On Controlling Modulus of Elasticity and Creep in High-Strength Concrete With

ON CONTROLLING MODULUS OF ELASTICITY AND CREEP IN HIGH-STRENGTH CONCRETE WITH MULTICOMPONENT MODIFIER

S.Kaprielov, N.Karpenko and A.Sheinfeld Research Institute for Concrete and Reinforced Concrete (NIIZhB) 2 Institutskaya 6 109428 Moscow, Russia FAX: (095)174-7591 E-mail: [email protected]

MS#LV40 2

On Controlling Modulus of Elasticity and Creep in High-Strength Concrete with Multicomponent Modifier

by S.Kaprielov, N.Karpenko and A.Sheinfeld

Synopsis: The deformability characteristics of high-strength concrete (HSC) including multicomponent admixture (modifier), consisting of silica fume (SF), fly ash (FA), superplasticizers (SP), setting retarder (SR) and air-entraining agent were investigated. A multicomponent modifier represents composite power-like material of 800 kg/m3 bulk weight with indicated ingredients in following quantities: SF - 43%, FA - 43%, SP and SR – 14%. The experimental studies were accomplished with mortars and concrete having compressive strength of 100,4-111,4 MPa. The total binder content (cement + modifier) varied from 660 to 1629 kg/m3, and the modifier dosage – from 0 to 34% by weight of binder. The tendencies of alteration of the elastic modulus and creep, and dependence of each of these properties on the quality and quantity of cement paste were re- vealed . The qualitative characteristics of cement paste can be regulated by dosing the modifier, i.e. the SF, FA, SP and quantitative ones – by using various aggregates and air-entraining agent. These tendencies are based on respective alterations of porosity of cement paste, and also on a balance between gel a crystalline hydrates. For the concrete of similar class in compressive strength the rate of varying of the elastic modulus can reach 20% and of the creep - 45-60%.

Keywords: air-entraining agent, cement paste, creep, crystalline aggregate, fly ash, gel, high-strength concrete, modulus of elasticity, superplasticizer, silica fume. 3

Simon Kaprielov, Dr. Sc. (Eng), Laboratory for Concrete Admixtures and Modifiered Concrete at the Research Institute for Concrete and Reinforced Concrete, Moscow. Nikolay Karpenko, Dr. Sc. (Eng), professor, Laboratory for Resistance and Strength Problems at the Research Institute for Construction Physics, Moscow. Andrey Sheinfeld, Ph. D. (Eng), Laboratory for Concrete Admixtures and Modifiered Concrete at the Research Institute for Concrete and Reinforced Concrete, Moscow.

INTRODUCTION

It is known that the elastic modulus and creep of concrete as a composite material depend on the deformability characteristics of its components, i.e. the cement paste, the mortar, the coarse aggregate, and the volume concentration of each of the said components. This is the basis of various mathematical mod- els which more or less precisely predict the elastic modulus and creep of concrete [1, 2]. Since high-strength concrete (HSC) is characterized with a higher than usu- al content of cement, the role of elastic modulus, creep, and shrinkage of the cement paste in the deformability characteristics of concrete is all the more im- portant. In addition the key factor in modern technology of HSC is a complex use silica fume, fly ash, metakaolin and superplasticizers which can essentially modify the structure of cement paste. Earlier research has shown the influence of silica fume (SF), fly ash (FA) and superplasticizer (SP) on the porosity and phase composition of cement paste, also the link of these characteristics with the concrete properties [3, 4, 5, 6]. We may note that by varying the doses of such admixtures and their combinations it is possible to regulate a wide range of concrete strengths, which cre- ates a pre-requisite for regulating the elastic modulus and creep of HSC.

