THEIR USES
ADDITIONAL TESTS REQUIRED FOR CONCRETE MIX DESIGN AND SPECIAL EVALUATIONS:
Density/water absorption
NZS 3111, Section 12 Method
of determining the density of water absorption of coarse aggregate
No specific limits set but affects mix design and workability.
NZS 3111, Section 16 Method
of determining the density and absorption of sand
NZS 3111, Section 19 Method
of determining lightweight particles in aggregate
No specific limits set but will affect performance under NZS 3111, Section 8.
Soluble salts ASTM C1152, Test method for acid soluble chloride in mortar and concrete
Prestressed concrete 0.5 kg/m3
Reinforced concrete moist/chloride 0.8 kg/m3 dry/protected 1.6 kg/m3.
No specific test method nominated for sulphate
Not to exceed 5% by mass of cement.
Moisture content
NZS 3111, Section 7 Method of
determining the moisture content of aggregates by drying
No specific limits. Information required for concrete batching.
Crushing and weathering
NZS 3111, Section 14 Method
of determining the crushing resistance of coarse aggregate
No specific limits set but affects NZS 3111, Section 8. See also AS 1141.22 details.
NZS 3111, Section 15 Method
of determining weather resistance of coarse aggregate
Recommended Quality Index.
Chapter 4 Water
Chapter 4 Water
Chapter 4
Water
This chapter discusses the effect of impurities in mixing water on the properties of concrete. It has been compiled largely from information presented by H.H. Steinour1, supplemented by data presented by A. Samarin2.
1
Steinour, H.H. 'Concrete mix water – how impure can it be?' Journal of the PCA Research and Development Laboratories, Vol. 2, No. 3, 1960, pp 32–50.
2
'Quality of mixing water', in Australian Concrete Technology, W.G. Ryan and A. Samarin (eds), Longman Cheshire, Melbourne, 1992.
INTRODUCTION 4.2
Relevant New Zealand and Australian Standards
4.1 CONTAMINANTS 4.2
4.1.1 General
4.1.2 Solids in Suspension 4.1.3 Organic Matter 4.1.4 Dissolved Salts
4.2 ACID AND ALKALINE WATER 4.4
4.2.1 General 4.2.2 Acidity 4.2.3 Alkalinity 4.2.4 Recycled Water
4.3 THE EFFECT ON CONCRETE
DURABILITY 4.5
Chapter 4 Water
Guide to Concrete Construction 4.2
INTRODUCTION
Most concrete specifications simply require that mixing water shall be potable, i.e. fit for drinking; or that it be clean and free from impurities harmful to concrete. NZS 3121 Water & Aggregates for Concrete requires that mixing water be from a source of acceptable quality, i.e. that:
service records of concrete made with that water indicate that it is not injurious to the strength or durability of the concrete nor to the materials embedded in it; or
the results of tests (in accordance with NZS 3111) are within the limits shown in Tables 4.1 and 4.2.Under normal circumstances, water drawn from reticulated town-water supplies will meet these limits and be suitable for making concrete. Chloride limits specified in NZS 3101 Concrete Structures are not exceeded.
On projects remote from town-water supplies it may be necessary to utilise water of unknown quality or, on occasions, water which, superficially at least, is unfit to drink because of its turbidity, its smell, its taste, or even its colour. Although such water may be shown by test to be acceptable, there may be impurities present which are potentially harmful to concrete. Some knowledge of their effects will then be required.
Relevant New Zealand Standards
NZS 3101 Concrete structuresNZS 3104 Specifications for concrete production NZS 3111 Methods of test for water and
aggregates
NZS 3121 Water and aggregate for concrete
Relevant Australian Standards
AS 1379 The specification and supply of concrete
AS 2758 Aggregates and rock for engineering purposes
AS 2758.1 Concrete aggregates AS 3600 Concrete structures
4.1 CONTAMINENTS
4.1.1 General
The solids content of water may have two components:
solid matter, generally very finely divided, which is carried in suspension, and
salts and/or organic matter which are dissolved in the water.4.1.2
Solids in Suspension
Solids in suspension normally comprise finely divided silts and clays which will settle from the water if it is allowed to stand for a sufficient length of time. In any event, even quite significant amounts of finely divided silt and clay have little effect on the strength or durability of concrete as long as they are evenly distributed throughout the mix.
As a rough guide, it may be noted that AS 2758.1 permits up to 2% of material finer than 2 mm (fine silt and/or clay) in the aggregate.
Clays which coat or adhere to the aggregate particles are always objectionable because they interfere with the cement-aggregate bond. On the other hand, evenly distributed in the mixing water, they are much less objectionable.
4.1.3 Organic Matter
Organic matter can be particularly objectionable because it affects strength and, in extreme cases, can prevent the concrete from setting.
For example, even very small amounts of sugar can have this effect, (note that water containing sugar will still be potable and hence simply requiring mixing water to be potable is an insufficient specification).
More usually, however, organic matter simply retards the rate of strength gain and may be able to be compensated for by allowing additional time for the concrete to gain strength or by increasing the amount of cement in the mix.
Where organic matter is suspected, there is really no satisfactory alternative to the making of trial mixes, with the water in question, to determine its compliance with the limits set out in Table 4.1 (page 4.3).
4.1.4 Dissolved Salts
General Steinour suggests that the salts commonly found in natural waters, that are not contaminated by industrial wastes, comprise mainly the following:
Chapter 4 Water