The objective of this work was finding out the most advisable testing conditions for an effective and robust characterization of the tensile strength (TS) of concrete disks. The independent variables were the loading geometry, the angle subtended by the contact area, disk diameter and thickness, maximum aggregate size, and the sample compression strength (CS). The effect of the independent variables was studied in a three groups of experiments using a factorial design with two levels and four factors. The likeliest location where failure beginning was calculated using the equations that account for the stress–strain field developed within the disk. The theoretical outcome shows that for failure beginning at the geometric center of the sample, it is necessary for the contact angle in the loading setup to be larger than or equal to a threshold value. Nevertheless, the measured indirect tensile strength must be adjusted to get a close estimate of the uniaxial TS of the material. The correction depends on the loading geometry, and we got their mathematical expression and cross-validated them with the reported in the literature. The experimental results show that a loading geometry with a curved contact area, uniform load distribution over the contact area, loads projected parallel to one another within the disk, and a contact angle bigger of 12° is the most advisable and robust setup for implementation of BT on concrete disks. This work provides a description of the BT carries on concrete disks and put forward a characterization technique to study costly samples of cement based material that have been enabled to display new and improved properties with nanomaterials.

The objectives of this research were to study (1) the dispersion of MWCNTs in an aqueous system by three commercial admixtures (CAds) for concrete, and (2) the effect of CAds and MWCNTs on indirect tensile strength and electrical conductivity of MWCNTs-high early strength (HE) cement-mortar composites. To achieve the objectives, we dispersed MWCNTs in an aqueous system with (1) hydroxylated polymers-based water reducing plasticizer (HPs), a nonionic compound, (2) Naphthalene based superplasticizer (SNF), an anionic compound, and (3) calcium chloride-based accelerating agent (CC) a neutral amphoteric salt. We prepared a total of 242 samples grouped in three sets: (1) Plain mortar [PM] (water + HE cement + Sand), (2) [PM+CAd], and (3) [PM+CAd+MWCNTs]. The three CAds dispersed MWCNTs in an aqueous solution. The CC and HPs admixtures have a two-time bigger dispersing power than the SNF. They demand half of SNF's ultrasound energy for optimal dispersion. Although the SNF (anionic) based superplasticizer resulted incompatible with the HE cement, it improved the indirect tensile strength of [PM+SNF+MWCNTs] composite. In contrast, the CC (amphoteric) based accelerating agent was compatible with the HE cement; the CC adsorption on the MWCNTs surface favors an improvement in the electrical conductivity of [PM+CAd+MWCNTs] composite.

This study presents the development of an eco-friendly brick for mining, a sustainable composite material manufactured from gold mine tailings and used cooking oil (UCO) through a thermal oxypolymerization process. Unlike conventional stabilization methods, which often require additional materials beyond tailings or have a high carbon footprint in their production, this approach uses oxypolymerization to transform these two waste products into novel building materials. The use of various percentages of UCO at different heating temperatures was evaluated to identify the optimal mixture, determining that a 9% UCO content and a 9 h cycle are key conditions for inducing fatty acid crosslinking. This logical relationship between heat treatment and dosage allows the organic binder to consolidate the mineral matrix, giving the material a compressive strength of 19.12 MPa and a flexural strength of 8.24 MPa, exceeding the thresholds of the NTE INEN 297 standard. The low water absorption (2.86%) is attributed to the densification of the matrix and the hydrophobic nature of the polymerized oil, indicators of its structural durability. This work is the first to use Ecuadorian tailings as the sole mineral aggregate, validating a high-efficiency, low-impact product for sustainable construction under the principles of the circular economy.

Traditional masonry production is energy intensive and faces significant construction challenges, driving the need for modern brick wall materials that incorporate technological advances through safe, cement-free, and unbaked alternatives. Alkali-activated geopolymers derived from mine tailings represent a promising solution for sustainable construction. This systematic review, conducted according to PRISMA 2020 guidelines across Web of Science, Scopus, and IEEE Xplore, identified 1131 records and selected 16 primary reports (15 independent studies). The findings reveal a predominance of iron (n = 10) and copper (n = 5) tailings, primarily activated using binary systems (Na₂SiO₃ + NaOH). Ambient curing (n = 10) proved effective for producing high-performance units (compressive strength ranging from 5.48 to 50.53 MPa) without requiring continuous heat treatment. The addition of reactive co-precursors compensates for the low reactivity of the tailings, while leaching tests confirm the effective immobilization of heavy metals. By meeting structural and building envelope requirements such as load bearing capacity, dimensional stability, and durability, these waste materials successfully substitute for virgin raw materials in wall construction. In conclusion, geopolymer technology addresses key construction challenges, fostering decarbonization and the circular economy.

This research studies the manufacture of a composite material based on gold mine tailings and metakaolin as a novel construction material through a geopolymer process. Geopolymers, derived from aluminosilicate-rich mining waste, offer a promising alternative to traditional construction materials by mitigating environmental pollution and reducing production costs. Different combinations and solution contents were used, with sodium hydroxide as the alkaline activator at different molarities and temperatures of 70°C and 110°C. To determine the optimal mixture, an indirect tensile test was performed to determine the optimization factor (Fopt), which resulted in a mixture of 60% tailings and 40% metakaolin in a 24% solution at a concentration of 6 molar and 110°C. Using the optimal mixture, brick tiles were manufactured, which were tested under simple compression, achieving a resistance of 6MPa; the specimens were also tested using the flexural strength test, obtaining a result of 11MPa, thus complying with the Ecuadorian standard for their use as a construction material.