EXPERIMENT

The object of research was to study HSC containing SF, FA, and SP mixed into a single powder-like substance produced in Russia as a concrete modifier of the MB-50C brand. MB-50C is a multicomponent powder-like material of 800 kg/m3 bulk weight composed of SF and FA, SP and setting retarder. MB modifier contains the indicated ingredients in the following quantities (in % of total mass): silica fume – 43; fly ash – 43; superplasticizer of naphthalene-formaldehyde polycondensate base – 13.9; setting retarder – 0.1. The idea of the experiment involved two tasks: the first was to compare concrete of similar compressive strengths, with equal volumes but different 4

qualities of cement paste; second, to compare concrete of similar strength, but with different volumes of cement paste of similar quality.

The comparison was carried out in such characteristics as the phase composition (the balance of hydrates) and the porosity of cement paste, also the elastic modulus and creep of concrete. For solving the first task, the fine-grained HSC containing approximately equal quantities of binder (cement + modifier), with similar water-binder content of 0.23, and, respectively, equal volumes of cement paste of 0.4 m3/m3 were examined. The specimens were prepared with different doses of modifier: 0% (reference), 10, 17 and 34% of the binder mass (or, respectively, 0, 11, 21, and 52% of the cement mass). The different doses of modifier in the mixtures permitted to vary the composition and porosity of cement paste. The reference mixture was with 50 mm slump, the specimens with modifier were with slump of 210-230 mm. To solve the second task, four specimens containing different quantities of binder (from 660 to 1629 kg/m3) and different volumes of cement paste (from 0.36 to 0.90 m3/m3), but with similar water binder content of 0.23 and similar doses of modifier equal to 17% of binder mass were compared. In this group we compared a specimen of cement paste without aggregate, two specimens of fine-grained concrete with air-entraining agent (AEA) and without it, and a specimen of concrete with coarse aggregate. The presence in the specimens of coarse aggregate and air-entraining component permitted us to vary the volume of cement paste and the porosity of concrete. The composition of concrete mixtures and their characteristics are shown in Table 2. Besides the multicomponent modifier MB-50C mentioned above the following materials were used: - portland cement of following bogue potential compounds composition (%):

C3S=59.0, -C2S=16.0, C3A=6.0, C4AF=13.0, CaSO42H2O=4.0; - quartz sand with 2.5 fineness modulus; - granite crushed rock of 5-20 mm size. And as AEA the neutralized vinsol resin was used.

The structure of cement paste was examined with several methods. The porosity in the range from 110-3 to 1103 m was ascertained with comple- mentary methods of small angular X-ray refraction, nuclear magnetic reso- nance, mercury porosimetry, and optical method. The composition of crystal hydrates in cement paste (phase composition) was found by X-ray and differential-thermal analyses [3, 4, 5, 6]. The elastic modulus, creep, and shrinkage were measured on 100100400 mm specimens. Shrinkage was measured on the specimens cured in the air under normal conditions (t=18-22oC, relative humidity 96-98%). Creep was measured at two levels of loading: 0.3 and 0.6 Rbn (prisms compressive strength) 5

on “sealed” specimens with isolated surface, cured previously during 28 days under normal conditions.

RESULTS

The partial replacement of cement by a multicomponent modifier with constant water-binder proportion results in higher flowability of the concrete mixture, higher volume of entrained air, and, conversely, a lower volume density of mixture. The tendency is more marked with higher doses of modifier and consequently more cement substituted in the concrete mixture (mix. #1-4 in Table 1). The introduction of AEA in the concrete mixture leads to more air entrained in the concrete (compare Mix.#3 and #6 in Table 1).

All the concrete specimens had approximately equal compressive strength (for cubes in the range of 100.4 to 116.9 MPa). In terms of this property all the concretes may be referred to the same class B80. Nevertheless we may note the following: in the specimens of fine-grained concrete with approximately equal content of binder (cement + MB) and volume of cement paste, the compressive and flexural strength exceeded the level of the reference specimen depending on the MB doses. The greatest increment was observed with the doses of MB constituting 10 and 17 % of the binder mass (compare mix.#1 with #2, 3, 4 in Table 2). The elastic modulus and creep in the same specimens with equal volume of cement paste vary respectively in the range from 38.5103 to 45.0103 МРа and from 13.710-6 to 34.010-6 МРа-1 depending on the share of MB in the binder reaching the maximum with the MB dose constituting 10% of the binder. As the volume of cement paste decreases and, conversely, the share of aggregate increases, the elastic modulus rises reaching the maximum (47.0103 МРа) and the creep drops to the minimum (16.210-6 МРа-1) if the concrete contains granite crushed rock (mix. № 3, 5, 6, 7 in Table 2). However with the dose of MB about 10% of the binder mass and with higher than average volume of cement paste, the elastic modulus and creep of fine-grained concrete are close to those characteristics of concrete with coarse aggregate (mix. #2 and 7 in Table 2).

