Degradation of Glaukonite Sandstone as a Result of Alkali-Silica Reactions in Cement Mortar

The mechanism of concrete degradation as a result of an alkali-silica reaction (ASR) largely depends on the mineral composition and microstructure of the reactive aggregate. This paper shows the reactivity results of quartz-glaukonitic sandstone, which is mainly responsible for the reactivity of some post-glacial gravels, available in Poland. After initial petrographic observations under a light microscope, the mode of sandstone degradation triggered by the reaction with sodium and potassium hydroxides was identified using scanning electron microscopy (SEM). It has been found that chalcedony agglomerates present in sandstone are separated from the rock matrix and subsequently cause the cracks formation in this matrix. Additionally, microcrystalline and potentially reactive silica is also dispersed in sandstone cement

The Impact of Ions Contained in Concrete Pore Solutions on Natural Zeolites

This article investigates the relationships between different chemical compositions of simulated cement concrete pore solutions and changes on the surface of zeolite rock with potassium clinoptilolite as its main component. The changes were studied using X-ray diffraction (XRD), thermal analysis (DTA-TG) and scanning electron microscopy (SEM). Zeolite powder samples and a ground section of 16–64 mm grain were tested. The simulated pore solutions were based on Ca, Na, K hydroxides and K2SO4. It was found that 100% of Ca(OH)2 in the systems could react between 7 and 180 days of hydration due to pozzolanic and side reactions. As the degree of clinoptilolite conversion increased, it became more difficult to detect it in X-ray patterns. At the same time, various microstructural changes could be observed. As a result of the reactions that occurred, hydrated calcium silicates, sulfate and carbonate compounds were formed. Potassium hydroxide had a more substantial effect on clinoptilolite reactivity than sodium hydroxide. This effect can be enhanced by the presence of SO23− ions in the solution

Correction: Czapik, P. Microstructure and Degradation of Mortar Containing Waste Glass Aggregate as Evaluated by Various Microscopic Techniques. Materials 2020, 13, 2186

The author wishes to make the following correction to this paper [...

Utilization of Waste Glass in Autoclaved Silica–Lime Materials

This paper aims to investigate the possibility of using waste glass of different colours as a complete substitute for quartz sand in autoclaved silica–lime samples. On the one hand, this increases the possibility of recycling waste glass; on the other hand, it allows obtaining autoclaved materials with better properties. In this research, reference samples with quartz sand (R) and white (WG), brown (BG), and green (GG) waste container glass were made. Parameters such as compressive strength, bulk density, and water absorption were examined on all samples. The samples were examined using a scanning electron microscope with an energy dispersive spectroscopy detector (SEM/EDS) and subjected to X-ray diffraction (XRD) analysis. The WG samples showed 187% higher compressive strength, BG by 159%, and GG by 134% compared to sample R. In comparison to the reference sample, volumetric density was 16.8% lower for sample WG, 13.2% lower for BG, and 7.1% lower for GG. Water absorption increased as bulk density decreased. The WG sample achieved the highest water absorption value, 15.84%. An X-ray diffraction analysis confirmed the presence of calcite, portlandite, and tobermorite phases. Depending on the silica aggregate used, there were differences in phase composition linked to compressive strength. Hydrated calcium silicates with varying crystallisation degrees were visible in the microstructure image

The Influence of HEMC on Cement and Cement-Lime Composites Setting Processes

In this article, the effect of hydroxyethyl methyl cellulose (HEMC), which is a polymeric viscosity modifying admixture on the mineral based composites setting processes, was studied. Previous studies available in the literature included the evaluation of the influence of this admixture on the hydration processes of cement or lime pastes. In this paper, the analysis of this issue was extended to include cement-lime composites. The composition of the pastes and mortars differed in the type of binder (the tests were carried out on cement-based and cement-lime-based materials, in which the cement was replaced in 50% with hydrated lime), as well as the amount and viscosity of the admixture. The study of mortars setting processes and hardening processes using the ultrasonic method was supplemented in the work with calorimetric measurements and phases analysis by the X-ray diffraction method. Finally, it was found that the HEMC reduces the rate of a hydration reaction in cement and cement-lime pastes. The amount of admixture used has a greater influence on the changes taking place during the setting process than the admixture viscosity or the type of binder

Chemical corrosion of external stairs – case study

On the basis of examinations of the efflorescences formed on the concrete surface, an attempt was made to analyze the sources of concrete corrosion without entering inside the construction. The concrete stairs revealed the symptoms of leaching, as a result of alkali-aggregate reactions developing beneath the surface. As a result of this corrosion process and the carbonation propagating from the concrete surface, the carbonate efflorescences were found. Their phase composition was determined by X-ray diffraction. In order to identify whether the efflorescences were the results of the alkali-silica reaction or alkalicarbonate reaction, the microstructure was investigated using the scanning electron microscope together with energy dispersive spectroscopy

