Papers by Author: O.E. Alutu

Abstract: The purpose of this study is to see if varying the vibration time and sand type during moulding of blocks would affect the strength of the blocks. To this end, seven types of sands: Okhuahie and Ovia river sands; Okhuahie, Ovia, Ikpoba flood and Okhoro erosion sands were collected for the study. A total of 315 blocks each in 150mm and 225mm sizes with cement to sand ratios of 1:6 were made using the seven brands of sand. The blocks were vibrated for 10, 15, 20, 25, and 30 seconds and tested for compressive strength at 7 days, 14 days and 28 days respectively. The result showed that the relationship between compressive strength of the blocks and the vibration time for various sand types was linear up to vibration time of 30 secs. The sand type also influenced the strength of the blocks as Okhuahie river sand gave the highest compressive strength followed by Ovia river sand and the least was Okhoro erosion sand. At least 52% increase in compressive strength of 150mm and 225mm sandcrete blocks were achieved by raising the vibration time from 15 seconds to 25 seconds in the seven types of sand and 100% increase was achieved by raising the vibration time from 15 to 30 seconds.

Abstract: The purpose of this study is to carry out tests on concrete made with a typical Benin City silty sand and determine the major concrete quality indicators such as pulse velocity, water/cement ratio and compressive strength in order to justify the continued utilization of such sands in concrete production in and around Benin City. To do this, concrete made with the selected sand were designed using DOE mix design method and test cubes were cast in three batches. Two cubes were cast for each of the sixteen consecutive tests carried out and averages taken for each design grade strength of 10,20,30,40 and 50N/mm2. Also, pulse velocity and rebound hammer tests were carried out on the cubes before testing the cubes destructively. The results show that concrete produced with the Benin City silty sands are of good quality in all respect but generally characterized by low 28th day – characteristic strength. The sands should therefore be used in construction provided that the mean strength aimed at during design is sufficiently higher than the characteristic strength by the strength margin (ks) from structural point of view to enable every part of the structure have adequate strength.

Abstract: This paper examines the production of calcite and calcite-cement stabilized laterite hollow blocks as low-cost masonry units. First, is the production of laterite hollow blocks solely stabilized with finely ground limestone or calcite followed by the production of laterite hollow blocks stabilized with calcite-cement composite. Laterite was sourced from three locations: Asoro, Evbuotubu and Ugbowo. Blocks were produced using a specially constructed machine with percentages of calcite and calcite-cement content varying from 4% to 16% respectively at compactive pressures of 10.32 and 13.75N/mm2. Equal amounts of calcite and cement are used in the composite. The blocks were then tested for 7, 14 and 28 days strengths after curing. The results show that laterite blocks stabilized with calcite alone do not satisfy the Nigerian Industrial Standards or British Standards for blocks but those stabilized with 8% calcite-cement content, i.e., 4% calcite with 4% cement do, at moulding pressure of 13.7 N/mm2. Based on the local cost data, the results also show that calcite-cement stabilized laterite hollow blocks are 17% cheaper than an equivalent cement-stabilized hollow block and 46% cheaper than the low quality sandcrete blocks sold in the market.

Abstract: The paper focuses on the effect which varying the type of sand used in concrete will have on the compressive strength of concrete and seeks to determine the suitability of each sand for use in concrete works. The sand samples used include Okhoro, Ikpoba, Ovia and Okhuahiaerosion sands and Ikpoba, Ovia and Okhuahia river sands. Particle size distribution of the sands was first determined and the result was used to design grades 20, 25, and 30 concretes to Department of Environment (DOE) mix design method. Twelve cubes were cast from one particular sand sample and three cubes were tested at 7, 14 and 28 days for each grade of concrete respectively .The result revealed that the sand samples that are well graded gave the highest compressive strength; while the poorly graded sands gave lower strengths. Okhuahia river sand gave the strongest concrete followed by Ikpoba, and Ovia river sands, Okhuahia, Ikpoba, Ovia and Okhoro erosion sands. Particle size distribution within a sand zone probably did not affect strength but the impurity content did. However, the inter-zonal differences in particle sizes probably did affect strength. The result also showed that only the river sands and Okhuahia erosion sand are good for concrete making.