A study of a water-reducing agent from cashew nutshell liquid

A study of a water-reducing agent from cashew nutshell liquid S K Agarwal, Irshad Masood and T C Phatak* Abstract - The water-reducing agent better known as superplasticizer is a recent development. A number of base materials have been used for the development of such water-reducing agents which can act better than ordinary plasticizers in concrete. The sulphonated salts of melamine, napthalene, lignin, hydroxycarboxylic acids and hydroxylated polymers are some typical compounds. Recently cashew nutshell liquid obtained from a natural product waste as a thick black phenolic compound has been converted into a water-reducing agent. This paper describes the results obtained on its effectiveness in influencing the theological properties of flow, viscosity, particle-size distribution, etc, of cement particles in hydrating cements and the water-reducing capabilities in cement mortars and concretes.

The use of chemical admixtures for controlling concrete properties has been accepted both nationally and internationally for the last two decades [1-3]. One of the most valuable and interesting developments in admixture technology has been the evolution of superplasticizers [2]. These superplasticizer admixtures are a functional extension of normal plasticizing admixtures. The use of superplasticizers in concrete benefits the construction engineer either in saving time, improved strength and more workable concrete placement in complicated and congested reinforcements, or in the appearance of the finished structure [4]. The main role played by such admixtures is related to the dispersing capability due to the presence of surface active constituents present in them. The long chain sulphonated compounds or hydroxycarboxylic acid groups etc promote the surface active properties of the admixture. These properties vary with the molecular size of the compound. Since superplasticizers - unlike normal plasticizers - do not markedly lower the surface tension of the water, they can therefore be used at very high dosage levels without entraining excessive air. Hence full advantage may be obtained from the water-reducing effect in terms of high initial and subsequent strength. In addition, its use with marginal-quality cement and aggregate may help to produce both good-quality and durable concrete at low water:cement ratios as well as flyash concrete, blast furnace slag concrete, lightweight concrete and f i b r e cement composites, etc, with reduced water requirements. This paper describes the salient properties of a superplasticizer synthesized [5] from cashew nutshell liquid (CNSL) or fractionated CSNL by sulphonating and condensing with formaldehyde in the presence of certain additives (labelled as CBRI-SP). Some of the preliminary investigations on the properties of flow, compressive strength, viscosity of cement pastes, dispersion of cement particles, etc, of the superplasticizer are presented and compared with some other commercially available superplasticizers.

Experimental materials • Cement: Ordinary Portland cement conforming to IS:2691976 (Ordinary and low heat Portland cements). • Sand: Standard Ennore sand conforming to IS:650-1966 (Specification for standard sand for testing of cement). • Superplasticizers: Ten commercially available superplasticizers were procured and labelled SP-I-SP-X, omitting their trade names. • CBRI-SP:A superplasticizer based on CNSL, synthesized at the Central Building Research Institute. Methods The percentage flow values of a 1:3 cement:sand (Ennore) mortar at various water:cement ratios for the control and at a

* Central Building Research Institute, Roorkee, India CONSTRUCTION & BUILDING MATERIALS VoI. 6 No. 4 1992

