Cost Optimization of Sandcrete Blocks through Partial Replacement of Sand with Lateritic Soil

This work finds a way in which lateritic soil within Ota, Ogun State of Nigeria could be used in the production of hollow sandcrete blocks. This replacement is intended to develop more economic sandcrete blocks since the cost of lateritic soil in Ota is much less than the cost of the conventional fine aggregate used in the production of sandcrete blocks without compromising the intergrity of the blocks. It was deduced from literatures that inclusion of lateritic soil in sandcrete block production results in a lesser quality blocks. However, this work found the maximum permissible replacement that still makes the blocks to be within the recommended standard. The blocks were produced with each lateritic soil sample from different sources replacing sand in steps of ten percent to 60% and their compressive strengths determined and compared with that of a standard sandcrete block to check for the acceptable percentage replacement. In the compressive strength test, 72 numbers of 225 x 225 x 450mm hollow laterised sandcrete block sizes were produced, cured and crushed to determine their twenty-eight-day compressive strength. Cost analysis was performed discovered that the inclusion of the lateritic soil saves the cost of production by 11.89%. This percentage replacement can be recommended to the block moulding industries within Ota with a view to reducing the production costs of the blocks

Effect of Nitric Acid Concentration on the Compressive Strength of Laterized Concrete

Laterized concrete is concrete in which some or all of the fine aggregates is from laterite. In this study, the effects of varying nitric acid concentrations (0%, 5%, 10%, 15%, and 20%), mix proportions (1:1:2, 1:1½:3), exposure period (28, 56, and 84 days) and percentage laterite content (0%, 25%, and 50%) on the compressive strength of laterized concrete were investigated. The tests were carried out with a view to simulating the performance of laterized concrete in contact with soluble nitrate-based substances. 100x100x100mm cubes of laterized concrete were cast and moist-cured for 28 days and the strength of concrete at this age was determined. The cubes were thereafter immersed in 0%, 5%, 10%, 15%, and 20% concentrations of nitric acid for a total of 84 days. Compressive strength tests were carried out at the end of 28 days, 56 days and 84 days of immersion. The results of the tests indicated that the compressive strength significantly reduces with increase in acid concentration, immersion period and laterite content. The effect of richness of mix on resistance of laterized concrete to the acidic aggression becomes more pronounced at the highest (50%) laterite content

RECYCLING FINE SANDCRETE BLOCK WASTE (FSBW) AS FINE AGGREGATE IN THE PRODUCTION OF SANDCRETE BLOCK

The study investigated the use of Fine Sandcrete Block Waste (FSBW) as fine aggregate in the production of sandcrete blocks with a view of controlling waste and decongesting block molding production sites. Standard sandcrete blocks of size 450mmX225mmX225mm were prepared from a mix ratio 1:6 (cement: fine aggregate) containing sand and FSBW as fine aggregates. The sand was partially replaced by FSBW in the mix within the range 0% - 90% in steps of 10%. The blocks were cured for 28 days and then tested for compressive strength. The physical properties of both the sand and FSBW were also determined. The results of the study revealed that the physical properties of FSBW compares favorably with those of conventional sand with the exception of water absorption. It further showed that the density and the compressive strength of the tested blocks decrease as the percentage replacement of sand with FSBW increases. The density of the blocks varied linearly with the compressive strength. Blocks prepared for mixes having 50% FSBW content or less were found to satisfy the minimum recommended compressive strength of 3.45N/mm2 (NIS 87:2000)

Effect of Nitric Acid Concentration on the Compressive Strength of Laterized Concrete

Laterized concrete is concrete in which some or all of the fine aggregates is from laterite. In this study, the effects of varying nitric acid concentrations (0%, 5%, 10%, 15%, and 20%), mix proportions (1:1:2, 1:1½:3), exposure period (28, 56, and 84 days) and percentage laterite content (0%, 25%, and 50%) on the compressive strength of laterized concrete were investigated. The tests were carried out with a view to simulating the performance of laterized concrete in contact with soluble nitrate-based substances. 100x100x100mm cubes of laterized concrete were cast and moist-cured for 28 days and the strength of concrete at this age was determined. The cubes were thereafter immersed in 0%, 5%, 10%, 15%, and 20% concentrations of nitric acid for a total of 84 days. Compressive strength tests were carried out at the end of 28 days, 56 days and 84 days of immersion. The results of the tests indicated that the compressive strength significantly reduces with increase in acid concentration, immersion period and laterite content. The effect of richness of mix on resistance of laterized concrete to the acidic aggression becomes more pronounced at the highest (50%) laterite content

