.

6.2 MEASURES TO PROTECT CONCRETE AGAINST

COMPOSITION-INDUCED INTERNAL SULFATE

ATTACK

As previously mentioned in Chapter 4, cement itself may be a source of

excessive sulfate in concrete. This is the reason why requirements of CEN,

ASTM (see ASTM C150; ASTM C1157, BS 5328) and other standards on

cement and clinker composition should be closely followed; this will assure

proper concentrations and ratios of the relevant clinker minerals to give sulfate

levels that will not lead to excessive expansion.

Aggregates and mineral additives are other potential sources of excessive

sulfate. Selected aggregates and intermixed mineral admixtures should not contain

© 2002 Jan Skalny, Jacques Marchand and Ivan Odler