The data in Table 3 shows that the dose of the composite admixture, i.e. SF, FA, and SP, in equally strength concretes with equal volume of cement paste and water binder proportion does not much affect the hydration degree of the cement, but makes a substantial influence on the content of hydration phases and differential porosity (Table 3). The hydration degree of cement in all specimens is on the level of 59-66%, i.e. practically similar. 6

With higher doses of modifier, the content of portlandite decreases three times (from 9.1% to 2.9%) and the quantity of hydrosilicates of the CSH(I) type rises eight times. Besides, higher doses of MB-50C greatly change the balance between gel (110-3d510-3 m) and capillary (510-3

DISCUSSION

Now we may try to evaluate the validity of changes in the elastic modulus and creep of HSC in view of the found characteristics of cement paste. Let’s proceed from the fact that the model under research – HSC – is a composite material containing cement paste, aggregate, and macro-pores (technological and capillary). The cement paste, in turn, may be subdivided into its gel and crystalline parts (Fig.2). By gel we mean a weakly crystallyzed solid phase (submicrocrystals) with a predominantly laminated structure consisting mainly of calcium hydrosilicates (CSH) which are held together through water layers by the Van der Vaals inter-molecular forces, i.e. the solid particles in the gel are linked with reversible coagulation contacts. To this we also refer the micropores less that 510-3 m in size which, as well as the space between layers, are usually filled with water, and also particles of SF and FA. By the crystalline part, we mean the crystalline growth permeating the gel. The crystal hydrates in that growth have a solid (not laminated) structure and are held together by chemical links. The particles of the solid phase in that component of cement paste are joined with crystallization contacts. We may class here portlandite (CH), ettringite (CASH), hydroaluminates (CAH), and hydroferrites (CAFH), also grains of unhydrated cement. The nature of elastic-plastic properties of cement paste lies in the breach of contacts between the solid phase particles under the impact of short-term and long-term loadings [7]. Therefore, the magnitude of deformability characteristics depends on the rigidity of cement paste components (measured by multi- plying the volume by the elastic modulus). The gel part of cement paste is prone to lose that rigidity under the of long- term static loading due to gradual decay of coagulation contacts while the crystalline part has the properties of perfectly elastic body thanks to its stronger crystallization contacts. Let’s calculate the measure of creep and elastic modulus of cement paste in view of correlation between the rigidity of its gel and crystalline parts. The ultimate measure of creep according to [7] is obtained by the following equation: q g E g С p  (1) qC EC  qg Еg  qC EC 7

where: qg and qc are the volumes of the gel and crystalline parts in a unit of cement paste volume; Eg and Ec are the elastic modulus of the gel and crystalline parts of cement paste; qgEg and qcEc are the rigidity of the gel and crystalline parts of cement paste. Bearing in mind that the deformability characteristics of such a composite material as cement paste consisting of gel and crystalline parts follows the so- called “mixtures rule” [12] we have the equation: qC EC  qg Еg  q p Е p  Е p (2) where: qp is the specific volume of cement paste equal to 1; Ep is the elastic modulus of cement paste.

