Resonant Frequency Ultrasonic P-Waves for Evaluating Uniaxial Compressive Strength of the Stabilized Slag–Cement Sediments

Marine sediments can be stabilized by ultra high-strength binders: cement, Cement Kiln Dust (CKD) and slag. The properties of the stabilized soil indicate potential to their reuse. This study investigated the performance of the unconfined compressive strength (UCS) in the marine sediments stabilized by binder (cement, CKD, slag), tested by ultrasonic P-waves. Materials include 194 specimens collected from the port of Gothenborg. The experiment was performed in Swedish Geotechnical Institute (SGI). The UCS of specimens stabilized by different ratio of binders (cement, CKD, slag) was tested by resonance frequencies of the elastic P-waves. The significant increase in the UCS (>1500 kPa) was recorded for the highest values of CKD and cement, and low values of slag. The correlation profiles of low water/high binder (LW/HB) cement/slag (40/60%) were controlled by curing time. The slag–cement–CKD simplex tests demonstrated UCS of samples with low/high water content and various binder ratio of cement (kg/m3). The ratio of cement binder and curing time play a critical role in the increase of UCS followed by mechanical properties of specimens and intensity of stress. The highest values exceed 1000 m/s in P-waves. The results shown high accuracy (97%) and non-contacting approach for testing UCS of sediments. Seismic methods can be applied to test the UCS of the stabilized sediments, and also in-situ via seismic CPT, surface testing or cross hole seismic testing.

Effects of Fluorogypsum and Flue-Gas Desulfurization Gypsum on the Hydration and Hardened Properties of Alkali Slag Cement

In order to explore the influence of the types of waste gypsum on the properties of alkali slag cement, fluorogypsum (FG) and flue-gas desulfurization (FGD) gypsum were comparatively investigated. Moreover, the action mechanisms of FG and FGD gypsum on the properties of alkali slag cement were analyzed. The results show that both the FG and FGD gypsum prolonged the setting time of the alkali slag cement paste. However, the prolongation effect of FG was more pronounced than the FGD gypsum. When the compressive strength was maximum, the contents of FG and FGD gypsum were 5 and 6 wt.%, respectively. At 3 and 28 days, compared to the control sample, the compressive strengths increased by 59.3% and 24.3%, and 66.9% and 33.9%, respectively. Furthermore, the XRD, TG-DTA and SEM-EDS results showed that, with the increase in the contents of FG and FGD gypsum, ettringite was more easily produced and the hydration products were more abundant in the system. The greater the gypsum content of the paste, the less accumulated was the heat of hydration. The change of micro-structure caused by the formation of ettringite was the main reason for the difference in the properties of cement.

Investigation of mineral hydraulic binders based on the slag-cement system obtained with the use of vortex electromagnetic homogenization

Из гранулированных доменных шлаков и портландцемента М500 с применением вихревой электромагнитной гомогенизации получены образцы минерального гидравлического вяжущего и искусственного камня на его основе. Исследованы физико-химические характеристики минеральных порошков: фазовый и химический состав, удельная поверхность, гранулометрический состав, механические свойства искусственного камня на основе вяжущих системы шлак‒цемент. Показано, что при введении в состав разрабатываемых материалов от 10 до 50 мас. % портландцемента предел прочности при сжатии образцов варьируется от 50 до 90 МПа, плотность ― от 2,1 до 2,5 г/см3. Данные материалы имеют низкую стоимость за счет использования доменного шлака в качестве сырья, а также благодаря применению энергоэффективной методики помола.