Genesis of Structure and Properties of the Zeolite-Like Cement Matrices of the System Na(K)-Al2O3-SiO2-H2O within a Temperature Range of 20–1200°C

The chapter deals with a genesis of structure and properties of the zeolite-like cement matrices of the Na(K)-Al2O3-SiO2-H2O system within a temperature range of 20–1200°С. Due to the fact that zeolite-like structures and their characteristics vary within wide ranges, materials with high-performance properties can be obtained through regulation of the structure formation processes. This can be provided by a proper choice of type of an aluminosilicate component, cation of an alkaline component and additives, including Ca-containing ones, and curing conditions. When the cement matrix formation process is appropriately directed, the zeolite-like products (hydrosodalite, analcime, chabasite, faujasite etc.) dominate in the microstructure that is formed. The ability of some zeolites to recrystallize with temperature increase into stable feldspar-like aluminosilicates without destroying the basic skeleton opens a pathway that is worth to explore in the production of materials similar to low temperature ceramics, intumescent coatings, high temperature and corrosion resistant structures, etc. The examples are given on how to use the above cement matrices for making some of the above listed materials.

Effect of nano-silica on Portland cement matrices containing supplementary cementitious materials

abstract: For a controlled granulometry, this study evaluates the effect of nano-silica on mechanical and rheological properties, as well in the microstructure of Portland cement matrices containing a fixed amount of supplementary cementitious materials and three different types of cements. The rheological behavior of cement pastes was evaluated by rotational rheometry and mechanical performance was measured througth the compressive strength. The microstructure was analyzed by intrusion mercury porosimetry and scanning electron microscopy. There was an increasing on the viscosity of the cementitious matrices, as a consequence of the reduction in the inter particle separation of these suspensions. The optimum content of nano-silica varied according to Ca/Si ratio of Portland cement matrices containing supplementary cementitious materials. The use of nano-silica allowed to modify the pore size distribution of cementitious matrices. And the structure of nano-silica in cementitious matrices has occurred in layers or agglomerates of nano-particles covered by hydration products.

Enhanced Mechanical Properties of Eucalyptus-Basalt-Based Hybrid-Reinforced Cement Composites

The present study describes the manufacturing of flat sheets of eucalyptus-basalt based hybrid reinforced cement composites (EB-HRCC). The potential of basalt fibrous waste (BFW) as a reinforcement agent in cement matrices and its effects on mechanical and interfacial properties were evaluated in detail. Significantly enhanced bending (flexural) strength and ductility were observed for all developed composite samples. BFW and eucalyptus pulp (EP) were utilized as reinforcement and filling agents respectively for EB-HRCC samples. Mechanical, microstructural and physical properties of EB-HRCC samples were investigated with different formulations of BFW with EP in cement matrices. The results showed that physical properties of the composite samples were more influenced by fiber content. For standard mechanical analysis, the composite samples were placed in sealed bags for two days, thermally cured at 60 °C for five days and immersed in water in ambient conditions for one day. The obtained results showed that samples prepared under optimized conditions (4% EP and 2% BFW) had significantly higher flexural strength and bulk density with lower water absorption and apparent void volume (porosity). Moreover, the higher percentage of BFW significantly enhanced the values of modulus of rupture (MOR), modulus of elasticity (MOE), specific energy (SE) and limit of proportionality (LOP). The effects of entrapped air under the four-point bending test on the mechanical behavior of hybrid composites were also investigated in this thematic study. The composites were designed to be used as roofing tile alternatives.