Influence Of Surface Additives On Strength Indicators Of Cement Systems

In the state predostavlena, v issledovaniy yavilos ustanovlennыe vliyaniya dobavok poverxnostno aktivnyx veshchestv na prochnostnыe pokazateli tsementnyx sistem. Definitions were made on cement of various mineralogical composition, svejemolotom and lejalom and on tsementno-peschannyx solutions and betonax.


INTRODUCTION
The purpose of the research in this section was to establish the effect of surfactant additives on the strength characteristics of cement systems. The determinations were carried out on cements of various mineralogical composition, freshly ground and buried, and on cement-sand mortars and concretes.
For the control samples and with additives, the same plasticity was selected, while the water-cement ratio than for various additives fluctuated within certain limits.
The ultimate strength in compression, bending and elastic modulus were determined for mortar samples on beams 4x4x16 cm and cubes 7.07x 7.07x 7.07 cm, and for concretes on cubes 10x10x10cm and 20x 20x20cm. It is known that in a number of cases when using mylonft there is some lack of strength at the initial stage. A decrease in the strength of products on hydrophobic cements was observed only on freshly ground cements when molding samples with a high watercement ratio. Therefore, a large number of comparative tests of the strength of samples on hydrophobic-plasticized and control  (I-B and I D and cement with a high content of C3C (3-C and 5-I).
As follows from the data in the table, cement mortars with OP with a decrease in the watercement ratio (with different plasticity) are characterized by increased compressive and flexural strengths in comparison with the control indicators at all test periods up to a year. In this case, the optimal dosage of OP is in the range of 0.15-0.30%, the strength of the samples on such cement samples increases by 10-12% compared to the control.
Mortars with OP additives, made at the same water-cement ratio as the control ones, are characterized by a shortage of strength (about 5%) in the initial hardening period (3 days) and equalization of the strength values to 28-day hardening (cement ID).
The addition of mylonft, in spite of a decrease in the water-cement ratio, in some cases yields a 5-8% shortfall in strength compared to the control ones even after 360 days of hardening. The greatest increase in strength is achieved when using a synthetic fatty acid of the C7-C9 fraction. The introduction of this additive increases the strength of samples at 3 days of age by 50%, at 28 days of age by 35% and 360 days of age -by 25%.
Table the results of tests of laboratory-salted cements and solutions based on these cements are presented. The addition of oxidized petrolatum causes in all cases an increase in the strength of the cement and when tested at 3,7 and 28 days of age, despite the increase in the normal density of the cement paste, the increase in strength is explained in this case. First of all, an increase in the specific surface of cements when grinding them with OP additives. The introduction of oxidized petrolatum in an amount of 0.25% increased the plasticity of the solutions (increasing the value of the slump of the cone), did not reduce the strength parameters even with water-cement ratios the same as those adopted for the control compositions.
The results of testing solutions on slag Portland cements and clinker cements are given in  sulfite-alcohol stillage and in this form was introduced directly during mixing. Solutions were prepared with a cone draft of 2 and 4 cm.
As follows from the results of these tests, oxidized petrolatum causes negligible air entrainment, equal to 1-1.15% for fatty systems and 5-7% for lean solutions. The strength of lean solutions with additives of OP on the 7th day at 37-52 and on the 28th day is 15-20% higher than that of the control.
The combined addition of OP and SNV reduces the strength of mortars in fatty systems by 16-22% and decreases their strength by 25-33% in lean cement mortars. The combined addition of OP and CER acts similarly to a mixture of OP and CER. A mixture of oxidized petrolatum with machine oil, introduced into solutions when replaced, showed an increase in strength by 7 days by 52% and at 28 days of age by 34%, compared with the control, in a mixture of OP and sulfite-alcohol stillage, respectively, by 65-50%.
The influence of the addition of oxidized petrolatum on the strength indicators was also tested in concretes / table 33/.
The composition of concrete was calculated using the absolute volume method, taking into account the restrictions adopted by GOST in relation to the consumption of cement, B and aggregates.