Physicomechanical and Antimicrobial Characteristics of Cement Composites with Selected Nano-Sized Oxides and Binary Oxide Systems

In recent years, increasing attention has been paid to the durability of building materials, including those based on cementitious binders. Important aspects of durability include the increase of the strength of the cement matrix and enhancement of material resistance to external factors. The use of nanoadditives may be a way to meet these expectations. In the present study, zinc, titanium and copper oxides, used in single and binary systems (to better the effect of their performance), were applied as additives in cement mortars. In the first part of this work, an extensive physicochemical analysis of oxides was carried out, and in the second, their application ranges in cement mortars were determined. The subsequent analyses were employed in determining the physicochemical properties of pristine oxides: Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray fluorescence (EDXRF), scanning electron microscopy (SEM), measurement of the particle size distribution, as well as zeta potential measurement depending on the pH values. Influence on selected physicomechanical parameters of the cement matrix and resistance to the action of selected Gram-positive and Gram-negative bacteria and fungi were also examined. Our work indicated that all nanoadditives worsened the mechanical parameters of mortars during the first 3 days of hardening, while after 28 days, an improvement was achieved for zinc and titanium(IV) oxides. Binary systems and copper(II) oxide deteriorated in strength parameters throughout the test period. In contrast, copper(II) oxide showed the best antibacterial activity among all the tested oxide systems. Based on the inhibitory effect of the studied compounds, the following order of microbial susceptibility to inhibition of growth on cement mortars was established (from the most susceptible, to the most resistant): E. coli < S. aureus < C. albicans < B. cereus = P. aeruginosa < P. putida.

Few-Layers Graphene-Based Cement Mortars: Production Process and Mechanical Properties

Cement is the most-used construction material worldwide. Research for sustainable cement production has focused on including nanomaterials as additives to enhance cement performance (strength and durability) in recent decades. In this concern, graphene is considered one of the most promising additives for cement composites. Here, we propose a novel technique for producing few-layer graphene (FLG) that can fulfil the material demand for the construction industry. We produced specimens with different FLG loadings (from 0.05% to 1% by weight of cement) and curing processes (water and saturated air). The addition of FLG at 0.10% by weight of cement improved the flexural strength by 24% compared to the reference (bare) sample. Similarly, a 0.15% FLG loading by weight of cement led to an improvement in compressive strength of 29% compared to the reference specimen. The FLG flakes produced by our proposed methodology can open the door to their full exploitation in several cement mortar applications, such as cementitious composites with high durability, mechanical performance and high electrical conductivity for electrothermal applications.

Performance of Alfa Fibres in Cementitious Materials Exposed to Diverse Surface Treatments

Alfa plant presents a great ecological and socio-economic interest in the Maghreb countries. It is used in several fields of applications such as craft production and paper industry. However, a few research work has been realized on the valorisation of Alfa fibres in the construction sector. The main objective of this work is to develop an Alfa fibre-reinforced mortar with significant mechanical properties for the facade panel’s manufacturing. It was highlighted that Alfa fibres enhance the flexural strength of reinforced mortars. Therefore, a decrease in the flexural strength of the composite after 90 days of curing. In addition, the incorporation of Alfa fibres reduced the compressive strength of the composite. In this regard, to enhance the mechanical properties of the composite, various treatments were explored: alkaline treatment with sodium hydroxide, hydrothermal treatment by water boiling, and coating with sulfoaluminate cement. It was noted that the treatments could provide a partial elimination of the non-cellulosic components and enhance the Alfa fibre roughness. Raw and treated Alfa fibres were incorporated into cement mortars at different lengths of the (10 and 20 mm) with an addition ratio of 1 %vol.. Compared to untreated fibres, fibres treated chemically provide an improvement of 38 % of the flexural strength at 28 days for both fibres length. Unlike the coated fibres, the efficiency of treatment was noted at 90 days of curing. Otherwise, a slight increase in compressive strength was observed compared to the untreated fibres mortar. These results were approved by porosity accessible to water and calorimetric tests.