water:cement ratio of 0.45 for different dosages of superplasticizer were measured according to IS:5512-1983 (Flow table for use in testing hydraulic cements and pozzolonic materials); see Table 1. The viscosity of the cement paste was measured using a Brookfield RVTDVII, digital model. The T-bar spindle No. 95 was used and the shear rate was maintained at 100 rpm. For each measurement the cement was mixed with a predetermined amount of water for 5 minutes before the viscosity and flow were measured. For the superplasticized paste, the superplasticizer was mixed with the required quantity of water and added to the cement to obtain the paste for experimental measurements. All these measurements were made in a constant temperature room maintained at 27 + 1°C and a relative humidity (RH) of about 50%. In another set of experiments the flow of the cement paste only was measured using a truncated cone open at both ends (height 60 mm, base diameter 40 mm, top diameter 20 mm) and using the flow table as in IS:5512-1983 to obtain the flow values (designated as minislump by some workers [6]) at different water:cement ratios. The results of the viscosity and flow of cement paste at different water:cement ratios are given in Table 2. The compressive strength of the concrete prepared with cement 1, sand 1.50 and aggregate 3 ( < 20 mm) was determined. A comparative evaluation of slump, compaction factor and compressive strength of the M15 concrete under field conditions (used for the construction of an indoor stadium at Dehradun in India) is given in Table 3. A Malvern (3600 Model) laser particle-size analyser was used to determine the effect of the addition of CBRI-SP on the particle-size distribution or dispersion of the cement particles. This was carried out in a non-aqueous medium (benzene) so that the change in the size of cement particles due to the small addition of water/superplasticizer solution was evident. The whole operation was automatically controlled and the final stage of the particles recorded using the analyser. The cell of the analyser was filled with about 20 ml of benzene and the instrument was set. About 0.010 g of dry cement powder was inserted in the organic liquid, stirred well and the distribution pattern recorded. Then a drop of water was added using a microsyringe, the liquid was stirred for 2 hours and the distribution pattern recorded. Similarly, the pattern was recorded after adding a solution of CBRI-SP (0.6%) to a fresh cement in benzene and stirring for 2 hours. The particle distribution patterns are given in Fig 1. The costs of the various commercially available superplasticizers provided by suppliers were collected and are compared along with their recommended dosage in Table 4.

Results and discussion The addition of water-reducing superplasticizing admixtures allows a similar or better workability, flow or slump, etc to be achieved by using less water than required for normal

0950- 0618/92/040235 - 03 (~ 1992 Butterworth-Heinemann Ltd

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Water-reducing agent from cashew nutshell liquid Table 2 Viscosity and flow of cement paste at different water:cement ratios and at 0.6% of superplasticizer I00 I

3

2

I

50

0

I

I

I I I1/I

10

I

I

100

~

I

Flow (mm)

Water: cement ratio

Dosage (%) 0.4

0.6

0.8

Control

0.30 0,35 0.40

4.7 x 103 25 x 103 12 x 103

CBRI-SP

0.30

2.0 x 103

175 (in 25 strokes) 250 (in 25 strokes) Paste flows on the flow table 250 0n 20 strokes)

Table 3 Properties of M 15 concrete with superplasticizer at similar dosage and water:cement ratio

Table 1 Comparison of flow (1:3 cement:Ennore sand) of various superplasticizers at various dosages

0.2

Flow (%)

1000

Fig 1 Particle distribution patterns: 1, cement in benzene; 2, cement, benzene and water; 3, cement, benzene and superplasticizer solution

0.0

n (cP)

IIIII

Particle size (lain)

Superplasticizer

Water:cement ratio

Mix 1:1.5:3

SP-I SP-II SP-III SP-IV SP-V SP-Vl SP VII CBRI-SP

120 129 153 195 120 120 120 120 120 120 120 120

-

-

130 126 130 120 120 125 130 130

135 130 136 130 120 125 135 142

150 140 145 140 120 130 144 153

157 143 150 140 120 130 145 160

Compaction factor

Compressive strength (100 mm cube) (kg/cm2; 28 days)

