This study investigates the effects of substituting fine aggregates with recycled plastic in recycled concrete, focusing on chloride penetration, compressive strength, workability, and porosity. Recycled plastic was incorporated at 10% (A10) and 20% (A20) by volume, and properties were evaluated across six mix designs. The control mix without plastic (Mix A) achieved the highest 28-day compressive strength (400 KSC), while A10 and A20 showed reduced strengths of 320 and 255 KSC, respectively. The addition of plastic increased mix porosity, resulting in reduced strength and workability due to diminished cement bonding and lubrication. Chloride ingress was assessed under cyclic wetting–drying exposure using a 3.5% NaCl solution. Results revealed progressive surface chloride accumulation over time. Notably, Mix A showed a 137.96% increase in chloride content at a 0–2 cm depth after 280 days, with Mix A20 exhibiting even higher surface concentrations. Chloride content consistently decreased beyond a 4 cm depth, indicating limited long-term penetration into inner layers. These findings highlight the importance of porosity control in mitigating chloride transport in recycled concrete. A clear relationship between plastic content, increased porosity, and enhanced chloride diffusion was observed. While 10% plastic substitution demonstrated acceptable performance, higher levels significantly compromised durability. The study recommends limiting plastic waste incorporation to 10% by volume and maintaining a concrete cover of at least 8–10 cm over reinforcement to enhance resistance against chloride-induced corrosion. These findings support the controlled reuse of plastic waste in sustainable concrete development, particularly for non-structural or low-exposure applications. Optimizing mix design and incorporating supplementary cementitious materials are suggested to improve long-term durability.

This paper aims to study the development of bricks without burning, mixing para rubber latex, and compressing them with the technology of interlocking block production. The ratio of cement, lateritic soil, and water used in the mix was 1:6:11, while the percentage of para rubber latex (PRL) added was 2.5, 5, 7.5, 10, and 12.5% of the cement weight. The optimal PRL content (2.5%–7.5% by cement weight) enhances compressive strength, reduces water absorption, and improves durability, meeting the Thai industrial standard (TIS 77-2545). The PRL7.5 mixture achieved the highest performance, with a compressive strength of 21.42 MPa and a water absorption rate of 7.55%. These advancements are credited to the polymer film network formed from PRL during the hydration process, which strengthens particle bonds and reduces porosity. However, PRL content exceeding 7.5% leads to performance reductions, attributed to thicker polymer films and particle aggregation, which create larger voids within the material. Furthermore, the modified unfired bricks demonstrated enhanced crack resistance, increased ductility, and superior thermal insulation properties. Thermal tests of masonry walls confirmed that unfired bricks provide better thermal insulation. Temperature measurements revealed that houses constructed with unfired bricks consistently maintained cooler indoor temperatures compared to those made with fired bricks, indicating improved thermal efficiency. Environmentally, unfired bricks eliminate carbon emissions from firing processes and offer simpler, more energy-efficient production methods. These bricks provide sustainable alternatives to fired bricks, promoting both environmental and economic benefits for brick-making communities. Doi: 10.28991/CEJ-2024-010-12-05 Full Text: PDF

Open burning of agricultural residues remains a significant source of air pollution and greenhouse gas emissions in Southeast Asia. This study evaluated a community-scale smokeless vertical charcoal kiln for biochar production from corncob residues under practical operating conditions. Carbonization at 415–435 °C for 150–180 min produced biochar yields of 23.3–28.3%, with the 150 min treatment giving the highest yield. The biochar exhibited high carbon content (71–71.5%), low volatile matter (15.7–16.7%), fixed carbon content of 51–54%, and moderately alkaline pH (8.97–9.08). Atomic H/C and O/C ratios (approximately 0.55 and 0.27) indicated moderate aromaticity and stability consistent with IBI Class 1 criteria, while SEM revealed a macropore-dominated porous structure. Theoretical carbon sequestration potential was estimated at 0.69–0.74 tCO₂-eq per tonne of dry feedstock. These findings demonstrate the technical feasibility of community-scale smokeless biochar production and provide physicochemical characterization of the resulting biochar, suggesting potential relevance for carbon storage and soil amendment; however, agronomic performance and emissions require direct evaluation, and results are specific to corncob feedstock. Overall, this work contributes to sustainable agricultural waste management by demonstrating a low-cost, community-accessible pathway that simultaneously supports climate change mitigation, air quality improvement, and socio-economic accessibility for smallholder farming systems in Southeast Asia.