ASTM C688 : 08

Standard Specification for Functional Additions for Use in Hydraulic Cements

Standard Details

1.1 This specification covers methods to investigate the effectiveness of a material to beneficially change the properties of hydraulic cements when the material is incorporated during manufacture of the cement.

1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.3 The effect of additions in cement may markedly change properties other than those they are intended to modify. This specification is designed to test for such changes. Table 1 sets forth values for those properties of cement pastes and mortars that would permit a judgment of the changes effected by an addition. Likewise, Table 2 sets forth similar criteria for concrete. Certain additions may be found effective for more than one purpose as indicated in 3.1.4 and 3.1.5.

TABLE 1 Criteria for Evaluating Neat Cement and Mortar Containing Functional Cement Additions

Tests	Type of Addition
Tests	Water Reducing	Retarding	Accelerating	Water-Reducing and Retarding	Water-Reducing and Accelerating	Set-Control
Normal consistency, deviation from control, percentage points^A	−1.0 min	+1.0 max	+1.0 max	−1.0 min	−1.0 mm	±1.0 max
Standard consistency (flow) deviation from control, percentage points^A	−4.0 min	+2.0 max	+2.0 max	−4.0 min	−4.0 min	±2.0 max
Setting time, (Gillmore) deviation from control, h:min
Initial
At least	...	1:00 later^B		1:00 later^B		...
Not more than	1:00 earlier	3:30 later	1:30 earlier	3:30 later	1:30 earlier	1:00 earlier
	nor		nor		nor	nor
	1:30 later		1:30 later		1:30 later	1:30 later
Setting time, Vicat Initial^C
At least	...	0:50 later^B	...		...	...
Not more than	0:50 earlier	2:50 later	1:15 earlier	0:50 later^B	1:15 earlier	0:50 earlier
	nor		nor		nor	nor
	1:15 later		1:15 later	2:50 later	1:15 later	1:15 later
Final
Not more than	1:00 earlier	3:30 later	1:00 earlier	3:30 later	1:00 earlier	1:00 earlier
	nor		nor		nor	nor
	1:30 later		1:30 later		1:30 later	1:30 later
Compressive strength, min, percent of control:^D
1 day in moist air	110	90	125^E	90	125	^F
1 day in moist air, 2 days in water	110	90	125^E	100	125
1 day in moist air, 6 days in water	110	90	100	110	110
1 day in moist air, 27 days in water	110	95	95	110	110
Autoclave Expansion max increase in % change in length compared to control	0.10	0.10	0.10	0.10	0.10	0.10
Drying Shrinkage of Mortar max % change in length compared to control	0.020	0.020	0.030	0.020	0.020	0.020

^A The minus sign indicates that the percentage of water required shall be less than that of the control cement by at least the indicated percentage points.

^B Or 50 % later, whichever is the lesser.

^C Either Vicat or the Gillmore time of setting method shall be used at the choice of the manufacturer.

^D The compressive strength of mortar containing the test cement shall be not less than 95 % of that attained at any previous test age. The objective of this limit is to require that the strength of mortar containing the addition under test shall not decrease with age.

^E In cases where the accelerated set time only is required, the strength can be reduced to 100 % of the control.

^F The grand average of the 1, 3, 7, and 28-day strengths shall be not less than 95 % of the grand average for the corresponding control cement.

TABLE 2 Criteria for Evaluating Concrete Containing Functional Cement Additions^A

Tests	Type of Addition
Tests	Water Reducing	Retarding	Accelerating	Water-Reducing and Retarding	Water-Reducing and Accelerating
Water content, max, percent of control	95	...	...	95	95
Time of setting, (penetration) deviation from control, h:min:
Initial
At least	...	1:00 later^B		1:00 later^B
Not more than	1:00 earlier	3:30 later	3:30 earlier	3:30 later	3:30 earlier
	nor
Final	1:00 later
Not more than	1:00 earlier	3:30 later	...	3:30 later	...
	nor
	1:30 later
Compressive strength, min, percent of control:^C
1 day^D	110	85	125^E	100	125
3 days	110	85	125^E	100	125
7 days	110	90	100	110	110
28 days	110	90	95	110	110
3 months	100	90	95	100	100
1 year	100	90	95	100	100
Flexural strength, min, percent of control:^C
1 day^D	100	85	110	90	110
3 days	100	85	110	100	110
7 days	100	90	100	100	100
28 days	100	90	90	100	100
3 months	100	90	90	100	100
1 year	100	90	90	100	100
Bond strength, percent of control:
28 days	100	90	100	100	100
Volume change, expressed as change in length, max, increase over control, percentage points:
28 days	0.010	0.010	0.030	0.010	0.010
3 months	0.010	0.010	0.030	0.010	0.010
1 year	0.010	0.010	0.030	0.010	0.010
Durability factor, min, percent of control^F	80	80	80	80	80

^A The values in the table are intended to allow for normal variation in test results. For example, the object of the 90 % compressive strength requirement for a retarding addition is to require a level of performance comparable to that of the reference concrete.

^B Or 50 % later, whichever is the lesser.

^C The compressive and flexural strength of the concrete containing the addition under test at any test age shall be not less than 90 % of that attained at any previous test age. The objective of this limit is to require that the compressive or flexural strength of the concrete containing the addition under test shall not decrease with age.

^D One-day strengths applicable only to Type III cement. One-year strength tests shall be made; however, the addition may be approved after completion of the 3-month strength results, at the discretion of the purchaser.

^E In cases where the accelerated set time only is required, the strength can be reduced to 100 % of the control.

^F This requirement is applicable only when the addition is to be used in air-entrained concrete.