This work aims to study the effect of MgCl[2] additive on the strength, heat of hydration, and phase composition of hydration products of the binder consisting of high-calcium fly ash and silica fume. Fly ash from Berezovskaya thermal power plant, containing a lot of CaO[free], in combination with silica fume does not expand and exhibits the properties of a binder. However, the strength of this binder is low. The MgCl[2] additive significantly increases the hardening rate and the final strength of the mix. The compressive strength of 32*32*32 mm specimens from the paste at the age of 7 days is 15.2 MPa and 3.7 MPa with and without the MgCl[2] additive, respectively. Exothermic data show that silica fume inhibits CaO hydration from the first minutes of the reaction to 2 days, after which the process accelerates and proceeds evenly. The total value of the thermal effect for 10 days is 500 kJ per 1 kg of binder. The MgCl[2] additive does not increase this final value, however, it accelerates the release of heat in the initial periods, excluding the indicated stagnation period. The results of XRD and DTA showed that in the presence of MgCl[2], calcium hydrochloraluminate (Friedel's salt) is formed, which was not previously observed in the composition of binder hydration products.

• Cementless binder consisting of high-calcium fly ash, silica fume and magnesium chloride
  • 1. Introduction
  • 2. Materials and Methods
    • 2.1. Materials
    • 2.2. Influence of early strength agents on fly ash expansion in presence of silica fume
    • 2.3. Determination of compressive strength of specimens with early strength agents
    • 2.4. X-ray Diffraction Analysis and Differential Thermal Analysis
    • 2.5. Heat of Hydration of mortar using Semi-Adiabatic Calorimetry
  • 3. Results and Discussion
    • 3.1. Evaluation of influence of early strength agents
    • 3.2. Compressive Strength and Water Resistance Test Results
    • 3.3. Influence of magnesium chloride on phase composition of hydration products of binder
    • 3.3.1. Results of X-ray diffraction analysis
    • 3.3.2. Results of differential thermal analysis
    • 3.4. Influence of magnesium chloride on heat generation of fly ash-silica fume binder
    • 3.5. Effect of magnesium chloride on the mortar strength
  • 4. Conclusions

Magazine of Civil Engineering / Санкт-Петербургский политехнический университет Петра Великого. — Санкт-Петербург: СПбПУ, 2020-. — Периодичность: 8 раз в год. — Выходит с 2020 г. — Загл. с титул. экрана. — Свободный доступ из сети Интернет (чтение, печать, копирование). — Электрон. журнал. — Текст: электронный

Magazine of Civil Engineering / Санкт-Петербургский политехнический университет Петра Великого. — Санкт-Петербург: СПбПУ, 2020-. № 7 (123), 2023. — 1 файл (9,5 Мб). — Свободный доступ из сети Интернет (чтение, печать, копирование). — Электрон. журнал. — <URL:http://elib.spbstu.ru/dl/2/j24-88.pdf>.