100 150

0.91 0.93

190 220

162

0.94

220

1.0

160 145 155 140 120 130 145 170

0.45 0.50 0.54 0.60 0,45 0.45 0,45 0,45 0.45 045 0,45 045

concrete. Recommended dosages allow a 5-20% reduction in w a t e r c o n t e n t f o r a s p e c i f i e d w o r k a b i l i t y . It w o u l d be r e a s o n a b l e to a s s u m e that the e x t e n t of w a t e r r e d u c t i o n by the a d d i t i o n of w a t e r - r e d u c i n g a d m i x t u r e s w o u l d be m a r k e d l y a f f e c t e d by c h a n g e s in m i x p a r a m e t e r s such as c e m e n t c o n tent, a g g r e g a t e size, s h a p e , g r a d i n g and the w a t e r : c e m e n t ratio. In o r d e r to e s t a b l i s h the s u i t a b i l i t y of the p r o d u c t d e v e l o p e d at o u r institute as a s u p e r p l a s t i c i z e r / w a t e r - r e d u c i n g a d m i x t u r e , it w a s i n c o r p o r a t e d in the c e m e n t - w a t e r s y s t e m and its r h e o l o g i c a l p r o p e r t i e s e v a l u a t e d . T h e r e l a t i o n s h i p b e t w e e n f l o w (mm) and d o s a g e of v a r i o u s s u p e r p i a s t i c i z e r s f o r 1:3 c e m e n t : s a n d m o r t a r s at a w a t e r : c e ment r a t i o of 0.45 is g i v e n in T a b l e 1 a l o n g with the c o n t r o l at v a r i o u s w a t e r : c e m e n t ratios. It is c l e a r f r o m this t a b l e that the f l o w v a l u e s i n c r e a s e with an i n c r e a s e in the d o s a g e of s u p e r p l a s t i c i z e r . The f l o w v a l u e of the plain m o r t a r (1:3 c e m e n t : s a n d ) , just a f t e r mixing, is 120 mm w h e r e a s with an a d d i t i o n of s u p e r p l a s t i c i z e r s it i n c r e a s e s up to 170 mm; the e f f e c t v a r i e s d i s t i n c t l y with the t y p e and d o s a g e of s u p e r p l a s t i c i z e r . It is c l e a r a l s o that the f l o w v a l u e of plain m o r t a r (153 mm) at a r a t i o of 0.54 is a l m o s t the s a m e as that of CBRI-SP (0.6%), SP-2 (0.8%), SP-4 (1%), SP-10 (1%) at a ratio of 0.45. T h e s e v a l u e s i n d i c a t e that a w a t e r r e d u c t i o n of a b o u t 18% f o r the s a m e m o r t a r and f o r the s a m e w o r k a b i l i t y is p o s s i b l e at v a r y i n g d o s a g e s of s u p e r plasticizer. T h e r e s u l t s of the v i s c o s i t y n (cP) and f l o w f o r n e a t c e m e n t p a s t e at d i f f e r e n t w a t e r : c e m e n t ratios, c o m p a r e d with the r e s u l t s o b t a i n e d with CBRI-SP (0.6% d o s a g e ) , a r e g i v e n in T a b l e 2. The v i s c o s i t y and f l o w of s u p e r p l a s t i c i z e d c e m e n t 236

Slump (mm)

Control 0.52 0.6% 0.48 SP-X (Napthalene based) 0.6% 0.48

Table 4 Control

Water:cement ratio

Comparison of cost of various superplasticizers

Designation

SP-I SP-II SP-III SP IV SP-V SP VI SP-VII SP-VIII SP IX SP-X CBRI-SP

Recommended dose by wt of cement (100 kg)

06-0.162 litres 200 300 ml 0.6 3.0% 0.5~.0% 0.3-0.6% 500 700 ml 0.6 101itres 015 0.30°'0 05 10% 600400 g 18 2 litres

Approx. cost at Approx cost of supersite (Rs/IRre) plasticizer (1:2:4 concrete cement content; 6.4 bags) in Rs

16/40/38/38/ 20/40/48/ 55/47/ 35/6/-

24- 44/ 88 120/64-200/64 200/ 36 72/116.172/116 172/ 49 99/117 280/ 63 87/35- 38/-