Alkaline activation of mortars made from solid construction waste [Activación alcalina de morteros fabricados a partir de residuos sólidos de construcción]

In the present investigation the influence of the percentage by weight of replacement of portland cement (PC) by recycled concrete powder (RCP), alkaline activated, in percentages of 10%, 20%, 30%, 40% and 50%, was evaluated. which were selected from construction rubble left in the Buenos Aires spa, Víctor Larco Herrera district, Trujillo province. After being washed, they went to the grinding and sieving process (400 mesh), using only the through material. Specimens were manufactured according to the ASTM C-109 standard for the compression test in cement mortars, for the alkaline solution NaOH (4M) was used. The mortars obtained were cured in an oven at 70 ° C for 72 hours, and subsequently the curing was completed at room temperature, for a total time of 28 days. The results of the average compression test were 12.15 MPa, in the case of the PC mortar and 14.25 MPa in the best case (PC mortar and RCP-10%), the increase being 17.28%. The mix design using coarse sand and binder was kept constant at (3: 1), while the water / cement ratio (w / c) was 0.6 in all cases. The reason for the increase in compressive strength is due to the reaction between the RCP particles, alkaline solution and the calcium hydroxide produced during the hydration of the cement particles, which generate gels (CASH), which occupy the spaces left by the hydration process of the aforementioned cement particles, as they need calcium hydroxide. For all cases of the compression test, a total of 10 repetitions were carried out.

Creep and Shrinkage Behaviour of Disintegrated and Non-Disintegrated Cement Mortar

One way to prevent cement from ending up in landfills after its shelf life is to regain its activity and reuse it as a binder. As has been discovered, milling by planetary ball mill is not effective. Grinding by collision is considered a more efficient way to refine brittle material and, in the case of cement, to regain its activity. There has been considerable research regarding the partial replacement of cement using disintegrated cement in mortar or concrete in the past few decades. This article determines and compares the creep and shrinkage properties of cement mortar specimens made from old disintegrated, old non-disintegrated, and new non-disintegrated Portland cement. The tests show that the creep strains for old disintegrated and old non-disintegrated cement mortars are close, within a 2% margin of each other. However, the creep strains for new non-disintegrated cement mortar are 30% lower. Shrinkage for old disintegrated and non-disintegrated cement mortar is 20% lower than for new non-disintegrated cement mortar. The research shows that disintegration is a viable procedure to make old cement suitable for structural application from a long-term property standpoint. Additionally, it increases cement mortar compressive strength by 49% if the cement is disintegrated together with sand.

Ground Waste Tire Rubber as a Total Replacement of Natural Aggregates in Concrete Mixes: Application for Lightweight Paving Blocks

The use of waste materials as alternative aggregates in cementitious mixtures is one of the most investigated practices to enhance eco-sustainability in the civil and construction sectors. For specific applications, these secondary raw materials can ensure adequate technological performance, minimizing the exploitation of natural resources and encouraging the circular disposal of industrial or municipal waste. Aiming to design and develop lightweight paving blocks for pedestrian or very light-traffic purposes (parking area, garage, sidewalk, or sports surfaces), this paper presents the material characterization of rubberized cement mortars using ground waste tire rubber (0–1 mm rubber powder and 1–3 mm rubber granules) to totally replace the mineral aggregates. Considering recommended requirements for concrete paving members in terms of mechanical strength, water drainage performance, acoustic attenuation, and dynamic and energy absorption behavior, a comprehensive laboratory testing is proposed for five different formulations varying the sand-rubber replacement level and the proportion ratio between the two rubber fractions. Tests highlighted positive and promising results to convert laboratory samples into pre-cast members. The “hot” finding of the work was to prove the feasibility of obtaining totally rubberized mortars (0 v/v% of sand) with suitable engineering performance and enhanced eco-friendly features.