Performance of Build-operate-Transfer Projects: Risks' cost implications from professionals and concessionaires perspective

Determining cost implication of risk factors on performance of Build Operate Transfer (BOT) projects is a major focus of this study. One-hundred and seventeen structured questionnaires were used to collect information randomly from the respondents which made up of professionals such as Builder, Architect, Quantity surveyor and Civil engineer. Content analysis was carried out on the responses for validation; data were further analyzed with Mean Item Score using Risk Mean Index and validated with regression analysis. Meanwhile, the most common risk to all the projects executed are inflation, variation to works, change in government policy and fluctuating nature of foreign exchange with inflation being the highest on rating scale of 0.1 to 1.0 with corresponding cost implications and years. Against the background of the research outcome therefore, cost and time is used in this context as a model typifying the extent of risk implication experienced on the projects

COST AND TIME PERFORMANCE INFORMATION OF BUILDING PROJECTS IN DEVELOPING ECONOMY

The construction industry plays a very important role in nation development and in construction project delivery and timely provision of shelter and dwelling units for the masses. The aim of the study therefore is to study cost and time performance on building project in developing economy, with a view to finding ways of improving cost and time performance on building projects. Some of the developing in used in this context includes: Nigeria, Togo, Cameroun, and Ghana. A population size of 70 was selected, and a total sample size of 59 respondents was used in this study, with questionnaire distributed to construction professionals. Variables pertaining to the above listed targets were identified and incorporated into questionnaires as the primary source of data. The data was collated and analysed, using mean item score ranking, percentages and the use of descriptive statistics. It was discovered that variables like rising prices of building materials, inclusion of additional work as a result of clients’ request, deterioration in economic situation, were identified as the top causes of variation in construction project from developing countries. Also, cost, poor planning and scheduling, delay in payment approval for additional work, work suspension by client, were identified as top causes of time and cost variations. The study recommend among other things that: full consideration should be given to projects from inception to completion, adequate and effective consultancy services for clients, as well as strict follow up of programme of works by every contractor for a construction project

Effect of Nitric Acid Concentration on the Compressive Strength of Laterized Concrete

Laterized concrete is concrete in which some or all of the fine aggregates is from laterite. In this study, the effects of varying nitric acid concentrations (0%, 5%, 10%, 15%, and 20%), mix proportions (1:1:2, 1:1½:3), exposure period (28, 56, and 84 days) and percentage laterite content (0%, 25%, and 50%) on the compressive strength of laterized concrete were investigated. The tests were carried out with a view to simulating the performance of laterized concrete in contact with soluble nitrate-based substances. 100x100x100mm cubes of laterized concrete were cast and moist-cured for 28 days and the strength of concrete at this age was determined. The cubes were thereafter immersed in 0%, 5%, 10%, 15%, and 20% concentrations of nitric acid for a total of 84 days. Compressive strength tests were carried out at the end of 28 days, 56 days and 84 days of immersion. The results of the tests indicated that the compressive strength significantly reduces with increase in acid concentration, immersion period and laterite content. The effect of richness of mix on resistance of laterized concrete to the acidic aggression becomes more pronounced at the highest (50%) laterite content. Keyword: compressive strength, laterized concrete, nitric acid concentrations, percentage laterite content

Recycling fine sandcrete block waste (FSBW)as fine Aggregate in the production of sandcrete Block

The study investigated the use of Fine Sandcrete Block Waste (FSBW) as fine aggregate in the production of sandcrete blocks with a view of controlling waste and decongesting block molding production sites. Standard sandcrete blocks of size 450mmX225mmX225mm were prepared from a mix ratio 1:6 (cement: fine aggregate) containing sand and FSBW as fine aggregates. The sand was partially replaced by FSBW in the mix within the range 0% - 90% in steps of 10%. The blocks were cured for 28 days and then tested for compressive strength. The physical properties of both the sand and FSBW were also determined. The results of the study revealed that the physical properties of FSBW compares favorably with those of conventional sand with the exception of water absorption. It further showed that the density and the compressive strength of the tested blocks decrease as the percentage replacement of sand with FSBW increases. The density of the blocks varied linearly with the compressive strength. Blocks prepared for mixes having 50% FSBW content or less were found to satisfy the minimum recommended compressive strength of 3.45N/mm2 (NIS 87:2000)

