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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 neighbouring 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.
The construction sector has traditionally been a source of employment in African regions. However, due to policy changes, cut backs in public investments as well as a fall in the number of employments in the private sector have been observed in many countries. Furthermore a shift from registered companies to informal contractors could be noticed. Many contractors offer services they do not provide permanently or for which the required equipment has to be borrowed. A study that was published in 2000 about the situation in Tanzania pointed out that only ca. 15% of the enterprises that offer concrete works own a concrete mixer. The building practice with concrete varies widely over the African continent. Whereas the level of technology and the infrastructure for cement and concrete in South Africa is elaborate, in East Africa and particularly those that were heavily suffering from civil war during the nineties of the last century, the availability of cement and concrete is poor and these materials are far from being everyday building practice. Most of the population relies on indigenous forms of construction requiring wood obtained from felling of forest trees and ultimately contributing to de-forestation. Informal settlements in South-Africa and Kenya are literal evidence where originally green natural vegetation has been turned into artificial desert-like landscapes.
Baupraxis und Infrastrukturentwicklung im Hinblick auf die Betonindustrie in Ost- und Südafrika
(2011)
Der Bausektor stellt in Afrika traditionell eine der stabileren Quellen für den Arbeitsmarkt dar. Durch ständige Wechsel in der Politik wurden jedoch in zahlreichen Ländern Einschnitte bei den öffentlichen Investitionen sowie ein Rückgang der Beschäftigtenzahlen im Privatsektor beobachtet. Darüber hinaus konnte eine Verlagerung von offiziell tätigen und registrierten hin zu nicht registrierten Bauunternehmen festgestellt werden. Zahlreiche Bauunternehmen bieten Dienstleistungen an, die sie nicht ständig ausführen oder für die sie sich das erforderliche Gerät leihen müssen. Einer im Jahre 2000 hinsichtlich der Situation in Tansania veröffentlichten Studie zufolge verfügen nur etwa 15 % der Unternehmen, die Betonbauarbeiten anbieten, über einen eigenen Betonmischer. Die auf dem afrikanischen Kontinent angewandten Baupraktiken im Betonbau weichen erheblich voneinander ab. Während Südafrika über eine fortgeschrittene Technologie und eine hoch entwickelte Infrastruktur im Hinblick auf die Zement- und Betonindustrie verfügt, sind Zement und Beton in den ostafrikanischen Ländern, insbesondere in jenen, die in den 90er Jahren des vergangenen Jahrhunderts von schweren Bürgerkriegen erschüttert wurden, kaum verfügbar und zählen keinesfalls zu den in der täglichen Baupraxis verwendeten Baustoffen. Hier wird auf einheimische Baumethoden, bei denen vorwiegend Holz verwendet wird, zurückgegriffen. Dieses wird durch Abholzung gewonnen, was schließlich zur Rodung ganzer Waldgebiete führt. Die ohne entsprechende Planung, Genehmigung und Erschließung errichteten Siedlungen in Südafrika und Kenia veranschaulichen erschreckend, wie einstmals von grüner Vegetation bedeckte Landstriche in künstliche, wüstenartige Landschaften verwandelt wurden.
The cement and concrete market in East, Central and Southern Africa is highly fragmented. The concrete industry in this area consists of multiple parties, including producers and suppliers of construction materials, formal and informal contractors, engineers and architects, unions of trades persons and workmen, governmental bodies and formal institutions of research and education. All these institutions mostly do not interact adequately, which makes building with cementitious materials susceptible to damage and failures. Completely opposed to the situation in Europe or North America, cement in Africa is often unaffordable, while manpower is cheap, which results in a questionable economisation of cement. Typically, there is not sufficient awareness of methods to sensibly reducing the cement content in concrete or replace Ordinary Portland Cement by adequate alternative materials. Research activities in this field of technology are often missing completely. Only few countries in the area, such as South Africa, are exempted from these issues.
This paper presents the SPIN project, which is a joint project of a consortium of 8 African and 3 European partners within the ACP Science and Technology Programme. The project is funded by the EC and ACP Secretariat is the project body. The main objective of the current project is to strengthen the cement and concrete industry in the East and Central African regions. The project shall generate reasonable solution strategies to implement clean, safe and sustainable cement and concrete technology on the African continent, including general and specific guidelines for sensible application. Furthermore it shall be the kick-off for future projects, research activities and the world-wide expansion of a European-African network.
The paper addresses special problems the cement and concrete market in Eastern, Central and Southern African countries has to face. Several options are presented in detail, which shall help overcoming the current situation. Customized solutions for the African market include rational methods for reducing the amount of cement used and the replacement of Ordinary Portland Cement with cheaper alternatives. The use of recycled concrete through a new and economically effective method, as well as the opportunity of using locally available resources is also discussed.
Calcined clays as supplementary cementitious materials (SCMs) have been identified and credited to be a viable solution in mitigating the CO2 emissions related to cement production and consumption. Calcined clays range from a variety of different clay types based on an assortment of varying minerals and compositions. While extensive data is available on kaolinitic clays (based on the 1:1 clay type), other clays such as brick clays (based on the 2:1 clay type) are currently understudied, although such clays are largely more available than the kaolinitic clays.
