Strength characteristics of lightweight concrete based on granular foam glass ceramics

Abstract

Introduction. Over the past 20–30 years, a wide range of effective porous aggregates with a high content of glass phase of various types and low-heat-conducting lightweight concretes of various structures based on them has been developed.In recent years, JSC Research Center of Construction has developed a new highly efficient single-stage technology for the production of porous granular foam glass ceramics (UCS). It is based on the production of raw granules by mixing and granulating a highly porous powder of opal-cristobalite rock with a sodium-containing solution. This ensures the maximum area of the interfacial boundary, the most uniform distribution of all components at the micro level and, as a result, ensures glass formation at a temperature that does not exceed the foaming interval of the finished glass phase.The aim of the publication is to study the problems of the features of the strength characteristics of lightweight concrete on granular foam glass ceramics.Materials and methods. The strength of cubes made of light concrete on the UCS under compression (R) was determined on samples with a size of 10 × 10 × 10 cm and 7 × 7 × 7 cm according to State Standard 10180-2012 with an assessment of strength according to State Standard 18105-2018.The prismatic strength coefficient (Kpp) was determined by the results of compression tests of samples-prisms with dimensions of 10 × 10 × 40 cm and 7 × 7 × 28 cm and samples made from the same batch-cubes with dimensions of 10 × 10 × 10 cm and 7 × 7 × 7 cm.Bending tensile strength (Rtb) (Figure 2) and splitting strength (Rtt) were determined, respectively, on 10 × 10 × 40 cm prism samples and 10 × 10 × 10 cm cube samples according to State Standard 10180-2012 with an assessment of strength values according to State Standard 18105-2018.Axial tensile strength (Rtb) and splitting strength (Rtt) were determined, respectively, on prism samples measuring 7 × 7 × 28 cm according to State Standard 10180-2012. The strength of the prisms (prismatic strength, Rb) was determined on samples of prisms 10 × 10 × 40 cm according to State Standard 24452-80.Results. The article presents the results of experimental and theoretical studies of the basic strength properties of thermal insulation and structural-thermal insulation lightweight concrete on granulated foam ceramic (UCS) with a density of 500 to 800 kg/m3, as well as structural lightweight concrete with a density of up to 1700 kg/m3 of optimal compositions (prismatic compressive strength, prismatic strength coefficient, axial tensile strength, tensile strength during bending and splitting).Various dependencies on the evaluation of the experimental data obtained are analyzed and recommendations are given for inclusion in regulatory documents, in particular, in SP 351.1325800.2017 "Concrete and reinforced concrete structures made of light concrete. Design rules".Conclusions. Experimental data have been obtained on a higher prismatic strength coefficient for lightweight concrete at the UCS, which in the future may be the basis for increasing the standard design strength resistance under axial compression for this type of lightweight concrete.The values and formulas for determining the prismatic strength and the prismatic strength coefficient of light concrete of the tested compositions at the UCS can be used in the calculation and design of large-format wall panels of a new type.Experimental and calculated data on the tensile strength of the tested compositions of lightweight concrete of a porous structure at the UCS have been obtained, which can be taken into account when adjusting regulatory documents.When using lightweight concrete of a porous structure on the UCS to increase the shrinkage crack resistance of such concrete for enclosing structures, it is advisable to use dispersed reinforcement with polymer fiber, which also increases the heat-protective properties of such structures. The article presents the results of studies of the main strength properties of thermal insulation and structural-thermal insulation lightweight concretes on the UCS with a density of 500 to 800 kg/m3, as well as structural lightweight concretes with a density of up to 1700 kg/m3 of optimal compositions.Various dependencies on the evaluation of the experimental data obtained are analyzed and recommendations are given for inclusion in regulatory documents, in particular, in SP 351. 1325800.2017 "Concrete and reinforced concrete structures made of light concrete. Design rules".