Datei im Netzwerk der BAM verfügbar ("Closed Access")
Filtern
Dokumenttyp
- Vortrag (3)
- Beitrag zu einem Tagungsband (2)
Sprache
- Englisch (5)
Referierte Publikation
- nein (5)
Schlagworte
- Sub-Saharan Africa (5) (entfernen)
Eingeladener Vortrag
- nein (3)
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.
In order to reduce CO2 emission in concrete and minimize the environmental impact, majority of research focuses on using supplementary cementitious materials (SCMs) such as Fly Ash (FA), blast furnace slag (GGBS) and Silica Fume (SF) or Microsilica as a replacement for ordinary Portland cement in concrete. However, in terms of sustainability, it is not economically feasible to use the above mentioned SCMs in countries where these materials are not readily available. In addition, when dealing with the carbon footprint of concrete, despite their positive influence in concrete, such SCMs cannot be said to be eco-friendly materials due to their high energy production process. In many developing countries in sub-Saharan Africa (SSA), agriculture is the leading economic sector. Generally, agricultural by-products are eco-friendly in terms of low energy in production, and they often have no further use for the environment. These by-products (baggase, cassava peels and rice husks) are mainly not the materials of discussion in this current day and age and especially in the northern hemisphere, where the majority of concrete technology originates. Hence, it is inevitable to consider other more sustainable resources in concrete for SSA. Nevertheless, optimization of these resources in concrete can only function with a clear understanding of the reactivity of the materials and its interaction and mechanism to adopt similar and workable properties as a normal performance cementitious system.
This paper addresses rice husk ash (RHA) as a main SCM in various cementitious systems with added limestone filler (LSF) and observes its performance in mortar. Superplasticizers such as polycarboxylate-ethers (PCEs) and lignosulphonates (LS) are incorporated in the cementitious systems to improve workability. The interaction of RHA with the superplasticizers was investigated by means of zeta potential (ZP). According to the results presented, it is shown that RHA powder has a positive compatibility with the chosen superplasticizers and its performance in mortar with LSF also shows increase in strength and workability.
There is a wide range of research worldwide on supplementary cementitious materials (SCMs) such as fly ash and slag for substituting Portland cement. Such materials are suitable to be considered in a cementitious system with ordinary Portland cement (OPC) due to their high pozzolanic properties. In addition, many of the SCMs are said to significantly improve concrete properties especially in terms of strength and durability. Unfortunately, the production of such SCMs is not entirely eco-friendly and also limited to certain parts of the world, hence one has to look at alternative options.
The issue of availability of resources is a strong concept that is ever-increasing, and the use of more eco-friendly SCMs in a cementitious system is furthermore attractive. Hence this paper addresses the use of eco-friendly SCMs in concrete such as rice husk ash (RHA). Despite the fact that extensive research has been done on this material, its application in a cementitious system to obtain sufficient concrete properties is still rather limited.
In a country like Tanzania, high strength concrete construction is applicable in special construction cases but certainly not a high priority. Majority of construction is still undertaken using normal strength concrete. In a ternary cementitious system consisting of OPC, RHA and other readily available resources such as limestone filler (LSF), normal strength concrete can still be produced having good performance and suitable for regular on-site construction. This paper explains a possible application of obtaining sufficient concrete properties from the available resources.
There is a wide range of research worldwide on supplementary cementitious materials (SCMs) such as fly ash and slag for substituting pure cement. Such materials are suitable to be considered in a cementitious system with ordinary Portland cement (OPC) due to their high pozzolanic properties. In addition, majority of the SCMs are said to significantly improve concrete properties especially in terms of increased strength and durability. Unfortunately, the production of such SCMs is not entirely eco-friendly and also limited to certain parts of the world, hence one has to look at alternative options.
The issue of availability of resources is a strong concept that is ever-increasing, and the use of more eco-friendly SCMs in a cementitious system is furthermore attractive. Hence this paper addresses the use of eco-friendly SCMs in concrete such as rice husk ash (RHA). Despite the fact that extensive research has been done on this material, its application in a cementitious system to obtain sufficient concrete properties is still rather limited. In a country like Tanzania, high strength concrete construction is applicable in special construction cases but certainly not a high priority. Majority of construction is still undertaken using normal strength concrete. In a ternary cementitious system consisting of OPC, RHA and other readily available resources such as limestone filler (LSF), normal strength concrete can still be produced having good performance and suitable for regular on-site construction. This paper explains a possible application of obtaining sufficient concrete properties from the available resources.
The economic use of chemical admixtures depends on supply chains. Therefore, in most regions ins sub-Saharan Africa (SSA), the use of admixtures is not common practice. This amplifies the unfavorable framework for concrete construction such as fragmentary supply chains, high local cement prices, and unfavorable construction site facilities in this region significantly. The use of superplasticizer (SP) and stabilizing agents (STA) can enhance the concrete technology in SSA, since they can disassociate the concrete quality from external boundary influences. After providing a general overview of the peculiarities of the SSA boundary framework, economic concepts are provided, how existing material solutions can be significantly improved by the use of SPs and STAs based on locally available materials such as lignosulphonates and cassava starch. Finally a three step optimization process is described that helps developing flowable concrete based on materials that can be accessed in most locations in SSA.