The aim of this thesis is to draw attention to the varying compositions present in two selected brick clays in Germany and elaborate on how such compositions affect their suitability to be used as SCMs in blended cement systems. The novelty of this thesis explains the relationship between the reactivity of the bricks to their varying compositions and their suitability for their employment as SCMs. This was based on their chemical and physical transformations in the calcination temperature range 650–900 or 950 °C, and the performance of the calcined brick clays in blended cement systems measured by their heat evolution, strength development and durability-related properties. The results of their performance were compared to two kaolinitic clays with varying compositions. While the kaolinitic clays generally exhibited the best performance as SCMs, the brick clay with a lower Fe2O3 content showed promising results similar to the kaolinitic clays when an optimum calcination temperature is applied and when substituted at a moderate cement substitution rate. Thus, this finding promoted further efforts made to improve the reactivity of the brick clay by producing a mixed clay composed of 50 % brick clay (with lower Fe2O3 content) and 50 % kaolinitic clay. The mixed clay was compared to the two individual brick clays and one kaolinitic clay, whereby optimum calcination conditions were performed in large-scale simulating an industrial-scale production of SCMs. All calcined clays exhibited pozzolanic reactivity, with the performance of the brick clays inferior to the kaolinitic clay, however, the mixed clay performed very similar to the kaolinitic clay.
At a similar degree of hydration compared to plain Portland cement, the good performance of the mixed clays was especially evident in the strength development and improved chloride penetration resistance, which was caused by a refinement in the pore structure in the cementitious systems. Moreover, it was deduced that not only the high surface area, but also, the solubility of Si and Al ions in the resulting calcinate of the mixed clays plays a significant role when calcined at ~600–700 °C, which points to viable options for optimal employment of brick clays in cementitious systems.
The development of low carbon cements has gained great importance over the last decades. In the effort to limit the carbon content related to its production, cement is often replaced with supplementary cementitious materials (SCMs). Commonly used SCMs such as fly ash and slag have undergone extensive research, but are currently limited in supply and availability. Among the researched SCMs, calcined clays have proven to be a suitable alternative pozzolan due to their worldwide availability and extremely low calcination temperatures when compared to clinker. This poster presents the results from an ongoing project, aimed at obtaining pozzolans, available in sufficient quantities for Portland-pozzolana cement production in Germany. The poster shows the analyses of seven brick clays from various deposits in central Germany. The chemical and mineral composition of the brick clays was evaluated through inductively coupled plasma – optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), and thermogravimetric analysis (TG/DTG). The particle size distribution (PSD) was also evaluated by laser granulometry. The results show that the brick clays contain a substantial amount of kaolinite, illite and smectite minerals, the relative proportions differing significantly between deposits. The suitable calcination temperature range of the clays is also evaluated through TG/DTG analysis to obtain the optimum degree of dehydroxylation from which the bricks clays can be suitable for use as a pozzolan.
The main objective of this project presentation was to evaluate the by-products of paddy farming (in Tanzania) into sustainable building materials optimised for construction of low-cost housing, and suitable to be adopted in rice-producing countries in Africa. In Tanzania, rice husks are seldom used as a fuel – if not burnt or dumped in landfills and there is lack of awareness or active research on optimising the by-product RHA in cement and concrete technology. Scientific research within this field of technology can advance development by obtaining suitable properties of the by-products that can provide an advantageous and alternative measure for their use as SCMs not only in its raw form i.e. husks for low-cost housing but also in its artificial form i.e. RHA as a high-tech as a substitute for cement in Africa.
Effect of rheological parameters on rice husk ash blended pastes with various superplasticizers
(2017)
Rice husk ash (RHA) is a low-energy efficient material with high pozzolanic characteristics compared to other supplementary cementitious materials (SCMs). The replacement of cement with RHA has extensive improvement on the mechanical properties of concrete. However due to the porous nature of the RHA particles, it requires a higher water demand when replaced with Portland cement. Therefore, superplasticizers (SPs) are essential to reduce the water demand and improve the workability of the mixes. There is very little information about the effect of RHA with added SPs in its fresh state. Hence, this paper investigates the interaction of RHA pastes with three types of SPs, i.e. one polycarboxylate-based SP and two different types of lignosulphonates. This paper presents results of the investigation related to the flow behaviour of blended mixes with increasing percentage of RHA. The yield stress for the pastes with and without the addition of SPs is investigated over time as well as the plastic viscosity.
Supplementary cementitious materials (SCMs) are largely used all over the world. The leading SCMs are fly ash (FA) and slag. However, such materials originate from industries that are not well established in sub-Saharan Africa (SSA). Therefore, it becomes extremely challenging and expensive to build up sustainable cement and concrete. For SSA, agriculture is one of the leading economic sectors. Agricultural by-products such as rice husk ash (RHA), can be a potential binder material beneficial for use in a cementitious system. RHA combined with limestone filler (LSF) is an option that can be practised for rice producing countries in Africa.