Influence of black gram (natural organic material) addition as admixture in cement mortar and concrete

CEMENTand CONCRETERESEARCH. Vol. 13,:pp, 423~4~0, 1983. Printed in the USA. 0008-8846/83/030423-08503.00/0 Copyright (c) 1983 Pergamon Press, Ltd.

INFLUENCE OF BLACKGRAM(NATURALORGANICMATERIAL) ADDITION AS ADMIXTUREIN CEMENTMORTARAND CONCRETE

S. Chandra and J. Aavik Div. of Building Materials Chalmers University of Technology S-412 96 GBteborg, Sweden

(Communicated by D.M. Roy) (Received Nov. 18, 1982) ABSTRACT Black gram, used as binder in mortar and plaster in ancient time in India, was mixed in cement mortar, structural lightweight aggregate concrete and normal concrete. Air entrainment, adhesiveness and hydrophobic properties i t imparted to cement mortar and concretes were tested. I t is seen that i t worked like air entraining agent, has improved the adhesiveness and hydrophobicity of cement mortar and concrete. Addition of oii along with black gram worked as a defoaming agent and has substantially improved the hydrophobic property of cement mortar and concrete. Introduction Use of polymers in concrete mortars and plasters is not a new subject. Many natural organic materials have been used in ancient times as admixtures and binders to the building materials. They gave good results that is what the people knew at that time. One of the examples of this is that some of the structures s t i l l exist in good shape. Though very l i t t l e is known about the theoretical approach of ancient builders. They must have had good empirical knowledge about the building materials. Not much work on these additives is documented in India. Mostly i t camethrough hereditary. Literature cited in (I, 2, 3} deals with the preparation of stucco to be applied on the walls for painting in Sirgiria and Ajanta caves in India. The stucco was based on lime with gram, molasses, pulp from fruits, different flowers soaked in oil etc. There are different types of grams in India, but of these only black and green grams were used in stucco preparation. Main contents of the gram are proteins and carbohydrates (4). Proteins like keratin and casein were also used in Egypt as described by Sayre / 5 / . Many other natural organic materials were used in ancient period and are described by Sickles (6). The aim of this work is to see how black gram (proteins and polysacharides) functions when mixed to cement mortar and not to analyze the admixture used in ancient times from historical or archaeological point of view. Synthetic polymer admixtures when added to cement mortars and concrete can influence 423

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Vol. 13, No. 3 S. Chandra, J. Aavik

its air entrainment, adhesiveness and hydrophobicity. With this in mind black gram was mixed in cement mortar to check i f i t works in parallel to admixtures used today. Further i t is known that oil works as defoaming agent as well as i t increases the hydrophobic character. In this work also the influence of oil along with gram is tested. Structural lightweight aggregate concrete was also made with gram and gram+oil emulsion. Their strengths and water absorption were tested and compared with the concretes made with other lightweight aggregate concretes made with other synthetic polymer admixtures. Trials were also made to make normal weight concrete with gram+oil emulsion. Materials and methods Cement mortar specimens, lightweight aggregate concrete and normal concrete were made using the following ingredients: Cement

Cement used was standard portland cement with specification as follows: C3S - 64%, C2S - 13%, C3A - 8%, C~AF - 10%, K20+Na20 - 1.6%, SO3 - 3.2%, specific surface area 337 m2/kg.

Sand

Normal sand I, 2, 3 was used for making mortar specimens as defined in Belgian standard NBN 715.

Lightweight aggregate Sintered expanded clay aggregates were used for making lightweight aggregate concrete. Admixture

Black gram paste was made by soaking i t in water so as to pass sieve 0.125 m. Gram-oil emulsion was made by mixing edible oil to the gram paste. Conventional air entraining agent and methacrylic microparticles were also used to make structural lightweight aggregate concrete.

