Key Engineering Materials Vol. 1026

Abstract: Over the years, plastic production has increased in direct proportion to the amount of plastic waste generated globally. Single-use plastics such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and polypropylene (PP) have increased significantly. Therefore, they can be used as aggregates in the production of concrete to reduce the generation of plastic waste in the environment. LDPE, LLDPE and PP were the plastic types used, with 25% and 50% of plastic aggregate replacing sand. The tests included Fourier-transform infrared spectroscopy (FTIR) analysis of the plastic granulate, density, and compression tests of the concrete specimens. The type of granulate used follows the type of plastic tested from the results of the FTIR characterization. It was found that the compressive strength of concrete containing 25% of plastic aggregates was higher than that of concrete containing 50% of plastic aggregates. The compressive strength of the LLDPE concrete specimens is 31.4 MPa, whereas the compressive strength of the LDPE concrete specimens is only 26.3 MPa and that of the PP concrete specimens is 30.4 MPa. Further research will be carried out to determine the optimum strength of concrete with plastic aggregates.

Abstract: This study explores the potential of self-healing concrete with bacteria encapsulated in calcium lactate and expanded clay (LECA) to enhance the durability and strength of concrete structures. The effect of encapsulating Lysinibacillus sphaericus bacteria in LECA on the mechanical properties of concrete was investigated, including compressive and tensile strength. Calcium lactate acts as a precursor and nutrient source for the biomineralization process through Microbially Induced Calcium Carbonate Precipitation (MICP). Experimental results demonstrate that concrete with bacteria encapsulated in LECA exhibits a significant increase in compressive strength compared to conventional concrete and concrete containing non-encapsulated bacteria. This increase is attributed to the protection provided by LECA to the bacteria and calcium lactate, promoting their self-healing activity and improving the concrete's ability to withstand loads. An increase in compressive load was observed for design DR-5 compared to DR-0 (control), with increments of 3.40%, 0.21%, and 6.92% on days 7, 14, and 28, respectively. However, challenges were identified regarding tensile strength, as design DR-5 was initially lower than design DR-0 by 24.25% and 19.51% on days 7 and 14, respectively. Nonetheless, on day 28, design DR-5 surpassed the control design by 1.45%. This study concludes that the encapsulation of bacteria in LECA, along with calcium lactate as a nutrient source, is a promising strategy for enhancing the performance of self-healing concrete, opening new avenues for research and applications in sustainable construction.

Abstract: This work presents interesting results on the manufacturing and mechanical response of new mixtures for geopolymeric mortars using soils collected from sites near the Khapia hill located in the Puno region (Peru). Four types of soils were collected and used as binder raw material within a geopolymeric mortar mixture with a binder: sand ratio of 1:3. In parallel and for comparative purposes, the mechanical response of conventional Portland cement mortars was manufactured and evaluated, with a binder: fine sand volumetric ratio also of 1:3. To obtain the geopolymeric mortars, the sodium hydroxide solution with a molarity of 12 was considered as the liquid phase. While for the conventional Portland cement mortar, water was used. For all cases, the liquid phase: binder ratio was 0.6. The mechanical results were variable, with maximum average mechanical strength values between 30.1 and 45.4 MPa for geopolymeric mortars and 37.4 MPa for conventional mortars. On the other hand, Young's modulus values were found between 5.9 and 10.4 GPa for geopolymeric mortars and 8.8 GPa for conventional mortars. Regarding the porosity estimated from real and apparent densities, values between 27.2 and 28.3 % were found for geopolymeric mortars and 30.2 % for conventional mortars. The microstructure found for both types of mortars studied was very similar, all mortars consisted of two well-identified phases, a continuous and homogeneous phase of binder (geopolymeric or Portland cement) that surrounded another dispersed phase of aggregate particles (fine sand).

Abstract: The application of modular systems is one of the new technologies worth considering. The modular system is a prefabricated steel structure where the floor decks, columns, beams, and walls are fabricated along with the utility system, mechanical-electrical, and finishing in one modular. The benefits of this system are constructability, positive aspects towards schedule, fewer on and off-site workers, quality and productivity aspects, and proper tests. A total solution is needed in the form of steel-based construction modular growing houses to support the National Development Program. Joint research is needed between Universities and Local Industries to produce technological innovations with high Domestic Component Levels in implementing the use of materials and steel manufacturing processes. The Krakatau Steel-Institut Teknologi Sepuluh Nopember (KSITS) Steel Modular Growing House Design is a steel-based construction that supports in a fast, precise, quality manner; and becomes a contributor in absorbing various locally produced steel products. From the analytical study and modeling of steel modular, the results showed that KSITS Steel Modular Growing House Design has fulfilled the requirements of structural and connection strength, serviceability control, management construction procedures, economical engineering, and manufacturing design in operational planning for the short-term and development of local steel technology downstream industries in the future. The results showed minor differences in ratios, with WF steel slightly surpassing HSS steel. HSS steel stands out due to its significantly lighter weight compared to WF steel, impacting structural dynamics and feasibility in modular house construction. This indicates that the moment capacity of HSS is lower than the moment capacity of WF. However, from the results of running, it is found that the criteria are the same, all components other than the beam, do not experience yielding prior to yielding in the beam. It means that the connection works properly according to the criteria.