Influence of pozzolanic activity of coal gangue on hydration products in coal gangue-cement system
Qualitative and quantitative analysis of the composition in the paste of complex cements have been determined by means of X-ray diffraction (XRD),differential scanning calorimetry (DSC) and directly-heating method. Results show that the composition of hydration products in coal gangue-cement complex system is similar to that in pure cement system, but the content of hydration products for per unit cement in former is higher than that in later at the early hydration stage. The pozzolanic reaction between coal gangue and cement hydration products mainly occurs in 3d. The content of Ca(OH)2 and that of C-S-H in the paste are related to the activity and the content of coal gangue. The content of C-S-H in high activity coal gangue-cement system is related to the activity of coal gangue rather than the content, but that is opposite in low activity one.
IMPACT OF ADDITIVE AND FINE MINERAL ADMIXTURE ON DURABILITY OF SELFCOMPACTING CONCRETE
Due to its low water-to-cementitious materials ratio and application of additive, fine mineral ad- mixtures, self-compacting concrete has favorable workability and filling property, as well as favorable mechani- cal property after setting. Meanwhile, self-shrinkage of self-compacting concrete becomes non-neglectable and is one of the major factors causing crack, having a strong impact on durability of self -compacting concrete. Therefore, certain amount of expansive agent shall be added into the self-compacting concrete for compensation of shrinkage. Effects of high efficiency water-reducing agent, fly ash of fine mineral admixture and expansive agent in self-compacting concrete are discussed herein.
Concrete Technology for Sustainable Development
With industrialization and urbanization there is a corresponding and growing demand for clean air, water, efficient waste disposal, rapid transport of people and goods and clean burning energy sources. Portland cement concrete is the material of choice for modern infrastructure needs and is today the largest consumer of natural resources such a water, sand, gravel, and crushed rock. Portland cement, the binder for modern concrete mixtures, uses tonnes of limestone and considerable fossil fuel and electrical energy each year. This article identifies the essential elements that are crucial to creating an environmentally friendly concrete industry. These elements are: conservation of concrete making materials, enhancement of the durability of concrete structures and a shift from reductionistic to an holostic approach in concrete technology research and education. Sustainable development is a concept with social, economic and environmental benefits yet to be fully explored or developed. The concrete industry, as the most important player in the infrastructure of modern and industrializing society and the largest consumer of natural resources, can begin the process of sustainable development through adoption of conservation technologies, durability enhancement and research and education.