Investigating the influence of volumetric hydrophobization on the formation of phase composition of cement stone and its physical-mechanical properties

Inna Trofimova,Nikolay Shpyrko

doi:10.15587/1729-4061.2019.176430

Abstract

We have examined the influence of the most widely used silicon-organic surface water repellent GKZH-11K on the physical-mechanical properties and the phase structure formation of cement is the fact that the introduction of the surface water repellent GKZH-11K to the composition of cement slurry leads to the formation of dispersive water-repellent films of various levels (size). These films adsorb at the surface of cement grains, as well as at the surface of hydrated components of cement particles, Са(ОН)2, calcium sulphoaluminates. It was determined that the disperse hydrophobic films partially block the penetration of water into the surface of cement grains and alter the kinetics of hydration.This leads to a decrease in the degree of hydration and the content of Са(ОН)2 in cement stone, resulting in the reduced shrinkage at hardening. At the same time, the disperse films adsorbed on neighboring hydrated cement particles within the contacts occurred in the process of their condensation can form hydrogen and chemical relationships. This interaction between the particles' films, despite the reduction in the degree of hydration, leads to a decrease in water absorption, improving the strength of cement stone, which in this case is also determined by the number and area of contacts per unit volume of cement stone. The overlap of pores with hydrophobic chains decreases the permeability of cement stone throughout its entire volume, which contributes to the growth of operational reliability and durability of structures, particularly thin-walled. Using this admixture for volumetric hydrophobization could greatly prolong repair-free operation of thin-walled products and structures, as well as bring down cost as there is no need to apply materials to protect the surface of concrete.

Highlights

The issue of durability of concrete structures and articles, thin-walled, exposed to atmospheric influence, is always relevant
By analyzing the main trends addressed in the studies of concrete with volumetric hydrophobization [3], it was revealed that the most widely used admixtures are those based on silicone-organic compounds: GKZH-94 (136‒157 m) − methylhydrosiloxane polymer, GKZH-11K – a solution of potassium or sodium methylsiliconate, product 119-215 − oligoethoxy-2-ethylhexoxyloxane [4] and water repellents based on silanes, which pass into silanols at hydrolysis
Results from X-phase study of cement stone samples with the admixture GKZH-11K and without admixtures are shown in Fig. 6, 7

Summary

Introduction

The issue of durability of concrete structures and articles, thin-walled, exposed to atmospheric influence, is always relevant. One way to enhance the operational efficiency of concrete that is exposed to such atmospheric effects over a long time as freezing, thawing, wetting and drying, as well to aggressive environments, is its volumetric hydrophobization. The largest degradation when concrete is exposed to the above factors is demonstrated by cement stone. In this regard, the studies were performed into the influence of volumetric hydrophobization of cement stone on its shrinkage, water absorption, and strength, which characterize its durability. The most common are the hydrophobic admixtures for the surface hydrophobization of concrete structures already in operation; the processes of corrosion render such a protection non-durable: in 2–5 years, there is again a need for applying a protective layer. The use of volumetric hydrophobization for thin-walled structures and buildings whose

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