Fine-Grained Fibre Concrete of Run-Of-Crusher Stone Using Volcanic Ash

The results of the studies on the creation of self-compacting fine-grained fiber-reinforced concrete based on run-of-crusher stone with the use of a polyfunctional additive D-5 are presented. Compositions of self-compacting fine-grained fiber-reinforced concrete with the use of basalt fiber have been developed, which significantly reduce cement consumption and improve the characteristics of fine-grained concrete mixture and concrete. Using a polyfunctional additive D-5in mixtures makes it possible to increase the strength properties of fine-grained fiber-reinforced concrete while improving the concrete mixtures’ rheological characteristics. Replacement of cement up to 10% of the mass by ash fraction d<0.14 min fine-grained concrete mixtures does not cause a noticeable decrease in the concrete strength properties. The developed self-compacting fine-grained fiber-reinforced concretes have increased strength properties and have a low-cost price due to the use of local raw materials and run-of-crusher stone.

OPTIMIZATION OF THE COMPOSITION OF A COMPLEX POLYFUNCTIONAL ADDITIVE BY THE STRENGTH CRITERION OF CEMENT STONE AND CONCRETE

В материале статьи приведены результаты исследований влияния новой комплексной полифункциональной добавки, содержащей пластификатор, ультрадисперсный микрокремнезем (УДМК) и ускоряюще-уплотняющий компонент, на кинетику твердения (темп роста) и уровень прочности на сжатие тяжелого конструкционного бетона. С применением методов математической статистики оценено влияние на процесс твердения (рост прочности) цементного камня и цементного бетона, составляющих полифункциональную добавку компонентов (при разном их соотношении в комплексе в целом). На этом основании (включая результаты экспериментальной оценки прочности образцов цементного камня и бетона) разработаны и запатентованы составы полифункциональной добавки в бетон, характеризующиеся оптимальным диапазоном содержания в ее составе компонентов: суперпластификатора на основе поликарбоксилатных смол ‒ 0,25 %...0,5 % от массы цемента, ультрадисперсного микрокремнезема (SiO2) ‒ 0,25 %...1,0 % от МЦ, ускорителя твердения ‒ сульфата натрия (Na2SO4) ‒ 0,35 %...0,5 % от МЦ и уплотняющей структуру добавки ‒ сульфата алюминия (Al2(SO4)3) ‒ 0,15 %...0,25 % от МЦ, при меньших значениях для тяжелого конструкционного бетона класса ≤ С50/60 и бόльших значениях для высокопрочного, особо плотного бетона класса ≥ С70/85 (прочностью fcm.28 ≥ 100 МПа). В исследованиях прочностных характеристик и эксплуатационных свойств бетона применены стандартизованные методики испытаний. Результаты экспериментальных исследований подтверждены производственными испытаниями разработки, их данные заактированы и подтверждают возможность экономии цемента на 10 %…15 % без снижения прочностных и эксплуатационных свойств бетона, при снижении затрат тепловой энергии на обогрев изделий из бетона с добавкой в 1,5…2,0 раза (за счет сокращения времени подачи теплоносителя до 1,5…2,0 ч (с последующим твердением по методу термоса) и снижения температуры разогрева бетона до 45 °С…50 °С). The article presents the results of studies of the effect of a new complex multifunctional additive containing a plasticizer, ultradispersed microsilica (UDMS) and an accelerating-sealing component on the hardening kinetics (growth rate) and the level of compressive strength of heavy structural concrete. Using the methods of mathematical statistics, the influence on the hardening process (growth of strength) of cement stone and cement concrete of the components constituting a multifunctional additive (with their different ratios in the complex as a whole) was evaluated. On this basis (including the results of an experimental assessment of the strength of cement stone and concrete samples), compositions of a polyfunctional additive to concrete have been developed and patented, characterized by the optimal range of content in its composition of components: superplasticizer based on polycarboxylate resins – 0.25 %...0.5 % of the mass of cement, ultradispersed microsilica (SiO2) – 0.25 %...1.0 % of WC, hardening accelerator – sodium sulfate (Na2SO4) – 0.35 %...0.5 % from WC and the additives that seal the structure - aluminum sulfate (Al2(SO4)3) – 0.15 %...0.25 % of WC, at lower values for heavy structural concrete of class ≤ С50/60 and higher values for high-strength , especially dense concrete of class ≥ С70/85 (strength fcm.28 ≥ 100 MPa). In studies of the strength characteristics and operational properties of concrete, standardized test methods were used. The results of experimental studies are confirmed by production tests of the development, their data are recorded and confirm the possibility of saving cement by 10 %...15 % without reducing the strength and operational properties of concrete, while reducing the cost of heat energy for heating concrete products with an additive of 1.5...2.0 times (by reducing the time of supplying the coolant to 1.5...2.0 h (with subsequent hardening by the thermos method) and reducing the temperature of concrete heating to 45 °C...50 °C).