STRUCTURAL CHARACTERISATION AND QUALITY ASSESSMENT OF PRIMARY REINFORCED CONCRETE BUILDING MATERIALS

This research assessed the structural characteristics and quality of reinforced concrete primary materials which are cements, aggregates (fine and coarse) and reinforcing steel used in concrete works in Lagos State with a view to determining the extent to which they conform with the requirements of relevant standards. This is achieved by using relevant laboratory procedures to determine their physical, mechanical, chemical and microstructural properties and compare them with the relevant standards. Concrete cube crushing and pullout bond strength tests were performed in standard manner to measure the performance of the studied materials in reinforced concrete. The results of the various tests were analysed using relevant statistical tools such as Analysis of variance, mean standard deviation and relevant characteristic formulae as recommended in the appropriate standards. The highest 28-day cement mortar strength developed by the tested cement brands was 45.06 MPa (Brand C3). Two of the tested cement brands had 28-day compressive strengths below 28 MPa and hence did not meet the strength requirements, 32.5 MPa or 42.5 MPa, as specified in standards and they were the brands whose strength details (strength class and type) were not displayed on the bags unlike the other brands that complied. The cement microstructures complements the findings in the chemical and mechanical analyses. The fine aggregates met most of the standard requirements but the river-dredged fine aggregates performed better than its burrow-pit counterparts with both containing higher chloride content of about 0.3% as against the specified maximum of 0.2% with the river-dredged sand recording higher values (0.304% average) than the burrow-pit sand (0.152% average). All the coarse aggregates possesses satisfactory mechanical properties with samples G3 and G4 slightly more satisfactory. The physical and chemical properties of the steel brands were marginally satisfactory though None of the tested steel samples measured up to the actual diameter. The reduced bar xix diameter reduced the strength further by as high as 23%. The performance of these primary materials in normal strength concrete was marginally satisfactory as they produced concrete of around 20 MPa but concretes made with cements brands with unbranded strength properties performed a little below standard (0.205 MPa mean deviation lower from the standard value) and others produced 2.893 MPa, mean deviation higher from the standard value; higher 28-day concrete compressive strengths were obtained with the river-dredged fine aggregate when compared with values recorded using the burrow-pit sand as fine aggregates in the tested concrete samples. The difference in the coarse aggregate performance was also marginal with the coarsest performing least in normal concrete. It was observed that interaction of fine aggregates and coarse aggregates had significant effects (α ˂ 0.05) on the compressive strengths of the resulting concrete. The 12mm diameter steel rebars possess better bonding properties than its 16mm counterpart and steels with higher relative rib area possess better bond strength with concrete. The best concrete performance was obtained with a combination of tested cement brand C3, fine aggregate sample S3 and coarse aggregate sample G3, with the recorded mean strength of 26.51 MPa, 32.5% above targeted mean value of 20 MPa. The study further revealed that the concrete’s primary materials available in Lagos State are adequate to produce a good normal concrete but the steel reinforcements possess deficient mechanical properties that could compromise its role in reinforced concrete structures. It is recommended that only branded cements with defined type and strength label be utilized in concrete production, fine aggregates be sieved and washed before application in concrete for optimum performance and Nigerian Standard Organizations should further monitor the steel industry for greater compliance with standards

COST AND TIME PERFORMANCE INFORMATION OF BUILDING PROJECTS IN DEVELOPING ECONOMY

The construction industry plays a very important role in nation development and in construction project delivery and timely provision of shelter and dwelling units for the masses. The aim of the study therefore is to study cost and time performance on building project in developing economy, with a view to finding ways of improving cost and time performance on building projects. Some of the developing in used in this context includes: Nigeria, Togo, Cameroun, and Ghana. A population size of 70 was selected, and a total sample size of 59 respondents was used in this study, with questionnaire distributed to construction professionals. Variables pertaining to the above listed targets were identified and incorporated into questionnaires as the primary source of data. The data was collated and analysed, using mean item score ranking, percentages and the use of descriptive statistics. It was discovered that variables like rising prices of building materials, inclusion of additional work as a result of clients’ request, deterioration in economic situation, were identified as the top causes of variation in construction project from developing countries. Also, cost, poor planning and scheduling, delay in payment approval for additional work, work suspension by client, were identified as top causes of time and cost variations. The study recommend among other things that: full consideration should be given to projects from inception to completion, adequate and effective consultancy services for clients, as well as strict follow up of programme of works by every contractor for a construction project