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Role of the acid-base nature of interphase interactions in structurization of composite construction materials
Integrating (19) at initial condition Ta (0), we would get
b - ac
e , C = —:—.
bc Ta (t) = — (at -1) + - + C
(20)
Considering t = U, we would find: u
bu ac - b . Ta (u) = — + —— I 1 - e
an
- kSu
1 - e
a
ku
n
1 - k. kD
(21)
Fig. 3. Addiction kD /k;
Solving the equation (21) graphically, we find the valuen. Figure 3 shows the dependences a from the relationship k^D / ksx built by determined values of n from (21). The curves 1 and 2 are built using tests results with loamy soils (presented in the Table), and the curves 3 and 4 at the values t = 13.30 kN/m 2, t= 12 sec., u = 0.180 mm. and Ta = 6.55 kN/m 2, t = 15 sec., u = 0.180 mm., respectively. Results of the study show that the values of oc for carried out tests are within the range (40 ^ 400)-103 kNsec/m 3 or ft = = (78 - 800) kNsec/m 2.
The values of oc for other cases (under the effect of transverse force, bending and torsional moments) may be found by similar way. It is suffice to know the values of interaction coefficient under the effect of dynamic load with different velocity of loading. However the experimentations present a lot of difficulties. So, considering that, it is proposed to make use of the data found under the effect of longitudinal force N, when determining viscosity parameters under the loads Q, Mu and Mk. Here the expression (2) may be used with a high degree of accuracy in the following form:
& = ajVx, (22)
where a - is one of viscosity coefficients under the effect of loads Q, Mu, Mk; a -viscosity coefficient under longitudinal force N; a^-the same as in (2).
In [3], when investigating horizontal oscillations of buildings under seismic effect and using Voigt and Maxwell-Kelvin linear-viscous-elastic model, it is shown that even two order change in viscosity parameters insufficiently effects on design results. This is true for above given statements.
Тable 1.
or:
D
uk
Soil Tests data Design data
t au, kN/m 2 t, sec u (r), mm n, sec-1 u(r), mm tmax sec u (t ), mm \ max )
Loamy soil 9.4 18 0.200 0.01 0.600 144 0.747
0.1 0.207 14 0.130
Gravel 7.55 3 0.220 0.01 2.676 120 1.267
0.1 0.203 17 0.48
References:
1. Rashidov T. R., Khozhmetov G. Kh. Seismic Stability of Underground Pipelines. - Tashkent: Fan, 1985. - 153 p.
2. Lyakhov G. M. Bases of the Dynamics of Explosive Waves in Soils and Rock Mass. - Moscow: Nedra, 1974.
3. Khojmetov G. K., Khodjimetov A. I., Yuvmitov A. S. Influence of Soil-Foundation Interaction Properties on Oscillations of the System "Building-Building" and "Building-Stack-Like Structure"//World Journal of Mechanics. USA. - 2015. - № 5. - P. 106-117.
Adilxodjayev Anvar Ishanovich, Soy Vladimir Mixaylovich, Tashkent Institute of Railway Transport Engineers E-mail: [email protected]
Role of the acid-base nature of interphase interactions in structurization of composite construction materials
Abstract: Modern ideas of polystructural theory of composite construction materials are presented in the article. Keywords: polystructural theory, composite materials, acid-base centers, microstructure, mesostructure, macrostructure.
The modern perceptions following from the polystructural theory of the composite construction materials (PT CCM) with mineral, combined and polymeric binding agents are based on the concept of their structurization based on the community of the levels of structure created by the founder of PT CCM academician Solomatov V. I. [1].
In construction mastics, glues, solutions and concrete on the basis of various binding agents are most of use. On the basis of PT
CCM, it is expedient to consider their structure in the following large- scale levels:
- microstructure (mastics, glues, sealants, etc.);
- mesostructure (solutions);
- macrostructure (concrete).
From the standpoint of structurization of CCM the greatest scientific interest is represented by the microstructure since the surface area of its disperse phase makes 90 and more percent [1].
Section 7. Technical sciences
The microstructure is formed when hardening of the material received generally from mix of the binding and particulate filler. The composition of such materials depends on the type of the binding agent, for example on:
- mineral (binding agent, filler, water, modifying agent);
- combined (mineral binding agent, polymeric admixture, filler, water;
- polymeric (synthetic resin, filler, hardening agent, plasti-cizing agent).
In structurization of such materials the important role belongs to the nature of interphase interactions. As a result of the numerous researches of the author carried out together with students the ideas of the acid-base nature of interphase interactions in structurization, the technology of the directed change of CCM properties on micro-, meso- and macrostructures are formulated and experimentally confirmed. Taking into account the acid-base mechanism of interphase interactions specific consistent patterns of structurization, technology and properties of effective construction materials based on cement, slag-alkalescent binding agents with chemical admixtures and fillers, ofpolymer-cement compositions, including on the basis of dry mixes, and filled polymeric compositions (glues, mastics, solutions and concrete) on the basis of acetone-formaldehyde resin and furfural-acetone monomer, are determined.
