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The use of Rice Husk Ash (RHA) as stabilizer in Compressed Earth Block (CEB) for affordable houses

Ojerinde, Adedamola 2020. The use of Rice Husk Ash (RHA) as stabilizer in Compressed Earth Block (CEB) for affordable houses. PhD Thesis, Cardiff University.
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Shelter is a basic human need for comfort and safety; however, Nigeria has a housing deficit of 17 million units. Modern construction materials are not affordable for most earners and have a significant environmental impact. This research investigates the suitability of substituting locally available rice husk ash (RHA) for up to 50% cement stabiliser in compressed earth blocks (CEB) over three different curing times. CEBs with up to 30% RHA substitution were produced with enough compressive strength for load-bearing use in 2 and 3 storey buildings. They also met initial hygrothermal requirements. Data from the mechanical and hygrothermal investigation were utilised in hygrothermal simulations for normal (eg bedroom, living room) and high relative humidity spaces (eg kitchen, bathroom) to establish likely issues with condensation (interstitial or surface) or mould growth on interior wall, which could affect occupant comfort and safety, or impair structure durability. Simulation was based on the tropical Savannah climate in Nigeria for full cavity and partially insulated cavity wall structures for CEB with up to 30% RHA substitution. 20% was the highest RHA substitution CEBs achieving acceptable results. In a full cavity wall structure, it was less likely to suffer condensation or mould (than in partial insulated cavity) but would benefit from treatment with a moisture retarding material if used in a high humidity space. Thermal simulation of a free-running building indicated that thermal comfort with 20% RHA substitution CEBs achieved similar hours at 90% satisfaction as a concrete wall, so replacement would not lead to disadvantage for occupants. In comparison to a typical concrete mixture (1 part cement, 2 parts sand, 4 parts aggregate) which contains 14% cement (dry mix), the 20% RHA substitution CEB had 8% cement (dry mix). This is a substantial reduction in a material which has high cost and environmental impact.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Architecture
Uncontrolled Keywords: Hygrothermal Nigeria Housing Rice Husk Ash (RHA) Compressed Earth Block (CEB) Affordable Houses
Date of First Compliant Deposit: 3 March 2021
Last Modified: 03 Mar 2021 10:46

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