Cement-sand mortar (1:3} was made with gram and gram+oil emulsion as admixture. Varying the water to cement ratios fresh densities were measured and the air content was calculated. The air content is calculated for I%, 3% and 5% admixtures at different water to cement ratios. The results are produced in Fig. la for only gram and in Fig. Ib for gram+oil emulsion. 4x4x16 cms prisms were made with 1:3 cement mortar and 0.50 water to cement ratio as reference samples (N). Mortar specimens with gram (G) and gram+oil emulsion (GO) were made keeping the consistency constant. Mechanical strengths and water absorption were measured. Water absorption was measured by capillary rise method on 4x4x8 cms specimens obtained by cutting 4x4x16 cms prisms in two parts. These specimens were put in a glass container with cover with their cut surfaces touching the water surface. The specimens were dried at I05vC and cooled to room temperature before water absorption test. The composition and some of the physical properties are shown in Table I and water absorption in Fig. 2. Structural lightweight aggregate concrete was made with gram and gram+oil emulsion, with conventional air entraining agent and with methacrylic pol~nner dispersion containing soft microparticles having filmforming a b i l i t y . Their mechanical strengths and water absorption are tested on 15x15x15 cms cubes. Water absorption was tested in the same manner as for mortar specimens but without cutting the cubes. The composition and some of the physical properties are shown in Table II and water absorption in Fig. 3. Trials were also made to see the influence of gram+oil emulsion in normal weight concrete (K 25). Its mechanical strength and water absorption were measured and compared with the normal concrete made without any admixture. The composition and some of the physical properties are shown in Table II and water absorption in Fig. 3

Vol. 13, No. 3

425 ORGANIC BINDER, BLACKGRAM,RYDROPHOBICITY,ADHESION, OIL

O =G I% & =G 3°1o a = G 5% 50 x =N .

60

~~.~1"~ ~ i~.,,,~"-:.,...

tO

u30

J°f°1°"'-

o

20

10

~= ~ ~ x,---_~ 0.35 0J,0 0./,5 0.50 0.55 0.60 0.65 Water- cement ratio |

FIG 1 a-b Air entrainment with different water-cement ratios. The amount of admixture is I, 3 and 5% of the cement weight. a) black gram {G); {N) is reference without any admixture b) black gram+oil emulsion {GO)

|

a)

60

o =GO t°/, & = GO 3% o = GO 5°1o

50

~0 C 0

u 30

L..

2O 10

o • ~ o ~ O |

•

o/°~°'''-° j •

•

•

0.35 0.~0 0.45 0.50 0.55 0.60 0.65 Water-cement ratio

b) i~J 3

•

o=G' o=GO x =N

o1

x~X..,.. ,-'x~--x~x ~ o

1 2 3 4 5

-'-'''<)-

10 TimelY"

FIG. 2 Water absorption of mortar specimens.

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Vol. 13, No. 3

S. Chandra, J. Aavik Table I. Composition and some Physical Properties of the Mortar Specimens made with Gram and Gram+oil Emulsion Cement:sand 1:3 Specimen W / C - Percent No.* r a t i o admixture used N G GO

0.50 0.40 0.38

I I

Percent air

28 days strength (MPa) Flexural

2 10 7.5

Compressive 43.0 46.8 47.5

7.0 7.6 7.8

* N - 4x4x16 cms prisms without admixture G - 4x4x16 cms prisms with I% black gram GO - 4x4x16 cms prisms with I% black gram+oil emulsion

o=OC o = GOC 7

4=

BC

v= PC += K

"E ~6

x =

GOK

c'-

o5 CI. O O

O

2 1

2 3 4 5

I0

15

Time V'h-

FIG. 3 Water absorption of concrete specimens. Results and discussions Air entrainment I t is seen from a i r entrainment diagram, Fig. la, that the gram used worked in the same way as other a i r entraining agents. In lightweight aggregate concrete as well as normal concrete also i t behaved as an a i r entraining agent l i k e conventional a i r entraining agent (CAEA) and polymer dispersion PC. With the addition of oil to the gram, i . e . by using