It is demonstrated that when forming the microstructure of cement concrete the structure of the adsorptive layers and nature of their bond with the surface area of disperse phase depends on the type of functional group of the chemical modifier. On this basis the assumption is formulated that subacidic (OH) groups of organic modifiers promote formation of discrete adsorptive films, and strongly acidic (COOH) groups — complete, low-permeable films and their interaction with the surface area of disperse phase is of acid-base nature [2]. Information set forth herein was confirmed also at research of influence of composition and structure of polycarboxylate superplasticiz-ing agent (PC SP) on formation of the adsorptive layer and nature of bond of the admixture molecules with the surface of particles of the hydrated cement [3]. Comb-shaped molecules of admixture of the PC SP are chemisorptived in the surface area ofhydrated compounds of cement on acid-base mechanism and form around granules of the binding agent the water permeable adsorptive polylayers. Also the acidic carboxyl groups of PC SP chemically interact with strongly acidic ions of calcium, and amide groups and groups of base nature with acid ions containing aluminum phases of the binding agent.
In the work [4] it has been demonstrated that the properties of slag-alkaline binding agent of concrete (SABA) depend not only on the specific surface area and structural and mechanical indicators, but to a large extent on the nature of active centers on the surface of disperse phase that is confirmed on the example of domain slag mixed with soda-sulfate float (SSF) and the admixture of gossy-pol (GR) and acetone-formaldehyde resin. The author has received quantitative characteristics of the active centers on the surface of SABA components, has specified the acid-base nature of interphase interactions, the influence of the type and nature of chemical admixture on them. The influence of the admixture ofwater-soluble acetone-formaldehyde resin of alkaline nature of hardening on the processes of hydration and curing of SABA, and also the bond of structure of the adsorptive film of polymer and kinetics of phase transformations in the binding agent are presented.
The interrelation of structural and physicochemical characteristics of the surface of particles of blown sand, concentration of the acid-base centers and the space occupied by one center with properties of fine concrete on the basis of SABA has been determined.
It is known that properties of the polymer-cement CCM with admixture of water-soluble resins depend not only on the structurization of the mineral binding agent but also on the formation of polymeric phase and its role in interphase interactions. It is demonstrated that proceeding from the acid-base nature of the latter, the use of admixtures of acid nature at receiving the polymer-cement CCM is ineffective, due to their negative effect on the processes of structurization of the mineral phase. On the example of acetone-formaldehyde resin it has been established that for receiving effective polymer-cement CCM it is more preferable not to use polymeric admixtures with the prevailing content of OH groups of alkaline curing. At the same time in the surface area of disperse phase the polymolecular adsorptive water permeable layers are formed. Along with that only some part of polymeric admixture on acid-base mechanism will be adsorbed on particles of binding agent or nuclei of hydrated newgrowths. The bigger part of the admixture, increasing viscosity of the liquid phase, will cover the surface of crystalline hydrates. Thus, in the polymer-cement CCM not so much surface activity of polymeric additive, as the nature of bond of reinforced adsorptive layers and volume properties of the disperse structures formed by them is used.
It is known that the need of application of fillers for cement CCM is dictated by incomplete hydration of clinker minerals of cement, technical, economic and ecological reasons. Taking into account possible topochemical reactions, the acid-base interactions in the surface area of disperse particles and phase interface we have drawn a conclusion on inexpediency of co-milling of cement clinker with mineral substances at receiving mixed binding agents and it is recommended to carry out introduction of fillers and admixtures of chemical modifiers at preparation of cement CCM. For confirmation of the above-stated researches on determination of force and concentration of the acid-base centers on the surface of particles of portland cement, fly ash, burnt clay, phosphoric sand slag, mixed binding agents and binary fillers on their basis have been executed for the first time [2; 5].
The criterion of activity of mineral disperse substances estimated by the relation of the sum of concentration of the acid and base centers of the surface is offered, which provides new scientifically based approach to the choice of fillers for cement and polymeric binding agents, comparative assessment of efficiency of processing methods of modification and activation of mineral disperse substances [2].
Taking into account this criterion, the efficiency of complex use of coarsely dispersed fillers (with dispersion twice lower, than cement) and the hydrous additives like acetone-formaldehyde resins for receiving economic concrete based on dense filler has been established. The role of finely dispersed (fly ash) and coarsely dispersed fillers (burnt clay and phosphoric slag) in processes of structurization, hydration and curing of cement stone, and the role of formation of morphology and pore volume of the microstructure are specified. The bond between dispersion, contents, acid-base properties of the surface of filler, the mechanism of action of additives of acetone-formaldehyde resin and the properties of cement mixtures and concrete has been demonstrated [2].
