A study on sustainable energy for cement industries in Rwanda

Rwanda is a landlocked country in the East Africa. It is surrounded by Uganda, Tanzania, Congo and Burundi. Rwanda is a fast developing country and it spends most of its revenues to import fossil fuels from either through Mombasa Port in Kenya or Dar es Salaam port in Tanzania because the energy production in Rwanda is not sufficient for its development. Transporting the fuels from these ports, add on to the cost of all materials, cement industry being no exception. There are three cement companies in Rwanda. The cement industries could not run in full production due to the shortage of fuel. Moreover, Rwanda is importing all the construction materials such as steel, roofing materials, etc from its neighboring countries. This increases the cost of construction and the common man find difficult to own a house. In order to sustain the energy needs of Rwanda, different sources of energies should be focused. They are Peat, Geothermal, Methane gas, solar, wind, waste materials and Municipal wastes. Without affecting the environment, there is an urgent need to find a solution on sustainable energy in Rwanda. This paper discusses about the possible sources of energy in Rwanda which will improve the energy sustainability and turn the economy of Rwanda

Characterization and behaviour of Autoclaved Aerated Concrete before Autoclaving

In order to achieve a high quality Autoclaved Aerated Concrete (AAC) product, certain steps need to be ensured: the characterization of the raw materials, a proper mixing and correct slurry behaviour to achieve a good green body during green curing. In the current research the emphasis is on all of these parameters. The influence of water-to-powder ratio on the viscosity, its effect on the final product properties and the foaming agent amount interference are quantified, and correlations between them are proposed based on the underlying physical phenomena

Water layer thickness evaluation in autoclaved aerated aoncrete slurries

A slurry is often described as solid material particles that are surrounded by a water film and with additional water within the voids that decreases the shear forces between the particles. In cement and concrete research the water amount is an important parameter. There needs to be enough water to create a proper slurry, and afterwards it is consumed by the hydration of the hydraulic phases. To distinguish between a moist powder and a slurry, the point where all particles are wetted, but no remaining water is filling the pores is defined. The thickness of the water layer can be determined by different methods and is already measured for various materials. In this research it is tried to apply the method not just to a single material, but to an AAC mixture of six different materials. The obtained values are compared with the ones known from pastes and mortars

Crushing of MSWI bottom ash towards material purification

Municipal Solid Waste Incineration (MSWI) reduces mass and volume of the waste by about 70% and 90%, respectively. Next to boiler and fly ash, solid MSWI Bottom Ash (hereinafter referred to as bottom ash; BA) makes up for 80% of the remaining material containing unburned matter, glass, ceramics, metals, and minerals. Despite its similar composition to concrete constituents, which suggests their applicability in this field, at present BA is landfilled or used in low-grade applications (e.g. road base material). In order to make a higher end application possible, correlations between physical properties, size fractions and mineralogical composition have been studied. This study looks into the crushing of the materials within BA and how certain fractions are enriched with specific types of material, therefore depleting and purifying other fractions making them better suitable for implementation in concrete

Robustness improvement of fresh concrete and mortar performance for challenging casting environments with focus on sub-Saharan Africa

For various concrete applications, the early properties are a major specification, determining the functioning, the mechanical properties, and the durability of structures. The rheological properties of cementitious systems are depending on the water-cement interaction as well as on interactions of chemical admixtures with the cement hydration. The cement hydration, however, is strongly affected by the environmental boundary conditions, such as the climate or the available equipment for the proportioning and dispersion of concrete. This paper presents strategies for the robustness improvement of fresh properties of cementitious systems for challenging and particularly warm climate conditions. After explaining the basic mechanisms affecting the workability, practical conclusions are drawn with special attention on the circumstances of sub-Saharan Africa, where the climatic conditions are difficult and the casting technology is often limited. Solutions are suggested, how despite the disadvantageous circumstances, highly elaborate engineered concrete and mortar can be applied safely and with consistent quality.</p

Processing disaster debris liberating aggregates for structural concrete

Worldwide, the removal of debris and reconstruction is requested when natural disasters and conflicts cause damaged or collapsed buildings. The on-site recycling of concrete waste into new structural concrete decreases transport and production energy costs, reduces the utilization of raw materials, and saves the use of limited landfill space. The application of recycled concrete aggregates (RCA) in structural concrete is currently limited, since concrete recycling involves application as road base material or in non-structural concrete with low strength requirements. Applying an optimised crushing method could improve the applicability of RCA in structural concrete. The quality of the initial concrete investigated is unknown, and embedded defects influence the quality of the final concrete made with RCA. Separating the hardened cement paste (HCP) from the aggregates through optimised crushing minimises the influence of the initial concrete on the quality of concrete made with RCA. In turn, the HCP can be extracted, reducing water absorption and minimising workability problems. Through this, optimised crushing makes the application of recycled concrete into new concrete far less troublesome, and therefore widely applicable and highly suitable for post disaster areas. This study primarily looks into the influence of the optimised crushing process on the resulting particles of the produced RCA. For this, concrete demolition waste is passed through the optimised crusher three times. An initial visual assessment of the RCA produced is made and the specific aggregated density measured shows promising results regarding aggregate quality

Application of glass recycling by-products in Autoclaved Aerated Concrete

Autoclaved Aerated Concrete (AAC) is a construction material with a large range of applications. In order to generate more sustainable materials, the possibility of the incorporation of by-products and left-over-materials from various processes is investigated. The focus of this research is the application of glass powder which is generated as a by-product from municipal waste glass recycling. This waste glass fraction is particularly suitable for incorporation in AAC due to its finess and high content of glassy silica with a high reactivity. The glass has an influence on the AAC fabrication by reducing the initial water amount and improving the final strength. The substitution amount is limited by an increased shrinkage

Robustness improvement of fresh concrete and mortar performance for challenging casting environments with focus on sub-Saharan Africa

For various concrete applications, the early properties are a major specification, determining the functioning, the mechanical properties, and the durability of structures. The rheological properties of cementitious systems are depending on the water-cement interaction as well as on interactions of chemical admixtures with the cement hydration. The cement hydration, however, is strongly affected by the environmental boundary conditions, such as the climate or the available equipment for the proportioning and dispersion of concrete. This paper presents strategies for the robustness improvement of fresh properties of cementitious systems for challenging and particularly warm climate conditions. After explaining the basic mechanisms affecting the workability, practical conclusions are drawn with special attention on the circumstances of sub-Saharan Africa, where the climatic conditions are difficult and the casting technology is often limited. Solutions are suggested, how despite the disadvantageous circumstances, highly elaborate engineered concrete and mortar can be applied safely and with consistent quality.</p