International Concrete Abstracts Portal

Coal bottom ash (CBA) remains underutilized as a cement replacement due to its low pozzolanic reactivity. This study provides the first systematic, side-by-side comparison of a hierarchy of pre-treatment methods – disk milling, ball milling, single alkaline activation, and multi-compound activation – within CBA coal fly ash (CFA) blended cements. Three composite mixes with up to 50% replacement of ordinary Portland cement (OPC) were developed and characterized. Ball milling emerged as the most effective mechanical treatment, reducing particle size to approximately 15 μm. Multi-compound activators (〖Na〗_2 〖SiO〗_3:NaOH= 2:1) outperformed single activators, increasing 28-day strength by up to 29%. A mixture containing 20% ball-milled CBA and 20% CFA achieved a 28-day compressive strength of 37.6 MPa, comparable to the pure OPC control mix (37.8 MPa). Microstructural analysis confirmed denser C-S-H and C A S H gel formation with reduced porosity. Combining ball-milled CBA with CFA enables high cement replacement without compromising compressive strength. Durability and long-term performance remain subjects for future investigation.

Tunnel excavation generates vast mineral waste, traditionally landfilled as inert spoil. This study presents a green, circular process for its integrated valorization, converting muck into secondary aggregates, sand, and powders for high-performance, low-carbon concrete. Five lithologies were evaluated to decouple chemical (powder) and physical (aggregate) roles. Micro-scale analysis revealed lithology-dependent mechanisms: carbonate powders (dolomite, limestone) acted primarily as nucleation sites, accelerating hydration, while siliceous powder (tuff) exhibited pozzolanic reactivity. These mechanisms governed macro-scale performance, correlating with hydration degree, silicate chain length, and capillary porosity. The dolomite-based system showed the highest synergy, yielding concrete with 6 to 7% higher compressive strength, alongside 25% lower carbon emissions and 27 to 29% cost reduction versus the conventional benchmark. A consequential, EN 15804-compliant life cycle assessment incorporated credits for avoiding virgin aggregate extraction and landfilling. Multi-criteria decision analysis confirmed dolomite as the top-ranking resource, balancing superior mechanical performance with the lowest environmental and economic footprints. This work provides a scientifically grounded strategy to transform tunnel muck into a cornerstone resource for sustainable construction.

Lined rock cavern (LRC) hydrogen storage requires concrete linings with high tensile ductility and stable crack-control capacity under circumferential tension. Although polyvinyl alcohol (PVA) fibers exhibit high tensile strength and good alkali resistance, their hydrophilicity may induce a loose interfacial transition zone (ITZ), thereby limiting effective fiber bridging. This study proposes a cost-effective fiber-surface modification strategy by combining polydopamine (PDA) with nano-CaCO3. Unlike conventional single surface-treatment methods, the proposed system simultaneously introduces a protective slip-buffering layer and a mineral particle-enhanced ITZ. The PDA layer serves as an adhesive carrier and a protective slip layer, reducing direct abrasion between the fiber and cementitious matrix during interfacial sliding. Meanwhile, nano-CaCO3 particles anchored on the PDA layer increase fiber-surface roughness and provide nucleation/filling sites for hydration products, promoting ITZ densification and stronger mechanical interlocking. SEM and FTIR results confirm the successful formation of the PDA/nano-CaCO3 coating, while tensile tests and DIC analysis show that the modified fibers promote stable strain hardening and more uniform multiple cracking. Numerical simulation further indicates that the improved HDC lining can disperse localized cracking and alleviate damage transfer to the surrounding rock. These results demonstrate that the PDA-assisted nano-CaCO3 modification provides an effective physicochemical route for enhancing PVA fiber-reinforced HDC used in LRC hydrogen storage.

The standard four-point bending test (ASTM C1609) for fiber-reinforced concrete (FRC) quality control is hindered by large specimens and complex setups. This study evaluates the Montevideo (MVD) test on cubic specimens as a simpler alternative by establishing a correlation between the two tests. An analytical model, based on rigid-body rotation, was developed and validated against an experimental program comprising ten FRC mixtures with various synthetic fibers, tested in Uruguay and Mexico. Results demonstrated a strong linear correlation (R2 ≈ 0.84) between the residual forces of both tests, yielding an experimental transformation factor (k4PB) of 4.4. This value showed excellent agreement (2% difference) with the theoretical derivation. A simplified equation to estimate equivalent ASTM C1609 flexural stress from MVD results is proposed. The MVD test, supported by a validated factor of 4.4, is concluded to be a reliable and practical alternative for routine FRC quality control.

Most of the provisions for concrete structural walls in ASCE/SEI 41-17 were developed in the late 1990s based on limited experimental data and judgment for FEMA-273 (1997a) and FEMA-274 (1997b). The only exception being the modeling parameters and acceptance criteria of shear-controlled walls, which were updated for ASCE/SEI 41-06 Supplement 1 (Elwood et al., 2007). As a result, the wall provisions tend to be, in many cases, inaccurate and conservative, and thus can produce uneconomical retrofit schemes. This study involves utilizing available experimental data from a large wall test database (more than 1,100 wall tests) and new information on the performance of structural walls to develop modeling parameters and acceptance criteria for diagonal shear-controlled walls that will produce improved seismic assessments of wall buildings. Assessment outcomes between the provisions of ASCE/SEI 41-17 and the proposed provisions showed that the current provisions in ASCE/SEI 41-17 are, in many cases, overly conservative for many structures.