Reckoning with the nature of the active centers on the surface of mineral substance allows making the scientifically based choice of disperse filler for cement concrete. So, in that respect, in the work [3] the efficiency of use of basalt filler has been proved, the role of basalt filler in interphase interactions with cement has been specified and their experimentally acid-base character has been determined for receiving of high-strength cement concrete on the
Substantiation of reliability of the trailer frame at designing
basis of an ordinary portland cement as M-400 and an additive of polycarboxylate superplasticizing agent. It has been demonstrated that on the surface of filler particles there are strongly acidic and base centers caused by the presence of basalt of oxides of iron and
aluminum, and also alkaline metals in the composition. That predetermines the possibility of their chemical interaction with the basic calcium-containing and acidic aluminum-containing phases of the binding agent, hardening of cement stone and concrete.
References:
1. Solomatov V. I., Takhirov M. K. and others. Polystructural theory of composite construction materials. - Tashkent: publishing house FAN of the Academy of Sciences, 1991. - 345 p.
2. Solomatov V. I., Takhirov M. K., Shakh Takher Jr. Intensive technology of concrete. - M.: Stroyizdat, 1989. - 289 p.
3. Takhirov M. K., Soy V. M. On the nature of interphase interactions of polycarboxylate superplasticizing agent and basalt filler with cement//Resource-saving technologies in construction. Interuniversity collection of scientific works. - ToshTYMI. - 2009. -Issue № 4. - P. 3-12.
4. Kerkar A. On the properties of the slag-alkalescent binding agent with admixture of acetone-formaldehyde and gossypol resin//Effective construction materials and technologies. Interuniversity collection of scientific works. - ToshTYMI. - 1993. - Issue № 1. - P. 98-102.
5. Takhirov M. K., Akhmedov D. Kh., Narov R. A. Acid-base properties of the surface of sandy filler of concrete//Effective construction materials and technologies. Interuniversity collection of scientific works. - ToshTYMI. - 1993. - Issue № 1. - P. 50-63.
Shermukhamedov Abdulaziz Adilkhakovich, Tashkent Automobile and Road Institute, professor, Head of Department of Reliability of Land Transport Systems
E-mail: [email protected] Salimdzhanov Ravshan Turaevich, senior teacher of Department of Reliability of Land Transport Systems
Togaev Anvar Abdusalomovich, assistant of Department of Reliability of Land Transport Systems
Substantiation of reliability of the trailer frame at designing
Abstract: Article looks through the justification of the projected frame reliability of the trailer and its components.
Given desired level of reliability for the frame as a whole promoted calculation of the required parameters of reliability, including the probability of failure-free operation and mean time between failures elements of the trailer frame.
Keywords: trailer, frame, method, testing, dependability, reliability, endurance tests, cycle of loading, complexity.
The importance of the calculated values of reliability standards in the manufacture of trailers and their structural elements is that they should serve as the main reference point in the design process in the manufacture, including the development of methods of calculation and choice of testing equipment.
The problem of distribution in general requirements for the reliability of the frame elements can be formulated as follows: the desired reliability index for the frame consisting of n elements is set; you need to determine what changes should have the norm of each element. For solve this type of problem are applied techniques given in the research [1].
It is most comprehensible to our calculations is the method based on the utility theory in the distribution requirements for non-failure operation of components of the system on the basis of the account of their complexity [2].
It is known, that the probability of non-failure operation (PNFO) of any difficult technical system consisting of n elements is estimated under the formula
P =]JPci, (1)
i=i
where Pe1, Pe2, Pe3, ..., Pen — according PNFO of each individual element of the system.
It should be noted that the trailer is the complex technical system consisting of large number of components and, therefore, make calculations for evaluating the reliability of the formula (1) represent the difficult mathematical task.
We propose to carry out calculations on the valuation of reliability of structural elements of the trailer according to the structurally functional scheme (SFS) of the trailer shown in figure 1 and data of the complexity of each frame member.
The standard of reliability of the element ofhigher level of hierarchy is the standard of reliability for elements of subordinate level of hierarchy. The demanded PNFO of elements calculated under the formula [2]:
P. = PsK-, (2)
where K — the coefficient characterising the quantitative measure of complexity of i — basic element of the trailer (complexity).
The complexity is defined by expression:
2 (n - i +1) »
K = ^—-r2, 0< K < 1, £K = 1, (3)
n (n +1) ' M '
where n — quantity of elements in the ranked series; i — number element in the ranked series.
This method of calculation Pei is most comprehensible at the design stage of trailers, in the absence of operational data about their refusals.
In the production of frames important indicator of reliability is mean time between failures (MTBF) ta, which will serve as the main reference in the test frame and its components. Definition of MTBF t , it is proposed to carry out the following steps: it is appointed PNFO Ps for the trailer in whole (in many cases Ps of the trailer it is equal Ps a tractor towing the trailer); composed of SFS of the trailer; it produced a ranking of the main
