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A reply to a discussion of the paper “effect of lactic acid on the hydration of portland cement” by R.J. Schultz
CEMENT and CONCRETERESEARCH. Vol. 17, pp. 367-368, 1987. Printed in the USA. 0008-8846/87 $3.00+00. Copyright (c) 1987 Pergamon Journals, Ltd.
A REPLY TO A DISCUSSION OF THE PAPER "EFFECT OF LACTIC ACID ON THE HYDRATION OF PORTLAND CEMENT" BY R.J. SCHULTZ N.B. Singh, (Smt) S. Prabha Singh and A.K. Singh Department of Chemistry Gorakhpur University Gorakhpur (U.P.), India
We thank Prof. Schultz for taking keen i n t e r e s t in our paper and drawing our attention towards certain facts associated with m, ~ hydroxy acids. We extended four studies with higher concentrations of l a c t i c acid and observed the following: I.
With 5% l a c t i c acid at w/s = 0.25, we could not even make the paste and considerable r i s e in heat occurred.
.
.
.
At w/s = 0.35, again we could not measure the i n i t i a l setting time in the presence of 5 wt% l a c t i c acid. The whole paste settled within two minutes giving appreciable strength. With I0 wt% l a c t i c acid at w/s = 0.5, again we could not measure the i n i t i a l setting time because the whole paste settled within less than two minutes with an increase in temperature of about 50°C and the whole mass because very hard.
500
,oo
W T
:0-S
TEMP= 30'I-.2 °C
~soo ,~ ~= ~2oo
FINAL SETTING
~F-
The i n i t i a l and final setting times are determined at 4,5, 6,7 and 8 wt% of l a c t i c acid at a w/s = 0.5. We could not perform this experiment in the absence of l a c t i c acid at t h i s water-solid r a t i o . The v a r i a t i o n of i n i t i a l and final setting times in the presence
*CCR 16 (4), 545-553 (1986). 367
F,
INITI
,oo
2
4
6
8
I0
C O N C E N T R A T I O N (VP,, °4, )
FIG. 1 Effect of d i f f e r e n t concentrations of l a c t i c acid on the i n i t i a l and final setting time of Portland cement.
368
Vol. 17, No. 2 DISCUSSIONS
of d i f f e r e n t concentrations of l a c t i c acid are given in Fig. I. The results indicate that l a c t i c acid accelerates the setting of cement even at higher concentrations. 5.
With 20 wt% l a c t i c acid at w/s = 0.5, again a very quick reaction occurred and no paste could be made. When l a c t i c acid solution was mixed, a temperature rise of about 70°C occurred indicating rapid increase in hydration.
The above results very c l e a r l y indicate that l a c t i c acid accelerates the hydration of Portland cement at d i f f e r e n t concentrations (0.I wt% - 20.0 wt%) contrary to other ~, B hydroxy acids.
A REPLY TO A DISCUSSION OF THE PAPER "EFFECT OF LACTIC ACID ON THE HYDRATION OF PORTLAND CEMENT" BY R.J. SCHULTZ N.B. Singh, (Smt) S. Prabha Singh and A.K. Singh Department of Chemistry Gorakhpur University Gorakhpur (U.P.), India
We thank Prof. Schultz for taking keen i n t e r e s t in our paper and drawing our attention towards certain facts associated with m, ~ hydroxy acids. We extended four studies with higher concentrations of l a c t i c acid and observed the following: I.
With 5% l a c t i c acid at w/s = 0.25, we could not even make the paste and considerable r i s e in heat occurred.
.
.
.
At w/s = 0.35, again we could not measure the i n i t i a l setting time in the presence of 5 wt% l a c t i c acid. The whole paste settled within two minutes giving appreciable strength. With I0 wt% l a c t i c acid at w/s = 0.5, again we could not measure the i n i t i a l setting time because the whole paste settled within less than two minutes with an increase in temperature of about 50°C and the whole mass because very hard.
500
,oo
W T
:0-S
TEMP= 30'I-.2 °C
~soo ,~ ~= ~2oo
FINAL SETTING
~F-
The i n i t i a l and final setting times are determined at 4,5, 6,7 and 8 wt% of l a c t i c acid at a w/s = 0.5. We could not perform this experiment in the absence of l a c t i c acid at t h i s water-solid r a t i o . The v a r i a t i o n of i n i t i a l and final setting times in the presence
*CCR 16 (4), 545-553 (1986). 367
F,
INITI
,oo
2
4
6
8
I0
C O N C E N T R A T I O N (VP,, °4, )
FIG. 1 Effect of d i f f e r e n t concentrations of l a c t i c acid on the i n i t i a l and final setting time of Portland cement.
368
Vol. 17, No. 2 DISCUSSIONS
of d i f f e r e n t concentrations of l a c t i c acid are given in Fig. I. The results indicate that l a c t i c acid accelerates the setting of cement even at higher concentrations. 5.
With 20 wt% l a c t i c acid at w/s = 0.5, again a very quick reaction occurred and no paste could be made. When l a c t i c acid solution was mixed, a temperature rise of about 70°C occurred indicating rapid increase in hydration.
The above results very c l e a r l y indicate that l a c t i c acid accelerates the hydration of Portland cement at d i f f e r e n t concentrations (0.I wt% - 20.0 wt%) contrary to other ~, B hydroxy acids.