Abstract
The effect of a methyl hydroxyethyl cellulose additive on the technical and physical-mechanical properties of the cement matrix has been investigated. The study involved cellulose ether of low (11,000–16,000 MPa∙s), medium (17,000–23,000 MPa∙s), and high (20,000–30,000 MPa) viscosity. The additives were introduced into cement in the amount of 0.25, 0.5, and 0.75 % by weight. It has been established that the introduction of cellulose ether in cement leads to an increase in the normal density of the slurry and extends the duration of the mortar setting. The normal density of cement slurry increases with the introduction of cellulose ethers of low viscosity (LV) and medium viscosity (MV) by 5.4‒16.8 %; when introducing the ether of high viscosity (HV), by 21.3–41.4 %. This confirms the high water-retaining capacity of methyl hydroxyethyl cellulose, which increases with increasing viscosity of the additives. The setting duration of cement slurry increases, depending on the concentration and viscosity of the additives, by 2‒4 times, compared with an additive-free material. There is also a significant reduction in the strength of the cement matrix in the early periods of hardening (1–7 days) depending on the concentration of the additives, by 2.2–4.2 times. The strength of the samples is least affected by the cellulose ether of low viscosity, largest – by that of high viscosity. The reduction of strength is observed at the age of 28 days, although not very much pronounced. Compared to the additive-free cement, the strength amount to: for the ester of low viscosity at concentrations: 0.25 % by weight – 14.3 %, 0.50 % by weight – 23.9 %, 0.75 % by weight – 40.5 %; for the ether of medium viscosity, respectively, 23.8, 26.2, and 33.3 %; for the ether of high viscosity, 28.6; 45.2, and 61.0 %. The corrosion resistance of the cement matrix with methyl hydroxyethyl cellulose additives is increased at a concentration of up to 0.25 % by weight and then gradually decreases. The above results make it possible to recommend using, in the production of dry construction mixtures, the cellulose ethers of low and medium viscosity, which would ensure the required time to maintain the solution mobility and the sufficient strength of the resulting material
Highlights
Production of dry construction mixes increases with each passing year [1, 2]
Introducing the additives of cellulose ester of low viscosity leads to a significant drop in the strength of the cement matrix compared with the starting cement in the early period of hardening (Fig. 2)
On the example of the methyl hydroxyethyl cellulose additive of low viscosity (Fig. 5), that the increase in the content of the additive in the cement leads to that the corrosion resistance monotonously reduces
Summary
Production of dry construction mixes increases with each passing year [1, 2]. The growing popularity of these materials is explained by the series of advantages for construction operations: increased productivity, reduced number of operations to prepare the mixes to use, improved quality of work, and others. The dry construction mixes include multicomponent mixtures, which necessarily contain in their composition a binder, a filler, and the modifying additives [3]. Each of these materials has its function. A binding component enables the strength of the hardened solution, its integrity, as well as the adhesion to a work surface. Fillers make it possible to lower the content of a binder, which reduces the amount of water and leads to obtaining a denser material. Given the ambiguous effect of organic additives on the strength characteristics of a cement matrix and its resistance against various types of aggression, it is a relevant task to study the effects of cellulose esters on the properties of cement
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