The use of rice husk ash as admixture in producing selfcompacting concrete

Admixtures are incorporated into concrete in today’s world in order to achieve variety of goals. This research study the use of rice husk ash as an admixture in producing selfcompacting concrete. The rice husk ash is varied in different percentages (5, 10, 15, 20, 25 and 30%) as partial replacement for ordinary Portland cement (OPC) to know if it improves the properties of fresh and hardened properties of the self-compacting concrete. The superplasticizer used was conplast SP 430 and the water cement ratio 0.35 was kept constant throughout all mix. Rice husk ash is a good super-pozzolan which is used to make special concrete mixes, in which the slump Flow, T50cm slump, V-funnel and the L-box test was used to test for the workability of the fresh concrete mix and the compressive strength of each mix was tested to know the specific strength of each self-compacting mix with varying percentage of rice husk ash at 7, 14 and 28 days of curing

Potential use of coconut stem as reinforcement in concrete slab

The utilization of an economical, eco-friendly, renewable building material has gained the attention of researchers lately. The construction sector is responsible for depleting large quantities of non-renewable resources. This activity not only generates millions of tons of mineral waste but millions of tons of carbon dioxide gas emissions as well. Research is thus needed on building materials based on renewable resources such as vegetable fibres. Investigated was on the possible use of coconut stem strips as reinforcement in concrete paste. The coconut stem was cut into various lengths, diameter, treated and coated with gloss paint and coal tar. Various tests in accordance to standard were conducted to determine the performance of the coconut stem strips. Compressive strength test and impact load tests were carried out on the concrete slab specimens to satisfy the desire of incorporating coconut stem as reinforcement in concrete slab. The compressive strength was performed on a large number of concrete cubes; 3 cubes each for day 7, 14, 21 and 28. As regards the impact loads test, 13 slabs were cast, 3 slabs each containing steel, dried coconut stem strips, gloss painted coconut stem strips, coal tar coated coconut stem strips with varying dimensions of 16 � 15 mm, 20 � 15 mm and 25 � 15 mm and plain slab without reinforcement serving as control. As expected, the slab reinforced with steel showed better strength in the cured state; however, the 2% of the coconut stripes reinforcement treated with coal tar would serve as good as the conventional steel reinforcement for normal concrete. The coal tar can be used for low-bearing load structures such as lintel and pavement

Incorporation of Silica Fume and Metakaolin on Self Compacting Concrete

This study carried out an experimental design investigating the reaction of mineral admixtures on fresh and hardened properties of sustainable self compacting concrete (SCC). Silica fume (SF) and metakaolin (MK) were partially replaced by Portland cement at 5, 10, 15, 20 and 25% in varying proportions. The workability on the fresh concrete was examined and the strength performance. The water cement ratio of 0.38 was kept constant for all the samples tested. The compressive strength was measured at 7, 14, 21 and 28 curing days. The test results indicated that with the influence of 2% superplasticizer, the fresh concrete showed a satisfactory workability, decreased the segregation to resistance, ease of flowing ability with the addition of silica fume and metakaolin. It was concluded in this study that, the replacement with silica fume was found to have an early strength gain in the compressive strength of SCC samples and a decrease at varying dosages. However, 15% metakaolin was considered to be a suitable replacement with 49.08 MPa at 28days compared with the control mix.

ENGINEERING PROPERTIES OF CONCRETE MADE FROM GRAVELS OBTAINED IN SOUTH-WESTERN NIGERIA

This study investigates the engineering properties of concrete produced from gravels and also verify the suitability of local gravel aggregates obtained from South-western Nigeria in place of crushed granite. Preliminary investigations were carried out in five selected states (Ogun, Oyo, Osun, Ondo and Ekiti) in southwestern Nigeria to determine the registered gravel mining pits. Fifteen gravel mining pits based on age and scale of mining operations were selected for this study. Appropriate gravel constituents in concrete mix were determined using Gs factor. Concrete cubes 150 mm, 150 × 300 mm cylinder modes and 150 x 150 x 750 mm beams were cast with collected gravel. 1:2:4 mix ratio was employed. Sieves analysis, density, water absorption were carried out on aggregates, while compressive, flexural and split-tensile strengths of the concrete were determined for 28 days using ASTM and BS methods. High concrete strengths resulted from high FM, low AAV and average Gs of gravels. Gravel location with highest compressive, flexural and split-tensile strengths of concretes had 24.8N/mm2, 3.5N/mm2 and 2.8N/mm2 satisfying the minimum requirement of BS 811: 1997 while that with lowest strengths had 9.6N/mm2, 2.2N/mm2 and 1.7N/mm2 respectively. Sources of gravel highly influence compressive, flexural and split-tensile strengths of the cubes and beam