Influence of Polyfunctional Additive on Hardening Process and Properties of Cement Concrete

The paper presents results of research aimed at developing a new semi-functional concrete additive that provides an increase in rate and level of its strength growth while reducing energy costs to accelerate hardening process, as a basis for reducing energy intensity in manufacturing of concrete and reinforced concrete products and structures. Experimentally a rational ratio of components for a polyfunctional additive has been found of mass cement: a superplasticizer based on polycarboxylate resins (for example, “Stachement 2000” or “Relamiks PC”) – 0.5 %, ultradispersed microsilica (SiO2) – 1.0 %, sodium sulfate (Na2SO4), hardening accelerator – 0.5 %, aluminum sulfate (Al2(SO4)3), sealing additive structure ‒ 0.25 %. The mentioned components ensure the largest increase in strength of cement stone and structural heavy concrete. Results of derivatographic and X-ray phase analyses have shown that strength growth is based on formation of a fine-crystalline form of low-base crystalline silicates of CSH-silicate group, which complements traditionally formed C2SH by the reaction of threeand two-calcium silicate cement with water, as well as it is based on an increase in the number of neoplasms due to the reaction of Ca(OH)2 with amorphous SiO2 and ettringite 3CaO × Al2O3 × 3CaSO4 × 32H2O, being formed due to reactions with cement aluminates these are accelerating-compacting additive components, that in total provides an increase in density and strength of cement stone. While having the case with concrete, the effect is complemented by hardening the zone of contact between aggregate surface and cement stone due to the reaction between Ca(OH)2 and SiO2. These effects have been confirmed by growth (up to 38 %) of water which is chemically bound with cement in presence of a multifunctional additive in samples of cement stone, which is characterized by the largest strength. While using standardized testing methods, effectiveness of a multifunctional additive has been experimentally confirmed and it has been expressed in growth of quality characteristics and properties of structural heavy concrete: compressive strength – up to 40–60 %, flexural strength – up to 15 %, reduction of shrinkage – up to 50 % and water absorption – by 1.5–2 times, increase in frost resistance from brand F250 to F500, water resistance – from W6–W8 to W20.

Medium-Fraction Materials for Processing of Coal-Thread Waste Drains for the Production of Wall Ceramics

The general characteristic of products of processing of waste heaps is given. Their characteristics by fractional composition are proposed: large-fractional, with grains from 2 to 150 mm in size, medium-fractional with a grain size of 0.5 to 2 mm, and fine-grained with a grain size of 0 to 0.5 mm. The results of work on the study of the chemical-mineralogical composition and physico-mechanical properties of the medium-fractionation products of the waste heaps processing with reference to the production of various wall ceramics products are presented. Their role is shown as a polyfunctional additive when introduced into ceramic masses and affects the properties of finished products. A preliminary classification according to the amount of coal component, mineralogical and petrographic composition, technological properties is proposed. The feasibility of their application in the production of wall ceramics with a reduced cost is given.

Application of the Dry Polyfunctional Additives at Radioactive Waste Cementation

One of the known methods directed to improving of the technological cementation process, the increasing quality of a cement compound and degree of radioactive waste incorporating into a final product, is use of the various additives to a cement compound. At present there are technological processes where one or two additives in a dry loose or liquid condition in quantity of 1–10% are used. The application of these additives is directed, as a rule, to improving of one or two properties of a cement compound. The magnification of a quantity of the additives and use of them in a different aggregation state is connected with rise in the cost of the technological process. At Institute of Ecology and Technology Problems and Moscow SIA “Radon” the polyfunctional modifying additives representing dry mixtures of original macro- and microadditives to cement have been developed. The polyfunctional additive is introduced by traditional, reliable and inexpensive equipment directly into liquid radioactive waste and intermixed together with the rest of cement. The quantity of additive varies from 5 up to 20% of cement weight. The additives considerably improve all regulated properties of a cement compound (compressive strength, radionuclides leaching, frost resistance, biological resistance, etc.) and allow modifying the required properties (penetrating ability, viability, disintegration, terms of setting, viscosity etc.). Such additives are used both at cementation of solid radioactive waste and cementation of liquid radioactive waste having a complicated chemical composition, for example, containing simultaneously boric acid, sulphates and great quantity of organic compounds. It is important, that the components of the additives did not change the action in a mixture with other ones. In the report the compositions of the polyfunctional additives developed for various waste and technological processes, their properties and results of practical application are represented.