AS 1141.35 pdf download

AS 1141.35 pdf download.Methods for sampling and testing aggregates
1 SCOPE
This Standard sets out a qualitative method for the detection of sugar in aggregates intended for use in the production of concrete. A positive reaction is given by one part of sugar in one thousand parts of aggregates. No visible reaction is given by one part of sugar in 10 000 parts of aggregates.
2 PRINCIPLE
The basis of the test is that, although Fehling’s solution does not react directly with cane sugar (sucrose), it does react with grape sugar (glucose). Therefore cane sugar, if present, is first converted into invert sugar (glucose plus fructose) by boiling with hydrochloric acid. The glucose so formed reacts with Fehling’s solution, giving a positive test. Although cane sugar is perhaps the most likely sugar source if concrete aggregate is accidentally contaminated, the test also detects contamination from honey, wine, fruit juices or other sources of glucose.
6 APPARATUS AND MATERIALS
The following apparatus, conforming to the relevant requirements of AS 1141.2, is required: (a) Balance of suitable capacity, with a limit of performance of ±0.05g. (b) Filter paper—white, double fine grade. (c) Fume cupboard. NOTE: Advice on suitable fume cupboards can be found in AS 2243.8. (d) Glassware—beakers, measuring cylinders and filter funnels. (e) Litmus paper.
7 REAGENTS
All reagents shall be of analytical grade. Distilled or de-ionized water shall be used for all stages of the test. Reagents shall be specified by name or formula and shall consist of the following: (a) Hydrochloric acid (HCl) (density = 1.16 kg/L). (b) Copper sulfate (CuSO 4 .5H 2 0). (c) Sodium hydroxide (NaOH). (d) Sodium potassium tartrate (KNaC 4 H 4 O 6 .4H 2 O) (Rochelle salt).
8 TEST PORTION
By coning and quartering, or using sample dividers, take a test portion of approximately 100 g from a laboratory sample obtained in accordance with the procedures of AS 1141.3.1. The test portion shall be used in the condition in which it was received.
9 SOLUTIONS REQUIRED
Prepare solutions as follows: (a) Solution A: Dissolve 17.3 g of CuSO 4 .5H 2 O in water, and dilute the solution to 250 mL. (b) Solution B: Dissolve 30 g of NaOH in water and warm the solution. Dissolve 86.5 g of Rochelle salt in the warm NaOH solution. Cool the solution and dilute to 250 mL. (c) Fehling’s solution: Mix equal volumes of Solution A and Solution B to make Fehling’s solution. This solution is used for detection of sugar. Fehling’s solution must be made immediately before use. It is not stable and must not be kept for more than 12 h. (d) 1 M HCl: To 600 mL of water in a graduated flask or graduated cylinder, add 89.9 mL of the concentrated HCl and make up the volume to 1 L. (e) 1 M NaOH: Dissolve 40.0g of NaOH in water and make the volume up to 1 L.
10 TEST PROCEDURE
The procedure shall be as follows: (a) Place a test sample of approximately 100 g of aggregate in a 250 mL beaker and cover it with water. Add 50 mL of 1 M HCl and boil the mixture for 5 min, then filter while still hot. (b) If the filtrate is acid to litmus paper, cool 5 mL of it, neutralize it with 1 M NaOH solution and remove any precipitate by filtration. Add 3 mL of Fehling’s solution, thoroughly stir the resultant mixture, and heat it in a boiling water bath for 5 min. (c) If sugar is present, a reddish-brown precipitate will be formed. (d) If the original filtrate is not acid to litmus paper, add a further 50 mL of 1 M HCl and boil the mixture for a further 5 min (this should ensure that the filtrate is acid to litmus paper), then continue as in Step (b) for a filtrate that is acid to litmus paper. NOTE: For this test it is intended that the filtrate be acid to litmus paper. A neutral or alkaline reaction indicates that the HCl has been neutralized by carbonates in the aggregate. This condition must be corrected by adding HCl and boiling the mixture.