The Constructor

6 Types of Deleterious Substances in Aggregate

Deleterious Substances in Aggregate

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Deleterious materials in aggregate are those substances which detrimentally effect the fresh and hardened properties of concrete for instance strength, workability, and long-term performance of the concrete in which such are used. Deleterious materials and highly undesirable constituents.

Organic impurities, clay, silt and crushed dust, salts, unsound particles, and alkali aggregate reactions. Adverse effects of deleterious materials on concrete includes the increase of water demand in concrete, impair bond strength between cement and aggregate, reduce durability, result in concrete popouts, and impair wear resistance.

There are tests such as colorimetric test recommended by ASTM C 40-92 which are used to determine aggregate organic content. The colorimetric test does not show the adverse effect of deleterious materials in aggregate. This is because high aggregate deleterious substance content does not infer that the aggregate is not fit for utilization that is why strength test based on ASTM C 87-90 is recommended for mortars with questionable sand.

1. Organic Impurities

Fig. 1: Colorimetric Test to Determine the Quantity of Organic Content in Concrete Fine Aggregate
Fig. 2: Washed Sand

2. Clay

 3. Silt and crusher dust

Fig. 3: Popout in Concrete Due to impurities in Aggregate
Fig. 4: Concrete Surface Popouts due to Deleterious Materials

4. Salts

5. Unsound Particles

6. Alkali- Aggregate Reactions

Fig. 5: Detrimental Influence of Reactive Alkali Aggregate on Concrete
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