Open Access

A long-term study was conducted on double-lap spruce wood-concrete joints to investigate their shear strength and stiffness over a 12-month period. These joints were manufactured using both wet and dry processes, each incorporating two adhesive types for bonding the wood to the concrete: a brittle epoxy and a ductile polyurethane (PUR). The experimental design exposed the joints to three specific long-term environments: (1) outdoor exposure, (2) indoor conditions with applied load, and (3) outdoor conditions with applied load. The wood concrete joints exposed to outdoor conditions were subjected to destructive shear testing at intervals of 0 (serving as the reference sample), 2, 4, 6, and 12 months, respectively. For joints subjected to both indoor and outdoor conditions with shear loading, the shear deformation of joints was monitored continuously over the 12 months before performing the destructive tests. A gradual reduction in the shear stiffness and strength of dry joints (produced using the dry bond method) exposed to outdoor conditions was observed over a 12-month period, primarily due to bond failure at the concrete-adhesive interface. The wet joints exhibited no degradation in shear stiffness and strength across long-term conditions over the same period. The bond failure observed in dry joints was predominantly associated with stresses arising from dimensional changes in the wood. No degradation was found in the cross-linking density of the adhesive or in the concrete’s compressive stiffness and strength.

Concrete is the most widely used construction material accounting for approximately half of all human production throughout history. The production of one ton of cement emits around 600 kg of CO2. With a global cement production estimate of 4.2 billion tons, this results in about 2.5 billion tons of CO2 emissions. This accounts for roughly 7.2% of the total global carbon emissions in 2021. Strategies to decrease carbon emissions in the cement and concrete industry include carbon capture and storage (CCS), reduced binders like ordinary Portland cement (OPC) clinker and optimizing material use through improved processes and structural design. This also means changing architectural vision [6], avoiding concrete where its structural performance is not required and use alternative materials instead, and optimizing the communication among the entire production value chain.

This study investigates the influence of bio-admixtures and bio-ashes from agricultural and aquaculture residues on the workability and strength of cement mortars. While bio-admixtures at low concentrations can enhance the strength, they create similar or lower yield stress as the reference. Bio ash, particularly at a 10% replacement level, maintained good strength, but higher replacements led to significant reductions in both strength and workability. These findings highlight the potential of sustainable construction materials but emphasize the need to balance performance specifications.

This study investigates the potential of bio-admixtures derived from Sargassum Natans (SN1E, SN2E), Sargassum fluitans (SFE), water hyacinth (WHE), miscanthus grass (ME), and plantain stem (PSE) as sustainable alternatives to polycarboxylic ether (PCE) superplasticizers in cement-based materials. The research examines their effects on rheology, hydration, microstructure, and mechanical properties to assess their suitability for eco-friendly construction applications. Cement pastes and mortars incorporating 0.1% and 1% bio-admixture dosages were analyzed using isothermal calorimetry, thermogravimetric analysis (TGA/DTG), static yield stress measurements, and compressive strength testing at 7 and 28 days. Results indicate that all mixtures containing admixtures exhibited lower initial yield stress values, indicating a liquefying effect initially. At 0.1% dosage, the admixtures exhibited comparable or slightly improved compressive strength relative to the reference (REF), with no significant losses. However, at 1% dosage, PCE, WHE, ME, and PSE showed notable strength reductions, particularly ME, which significantly impaired both 7-day and 28-day strengths. Hydration studies revealed that bio-admixtures exhibited lower retardation effects compared to PCE, with SN1E, SN2E, and SFE promoting early hydration and portlandite (CH) formation. Conversely, ME and PSE exhibited delayed hydration, leading to lower early-age strengths but a more sustained hydration process over time. Thermal analysis further confirmed these trends, with bio-admixture-modified pastes maintaining stable hydration profiles, while PCE exhibited the strongest retardation effect, as evidenced by its lower total weight loss, and reduced CH content. These findings highlight the potential of bio-admixtures as sustainable modifiers in cementitious materials, providing workability benefits while minimizing hydration delay, making them promising candidates for green construction.