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Limestone calcined clays are a promising technology as they offer similar performance to OPC from 7 days onwards, while enabling a reduction of the clinker content of 50%. In some regions of the world like South America, pozzolanic cements (i.e., blended cements that combine clinker with natural pozzolans) have been used for decades as an effective solution to reduce the clinker content. Their clinker factors range from 80 down to 60% on average. However, their mechanical properties are in general lower as compared to OPC/CEM I. In this study, we show that by using LC3-type formulations, cements with the same performance as commercial pozzolanic cements can be produced with clinker contents significantly below 50%. This is explained by the high reactivity of calcined clays and the synergetic reaction of metakaolin and limestone that allows offsetting the clinker reduction.

DNA topoisomerase I inhibitors, both synthetic and of natural origin, are receiving increasing consideration primarily as drugs against refractory tumors. Alkannin and shikonin, two enantiomeric dyes from Alkanna tinctoria and Lithospermum erythrorhizon, have been known over many centuries as dyestuff, wound healing, anti-inflammatory, antibacterial and antitumor substances. Although multiple mechanisms appear to be implicated, their potency is associated with the inhibition of topoisomerase I and with the redox properties of the naphthazarin scaffold. Here, the synthesis of new naphthalene and naphthoquinone derivatives inspired by alkannin and shikonin is described and their structural and biological properties were examined. Different oxidation states of the naphthalene nucleus were examined to observe the effect of this parameter on cytotoxicity. Antiproliferative activities against a panel of human cancer cell lines were evaluated and the implication of topoisomerase I was assessed.

Cold weather concreting often requires the use of chemical accelerators to speed up the hydration reactions of the cement, so that setting and early-age strength development will occur in a timely manner. While calcium chloride (dihydrate – CaCl2·2H2O) is the most commonly used chemical accelerator, recent research using fine limestone powders has indicated their high proficiency for physically accelerating early-age hydration and reducing setting times. This paper presents a comparative study of the efficiency of these two approaches in accelerating hydration (as assessed via isothermal calorimetry), reducing setting times (Vicat needle), and increasing early-age mortar cube strength (1 d and 7 d). Both the CaCl2 and the fine limestone powder are used to replace a portion of the finest sand in the mortar mixtures, while keeping both the water-to-cement ratio and volume fractions of water and cement constant. Studies are conducted at 73.4 °F (23°C) and 50 °F (10 °C), so that activation energies can be estimated for the hydration and setting processes. Because the mechanisms of acceleration of the CaCl2 and limestone powder are different, a hybrid mixture with 1 % CaCl2 and 20 % limestone powder (by mass of cement) is also investigated. Both technologies are found to be viable options for reducing setting times and increasing early-age strengths, and it is hoped that concrete producers and contractors will consider the addition of fine limestone powder to their toolbox of techniques for assuring performance in cold weather and other concreting conditions where acceleration may be needed.

We report herein the viability of a novel nanoparticles (NPs) conjugated system, namely the attachment, based on ionic and hydrophobic interactions, of different sulfonated organic salts to positively charged poly(methylmethacrylate) (PMMA)-based core-shell nanoparticles (EA0) having an high density of ammonium groups on their shells. In this context three different applications of the sulfonates@EA0 systems have been described. In detail, their ability as cytotoxic drugs and pro-drugs carriers was evaluated in vitro on NCI-H460 cell line and in vivo against human ovarian carcinoma IGROV-1 cells. Besides, 8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt (HPTS) was chosen for NPs loading, and its internalization as bioimaging probe was evaluated on Hep G2 cells. Overall, the available data support the interest for these PMMA NPs@sulfonates systems as a promising formulation for theranostic applications. In vivo biological data strongly support the potential value of these core-shell NPs as delivery system for negatively charged drugs or biologically active molecules. Additionally, we have demonstrated the ability of these PMMA core-shell nanoparticles to act as efficient carriers of fluorophores. In principle, thanks to the high PMMA NPs external charge density, sequential and very easy post-loading of different sulfonates is achievable, thus allowing the preparation of nanocarriers either with bi-modal drug delivery behaviour or as theranostic systems.

This paper details the main factors influencing the performance of limestone calcined clay cements (LC3). The kaolinite content plays a major role in the rheological properties as well as strength development. Even in the presence of secondary phases, kaolinite can be accurately quantified by thermogravimetric analysis. The performance of LC3 is slightly influenced by the calcination process of clay, but it can be optimized by using the correct calcination temperature and applying a specific mix design with adjusted sulfate and alkali content. The hydration reactions of LC3 are fully characterized. They vary slightly from plain cement. There is no significant change in terms of phase assemblage. The main properties of LC3 are also described. LC3 blends show a lower creep compliance and a delay in shrinkage strains compared with plain cement. Concerning durability, LC3 blends show outstanding performance with respect to resisting chloride ingress and expansion from the alkali-silica reaction.

Hardened cement paste in concrete wastes can be a valuable precursor material for the production of recycled cements. In the reported study, X-ray diffraction data of cementitious materials obtained by thermal processing of hardened pastes were quantitatively analyzed using Rietveld refinement to explain the effect of process parameters on their hydration reactivity and on the strength gain of pastes made with them. The parameters studied were annealing temperature, residence time, and cooling rate. Across the annealing temperature range explored C2S polymorphs were found to comprise the larger fraction of the resulting materials. However, their relative concentrations varied. Results indicate alpha'(H)-C2S formed at low temperature is highly reactive and remains stable on cooling due to its smaller crystallite size, whereas at higher temperatures most of it converts to the less reactive beta-C2S on cooling. Accordingly, materials obtained at lower temperatures exhibited higher heats of hydration and much higher strength gain rates.

Cement is the most energy and CO2 emission intensive part of concrete production. The most promising solution to reduce CO2 emissions by another 25% by 2030, using existing industry infrastructure, is to substitute clinker in large quantities with supplementary cementitious materials (SCM). In this study, the environmental and mechanical performance of concrete with low CO2 cements produced from a combination of Croatian natural clays and limestone is investigated. A detailed raw material screening study served as the basis for the selection of SCMs. The environmental contribution was evaluated using a Life Cycle Assessment (LCA) tool with a cradle-to-gate approach. The results were compared and evaluated according to the mechanical strength of each blend. Subsequently, this study highlights the positive impact that the use of such a material could have at a regional level.

The use of blended cements to mitigate carbon emissions has risen dramatically in recent years. Cementitious mixtures incorporating calcined clays are gaining popularity due to their good performance and widespread availability of clays— particularly the combination of limestone and calcined clay (LC3). The availability of clay and limestone, as well as the impending scarcity of other materials like fly ash and slag, make LC3 an appealing option to the cement industry. While the clays have been deposited all over the world, the kaolinite content, which is the key factor in their overall performance, varies from region to region. Clays with at least 40% kaolinite perform as well as ordinary Portland cement, according to the majority of studies. Within project ACT, funded by Swiss and Croatian Science Foundation fifteen different sources of clay were investigated, among which the highest found kaolinite content was 18%. Additional to low content of kaolinite, some of the clays had quartz and impurities in high concentrations, which can act detriment to the clay's cementitious properties in concrete. Therefore, the removal of these impurities, mainly quartz, could enhance the reactivity of clay, which could consequently give better performance in cementitious system. Particle separation techniques could be used to remove the coarser particles. In this paper, the feasibility and efficiency of particle separation of Croatian clay with low kaolin content are discussed.