p a s t e at a r at i o of 0.30 f al l s b e t w e e n the v i s c o s i t y o b t a i n e d at a r at i o of 0.35-0.40 of the c o n t r o l c e m e n t paste, t h u s indicating the w a t e r - r e d u c i n g c a p a b i l i t y of the CBRI-SP. T h e s l u m p (mm), c o m p a c t i o n f a c t o r a n d c o m p r e s s i v e s t r e n g t h (28 d a y s ) f o r the M15 c o n c r e t e p r e p a r e d at the field site a r e g i v e n in T a b l e 3. It is c l e a r f r o m the t a b l e that with the a d d i t i o n of 0.6% s u p e r p l a s t i c i z e r (CBRI-SP) the s l u m p i n c r e a s e s f r o m 100 mm of c o n t r o l at a r at i o of 0.52 to 162 mm with a r at i o of o n l y 0.48, w h e r e a s it i n c r e a s e s to 150 mm on the a d d i t i o n of c o m m e r c i a l s u p e r p l a s t i c i z e r SP-X, w h i c h is c l a i m e d to be a n a p t h a l e n e s u l p h o n a t e f o r m a l d e h y d e c o n d e n s a t e . Thus, this i n d i c a t e s the b e t t e r f l u i d i z i n g effect of CBRI-SP. H o w e v e r , in the c a s e of s u p e r p l a s t i c i z e d c o n c r e t e , the i n c r e a s e in s t r e n g t h is the s a m e (220 kg/cm 2) with both the s u p e r p l a s t i c i z e r s c o m p a r e d with 1 9 0 k g / c m 2 f o r the unplasticized concrete. T h e p a r t i c l e - s i z e d i s t r i b u t i o n c u r v e s 1,2,3 (Fig 1) f o r the n e a t c e m e n t , h y d r a t i n g c e m e n t and s u p e r p l a s t i c i z e d h y d r a t ing c e m e n t , r e s p e c t i v e l y , c l e a r l y s h o w that the c e m e n t u n d e r g o e s d i s p e r s i o n on h y d r a t i o n but the p r o c e s s is slow. On the a d d i t i o n of s u p e r p l a s t i c i z e r (CBRI-SP) c u r v e 3 s h o w s that d i s p e r s i o n is i n c r e a s e d b e c a u s e the n u m b e r of f i n e r and c o l l o i d a l p a r t i c l e s is a p p a r e n t l y large. It is c l e a r f r o m T a b l e 4 that the cost of CBRFSP is l o w e r t h a n that of o t h e r c o m m e r c i a l l y a v a i l a b l e w a t e r - r e d u c i n g / s u p e r CONSTRUCTION & BUILDING MATERIALS Vol. 6 No. 4 1992

S KAgarwal, Irshad Masood and T C Phatak

plasticizing admixtures. CBRI-SP is based on CNSL but the base material for the other products given in Table 4 (except SP-X, which is napthalene based) is not mentioned by the manufacturers in their product catalogues. However, on the basis of the amount required for the same quantity of cement, CBRI-SP is about 30% more economical compared with the napthalene-based superplasticizer.

(4)

(5)

CBRI-SP behaves like the well-established sulphonated napthalene formaldehyde condensate superplasticizer. CBRI-SP is less costly and more than 30% economical than other commercial superplasticizers.

Therefore this product is recommended as a cheaper, good, water-reducing admixture/superplasticizer for commercial utilization.

Conclusions As a result of the investigations carried out using CBRI-SPand other commercial water-reducing/superplasticizing admixtures in cement pastes, mortars and concrete in order to determine viscosity, flow and strength properties, it can be said that: (1)

(2)

(3)

The viscosity obtained with CBRI-SP at a water:cement ratio of 0.3 falls between those obtained without superplasticizer at ratios of 0.35 and 0.40. The same holds for minislump. CBRI-SPproduces a large flow in mortar better than all the commercially available products studied for this purpose at the same water:cement ratio and dosage level. In concrete the 0.6% dosage of CBRI-SP and the naphthalene-based commercial SP-X at a ratio of 0.48 results in a better compaction factor than that obtained in concrete without superplasticizer at a ratio of 0.52. In these cases the slump is improved from 100 mm to 150 mm and the 28 day compressive strength increases to 22 MPa compared with 19 MPa for the neat concrete.

CONSTRUCTION & BUILDING MATERIALS Vol. 6 No. 4 1992

Acknowledgements The subject matter of this paper forms part of the normal research p r o g r a m m e of the institute and is published with the permission of the Director, Central Building Research Institute.

References 1 Ramachandran, V S. Concrete Admixtures Handbook, Noyes Publication, NJ, 1984 2 Dransfield, I M. Developments in superplasticizers. Concrete, 1984, 7 3 Rixom, M R and Mailvaganam, N P. Chemical Admixtures for Concrete, Spon, London, 1986 4 Malhotra, V M. Developments in the use of superplasticizer. ACISP-68-1981 5 Phatak, T C and Agarwal, S K. Process for the preparation of polymeric sulfonates from cashew nut shell liquid. Indian Patent (applied for) Ref. 287/Dec. 1990 6 Perencho, W F, Whiting, D A and Kantro, D L. Proc. Int. Symp. on Superplasticizers in Concrete, Dept. of Energy, Mines and Resources, Ottawa, Vol. I, 1978, p295

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