Case Studies in Construction Materials (Jul 2024)
Examining the early-stage performance and mechanical performance of limestone powder-silica fume binary cement-based materials
Abstract
To reduce carbon emissions associated with substantial concrete usage in construction and achieve the objectives of green and low-carbon construction, this study innovatively develops a low-carbon binary material by adding limestone powder (LP) and silica fume (SF) into the conventional cement-based material, enhancing the comprehensive utility value of LP. The experimental results show that the addition of 15% LP and 5% SF increases the yield stress of the mortar yet substantially reduces the plastic viscosity to 2.84 Nmm·min, representing a 44.5% decrease compared to pure cement slurry. This reduction is conducive to long-distance pumping of the cement-based material. Moreover, the addition of 5% SF compensates for the 18.8% (mid-stage, 28-d) and 15.8% (late-stage, 90-d) strength loss in mortar caused by LP while simultaneously improving the strength of the co-mixed system by 10.4% (mid-stage) and 10.8% (late-stage). In the early-stage measurements of the LP-SF binary cement-based materials, it is observed that while SF slightly increases the hydration heat release, LP suppresses the early hydration heat release. Therefore, the total heat release observed in the 15% LP and 5% SF group after 72 h is only 254 J/g, demonstrating favorable temperature control and crack prevention effects. In addition, X-ray diffraction (XRD) and thermogravimetric/differential thermogravimetric (TG/DTG) phase analysis reveal a notable increase of 53.56% in CH consumption. Besides, the weight loss on ignition of C-S-H crystals increases, indicating that the secondary hydration of LP and the pozzolanic reaction of SF promote the production of C-S-H in the system. Combined with the late-stage strength and water absorption characteristics, it is concluded that the system exhibits good mechanical properties and compactness. This study presents a use of mixed proportion that enables excellent mechanical properties, good pumping performance, and low hydration heat. Moreover, the analysis indicates that the carbon emission of each cubic meter of the as-developed mortar is reduced by approximately 16.7–23.9%, promoting the efficient and clean utilization of LP and SF.