Thus, formula (1) is:

1 q g Е g С p   (3) Е p qС ЕС Taking into account that the creep of fine-grained concrete is determined by the creep of cement paste and that the elastic modulus of sand is equal to 60103 MPa [7], on the basis of the experimental results quoted in Table 2 on the deformability characteristics of fine-grained concrete, we can calculate the elastic modulus and creep of cement paste (Table 3 and Fig 3). The volume of the crystalline part is found from the data [8, 9, 10, 11] on the density (pc) of portlandite, ettringite, C3AH6, C4AFH8 according to the formula:

mС VС  (4) С where: mc and c are respectively the mass and density of the crystalline part of cement paste;

In turn, the mass of the crystalline part is calculated according to [7] on the basis of the mineral composition of the cement plus the experiment al data (Table 3) on the hydration degree and the quantity of Ca(OH)2 according to the formula: -4 mc = С (0.32C3S + 1.4C3A + 1.3C4AF + 1.66G/)10 (5) where:  is the hydration degree of cement (%); C is the cement content in the concrete composition (kg/m3); C3S; C3A; C4AF; G – are the content of minerals and gypsum dihydrate in the cement (%). The volume of the gel part of cement paste is found according to the ac- cepted structural model of concrete (Fig.2) plus the data [8] on the density (pg) of the calcium hydrosilicates by the formula: 8

mg Vg  (6)  g where: mg is the mass of the gel part of cement paste defined as the difference between the masses of cement paste and its crystalline part; 3 g is the density of the gel part of cement paste equal to 2.8 g/cm as per [8]. The volume of technological and capillary pores (porosity) is calculated as the difference between the volumes of concrete and cement paste with aggregate. The information on the calculated data (on the volume, mass, and density) of components of fine-grained concrete and cement paste including its gel and crystalline parts is presented in Table 4. Observe that the volume of cement paste in fine-grained concrete with various doses of multicomponent modifier is approximately similar in the narrow range of 0.409-0.429 m3/m3. However, larger doses of modifier change the structure of cement paste increasing its gel part (Curve 1, Fig.4) and conversely decreasing the volume of its crystalline part (Curve 2, Fig.4). Using the data given in Fig.3 and Fig.4 and the formula (3) we can obtain information on the influence of the modifier on the correlation of rigidity and elastic modulus in the component parts of cement paste. The correlation of elastic modulus in the gel and crystalline parts of cement paste diminishes considerably with the increasing dose of multicomponent modifier (Curve 2, Fig.5). This can be explained by the changing quality of the cement paste, i.e. by the rising quantity of CSH(I) and volume of the gel pores and, conversely, by the falling quantity of Ca(OH)2. The shape of the curve of correlation between the rigidities of the gel and crystalline parts of cement paste (Curve 1, Fig.5) fully corresponds to the tendency of changing of creep in fine-grained concrete and cement paste (Fig.3b). This prompts the conclusion concerning the objectivity of the chosen structural model (Fig.2) and the reliability of the obtained experimental data on the influence of dosing SF, FA, and SP on the quality of cement paste and consequently on the elastic modulus and creep of concrete.

Let’s compare specimens #3, 5, 6, 7 in Table 1 with equal doses of modifier, but different volumes of cement paste. The ultimate magnitude of concrete creep allowing for the volumes of cement paste and its aggregate, also for the porosity of concrete, can be calculated according to [6] by the following formula: BЕ  (1   W / Т )2  Т С  g с  10 3 2 (7)  ( АЕс  BЕg )АЕс  К where: Eg and Ec are elastic modulus of cement paste gel and crystalline parts; A and B are characteristics depending on the mineral composition of cement: 9

m m А  с ; B  g (8) C C where: mc and mg are the masses of crystalline and gel parts in a volume unit of concrete (Table 4);  is the hydration degree of the cement (Table 3); C is the cement content in volume unit of concrete (Table 4);

 and c are the density of cement and the average density of hydrates in the rystalline part of cement paste (Table 4); T is the mass of binder (C + MB) in volume unit of concrete (Table 4); W/T is the water binder component [W/(C +MB)] (Table 1); K is the characteristic of the porosity of concrete: К=1-Vn (9) where: Vn is the volume of technological and capillary pores in a volume unit of concrete (Table 4). Bearing in mind that the tested concrete specimens contained cement paste of similar structural characteristics with doses of MB equal to 17% of the binder mass we can write the following equation (7): Т С  S (10) 1 Vn Where S is the characteristic depending on the quality (the composition of crystallohydrates) of cement paste. BЕ  (1   W / Т )2 S  g с  10 3 2 (11)  ( АЕс  BЕg ) АЕс From Tables 3 & 5 we can take the data on the cement paste with 17% of modifier needed for finding the S characteristic:

