Effect of wetting and air curing durations on strength of stabilized sands
- Moatlhodi, Lerato J., Okonta, Felix N.
- Authors: Moatlhodi, Lerato J. , Okonta, Felix N.
- Date: 2014
- Subjects: Sandcrete blocks , Low-cost houses - South Africa , Building materials , High strength concrete , Portland cement , Fly ash
- Type: Article
- Identifier: uj:5076 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13647
- Description: Low cost houses in most developing countries are constructed from sandcrete blocks manufactured from sand-cement mortar. In South Africa, failure of many of these blocks has been experienced leading to collapse of the structures. Lack of sufficient compressive strength in the manufactured blocks was attributed as the main cause of the failures. The unconfined compressive strength (UCS) of sandcrete blocks can however be improved by curing the blocks under different conditions. Therefore the objective of this study was to evaluate the effect of different wetting and air drying durations would have on the strength and the stiffness of the cubes produced. Weakly cemented sand cubes, with different cement contents and cement-fly ash binder ratios compacted at the optimum moisture content, were prepared. The 28 days UCS was determined, modulus of elasticity and moisture contents of sample specimen was also determined. The results showed that curing cubes under water for 7 days and then air curing for 21 days yield maximum UCS and modulus of elasticity for sands cemented by plain Portland cement, and that 3 days under water curing produced maximum results for sands stabilized by cement-fly ash binder. It was however found that under water for 28 days results in minimum strength. Therefore the longer the cubes are cured under water minimum strengths were achieved.
- Full Text:
- Authors: Moatlhodi, Lerato J. , Okonta, Felix N.
- Date: 2014
- Subjects: Sandcrete blocks , Low-cost houses - South Africa , Building materials , High strength concrete , Portland cement , Fly ash
- Type: Article
- Identifier: uj:5076 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13647
- Description: Low cost houses in most developing countries are constructed from sandcrete blocks manufactured from sand-cement mortar. In South Africa, failure of many of these blocks has been experienced leading to collapse of the structures. Lack of sufficient compressive strength in the manufactured blocks was attributed as the main cause of the failures. The unconfined compressive strength (UCS) of sandcrete blocks can however be improved by curing the blocks under different conditions. Therefore the objective of this study was to evaluate the effect of different wetting and air drying durations would have on the strength and the stiffness of the cubes produced. Weakly cemented sand cubes, with different cement contents and cement-fly ash binder ratios compacted at the optimum moisture content, were prepared. The 28 days UCS was determined, modulus of elasticity and moisture contents of sample specimen was also determined. The results showed that curing cubes under water for 7 days and then air curing for 21 days yield maximum UCS and modulus of elasticity for sands cemented by plain Portland cement, and that 3 days under water curing produced maximum results for sands stabilized by cement-fly ash binder. It was however found that under water for 28 days results in minimum strength. Therefore the longer the cubes are cured under water minimum strengths were achieved.
- Full Text:
Palm kernel incinerated ash as low cost concrete component
- Agbenyeku, Emem-Obong Emmanuel, Okonta, Felix Ndubisi
- Authors: Agbenyeku, Emem-Obong Emmanuel , Okonta, Felix Ndubisi
- Date: 2014
- Subjects: Lightweight concrete , High strength concrete , Incineration
- Type: Article
- Identifier: uj:5058 , ISBN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13620
- Description: The incorporation of commercially available fly ash (FA) as low cost material in concrete has long been established. Large quantities of FA are utilized for research and field applications because of the pozzolanic characteristics. One of many pozzolanic materials is palm kernel incinerated ash (PKIA). The abundance of PKIA as an agricultural waste material in West Africa obtained by the incineration of palm kernel husk and shells in milling boilers paved way for this study. Specimens containing 50%PKIA were cast and cured both in water and air and their compressive strength and shrinkage behaviours were investigated with and without the addition of superplasticizer (hydroxylated carboxylic (HC) acid) in comparison with controlled specimens containing 100%OPC. Results showed that the strength development in PKIA green concrete at all ages of curing; 7,14 and 28 days were lower than OPC concrete. On the addition of superplasticizer, strength of 36.9N/mm2 was observed for specimens with superplasticizer as against 31.7N/mm2 for specimens without superplasticizer on the 28day. The water curing method produced the best results while the predicted shrinkage strain of the green concrete in accordance to ACI 209R-92 standard was higher than the control specimens.
- Full Text:
- Authors: Agbenyeku, Emem-Obong Emmanuel , Okonta, Felix Ndubisi
- Date: 2014
- Subjects: Lightweight concrete , High strength concrete , Incineration
- Type: Article
- Identifier: uj:5058 , ISBN 9781614994657 , ISSN 9781614994664 , http://hdl.handle.net/10210/13620
- Description: The incorporation of commercially available fly ash (FA) as low cost material in concrete has long been established. Large quantities of FA are utilized for research and field applications because of the pozzolanic characteristics. One of many pozzolanic materials is palm kernel incinerated ash (PKIA). The abundance of PKIA as an agricultural waste material in West Africa obtained by the incineration of palm kernel husk and shells in milling boilers paved way for this study. Specimens containing 50%PKIA were cast and cured both in water and air and their compressive strength and shrinkage behaviours were investigated with and without the addition of superplasticizer (hydroxylated carboxylic (HC) acid) in comparison with controlled specimens containing 100%OPC. Results showed that the strength development in PKIA green concrete at all ages of curing; 7,14 and 28 days were lower than OPC concrete. On the addition of superplasticizer, strength of 36.9N/mm2 was observed for specimens with superplasticizer as against 31.7N/mm2 for specimens without superplasticizer on the 28day. The water curing method produced the best results while the predicted shrinkage strain of the green concrete in accordance to ACI 209R-92 standard was higher than the control specimens.
- Full Text:
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