Constr. Mater., Volume 2, Issue 1 (March 2022) – 5 articles

Blast furnace slag (BFS) is a mortar additive in which the utilization of varied curing conditions and the basicity of BFS determine the fineness of the resulting mortar and, thereby, its salt prevention properties. This study evaluates and compares the salt-prevention properties of mortar prepared by either steam curing or water curing. The physical properties, for example, the BFS fineness, revealed the factors significantly affected by basicity that influence the salt-preventive properties of mortar in the specimens examined, such as the lead time and diffusion coefficient. Furthermore, these factors were also significantly affected by differences in curing conditions and other physical properties. However, few studies have examined its use in reducing chloride ion permeability as the main factor of corrosion reactions. Thus, this study evaluates specific surface, water/binder ratio (W/B), and curing conditions on the chloride penetration in cementitious materials with blast furnace slag as cement addition in terms of delaying chloride ion penetration, which affects corrosion reactions. Results of the study are intended to guide development of products for use in the precast concrete industry, toward extending the life of concrete structures, especially reinforced concrete structures in marine environments. In addition, the resulting durability measurements from the experiment conducted are illustrated. This study indicates that differences in Blaine size properties significantly influence water curing. Furthermore, results reveal the effects of combining BFS with various Blaine values and ratio-affecting properties on mortar. In conclusion, concrete materials that decrease durability against chloride attack and improve mechanical properties for precast manufacturer industrial applications are successfully developed in this study. In addition, the use of water-curing conditions, high Blaine value, high cement replacement ratio, and W/B tend to improve the general mechanical property performance and durability against chloride ion attack. Full article

Over the last two decades, there was been intensive study of pozzolans on the surface of the Los Frailes Caldera (Spain) for possible use as construction materials; however, research into the deepest underlying horizons has not yet been done. The main object of this paper is to present the results of the research carried out at different levels of depth, down to 30 m, to locate and demonstrate the presence of pozzolans in the depths of the Los Frailes Caldera. To achieve this, a series of analyses were carried out to classify the samples extracted from the various levels of depth, starting at the surface and continuing down to 30 m, which consisted of XRD, XRF, and SEM. Other technological tests were also performed such as chemical analysis of pozzolanic quality (CAQP) and pozzolanicity (PT) tests, at 8 and 15 days. Lastly, a geophysical study using electrical resistivity tomography (ERT) was developed to define the thickness and physical properties of the horizons of pozzolanic materials at depth, as well as to establish the depth of the deposit. The results obtained by XRD, XRF, and SEM confirmed the presence of pozzolans consisting of strongly zeolitized and bentonitised tuffs (ZBVT) in the lower levels of the Los Frailes Caldera, indicating that these horizons continue uninterruptedly beyond 30 m deep. The results of the CAQP and PT established that the ZBVTs that lie in the depths have pozzolanic qualities. On the other hand, the ERT study showed that ZBVT levels continue into the depths, thus proving that the lower limit of the deposit is even deeper. The results obtained in this work could have a positive impact on an increase in the reserves of pozzolanic raw materials in the researched area and could be used in the manufacture of light aggregates for mortars, concretes, and pozzolanic cements, consistent with the environment and effective in reducing CO₂ emissions during the production process. Full article

The construction sector is currently challenged by environmental concerns, reducing energy consumption, and optimising the use of raw materials, hence the need to use new technologies and materials that have a better lifecycle performance. Recycling end-of-life materials or using industrial by-products is a solution in which resources are used efficiently. The considerable contribution of the production of hydraulic lime mortars to the environment, especially in relation to carbon dioxide emissions, is noteworthy. The study and use of nanotechnology and by-products, such as microgranulated corks, are solutions for more sustainable options, as they are more durable, and their properties are similar to conventional mortars. In this study, we explored the environmental benefits of mortars; to this end, we added different percentages of nano-TiO₂ and microgranulated cork that can be used in the production of mortars based on hydraulic lime but with antifungal properties. With the analysed results, we verified that these two additives, besides presenting benefits regarding antifungal properties, are viable alternatives to chemical biocides and sustainable options for the mortar industry to improve its environmental performance. The best environmental performance is obtained with mortar with 2% microgranulated cork. Full article

Due to routine maintenance of aircraft on the concrete pavement at army airbases, a large part of the pavement surface is often found saturated with different hydrocarbon-based oil, fuel, and fluid. In addition, the pavement concrete is subjected to the aircraft’s exhaust temperature during operation. This study examined the resistance ability of 3 different cementitious materials: (i) epoxy, (ii) fly ash (FA) based geopolymer with various alkali to fly ash (AL/FA) ratios and (iii) Portland cement (PC) mortar under a simulated airfield circumstance. The mortar specimens were repetitively exposed to a mixture of synthetic engine oil, hydraulic fluids, jet fuel and elevated temperatures (175 °C) for 5 months simultaneously. During the exposures, geopolymer and PC mortar both suffered saponification. The degree of saponification of geopolymer samples is found to be highly reliant on the AL/FA ratios. On the contrary, the epoxy mortar was found to be resistant to saponification. It was also found that the PC mortar developed numerous thermal cracks but epoxy and geopolymer did not experience any visual thermal cracks under the same conditions. Full article

This paper examines the influence of biochar on the properties of alkali-activated slag pastes using two activator solutions, namely NaOH and Na₂CO₃. The biochar demonstrated different absorption kinetics in the mixture of slag and the two activator solutions. The pastes with biochar showed a delay in the heat flow peak, compared to the pastes without biochar, but the cumulative heat release in these pastes at later hours was increased, compared to the pastes without biochar. It was found that the use of biochar reduced autogenous shrinkage in the pastes and the reduction in autogenous shrinkage was more pronounced in the alkali-activated slag with NaOH, compared to Na₂CO₃. The void structure of the pastes was investigated using x-ray micro-computed tomography. It was found that refined pore structure due to reduced effective solution/slag in the pastes with biochar was able to compensate for the decreasing effect of biochar voids on compressive strength. The electrical resistivity was shown to be lower in the pastes with biochar. Full article