=0.64; W/Т=0.235; =3.1; с=2.56; А=0.993; B=1.338

Knowing the actual elastic modulus (25300 MPa) of concrete with 17% of modifier without aggregate (Mix #5, Table 2) and the actual volume of cement paste (0.903 m3/m3) in a volume unit of this concrete (Mix #5, Table 4), also using the data from Fig.4 (qg=0.63; qc=0.37) and Fig.5 (Eg/Ec=0.9) the dependence (2) can be expressed thus: 0.63(0.9Ес)+0.37Ес=25300 / 0.903

hence: Ec=29900 MPa and Eg=26910 MPa. Substituting the obtained data in the formula (11) we find S=2.29610-8 modifier for concrete with 17% of modifier in the binder mass.

Thus, the general formula (10) in the case of modifier dose of 17% in the binder mass looks like this: Т С  2.296  10 8 (12) 1  Vn Calculated according to (12), theoretical and actual measured creep of the tested concretes are shown in Fig.6 which demonstrates that the results coin- 10

cide 5-10%. This permits the conclusion on the objectivity of the chosen structural model of concrete with the multicomponent modifier MB-50C consisting of SF, FA, and SP and the reliability of the obtained experimental data on the influence of the cement paste volume, also of the type of aggregate and porous structure on the deformability of HSC. The general character of changing compressive strength, elastic modulus and creep of HSC depending on the quality of cement paste and consequently on the doses of modifier, as well as on the volume of cement paste in the composition of concrete is presented in Fig.7. Changes in the quality of cement paste (its composition) affect the creep more than the compressive strength and elastic modulus of concrete (Fig.7a). The creep can be diminished by 45-60% with the optimal doses of modifier (Curve 3, Fig.7a) while the elastic modulus and compressive strength can be increased only by 20% (Curves 1 & 2, Fig.7a). Changes of the cement paste volume only slightly affect the compressive strength, but make a more substantial influence on the elastic modulus and creep of concretes (Fig.7b). Depending on the porous structure of concrete the compressive strength changes in the range from 5 to 20% (Zone 4, Fig.7b), the elastic modulus - from 60 to 90% (Zone 5, Fig.7b), the creep – from 45 to 60% (Zone 6, Fig.7b). Note that equal changes of creep can be achieved both by varying the doses of modifier, i.e. SF, FA, and SP, with constant volume of binder and cement paste and by varying the volumes of cement paste, aggregate, and the porous structure with constant doses of modifier.

CONCLUSIONS

1. Changing the elastic modulus and creep of HSC with multicomponent modifier containing SF, FA, and SP depends on changing the qualitative characteristic of cement paste, i.e. the balance between its gel (submicrocrystals of the gel) and crystalline parts, as well as on the quantitative characteristic, i.e. the correlation of volumes in cement paste, aggregate, and pores. The qualitative characteristics can be regulated by dosing the modifier, i.e. the mixture of SF, FA, and SP, and the quantitative ones – by using various concrete aggregates and air entraining agents.

2. For the strength and deformability characteristics the optimal dosing of modifier is in the range of 10-17% of the binder mass as this minimizes the quantity of Ca(OH)2 in cement paste providing approximately equal volumes of gel and crystalline parts and equal rates of elastic moduli.

