Pozzolanic activity and hydration properties of feldspar after mechanical activation

Investigation of mechanical activation effect on high-volume natural pozzolanic cements

Mechanical activation is one of the most preferred methods to increase the reactivity of mineral, mining, and industrial wastes or materials with low pozzolanic content in cement production. The mechanical activation process of such materials takes a long time and requires high grinding energy. Although it seems like an advantage to using the materials in cement production by gaining reactivity thanks to mechanical activation, mechanical activation is a long duration and expensive process, causing an increase in cement production costs. In this study, a hybrid method is proposed for the mechanical activation of materials in a shorter duration and with lower energy consumption. A roller press and a hammer grinder were integrated before the laboratory type ball mill to realize the mechanical activation processes. To perform the mechanical activation processes in this way, two different hybrid grinding methods were tested and compared. Both methods activated volcanic tuff samples with low pozzolanic properties were investigated particle microstructures, energy consumption differences, mechanical activation durations and their effects on the cement performance, and mortar microstructures. The hybrid grinding method integrated with roller press and ball mill was determined to be the best mechanical activation method.

Properties of Air Lime Mortar with Bio-Additives

Lime mortar has been a primary binding material in ancient mortar, and is one of the main reasons behind solid and stable constructions that remain stable even after thousands of years. The benefits of lime are innumerable: it is minimally processed and used with a lesser carbon footprint and embodied energy and, most crucially, it is a carbon absorbent. This research experiments with the strength properties (compression) of lime at 28, 56, and 100 days of air curing. The investigation studies the durability using water absorption, UPV test, and carbonation parameters after 100 days of exposure to air. The tested materials are subjected to SEM analysis to find the morphology of the reaction that takes place and the products that are formed. We also performed a comparative study of two different fermented additives by the duration of fermentation (1 day and 10 days) and two different doses of additives (Jaggery and Kadukkai) with air lime. The bio-additives were experimented with using gas chromatography and mass spectroscopy for the formation of new enriching compounds, which improved the qualities of traditional lime mortar. The formation of fat and protein in the additives was found using IS 7219-1973 (a method for the determination of protein in foods and feeds). Using the AOAC method, the presence of fat confirms the improvement in strength and durability properties. The phytochemical analysis details the alkaloids, terpenoids, steroids, phenols, flavonoids, tannins, glycosides, and saponins. Quantification of phenols and flavonoids adds to the beneficial aspects of the fermented additives. The experimental results indicate that using naturally fermented organic materials in the lime has made the structures stronger with the stable build of calcite and vaterite components. The self-healing capacity of lime mortar makes it time resistant.

Effect of Ultrafine Metakaolin on the Properties of Mortar and Concrete

This study investigated the influence of ultrafine metakaolin replacing cement as a cementitious material on the properties of concrete and mortar. Two substitution levels of ultrafine metakaolin (9% and 15% by mass) were chosen. The reference samples were plain cement concrete sample and silica fume concrete sample with the same metakaolin substitution rates and superplasticizer contents. The results indicate that simultaneously adding ultrafine metakaolin and a certain amount of polycarboxylate superplasticizer can effectively ensure the workability of concrete. Additionally, the effect of adding ultrafine metakaolin on the workability is better than that of adding silica fume. Adding ultrafine metakaolin or silica fume can effectively increase the compressive strength, splitting tensile strength, resistance to chloride ion penetration and freeze–thaw properties of concrete due to improved pore structure. The sulphate attack resistance of mortar can be improved more obviously by simultaneously adding ultrafine metakaolin and prolonging the initial moisture curing time.

Self-Immobilizing Metals Binder for Construction Made of Activated Metallurgical Slag, Slag from Lignite Coal Combustion and Ash from Biomass Combustion

Research on the effective use of secondary products is gaining more and more importance in Poland due to the intensively implementing idea of the circular economy. The solution used in this work are one of many tests useful in construction. The subject of this work was therefore the formation and testing of a new ecological construction binder, in particular for mortars or prefabricated elements working in the environment with high humidity. The binder was made of alkaline activated ground granular blast furnace slag (AAS), fly ash from biomass combustion (BFA) and furnace slag from brown coal combustion (LFS). The mixture was modified by introducing the zeolite to check the degree of metals immobilization contained in the ingredients of the mixture. A series of three mixtures were prepared: without and with zeolite soaked in distilled water or calcium nitrate. The strength of binders in time in dry and wet curing were tested and compared with the microstructure. The maximum compressive strength values at the eighth week were about 30 MPa. The strength values after 4 weeks of dry and wet curing were also compared. It was shown that 28-day wet curing increased the bending strength of the beams more than twice, but slightly decreased the compressive strength. The microstructure of the mixture with the highest values of compressive strength was the densest and the one with the lowest values of compressive strength, the most loosened with the most differentiated topographically fracture. The impregnation of zeolite with calcium nitrate decreased the compressive strength of the binder significantly. The bending strength of samples curing in dry conditions decreased during hardening. The results of the metals leaching test showed that the mixtures were safe for the environment, and due to the impregnation of zeolite with calcium nitrate, the binding effect of copper and zinc in the first weeks was greater than in the other mixtures.