PORTLAND CEMENT CONCRETE - Materials for Civil and Construction Engineers - page 243

T ABLE 7.4 Requirements for Concrete Exposed to Sulfates in Soil or Water*

Maximum Minimum

Water-Soluble Sulfate Water- Design

Sulfate ( SO 4 ) ( SO 4 ) in Cementitious Compressive

f œ ,

Sulfate in Soil, Percent Water, Material Ratio Strength,

Exposure by Weight** ppm** Cement Type*** by Weight MPa (psi)

Negligible Less than 0.10 Less than 150 No special type

required — —

Moderate**** 0.10-0.20 150-1500 II, MS, IP(MS),

IS(MS), P(MS),
I(PM)(MS),
I(SM)(MS) 0.50 28 (4000)

Severe 0.20-2.00 1500-10,000 V, HS 0.45 31 (4500)

Ve ry Severe Over 2.00 Over 10,000 V, HS 0.40 35 (5000)

*Adopted from American Concrete Institute (ACI 318), 1999.
**Tested in accordance with the Method for Determining the Quantity of Soluble Sulfate in Solid (Soil
and Rock) and Water Samples, Bureau of Reclamation, Denver, 1977.
***Cement Types II and V are in ASTM C150 (AASHTO M85), Types MS and HS in ASTM C1157, and
the remaining types are in ASTM C595 (AASHTO M240). Pozzolans or slags that have been
determined by test or severe record to improve sulfate resistance may also be used.
****Sea water.

Sample Problem 7.2

A structure is to be built with concrete with a minimum dimension of 0.2 m, minimum
space between rebars of 40 mm, and minimum cover over rebars of 40 mm. Two types
of aggregate are locally available, with maximum sizes of 19 mm and 25 mm, respec-
tively. If both types of aggregate have essentially the same cost, which one is more suit-
able for this structure?

Solution

25 mm 6 1 1/5 21 200 mm 2 minimum dimensions.

25 mm 6 1 3/4 21 40 mm 2 rebar spacing.

25 mm 6 1 3/4 21 40 mm 2 rebar cover.

Therefore, both sizes satisfy the dimension requirements. However, 25 mm aggre-
gate is more suitable, because it will produce more economical concrete mix.