3. The elastic modulus and creep of fine-grained HSC, with equal compressive strength, can be regulated in a wide range by varying the doses of modifier and introducing AEA in the composition of concrete. Changes of the elastic modulus can reach 20% and of the creep – 45-60%. 11

4. Varying the doses of modifier helps regulate the deformability characteristics and obtain fine-grained HSC with elastic modulus and creep levels com- parable to heavy-weight concrete with coarse aggregate, of similar compressive strength. 5. Controlling the creep level of HSC can be achieved as well by varying doses of SF, FA, and SP as by varying the correlation between the volumes of cement paste, aggregate, and AEA.

REFERENCES

1. Baalbaki W., Aitcin P-C., Ballivy G., “On Predicting Modulus of Elastic in High-Strength Concrete”, ACI Materials Journal, 1992, Sept-Oct., p.p.517-520 2. Gardner N.J., Zhao J.W., “Creep and Shrinkage Revisited”, ACI Materials Journal, 1993, May-June, p.p.236-246 3. Kaprielov S., Sheinfeld A., “Influence of Silica Fume – Fly Ash – Super- plasticizer Combinations in Powder-like Complex Modifier on Cement Paste Prosity and Concrete Properties”. Sixth CANMET/ACI Int.Conf. on Superplasticizers and other Chem. Admixtures in Concrete. Nice, France, Oct. 2000, Proceedings, pp.383-400 4. Batrakov V., Kaprielov S., Sheinfeld A., “Influence of Different Types of Silica Fume Having Varying Silica Content on the Microstructure and Properties of Concrete”. Fourth Int Conf. On Fly Ash, Silica Fume, Slag and Natural Pozzolans in Concrete , Istanbul, Turkey, May 1992, Pro- ceedings, pp.943-964 5. Kaprielov S., Sheinfeld A., Krivoborodov Yu. “Influence of Cement Paste Structure with Silica Fume and Superplasticizer on the Properties of Con- crete”. Concrete and Reinforced Concrete No.7, 1992, pp.4-7 (in Russian) 6. Kaprielov S., Sheinfeld A. “Influence of the Composition of Organ- ic-Mineral Modifiers of MB Series on their Effectiveness”, Concrete and Reinforced Concrete No.5, 2001, pp.11-15 (in Russian). 7. Sheikin A., Chekhovsky Yu, Brusser M. “Structure and properties of Ce- ment Concretes”. M., Stroyizdat, 1979, p.344 (in Russian) 8. Kuznetsova T. “Aluminate and Sulphuraluminate Cements”, M., Stroyiz- dat, 1986, p.208 (in Russian) 9. Tailor H.F.W. “The Chemistry of Cements”. M., Publishers of Literature on Building Industry, 1969, p.501 (in Russian) 10. Akhverdov I.N. “Basic Physics of Concrete”. M., Stroyizdat, 1981, p.464 (in Russian) 11. Butt Yu. “Technology of Cement and other Binding Materials”, M., Stroyizdat, 1976, p.407 (in Russian) 12. Fudziy T., Dzako M. “The Mechanics of Decay of Composite Materials”, M., Mir Publishers, 1982, p.232 (in Russian) 12

Table 1 - Mixture proportions and characteristics

3 MB Mixture proportion, kg/m Properties of mixtures № coarse dosage, , slump, * cement МB sand aggre- water SP AEA W/(C+МB) VAE , % binder kg/m3 mm gate % 1 0 762 - 1356 - 179 23 - 0.235 2320 5 6.0 2 10 706 75 1296 - 183 - - 0.235 2260 21 7.5 3 17 631 133 1310 - 178 - - 0.235 2254 22 9.0 4 34 487 255 1220 - 168 - - 0.235 2130 23 9.5 5 17 1356 273 - - 353 - - 0.235 2012 28 2.2 6 17 622 131 1216 - 174 - 0.112 0.235 2143 23 15.0 7 17 545 115 575 995 155 - - 0.235 2385 22 3.6

* VAE – volume of entrained air.

