Lime-based mortars with various binder composition: characterization and freeze-thaw resistance assessment

The study focused on lime mortars with different lime binder types regarding the frost attack effects on their microstructure and mechanical characteristics. The performances of studied mortars in hardened state was significantly influenced by the amount of mixing water and by curing conditions. Inhomogeneous microstructure was observed inside the 360 days old specimens with dimensions 40 × 40 × 160 mm in the case of all lime mortars types. The different state of the binder hardening with respect to various distances from the specimen surface and the different behaviour of matured outer part and immature inner part of lime mortar specimens influenced performed tests and reflected in all results. After 10 and 20 freeze cycles, respectively, the compressive strength of all lime mortar specimens with the hydraulic binder component increased, indicating a beneficial effect of the water on the hydration previously unreacted hydraulic binders. On the other hand, the flexural strength of the frost-aged specimens decreased significantly, indicating the drastic procedure of the test performed concerning lime mortars characteristics, especially when the pure air lime binder was used. Improvement of the testing procedure especially for lime mortars, which are characterized by slow hardening, was recommended.

SPECIFIC FEATURES OF THE FORMATION OF THE MICROSTRUCTURE OF GRANULAR AGGREGATES ON DIFFERENT BINDING COMPOSITIONS (PART 3)

This article represents a logical continuation of the research results presented in the previous publication and reflects the results of studies of the effect of the binder composition No. 3 (BC-3) on the formation of the microstructure and physical and mechanical properties of granular aggregates. The experimental results demonstrate that the best indicators of the strength of granular aggregates are provided with the adding of BC-3 in an amount of 15%, regardless of the fractional composition of quartz sand. In addition, the density of crystalline formations reflecting the microstructure of the samples directly affects the physical and mechanical properties of the composites. On dispersed micro fillers, as on a base plate, a dense microcrystalline structure of new formations of hydrated calcium silicates is formed. The addition of 15% binder composition No. 3 (BC-3) to the component composition of granular aggregates ensures the stability of physical and mechanical properties. Thus, they can be recommended for use as coarse aggregates in the preparation of special-purpose mortar mixtures

Investigation of the Rheokinetic Properties and Penetration Depth of Aluminosilicate Adhesive in Pine Wood

Practical work and is devoted to the study of the rheological and deformative properties of Geofip aluminosilicate glue, obtained on the basis of an alkaline aluminosilicate binder composition Na2O Al2O3×6SiO2×20H2O, modified with 5% Cr2O3, when gluing wooden trusses in the field. The rheological and deformative properties of an aluminosilicate adhesive based on an alkaline aluminosilicate binder composition of Na2O×Al2O3×6SiO2×20H2O modified with 5% Cr2O3 have been investigated. It is noted that the dynamic viscosity of the adhesive slurry in the speed range from 0.1 to 0.8 RPM varies from 147600 to 144600 cP, and the average plastic viscosity in the same speed range is 87.39 cP. It was found that at shear rates from 0.021 to 0.168 1/s, an increase in shear force from 31 to 242.9 dyne/cm2 is observed due to the stabilization and uniformity of the dispersion phase particle distribution in the dispersion medium of the adhesive. It is shown that the aluminosilicate adhesive at a surface tension value of 88.1 mN/m is characterized by coefficients of wetting (s = 0.648) and fluidity (f = -62.02 mN/m), which ensures the uniformity of its application to the pine substrate. The average thickness of the adhesive layer was 1.25 mm, and the average depth of penetration of the aluminosilicate adhesive into the wood substrate, respectively, 0.12 mm. The destruction of the adhesive seam occurred at shear stresses of 515 MPa. The relative shear deformations were 162.5×10-5 mm.

FEATURES OF THE FORMATION OF THE MICROSTRUCTURE OF GRANULAR AGGREGATES ON DIFFERENT BINDING COMPOSITIONS

This work includes a study of the microstructure of granular aggregates prepared on various binding compositions. The presented work includes three parts devoted to the analysis of the microstructures of granular aggregates taking into account the change in the percentage of the mineral filler in binding compositions. The article deals with the main aspects of the formation of the structure of granular aggregates during the hydration of Portland cement (PC 500-D0-N) and a binder composition (PC 500-D0-N + 10 % quartz sand) prepared in a vortex jet mill. The main regularities of the influence and dispersion of quartz mineral filler (fractions ≤0.16; ≤0.315; ≤0.63 mm) on structure formation during the hydration of binding components differing in the composition and particle dispersion are revealed. The paper analyzes physical and mechanical tests of the most promising samples with a study of their microstructure features. The study of the sample microstructures reveals the general regularities of the growth of crystalline phases of different densities. It is established that the introduction of 1 0% mineral fine-dispersed filler, in the form of quartz sand, contributes to the formation of sub-microcrystalline hydrate phases, which are centers of hydration, additionally binding individual grains of granular aggregates and compacting the structure of the overall system. In all samples, the formation of a block-rhythmic structure is observed, with the presence of individual block-aggregates. There is an overgrowth of microscopic pores with small crystalline neoplasms of calcium hydrosilicates. It is revealed that the structure of granular aggregates prepared on the basis of binder composition No. 1 (BK-1) has higher density than on Portland cement PC 500-D0-N.

INCREASING THE RESISTANCE OF MACADAM-MASTIC ASPHALT CONCRETE TO RUT FORMATION DUE TO THE USE OF POLYMER MODIFIERS

Rutting is an important problem in Russia today. One of the ways to improve the properties of asphalt concrete mixtures and reduce wear on road surfaces is to modify the binder with polymer additives. The aim of the work was to test the selected compositions of MMAC mixtures containing bitumen modified with the addition of sevilene and rubber for rutting resistance, which make it possible to predict the formation of plastic rut. It was revealed that when using sevilen in its composition, with an increase in the concentration of vinyl acetate, the depth of the track increases in comparison with the industrial polymer-bitumen binder. It is shown that with the introduction of a complex additive based on sevilen and rubber into the binder composition, its rutting decreases and the service life of the road surface increases, which indicates a high elasticity of the complex-modified binder. In this work, the calculation of the service life of the coating before the formation of a critical rut requiring repair of the coating is carried out. It was found that in terms of the slope of the rutting curve and the proportional depth of the rut, the compositions with sevilene and rubber are not inferior to traditional industrial PBB.

The effect of ground limestone on the properties of composite gypsum binder using thermally activated clay as a pozzolanic component

The purpose of this research is to study the effect of methods of preliminary preparation of thermally activated clay, which is a pozzolanic component in water-resistant composite gypsum binders, as well as the effect of mechanochemical activation in the joint grinding of thermally activated clay with the addition of a plasticizer on the pozzolanic activity and the change in the required number of pozzolanic component in the composition of composite gypsum binders. It was found that the required amount of thermally activated clay as pozzolanic component in the gypsum-cement-pozzolan composition when ground to specific surfaces of 200-500 m2/kg together with the addition of Melflux 2651 F plasticizer, based on the exclusion of conditions for the formation of an unacceptable amount of ettringite, decreases by 20-25% compared with the use of thermally activated clay ground without the introduction of a plasticizer. The optimal amount of Melflux 2651 F plasticizer introduced by grinding with thermally activated clay has been determined. The significance of the results for the construction industry lies in the fact that the use of the technology of obtaining composite gypsum binders of grinding thermally activated clay to a certain dispersion with the introduction of a plasticizer additive due to the effect of mechanochemical activation makes it possible to reduce the consumption of the pozzolanic component in the binder composition or energy consumption for grinding.