Vol. 13, No. 3

427 ORGANIC BINDER, BLACKGRAM, HYDROPHOBICITY, ADHESION, OIL

gram+oil emulsion the air entrainment is reduced. This is evident from Fig. lb. In the case of lightweight aggregate concrete a more dense concrete (GOC) could be obtained with 9ram+oil emulsion, i.e. the amount of air entrained was lesser than the one (GC) without oil addition. In normal concrete gram+oil addition gave very l i t t l e amount of air. Proteins are b u i l t up by amino acid residues, arranged in the long chains and joined by so called peptide bond - CO-NH -. In nature the sequence of amino acid residues along the chain is unique. Some typical features of the side chains are illustrated in Fig. 4. I t is common to say that protein chains are b u i l t up by segments. Each of these segments contains a number of amino acid residues. These segments can have polar and nonpolar character, depending upon which amino acid predominates. Polar segments make the chain hydrophilic while the nonpolar one makes i t hydrophobic. Thus a single protein molecule may have several hydrophobic and hydrophilic segments along the chain. Ionic bonds prevail in hydrophilic region while nonpoTar bonds in hydrophobic regions. This fact gives to many proteins surface activity. This surface activity may be the principal cause of air entrainment. Due to the addition of oil some of the surface active agents are used in order to make an emulsion with gram. This can be the reason of decrease in air entrainment due to oil addition. MAIN

CMAIN

N[

~

I

[~ CO0-

o

i\

0I

H

MAIN CHAIN

0

0

C

C=O

[

!

I

~

INTERPEPTIDE HYDROGEN BOND

i

%.~R.o#

1 ii

I f.R

I

SlOE CHAIN HYDROGEN BOND

IONIC BOND

A POLAR OR HYDROPHOBIC BOND

FIG. 4

Adhesion

Schematic diagram illustrating the types of non covalent bonds (5).

I t was observed during specimens making that the addition of gram gave fresh mortar excellent adhesion between cement and aggregates and very sticky mortar and concrete was obtained. Mortar specimens with black gram addition entrained more a i r than normal (without any addition). S t i l l its strength was on the higher side than normal (Table I ) . This may be due to the better adhesion. This adhesion was decreased by the addition of oil+gram emulsion. But i t entrained less amount of air and i t was possible to work with l i t t l e less water/cement ratio. Not much difference in the strengths could be noticed between the mortar specimens made with gram and gram+oil emulsion. Due to decrease in the adhe-

1.5 1.5 0.05 1.5

255 255

345 380 353 320

280 305 340 305

140 155 135 120

265 295 320 290 1100 1100

800 800

Lightweight aggregate concrete with gram paste as admixture Lightweight aggregate concrete with gram+oil emulsion admixture Lightweight aggregate concrete with conventional a i r entraining agent Lightweight aggregate concrete with polymer admixture containing soft microparticles Nor~l weight concrete (K-25) with gram+oil emulsion Normal weight concrete (K-25 without admixture

K GOK

Normalweight concrete

GC GOC BC PC GOK K -

GC GOC BC PC

0.648 0.60

0.594 0.595 0.574 0.584

Sand/gravel (kg/mJ) w/c Sand/Leca (kg/m3) Speci- Admixture Cement ratio (percent to :(kg/m3) men Gravel Sand Leca Leca Sand cement by No. (0-4 mm) (2-4 ram) (4-12 n~rn) (0-12 mm) (8-16 mm) weight)

Lightweight aggregate concrete

Type of concrete

Concrete Composition, Density, and Compressive Strength.

TABLE I I

2320 2308

1231 1357 1350 1222

29.0 27.5

19.0 22.5 20.4 18.0

st(ath

Fresh 28 days density compres(kg/m~) slve

-C ..J.

C.~

C)"I

0

J~

Z 0

(.~

--J

0

O0

429

Vol. 13, No. 3 ORGANIC BINDER, BLACKGRAM, HYDROPHOBICITY,ADHESION, OIL

sion the strengths could reduce but due to lower air content, i t may have a more dense structure. This difference'is more prominent in the case of structural lightweight aggregate concrete (Table I I ) , where with gram+oil emulsion, more dense concrete (GOC), with higher strength was obtained. In normal concrete i t was possible to work with l i t t l e less water/cement ratio and in spite of the air entrained, not much difference in the strength was noticed. This adhesive character in concrete is due to the black gram used. The major components of black gram are protein and carbohydrates (4). Carbohydrates mostly consist ofpolysacharides such as starch. I t is well known that polysacharides and proteins act as adhesives (8). Hydrophobic character Fig. Z shows that mortar specimen with gram absorbed less water in comparison to the mortar specimen without i t . Minimum amount of water was absorbed by the specimens with gram+oil emulsion. Water absorption of lightweight aggregate concrete with black gram lles in the same area as of lightweight aggregate concrete with CAEAand with pol)nner PC (Fig. 3). Lightweight aggregate concrete and normal concrete made with black gram+oil emulsion have shown substantial improvements in hydrophobicity. This hydrophobic character in concrete is attributed to the proteins present in the black gram. In the native form most soluble proteins are globular, which means that the chains are folded in a precise manner. On heating, exposer to extreme pH values which is the case in concrete (pH of cement during hydration > 12) etc. they denature, that is the chains are unfolded and more hydrophobic parts are exposed. This is shown in Fig. 5. NATIVE FORM

FIG. 5 Protein denaturation.