Table 2 - Concrete properties

Strength of concrete Deformability properties № МB creep at loading (Ta- dosage, compressive compressive flexural elastic Poisson`s shrink- ble.2) % binder strength of strength of strength, modulus, ratio age, levels…, МPа cubes, МPа prisms, МPа МPа МPа10-3 105 * * =0,3Rbn =0,6Rbn 1 0 101.5 80.9 3.8 39.1 0.25 688 34.0 - 2 10 111.4 82.6 4.6 45.0 0.27 72.5 13.7 - 3 17 112.1 81.2 5.0 42.3 0.24 74.5 18.4 25.2 4 34 104.6 76.0 4.2 38.5 0.24 71.3 20.6 - 5 17 100.4 84.0 4.8 25.3 0.28 102.1 38.5 52.1 6 17 103.0 70.0 4.1 37.5 0.25 77.0 23.2 26.8 7 17 116.9 86.3 6.1 47.0 0.25 36.0 16.2 21.0

* Rbn – compressive strength of the prisms.

Table 3 - Characteristics of cement pastes after 210 days moist curing (RH=96-98%, t=202oC)

Properties of cement pastes МB experimental data calculated data № dosage, degree C-S-H (I), (Ta- W/(C+МB) porosity* elastic % binder of hy- Ca(OH) in creep rate, ble.2) 2 gel capillary total modulus, dra- content, arbitrary МPа-110-6 pores, pores, porosity, МPа10-3 tion, % % units % % % 1 0 0.235 63 9.1 1.0 17.5 12.5 32.5 20.49 72.1 2 10 0.235 59 5.9 1.4 21.7 9.0 33.6 38.48 30.8 3 17 0.235 64 3.2 2.6 23.3 6.7 33.6 30.21 40.8 4 34 0.235 66 2.9 8.1 27.9 3.1 34.5 25.47 50.4 13

* gel porosity – pores diameter 110-3 m…510-3 m; capillary porosity – pores diameter 510-3 m…2101 m; total porosity – pores diameter 110-3 m…1103 m. Table 4 - The parameters of the main structural constituents of high-strength concrete

3 № МB Mixture composition, on 1 m Concrete Cement paste Gel part Crystalline part (Tab- dosage, Indi-ca- Con- ag- ce- crys- gel water particles unhy- crys- le 2) % tor* coarse crete macro gel binder cement МB sand aggre- water SP AEA gre- ment talline hy- in gel of SF drated talline pores part gate gate paste part drates pores and FA cement hydrates V 0.246 - 0.512 - 0.179 - - 1.000 0.512 0.409 0.079 0.193 0.216 0.118 0.075 0 0.91 0.125 1 0 m 762 - 1356 - 179 23 - 2320 1356 964 - 420 544 330 90 0 282 262  3.10 - 2.65 - 1.00 - - 2.32 2.65 2.36 - 2.18 2.52 2.80 1.20 0 3.10 2.10 V 0.228 0.034 0.489 - 0.183 - - 1.000 0.489 0.420 0.091 0.229 0.191 0.100 0.095 0.034 0.093 0.098 2 10 m 706 75 1296 - 183 - - 2260 1296 964 - 468 496 279 114 75 290 206  3.10 2.20 2.65 - 1.00 - - 2.26 2.65 2.30 - 2.04 2.60 2.80 1.20 2.20 3.10 2.10

