Abstract
The problem of the possibility of cement saving in concretes with admixture of sodium salt of formaldehydic polycondensates of sulphonic‐napthalene acids (SNF) is presented. Executed investigations show a strong plastifying performance of this admixture as well as an elongation of setting time of Portland cements. On adding 1,5 % of admixture it is possible to obtain a substantial saving of cement with simultaneous reduction of water amount (constant W/C ratio), without a change of consistency of concrete mixture apparent density, compressive strength, absorption and water penetration of concrete. For the estimation of economic effectiveness of superplasticiser SNF it is proposed to introduce an index of cement saving Sc and an index of cement utilisation in concretes Iec .
Highlights
The basic functions of plasticising and high-range water reducing admixtures used in cement materials are following [1,2,3,4,5]: a) the reduction of W/C ratio while maintaining the initial consistency of concrete mixture constant, b) the reduction of cement and water content without worsening the fluidity of concrete mixture and while sustaining the same value of compressive strength as for the control concrete, c) the change of concrete mixture consistency into more fluid while maintaining W/C ratio constant
The aim of this paper is to present the results of investigations into cement concrete with admixture of superplasticiser SNF and control concrete, focusing on the reduction of cement and water content in concrete mixture, in the aspect of usefulness in building practice
Superplasticiser SNF was added together with mixing water from 0,8 to 2,0 % according to the mass of cement
Summary
The basic functions of plasticising and high-range water reducing admixtures used in cement materials are following [1,2,3,4,5]: a) the reduction of W/C ratio while maintaining the initial consistency of concrete mixture constant, b) the reduction of cement and water content without worsening the fluidity of concrete mixture and while sustaining the same value of compressive strength as for the control concrete, c) the change of concrete mixture consistency into more fluid while maintaining W/C ratio constant (no changes in basic content of concrete mixture). Characteristics of superplasticisers performance are still a subject of ongoing investigations with respect to their adsorption to cement particles [8], the porosity of paste [9], the changes of zeta potential [10] and the compatibility with different cements [11, 12]. The changes of concrete mixtures fluidity in the function of time were analysed in [13,14,15], while the selection of optimal adding time of admixture and its influence on adsorption and workability of mixtures in papers [11, 16]. The main effects of superplasticisers performance: the dispersion of cement granules and plasticising effect associated with this phenomena, the adsorption on the surface of cement granules, causing their repulsion, the increase in shear resistance and the stabilization of paste through electrostatic repulsion, were outlined [1,2,3,4, 7].
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