Effects of sulphuric acid on the compressive strength of blended cement-cassava peel ash concrete
- Authors: Olonade, Kolawole Adisa , Olajumoke, Akinropo Musiliu , Omotosho, Ayoade Oluwaseun , Oyekunle, Funso Ayobami
- Date: 2014
- Subjects: Sulphuric acid , Reinforced concrete , Concrete - Mixing
- Type: Article
- Identifier: uj:5065 , http://hdl.handle.net/10210/13636
- Description: Influence of sulphuric acid on compressive strength of concrete made with blended cement-cassava peel ash was investigated in this study. This is with a view to determining the level of resistance of such concrete to acidic exposure. Cassava peel ash (CPA) prepared from uncontrolled burning was used to substitute cement at 5, 10, 15 and 20% by weight of cement as binder. Concrete mix proportions of 1:2:4 (batching by weight) were prepared with the slump value within 6010 mm while water-binder ratios (w/b) were being noted. A total of 90 cubes of the concrete mixture of sizes 150 mm were cast and cured in fresh water (as control), 0.5, 1.0 and 1.5 M concentrations of sulphuric acid solution (H2SO4) for 7, 28, 56 and 90 days. The compressive strength was determined at the expiration of each curing age. The results showed that the w/b increased with increase in the quantity of CPA in the mixture. Compressive strength of concrete made with cement-CPA as binder and cured in fresh water was comparable to that of normal concrete when up to 15% CPA was used, but relatively low strength was obtained when cured in H2SO4 solutions, depending on the quantity of CPA. Leaching of Porlandite in the concrete cubes was observed with worse condition in the case of concrete containing 20% CPA in sulphuric acid solution of 1.5 M. The compressive strength reduced with increase in concentrations of the acid as well as with increase in the content of the CPA. It is concluded that CPA did not mitigate the adverse effects of sulphuric acid on the compressive strength of blended cement-CPA concrete.
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Methods for flexural strengthening of reinforced concrete elements using steel plates
- Authors: Olajumoke, Akinropo Musiliu , Dundu, Morgan
- Date: 2014
- Subjects: Concrete beams , Plates, Iron and steel , Reinforced concrete , Flexure
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/380017 , uj:5078 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13649
- Description: When reinforced concrete elements are incapable of safely sustaining the anticipated load, flexural strengthening may be necessary. Two major construction methods have been reported in literature for strengthening reinforced concrete (RC) elements in bending. These methods include Externally Bonded Reinforcement (EBR) and Near Surface Mounting (NSM). The aim of this paper is review these methods, including the extensive surface preparation that must be performed on bonded elements. Previous investigations have shown that these techniques are effective in salvaging old and distressed reinforced concrete structures. This paper identifies the problems associated with the utilisation of steel plates as strengthening material for RC elements in EBR and NSM techniques.
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Flexural failure modes of steel plate-strengthened reinforced concrete elements
- Authors: Olajumoke, Akinropo Musiliu , Dundu, Morgan
- Date: 2014
- Subjects: Reinforced concrete , Composite materials - Bonding - Congresses , Concrete beams - Maintenance and repair , Plates, Iron and steel
- Type: Article
- Identifier: uj:5071 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13642
- Description: Failure of plate strengthened flexural reinforced concrete (RC) member can be crushing of the concrete at the compression face or premature debonding of the plate from the concrete element at the tension face. Debonding can be classified into three groups; namely, intermediate crack debonding (ICD), delamination and plate-end debonding (PED). Intermediate crack debonding is caused by flexural or flexural-shear stress, and plate-end debonding and delamination are caused by interfacial stress. This paper reviews the failure modes of flexural strengthened RC elements in bending, using epoxy-bonded steel plates. It also attempts to establish the width-to-thickness ratios of plates that can achieve the full flexural strengths of the strengthened element and promote a ductile failure.
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