Materials and Structures最新文献

Asphalt modification with inorganic whiskers is a novel and green method to improve the performance of asphalt pavement, but it is still limited by the high costs and uneven dispersion of whiskers. In this study, an innovative asphalt modifier that can in-situ generate whiskers in hot mix asphalt (HMA) was developed by the alkali activation method using waste dolomite dust as raw material. The morphology and distribution of the alkali-activated waste dolomite dust (AWD) whiskers were examined by scanning electron microscopy and fluorescence microscopy, and the effects of AWD curing time, processing mode and dosage on the rheological and adhesion properties of the modified asphalt binder were evaluated. The results indicate that AWD can spontaneously form whiskers in the asphalt matrix under the flowing temperature of HMA, and the optimal performance enhancement effect on asphalt binder is achieved when the AWD curing time is 1 day, and its dosage is 5% of the asphalt binder mass. Compared with neat binder, the modified binder with AWD shows a 65% increase in rutting factor and a 2-level improvement in adhesion grade, while the costs of AWD are only 1/27 of those of commercial CaCO₃ whiskers. These findings demonstrate that AWD is a cost-effective, eco-friendly and high-performance asphalt modifier, which has great potential for application in asphalt pavement engineering.

This study focused on characterizing the carbonation behavior of 90-day aged alkali-activated fly ash/slag blended by MgO. Effects of MgO reactivity on the carbonation behavior of the synthesized binders were explored. A 0.3% CO₂ concentration was adopted for an accelerated carbonation environment. The samples were characterized using compressive strength tests, X-ray diffraction, thermogravimetry, ²⁷Al solid-state magic angle spinning nuclear magnetic resonance spectroscopy, and scanning electron microscopy with energy-dispersive spectroscopy. Notably, the compressive strengths of all the samples significantly increased after 28 days of carbonation. Moreover, aragonite was identified as the major carbonation product formed in all samples; nevertheless, its precipitation was scarcely affected by the degree of MgO reactivity. In particular, carbonation results in the decalcification of calcium silicate hydrate gels and the formation of layered double hydroxides. The results illustrate that the sample with relatively higher MgO reactivity exhibits improved carbonation durability.

Thermal and themo-mechanical properties of alkali-silica reaction (ASR) products are poorly studied. The existent property data refers to theoretical considerations and do not account for the fact that ASR products can be crystalline, nanocrystalline and potentially amorphous. Here, the thermal conductivity, heat capacity, and coefficient of thermal expansion of crystalline structures (based on Na- and K-shlykovite), nanocrystalline structure (based on defective K-shlykovite structures), and amorphous ASR product are calculated using molecular simulations. Semi-classical estimates of the thermal conductivity, heat capacity, and standard molar entropy are provided. The anisotropy of thermal conductivity and thermal expansion is quantified. Nanoacoustics parameters (sound velocities, phonon free path and relaxation time) are calculated. These results contribute to completing property data for ASR products.

The interest of reinventing raw earth is for the purpose of drastically reducing the environmental impact of the continuous human urban growth. This paper discusses the use of cellulose synthesized by bacteria as a new source of microfibers to reinforce the soil matrix. It presents firstly, the bacterial cellulose (BC) and its production method then it focuses on defining its microstructural characteristics. In the second part, the soil-BC association is studied. Commercial soil (DW-earth) and bentonite clay were tested with 3 and 8% of BC. The objective is to evaluate the impact of BC addition on the soil’s physcio -mechanical properties. Shrinkage and mechanical performance tests were carried out. The results showed a material with better mechanical performances and high cracks resistance. The shrinkage percentage decreased significantly for DW-earth with a similar water/solid ratio when adding BC, by about 18 and 22% when adding 3 and 8% BC for water content of 35%. In the case of bentonite clay the BC addition has only a positive impact on limiting cracking. The mechanical tests showed that 8% of BC increases the compressive strength of the cylindrical specimens by + 28 and + 649%, respectively for the DW-earth and bentonite clay, whereas the flexural strength of the prismatic specimens increases by + 39 and + 556%.