V 0.204 0.060 0.494 - 0.178 - - 1.000 0.494 0.419 0.087 0.262 0.157 0.105 0.097 0.060 0.073 0.084 2 3 17 m 631 133 1310 - 178 - - 2254 1310 944 - 543 401 294 116 133 227 174  3.10 2.20 2.65 - 1.00 - - 2.25 2.65 2.25 - 2.07 2.55 2.80 1.20 2.20 3.10 2.10 V 0.157 0.116 0.460 - 0.168 - - 1.000 0.460 0.429 0.111 0.309 0.120 0.073 0.120 0.116 0.053 0.067 4 34 m 487 255 1220 - 168 - - 2130 1220 910 - 604 306 205 144 255 166 140  3.10 2.20 2.65 - 1.00 - - 2.13 2.65 2.12 - 1.95 2.55 2.80 1.20 2.20 3.10 2.10 V 0.437 0.124 - - 0.383 - - 1.000 - 0.903 0.097 0.567 0.336 0.215 0.228 0.124 0.158 0.178 5 17 m 1356 273 - - 383 - - 2012 - 2012 - 1150 862 603 274 273 488 374  3.10 2.20 - - 1.00 - - 2.01 - 2.23 - 2.03 2.57 2.80 1.20 2.20 3.10 2.10 V 0.200 0.060 0.459 - 0.174 - - 1.000 0.459 0.409 0.132 0.255 0.154 0.104 0.091 0.060 0.072 0.082 6 17 m 622 131 1216 - 174 - 0.112 2143 1216 927 - 532 395 292 109 131 224 171  3.10 2.20 2.65 - 1.00 - - 2.14 2.65 2.27 - 2.09 2.56 2.80 1.20 2.20 3.10 2.10 V 0.176 0.052 0.217 0.369 0.155 - - 1.000 0.586 0.364 0.050 0.229 0.135 0.089 0.088 0.052 0.063 0.072 7 17 m 545 115 575 995 155 - - 2385 1570 815 - 469 346 248 106 115 196 150  3.10 2.20 2.65 2.70 1.00 - - 2.39 2.68 2.24 - 2.05 2.56 2.80 1.20 2.20 3.10 2.10

* V – volume (m3) m – weight (kg)  – density (g/sm3) 13

Fig.1. SEM micrograph of cement paste а - cement paste without multicomponent modifier b - cement paste with 34% modifier of binder by weight

High-strength concrete

Macro pores Aggregate Cement paste

Gel part Crystalline part

Gel hydrates Gel pores Particles of silica Unhydrated Crystalline hydrates (C-S-H) (1 10-3 < d < 5 10 -3 m) fume and fly ash cement (CH, CASH, CAH, CAFH)

Fig.2. Structural model of high-strength concrete with multicomponent modifier MB-50C 14

а) Elastic modulus b) Creep

Е С 80 50

l , 40 u 30 e

E 20 20

10 0 0 10 17 34 0 10 17 34 Dosage of modifier, % binder Dosage of modifier, % binder

Fig.3. The influence of multicomponent modifier on deformability properties of cement pastes and fine-grained concretes

- experimental data for fine-grained concretes - calculated data for cement pastes

0.8 1.8 gel part (q ) g 1 0.7 1.6

ratio of rigidities (qg E g / q c E c ) 0.6 1.4

n 0.5 1.2

r a 0.4 1.0

r A 0.3 0.8 2 A crystalline part (qc) 0.2 0.6 2 elastic moduli ratio (Eg / E c ) 0.1 0.4

0 0.2 0 10 17 34 15 0 10 17 34 Dosage of modifier, % binder Dosage of modifier, % binder

Fig.4. The influence of multicomponent Fig.5. The influence of multicomponent modifier on calculated volume modifier on the ratio of rigidities of the gel (1) and crystalline (2) (1) and elastic moduli (2) of gel parts of cement pastes and crystalline parts -1 6 -1 6 а) experimental data, МPа х 10 b) calculated data, МPа х 10

41.4 38.5

23.2 20.0 19.2 18.4

16.2 16.0

C p C p C

Fig.6. Creep rates of concretes with the constant modifier dosage (17%) and various volume of cement paste and porosity

а) Influence of cement paste quality b) Influence of cement paste volume in concrete 200 200

180 180

5 160 160 (e las tic

% 140 140 u lu

, % s)

i 120 1 n 120 4 (compress n (comp ive ressive st u streng ren th u gth) )

r r 100 100

r r (el t ast t i i c mod i b u lus b r ) ) 80 r 80 eep A cr

A ( 6 60 60 eep) 3 (cr 40 40

0 10 17 34 0 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Dosage of modifier, % binder Cement paste volume in concrete, m3 /m 3

Fig.7. Influence of cement paste on compressive strength, elastiс modulus and creep of the concrete