Wpływ stosowania szkła odpadowego na właściwości zaprawy cementowej

In this paper the influence of waste glass on the properties of cement mortar was described. The coloured waste glass in two different forms was used: the glass cullet with a particle size of 0.125-4.00 mm as a fine aggregate and the glass powder with a particle size below 0.125 mm as cement replacement. Both types of glass were obtained by crushing and milling brown glass bottles. The tests were carried out on mortars in which sand was entirely replaced by glass cullet or 20% of cement was replaced by glass powder. The effect of glass cullet and glass powder on the properties of cement mortar, such as setting time, consistency, flexural and compressive strength was determined. Moreover, the role of glass cullet as a potential source of expansion resulted from the alkali-silica reaction was investigated. The microstructure of hydrated composites was also examined with a scanning electron microscope.W niniejszym artykule opisano wpływ szkła odpadowego na właściwości zaprawy cementowej. Do badań zastosowano barwione szkło odpadowe w dwóch formach: stłuczki szklanej o uziarnieniu 0,125-4 mm wykorzystywanej jako kruszywo drobne i mączki szklanej o uziarnieniu poniżej 0,125 mm wykorzystywanej jako zamiennik cementu. Oba rodzaje szkła uzyskano w wyniku kruszenia i mielenia brązowych szklanych butelek jednego pochodzenia. Badania prowadzono na zaprawach, w których piasek w całości został zastąpiony stłuczką szklaną lub cement w 20% został zastąpiony przez mączkę szklaną. W pracy określono wpływ stosowania stłuczki szklanej i mączki szklanej na podstawowe własności technologiczne zaprawy cementowej, tj. na czas wiązania, konsystencję oraz wytrzymałość na ściskanie i zginanie. Ponadto określono czy stosowanie stłuczki szklanej może być przyczyną wystąpienia ekspansji na skutek zachodzenia reakcji alkalia-krzemionka. Zbadano też mikrostrukturę próbek pod skaningowym mikroskopem elektronowym

The Influence of Sewage Sludge Content and Sintering Temperature on Selected Properties of Lightweight Expanded Clay Aggregate

Wastewater treatment processes produce sewage sludge (SS), which, in line with environmental sustainability principles, can be a valuable source of matter in the production of lightweight expanded clay aggregate (LECA). The literature on the influence of SS content and sintering temperature on the properties of LECA is scarce. This paper aims to statistically evaluate the effects of SS content and sintering temperature on LECA physical properties. Total porosity, pore volume, and apparent density were determined with the use of a density analyzer. A helium pycnometer was utilized to determine the specific density. Closed porosity was calculated. The test results demonstrated a statistically significant influence of the SS content on the specific density and water absorption of LECA. The sintering temperature had a significant effect on the specific density, apparent density, total porosity, closed porosity, total volume of pores, and water absorption. It was proved that a broad range of the SS content is admissible in the raw material mass for the production of LECA

Sposoby ograniczenia reaktywności kruszywa żwirowego

Effectiveness of selected chemical admixtures and mineral additives to mitigate alkali-silica reaction was compared based on reactive gravel aggregate. Lithium compounds in the form of nitrate and lithium polysilicate were used as chemical admixtures. Natural pozzolans containing zeolite were used as mineral additive. Efficiency of the additive was enhanced by modification with ammonium ions. Linear changes of mortars with crushed gravel aggregates were studied with the accelerated and long-term methods. Additionally, scanning electron microscopy was used for microstructural observations. It was demonstrated that at elevated temperatures the application of lithium compounds provided better protection. Under conditions similar to those in the field, 20-30% of natural pozzolans proved to be more effective in inhibiting the expansion. Regardless of the method of protection applied, the presence of alkali-silica reaction products was detected in the microstructure of the mortars.Na przykładzie reaktywnego kruszywa żwirowego porównano efektywność ograniczenia reakcji alkalia-kruszywo przy pomocy wybranych domieszek chemicznych i dodatków mineralnych. Jako domieszki chemiczne zastosowano związki litu w postaci azotanu i polikrzemianu litu. W przypadku dodatków mineralnych zastosowano naturalną pucolanę, zawierającą zeolit, której efektywność zwiększano poprzez modyfikację jonami amonowymi. Wykonano badania zmian liniowych zapraw z rozdrobnionym kruszywem żwirowym metodą przyspieszoną i długoterminową. Dodatkowo wykonano obserwacje mikrostruktury z wykorzystaniem elektronowego mikroskopu skaningowego. Wykazano, że w warunkach podwyższonej temperatury lepsze zabezpieczenie uzyskano po zastosowaniu związków litu. W warunkach zbliżonych do eksploatacyjnych zastosowanie 20-30% pucolany naturalnej skuteczniej hamowało ekspansję zapraw z kruszywem reaktywnym. Niezależnie od sposobu zabezpieczenia, w mikrostrukturze zapraw wykryto obecność produktów reakcji alkalia-krzemionka

Condition assessment of selected reinforced concrete structural elements of the bus station in Kielce

The paper presents the results of the research aimed at assessing the condition of reinforcement and concrete cover in selected elements of the structure of the most recognizable structure in Kielce, i.e. PKS station, located at Czarnowska Street. Currently, demolition works are underway resulting from the planned modernization. The assessment of the corrosion risk of the reinforcement in the construction elements was carried out with the use of a semi-non-destructive electrochemical method. The use of this method made it possible to determine the probability of reinforcement corrosion in the selected areas and to estimate its rate. The protective properties of concrete cover were checked by the carbonation test (test using a 1% phenolphthalein solution) and phase composition analysis (X-ray diffraction analysis). In order to determine the position of the reinforcing bars and to estimate the concrete cover thickness distribution in the areas corresponding to the aforementioned measurements, ferromagnetic detection system was used