International Concrete Abstracts Portal

Limestone calcined clay cement (LC3) has the potential to provide high clinker replacement in cement blends while providing excellent engineering properties and durability with low environmental impact, but such blends of clinker, limestone, and calcined clay are still in the industrial trial stage in the United States (US). In this study, it is proposed that sources of calcined clay (C), Type IL portland cement (IL), and additional limestone powder (L) can be blended into a “CC·I·L” cement to speed up the implementation of LC3-like systems in the US by combining already commercially available components during concrete mixing. In this investigation, regional CC·I·L blends were prepared using ASTM C595 Type IL cements and calcined clays, replacing 20% - 30% of the cement, from suppliers in the east, west, central, and mountain areas of the US, with additional ground limestone to reach a total limestone content of up to 15% by mass of the total cementitious system. To investigate the feasibility of this approach, fresh properties, early and late age performance, and durability of pastes and mortars made with the CC·I·L blends were examined and compared to ASTM C595 standard performance requirements and performance of regionally available Type IL cements. The results showed that 30% calcined clay and 15% limestone can be used to produce CC·I·L blends in each studied region to meet the ASTM C595 strength requirements. However, gypsum adjustment up to 5.0% was necessary to address undersulfation of CC·I·L blends in some of the regional blends. The results demonstrate the feasibility of using CC·I·L in the US without intergrinding, by taking into account key design factors such as the reactivity of calcined clays, sulfate balance, performance, durability, and possible environmental impact.

This study evaluated the performance of recycled brick-concrete aggregate concrete (RB-CAC) incorporating both recycled brick aggregate (RBA) and recycled concrete aggregate (RCA). It further examined the reinforcement effects of polypropylene macrofibers (PPMF) on the composite and assessed its mechanical properties and frost resistance. The results showed that incorporating 15% RBA reduced the compressive and splitting tensile strengths of concrete by less than 20%, while the peak load decreased by 28.8%. Fiber incorporation effectively mitigated compressive strength degradation and significantly enhanced tensile strength, with the optimum fiber dosage at 0.9% by volume. However, RBA incorporation reduced frost resistance, resulting in a 37.6% strength loss and a 40.6% mass loss after 100 freeze-thaw cycles. In contrast, a 0.6% fiber admixture improved frost resistance, reducing strength loss and increasing the relative dynamic elastic modulus by 26.7%. Finally, the study established a frost-resistance durability prediction model based on PPMF and RBA content.

This paper presents an experimental and analytical study conducted on concrete cores extracted from the Hungry Horse Dam, located in Montana, United States. The dam, constructed over a five-year period (1948–1953), represents the first major application of fly ash as a pozzolan for the partial replacement of portland cement in structural and mass concrete. Two cores were obtained from the same borehole at different depths, representing the interior and exterior mixtures. The measured mechanical properties of both concretes are largely consistent with values reported in the literature. Bulk electrical resistivity tests reveal significant differences in concrete quality, which are subsequently substantiated by microstructural and analytical investigations that identify variations in both the cementitious materials used and the current condition of the concretes. Microstructural examination exhibits evidence of deleterious alkali-silica reaction in the exterior concrete, while both interior and exterior concretes are found to contain reactive aggregates, as confirmed by petrographic analysis and gel pat testing. The study highlights and attempts to explain the remarkable long-term concrete durability enabled by a pozzolan after more than 70 years of deterioration-free field service offered by the Hungry Horse Dam concrete.

The pressing need to reduce CO₂ emissions from construction materials has driven the development of sustainable alternatives to ordinary Portland cement (OPC). This study investigates a low-carbon ternary binder system—OMF-0.75—comprising 50% OPC, 30% reactive MgO, and 20% fly ash, with 0.75 M magnesium acetate as a hydration agent. Concrete with OMF-0.75 was exposed to 5% Na₂SO₄ and 5% H₂SO₄ solutions for up to 9 months, and its performance was compared to that of OPC concrete. OMF-0.75 exhibited better chemical resistance, with lower mass loss (4.14% in sulfate, 23.75% in acid) and reduced strength degradation (22.23% and 67.65%) compared to OPC (5.68%, 34.22%; 31.22%, 85.58%). UPV retention was higher in OMF-0.75 (3.32 km/s sulfate, 1.66 km/s acid) than in OPC. Microstructural analysis revealed stable M–S–H formation in OMF-0.75, while C–S–H in OPC deteriorated, as evidenced by a Ca/Si ratio below unity. These findings confirm that OMF-0.75 enhances durability and potential as a low-carbon binder for aggressive environments.

Geopolymer concrete offers a lower-carbon alternative to OPC concrete, but long-term durability under aggressive exposure remains critical for field adoption. This study evaluated low-calcium fly ash geopolymer concretes with 0%, 10%, and 20% OPC replacement (denoted GPC100C0, GPC90C10, and GPC80C20) after immersion in tap water, seawater (pH ≈ 7.25), an alkaline solution (pH ≈ 12.5), and an acidic solution (pH ≈ 2.5). Compressive strength and ultrasonic pulse velocity (UPV) were measured at 1, 3, 6, 9, and 12 months. Across all conditions, net mass change remained below 3%. In tap water, 12-month reference compressive strengths were approximately 22 MPa (GPC100C0), 40 MPa (GPC90C10), and 43 MPa (GPC80C20). After 12 months, compressive-strength loss was clearly dependent on the exposure medium. In seawater, losses ranged from about 20% (GPC80C20) to 30% (GPC90C10). In alkaline solution, losses were about 5% (GPC100C0), 20% (GPC90C10), and 33% (GPC80C20). In acidic solution, GPC80C20 showed the lowest loss (about 8%), whereas GPC90C10 showed the highest loss (about 30%). UPV in tap water was approximately 3.2 to 3.9 km/s, and UPV–strength relationships were mixture- and exposure-specific (best-fit R² ≈ 0.84). These results provide practical guidance for durability-oriented mix selection and UPV-based in-service condition assessment.