Eco-friendly High-Strength Refractory Concrete Containing Calcium Alumina Cement by Reusing Granite Waste as Aggregate

Besides preventing valuable natural resources from going to waste, using stone waste from stone processing plants in concrete helps reduce environmental pollution and, therefore, offers a convenient route to sustainable development. The present study aims to use granite waste (GW) in high-strength refractory concrete. Sixteen high-strength refractory concrete mixes, including two water-to-binder ratios (W/B = 0.17 and 0.2), two silica-fume-to-binder ratios (SF/B = 0.15 and 0.2), two binder contents (B = 1200 and 1400 kg/m3), and two replacement ratios of silica sand by granite waste (GW/Agg = 0 and 50%) were designed and prepared with high-alumina cement (HAC). The concrete specimens were exposed to 1200 °C. Compressive and flexural strength and scanning electron microscopy (SEM) tests were performed on specimens of concrete mixes before and after heating. It was found that in specimens with high binder content (1400 kg/m3), replacing 50% silica sand with GW (GW/Agg = 50%) in refractory concrete improves compressive and flexural strengths by 3–15 and 4–24% before heating, respectively. It was also shown that using GW to replace silica aggregates in concrete specimens with a 1200 kg/m3 binder content not only did not undermine, but also improved the compressive and flexural strengths of refractory concrete after heating by 20–78% and 15–60%, respectively, as a result of sintering. Meanwhile, in the case of the concrete with 1400 kg/m3 binder content, adding GW exacerbated its loss of compressive and flexural strengths after heating due to little or lack of sintering.

Refractory concrete based on high-alumina cement and clinker aggregate

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The Effect of Fine-Ground Glass on the Hydration Process and Properties of Alumina-Cement-Based Composites

This paper discusses studies regarding the impact of fine-ground glass additives on the hydration and properties of alumina cement pastes and mortars. Fine-ground glass was added to pastes and mortars instead of high-alumina cement and calcium aluminate cement in quantities of 5% and 10%. The findings are inconclusive as to the impact of glass on the properties of tested alumina cement types. The effect produced via the addition of glass instead of cement depends on the type of alumina cement used. Adding fine-ground glass to high-alumina cement enhances the paste’s density while improving paste and mortar strength. Using the same additive for calcium aluminate cement reduces its density and strength. The addition of glass to high-alumina cement adversely affects its strength at higher temperatures.

Experiment Planning for Prospective Use of Barium-Containing Alumina Cement for Refractory Concrete Making

The prospect of further use of refractory concrete based on barium-containing alumina cement was justified, with the help of a simplex-lattice method of the experiment planning, the granulometric composition of concrete was selected and its physical, mechanical and technical properties were determined, which exceed the properties of the used analogues.

STUDY OF THE CHEMICAL INTERACTION OF GLASS FIBER WITH CEMENT HYDRATION PRODUCTS

Reinforcement of concrete with fiberglass improves the performance properties of concrete. The object of the study is fiberglass concrete, where Portland cement or alumina cement is used as a binder, and silica fiberglass is used as a filler. The chemical and phase compositions of Portland cement and alumina cement have been studied. The influence of the products of hydration of Portland cement and alumina cement on the chemical resistance of glass fiber has been investigated. The phase composition of Portland cement and alumina cement after hydration is studied using X-ray phase analysis. It is revealed that the following phases are present in alumina cement: CaОAl2O3, MgОAl2O3, 12CaO•7Al2O3, 2CaO•Al2O3•SiO, the phase composition of Portland cement is Ca6Al2(SO4)3(OH)12•12H2O, Ca2,25(Si3O7,5(OH)1,5)•(H2O), Ca(OH)2, CaCO3. It has been found that when hydrated, Portland cement has a negative effect on fiberglass due to the presence of Ca(OH)2 in it. The phase composition of the alumina cement after hydration shows the absence of Ca(OH)2. The chemical composition of fiberglass is investigated using X-ray fluorescence analysis. The use of alumina cement when using non-alkali-resistant fiberglass in a composite material is substantiated. The study of the stability of fiberglass in the environment of cement drawing has been carried out. Studies have shown that KV-11 grade fiberglass interacted less with hydration products of alumina cement than with hydration products of Portland cement.

RAPID ASSESSMENT OF POZZOLANIC ACTIVITY IN DETERMINING THE EFFECTIVENESS OF EXPANSIVE SULFO-ALUMINATE TYPE ADDITIVES ABSTRACT

Применение расширяющихся добавок на основе сульфоалюминатных композиций для модификации цементных систем позволяет не только компенсировать усадку, но в ряде случаев получить расширение и самонапряжение. На сегодняшний день рынок изобилует расширяющимися добавками на основе сульфоалюминатных композиций, представляющими собой как искусственно синтезированные материалы, так и механические смеси на основе метакаолина, глиноземистого цемента и гипса (цемент типа «М»). Выбор того либо иного вида добавки, а также ее дозировка назначаются в зависимости от проектных требований к бетону: компенсация усадки, достижение требуемых величин линейного расширения и самонапряжения и т. п. Каждый индивидуальный случай применения такого рода добавок в бетоне требует дополнительных исследований в бетоне по действующим ТНПа, которые занимают от 14 до 28 сут. В ряде случаев такой период испытаний является слишком длительным, и требуются ускоренные методы определения эффективности. В данной статье представлены исследования возможности применения в качестве одного из критериев эффективности расширяющейся добавки пуццолановой активности. Обоснована возможность определения пуццолановой активности по ускоренной методике Чапеля, что позволит в короткий период времени (1-2 сут) определиться с выбором той либо иной расширяющейся добавки. В качестве исследуемых добавок рассмотрены расширяющиеся комплексы на основе механических смесей глиноземистого цемента и гипса, метакаолина и гипса, также с добавлением извести. Предложен диапазон необходимых для получения цементов с компенсированной усадкой или самонапряжением 1 МПа значений пуццолановой активности. The use of expansive additives based on sulpho-alumina compositions to modify cement systems not only compensates for shrinkage, but in some cases allows for expansion and self-stressing. Today the market is replete with expansive additives based on sulfoaluminate compositions, which are both artificially synthesized materials and mechanical mixtures based on metakaolin, high alumina cement and gypsum (type “M” cement). The choice of a particular type of additive, as well as its dosage, is determined depending on the design requirements for concrete: shrinkage compensation, achieving the required values of linear expansion and self-stress, etc. Each individual case of this type of concrete admixture requires additional research in concrete under the existing norms, which take 14 to 28 days. In some cases, such a test period is too long and requires accelerated methods to determine efficiency. This article presents research into the possibility of using the pozzolana activity of expansive additive as one of the performance criteria. It has been substantiated that pozzolanic activity can be determined using the accelerated Chapelle test, which will allow a short period of time (1-2 days) to determine the choice of a particular expansive additive. Expansive complexes based on mechanical mixtures of alumina cement and gypsum, metakaolin and gypsum, also with the addition of lime, have been considered as additions under study. The range of pozzolanic activity values required to produce cements with compensated shrinkage or self-stress of 1 MPa is proposed.