Linda Krage

The Formation of Microstructure in High Strength Concrete Containing Micro and Nanosilica

This article presents the results of microstructural investigation of high strength concrete containing microsilica and nanosilica (amorphous SiO2) as an active pozzolanic admixture. Micro and nanosilica react with calcium hydroxide producing calcium silicate hydrates (C-S-H), thus the voids and pores within concrete are filled and new minerals are formed in the gaps between cement grains and aggregate particles. Unreacted round microsilica and nanosilica particles were registered using SEM even in 6 month old samples. The compressive strength results indicate that concrete still continues to harden after the 28-days of curing.

Characterization of glass-ceramics microstructure, chemical composition and mechanical properties

Given paper presents the results of industrial waste recycling - steel cooling refuse, etching refuse and alumina containing waste. In order to characterize the microstructure and chemical composition of a glass-ceramic material obtained from Latvian industrial waste, the scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analyses were used. In the glass-ceramic material various crystalline phases such as quartz, hematite, anorthite, spinels etc. were identified. The crystalline phases contain a higher amount of metallic elements (e.g. Al, Cr, Fe, Ni and Zn and most probably also other heavy metals) than the residual glassy phase. Relations between microstructure, chemical composition and mechanical properties were established.

Mechanical properties of materials obtained via alkaline activation of illite-based clays of Latvia

Materials has been synthesized in the temperature range from 60-100 °C from two illite based clays of Latvia under activation of KOH and NaOH solutions (4-6 M). Compressive strength and apparent porosity were measured. The effect of concentration of KOH and NaOH solutions on the material mechanical properties was investigated by means of infrared spectroscopy (IR). Compressive strength data of the materials showed that via such activation could obtain building materials with good quality.

Use of Industrial Waste and Raw Materials in Iron Sorption

This work focuses on pellets made by Latvian industrial waste (waste cullet glass, sewage sludge, metallurgical slag and alumina scrap metal processing waste and raw mineral materials (limeless clay) to gain high porosity and water sorptiom. Iron sorption using ceramic pellets is explored more detailed. Physical-chemical properties and microstructure were researched to obtain a deeper understanding of how these qualities affect water purification from iron compounds. Three pellets with different properties were made in this paper : B5, A5 and E1. Composition B5 indicates highest iron sorption rate at sintering temperature 1100 °C and shows considerable iron reduction in a solution after one week.

Chemical and Physical Processes in the Synthesis of Romancement from Clay and Dolomite

This work deals with the synthesis of binder, similar to historic dolomitic romancement, from mixture of clay and dolomite instead of traditionally used marlstone, thus widening the range of raw materials. In the territory of Latvia dolomitic romancement was widely known and applied in the construction of buildings since late 19th till the middle of 20th century. Nowadays the local dolomitic marlstone is not sufficiently available. As the scientists have faced the problem adjusting compatible material for restoration of historical buildings of given time period, research is done with the aim to investigate the synthesis of romancement type binder from widespread local mineral raw materials for the restoration purposes. In given paper the chemical and physical processes in the synthesis and also obtained properties are discussed.