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Alkali–silica reaction (ASR) is a sequence of complex chemical processes, resulting in the formation of alkali silica gels with high swelling ability. ASR leads to the expansion of concrete and the degradation of its microstructure. The susceptibility of aggregates to alkali reaction depends, among other factors, on the type and origin of the aggregate, the presence of reactive forms of silica, the mineral composition, and the geometric properties of the aggregate, such as shape and grain size. This study aimed to investigate the impact of the grain size of polymineral post-glacial gravel aggregate, originating from the northern regions of Poland, on its susceptibility to ASR. The expansion of mortars made from polymineral aggregate and the cracking of grains and cement matrix due to the occurring reactions were analyzed. Based on the conducted research, it was observed that the expansion of mortars depends on the grain size of the aggregate. It was demonstrated that the fraction of reactive aggregate generating the most significant elongation of mortars is in the range of 1.0–2.0 mm. The reaction of silica with alkalis continued until the depletion of reactive components in the aggregate. The relationship between the progress of corrosive processes and the grain size of the aggregate was evident in the form of different linear elongation increments of mortars over time. The expansion of mortars was caused by the swelling ASR gel, inducing stress in the grain and the surrounding cementitious paste.

The limited availability of natural resources, such as sand, and the need to reduce CO2 emissions, which are produced in large quantities in the production of binding materials, indicate the need to look for alternative raw materials used in construction materials. At the same time, there is a strong need to utilise waste packaging materials, the global production of which is constantly increasing. This work aims to investigate the possibility of using recycled polyethylene terephthalate (PET), utilised as a partial substitute for fine aggregate, and waste glass, implemented as powder, serving as a partial substitute for cement in the manufacturing of the cementitious composites. An experimental study was carried out to evaluate the physical and mechanical properties of the resultant cementitious composites. The incorporated PET aggregate comprised 0%, 5%, and 10% by volume of silica sand and 0%, 10%, and 20% glass powder by weight of cement. The addition of waste raw materials augmented the flow of fresh mortars, predominantly subsequent to the introduction of PET recyclate. The deployment of artificial aggregate in mortars induces a decrease in the volumetric density. Concurrently, the mechanical properties of mortars enriched with waste materials exhibited a reduction, in terms of both compressive and flexural strength, with the detriment escalating in conjunction with the content of waste raw materials. An analysis of statistical significance of effects, grounded in an analysis of variance, is delineated within this document, pinpointing the quantities of waste raw materials that can be assimilated in mortars without inducing a substantial deterioration of strength properties. Through studies on phase composition, it has been demonstrated that the utilised glass waste, possessing a grain size analogous to cement, exhibited poor pozzolanic properties. The test results indicate that it is possible to partially replace cement with glass powder, up to 10%, and fine aggregate with PET waste, up to 5%, without a significant reduction in the mechanical properties of the material.

Heritage building structures in many situations contribute unique value to national cultural heritage. In engineering practice, monitoring of historic structures includes visual assessment. This article assesses the condition of the concrete in one of the most recognizable buildings in Łódź, the former German Reformed Gymnasium, located at Tadeusza Kościuszki Avenue. The paper reports a visual assessment of the structure and the degree of technical wear affecting selected structural components of the building. A historical analysis of the building’s state of preservation, characterization of the structural system, and an assessment of the condition of the floor-slab concrete were carried out. The state of preservation of the eastern and southern facades of the building was found to be satisfactory, while on the western side (with the courtyard) the facade is in a poor state of preservation. Tests were also conducted out on concrete samples taken from individual ceilings. The concrete cores were tested for compressive strength, water absorption, density, porosity, and carbonation depth. Corrosion processes including the degree of carbonization and the phase composition of the concrete were identified by X-ray diffraction. The results are indicative of the high quality of the concrete produced more than 100 years ago.

The best known and effective methods for the reduction of the negative effects of an alkali–silica reaction in concrete include the application of mineral additives with an increased aluminium content and reduced share of calcium, as well as chemical admixtures in the form of lithium compounds. Because both aluminium and lithium ions increase the stability of reactive silica in the system with alkalis, it is possible to presume that the application of both corrosion inhibitors together will provide a synergistic effect in the ASR limitation. The paper presents the results of studies on the influence of combined application of metakaolin and lithium nitrate on the course of corrosion caused by the reaction of opal aggregate with alkalis. The potential synergistic effect was studied for the recommended amount of lithium nitrate, i.e., the Li/(Na + K) = 0.74 molar ratio and 5%, 10%, 15%, and 20% of cement mass replacements with metakaolin. The effectiveness of the applied solution was studied by measurements of mortars expansion in an accelerated test, by microstructure observations, and by determination of the ASR gels composition by means of SEM-EDS. The influence of metakaolin and the chemical admixture on the compressive and flexural strengths of mortars after 28 and 90 days of hardening were also analysed. The results of the studies revealed a synergistic effect for mixtures containing metakaolin at 15% and 20% cement replacement and lithium nitrate admixture in alkali–silica reaction expansion tests. It was found that corrosion processes in mortars with 5 and 10% levels of metakaolin became more severe after adding a lithium admixture to mortars with metakaolin only. The obtained results were confirmed by observations of the mortars’ microstructures. There was no synergistic impact of lithium nitrate and metakaolin on compressive strength characteristics. The compressive strength of mortars containing a combination of metakaolin and lithium nitrate decreased both after 28 and after 90 days, compared to mortars with metakaolin alone.

This study examined the physical properties of a three-component mineral binder that is typically used in deep-cold recycling. Test binders were produced using Portland cement, hydrated lime, and cement bypass dust (CBPD) as a byproduct derived from cement production. The suitability of CBPD for use in road binders was assessed. Effects of the three-component binder composition on the setting time, soundness, consistency, and tensile and compressive strengths of the cement pastes and mortars were determined. The pastes and mortars of the same consistency obtained at different w/b ratios were tested. On this basis, the mixture proportions resulting in road binders satisfying the requirements of PN-EN 13282-2:2015 were determined. By mixing cement, lime, and CBPD during the tests, binder classes N1 to N3 were obtained. The replacement of 40% of cement mass with the CBPD high in free lime produced road binders suitable for recycled base layers. The total content of CBPD and hydrated lime in the road binder should not exceed 50% by mass. The potential risk of mortar strength reduction due to KCl recrystallization was discussed.

The study analyzed the possibility of using the acoustic emission method to analyse the reaction of alkali with aggregate in the presence of lithium nitrate. Lithium nitrate is a chemical admixture used to reduce adverse effects of corrosion. The tests were carried out using mortars with reactive opal aggregate, stored under the conditions defined by ASTM C227. The acoustic activity of mortars with a corrosion inhibitor was referred to linear changes and microstructure of specimens in the initial reaction stages. The study found a low acoustic activity of mortars with lithium nitrate. Analysis of characteristic parameters of acoustic emission signals, combined with the observation of changes in the microstructure, made it possible to describe the corrosion processes. As the reaction progressed, signals with different characteristics were recorded, indicating aggregate cracking at the initial stage of the reaction, followed by cracking of the cement paste. The results, which were referred to the acoustic activity of reference mortars, confirmed that the reaction of opal aggregate with alkali was mitigated in mortars with lithium nitrate, and the applied acoustic emission method enabled the detection and monitoring of ASR progress.