OIL

D~

An explanation of the observed phenomenon is that the hydrophilic part of the protein interacts with the hydrophilic surfaces of the hydrated cement paste whereas the hydrophobic part became exposed to the air-cement interface in the pore and capillary structure. Thus hydrophobic inner surfaces of pores and capillaries are obtained. The interaction of hydrophilic part of proteins with cement is increased by the reaction of Ca+z ions with the carboxylate groups present in the proteins as is hypothesized by Chandra et al (9). Conclusions On the basis of the tests done following conclusions are drawn: 1. Black gram used worked as a i r entraining agent in cement mortar as well as in structural lightweight aggregateconcrete in the same manner as conventional a i r entraining agent or as the polymer dispersion used. With the addition of o i l the a i r entrainment is reduced.

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VoI. 13, No. 3 S. Chandra, J. Aavik

2. Black gram addition gave air to the mortar specimens but their strength were on the increasing side. This indicates better adhesion. The same tendency was shown in the structural lightweight aggregate concrete. With the addition of oil the adhesiveness is reduced but not much difference could be noticed in the final strength. 3. Black gram addition increased the hydrophobic property of the cementmortar and of the structural lightweight aggregate concrete. Oil addition further improved the hydrophobic property. 4. Addition of gram+oil emulsion to the normal weight concrete substantially improved its hydrophobic character. I t is seen that the black gram used works as an air entraining agent, increases the adhesiveness of the fresh concrete and hydrophobic property of cement mortar and concrete. Addition of oil further improved the hydrophobic property. I t is very interesting to note that black gram works in parallel to the synthetic polymer admixtures. This may give another turn to modern concrete technology. More work is to be done to study its durability before i t can be used in industry. Further care should be taken in using natural organic admixture as they can vary in composition, depending upon various factors such as climate, soil etc. Acknowledgements The authors are grateful to Dr. M.S. Shivaraman, Department of Electronic Physics, Chalmers University of Technology, for continuous encouragement in writing this paper. Thanks are also due to Dr. S.K. Mitra (biochemist) for his suggestions. The authors are grateful to Mr. Muni Sing of National Research Laboratory for Conservation of Buildings, Lucknow, India, for f r u i t ful discussion, Prof. R. Malinowski for constructive criticism of the text, prof. P. Flodin of Polymer Technology, Chalmers University of Technology, for his help in writing this paper and finally to Miss B. Lendheim for preparing the text. References I. 2. 3.

4. 5. 6. 7. 8. 9.

C. Sivaramamurty, Chitrasutra of Vishnu Dharamotra, N. Delhi, India (1978). B.N. Goswami & A.L. Dallapiceola, An Early Documentation of Indian Art, The Chitra-Lakhshan of Nagnajit, N. Delhi, India (1978). R. Shamasatri, Abbilashitasth Shuntamani (Mansoullas), Mysore, India (1976). C. Gopalan, Neutritive Value of Indian Food. Publ. National Institute of Neutritian, Indian Council of Medical Research, Hyderabad, India (1980). E.V. Sayre, Deterioration and Restoration of Plaster, Concrete and Mortar, in preservation and conservation, principles and practices ed. Sharon Timmors, Washington (1976). L.B. Sickels, Organics vs. Synthetics, their Use as Additives in Mortars, Symposium on Mortars, Cements and Grouts used in the Conservation of Historic Buildings, Rome (1981). R.H. Haschemeyer & A.E.V. Haschemeyer, Proteins. John Wiley & Sons (1973). W.C. Wake, Adhesion and the Formulation of Adhesives. Applied Science Publication, London (1976). S. Chandra, P. Flodin and L. Berntsson, Interaction between Calcium Hydroxide and Styrene-Methacrylate Polymer Dispersion. Third International Congress on Polymers in Concrete, Koriya~, Japan (1981).