Low-Temperature Curing Strength Enhancement in Cement-Based Materials Containing Limestone Powder.

Current research in construction materials emphasizes sustainable alternatives to traditional cement. Limestone powder has gained attention for its potential to influence hydration processes. While prior studies have explored limestone's role in accelerating early hydration, less is known about its effects at low curing temperatures. Established knowledge shows limestone can act as a nucleation site for hydration products. However, the specific relationship between heat release and strength development at low temperatures remains unclear. This gap motivated the current investigation. No prior work had resolved how limestone affects strength at 10 °C versus 23 °C. Understanding this could improve low-temperature construction practices. Theoretical models suggest limestone may alter hydration pathways. Yet, empirical validation is limited.

This study aimed to examine how low-temperature curing affects the strength of mortars containing limestone powder. The specific problem addressed is the observed strength enhancement at 10 °C compared to 23 °C. The motivation stems from the need to optimize cement hydration under cold conditions. The study focuses on mortars made with Portland-limestone cement (PLC) containing 10 % limestone. The goal is to determine if limestone powder can enhance strength per unit heat release. The researchers propose that limestone alters hydration product formation. This could lead to better performance in cold climates. The study also seeks to validate theoretical models of phase distribution.

The study compared mortars cured at 10 °C and 23 °C using PLC with 10 % limestone additions. Heat release and compressive strength were measured after 7 days of curing in lime water. Thermodynamic modeling was used to predict phase distributions and hydration product formation. For a subset of cements, thermogravimetric analysis (TGA) was conducted to assess reaction rates. Quantitative X-ray diffraction (XRD) provided data on crystalline phase content. Scanning electron microscopy (SEM) examined microstructural differences. The researchers propose that these methods reveal how temperature and limestone content influence hydration. The study design allows for direct comparison of low- and standard-temperature curing effects.

Mortars with 10 % limestone showed higher strength per unit heat release after 7 days at 10 °C. In some cases, the absolute strength at 10 °C exceeded that at 23 °C. This strength enhancement was observed in PLC cements but not in conventional mixtures. Thermodynamic modeling indicated that carbonates influence hydration product formation. TGA confirmed differences in reaction rates between the two temperatures. XRD revealed distinct phase distributions in 7-day pastes. SEM images showed microstructural variations linked to temperature. The researchers propose that limestone alters hydration pathways at low temperatures.

The study found that limestone powder in PLC cements enhances strength at low curing temperatures. This effect is linked to hydration product formation influenced by carbonates. The authors propose that limestone alters phase distribution and reaction rates. The results suggest that limestone can improve performance in cold climates. The strength per unit heat release is higher at 10 °C than at 23 °C. The findings trace to the observed differences in phase content and microstructure. The study supports the use of limestone in PLC for low-temperature applications. The authors conclude that limestone modifies hydration mechanisms in a temperature-dependent way.