Compressive Strength of Volcanic Ash/Ordinary Portland Cement Laterized Concrete

This study investigates the effect of partial replacement of cement with volcanic ash (VA) on the compressive strength of laterized concrete. A total of 192 cubes of 150mm dimensions were cast and cured in water for 7, 14, 21, and 28 days of hydration with cement replacement by VA and sand replacement by laterite both ranging from 0 to 30% respectively, while a control mix of 28-day target strength of 25 N/mm2 was adopted. The results show that the density and compressive strength of concrete decreased with increase in volcanic ash content. The 28-day, density dropped from 2390 kg/m3 to 2285 kg/m3 (i.e. 4.4% loss) and the compressive strength from 25.08 N/mm2 to 17.98 N/mm2 (i.e. 28% loss) for 0-30% variation of VA content with no laterite introduced. The compressive strength also decreased with increase in laterite content; the strength of the laterized concrete however increases as the curing age progresses

Influence of curing Media on the Compressive strength of Palm Kernel Shell (PKS) concrete

The influence of curing media on the compressive strength of palm kernel shell concrete with varying coarse aggregate sizes (5-10 mm, 5-14 mm and 5-20 mm) and replacement level of granite with palm kernel shell (0- 100 % in steps of 25 %) were investigated in this study. The results showed that the compressive strength was significantly influenced by the curing media. Compressive strength of palm kernel shell concrete decreased from curing media CM-1 to CM-3 (CM-1: complete immersion; CM-2: partial immersion; CM-3: no immersion) with increase in percentage replacement of granite with palm kernel shell from 0 % (control) to 100 % in steps of 25 %. However, compressive strength increased from curing media CM-1 to CM-3 with increase in coarse aggregate sizes. The ANOVA showed that the curing medium had significant effect on the compressive strength. The Duncan’s multiple range tests revealed that the mean compressive strengths at different aggregate sizes, replacement levels and curing media were significantly different

Effect of Coarse Aggregate Sizes and Replacement Levels on the Strength of Palm Kernel Shell (PKS) Concrete

The maximum coarse aggregate size used in concrete can impact on its strength. An investigation of the effect of coarse aggregate size and replacement level of granite with palm kernel shell (PKS) on the compressive and tensile strengths of PKS concrete were investigated. Mix proportion by weight of 1:1½:2 with w/c of 0.50 were used. All samples were tested at 7 and up to 90 days. Results showed that both compressive and splitting tensile strengths increased with increase in aggregate sizes. Both strengths however decreased with increase in replacement levels of granite with PKS. Optimum replacement level of granite with PKS was 25% with compressive and tensile strengths of 22.97 N/mm2 and 1.89 N/mm2 respectively at maximum coarse aggregate size of 20 mm. However, at 50% PKS content, which results in lightweight concrete, compressive strength was 18.13 N/mm2 which is above the minimum value of 17 MPa for lightweight concrete

Influence of Curing Age and Mix Composition on Compressive Strength of Volcanic Ash Blended Cement Laterized Concrete

This study investigates the influence of curing age and mix proportions on the compressive strength of volcanic ash (VA) blended cement laterized concrete. A total of 288 cubes of 100mm dimensions were cast and cured in water for 3, 7, 28, 56, 90 and 120 days of hydration with cement replacement by VA and sand replacement by laterite both ranging from 0 to 30% respectively while a control mix of 28-day target strength of 25N/mm2 (using British Method) was adopted. The results show that the compressive strength of the VA-blended cement laterized concrete increased with the increase in curing age but decreased as the VA and laterite (LAT) contents increased. The optimum replacement level was 20%LAT/20%VA. At this level the compressive strength increased with curing age at a decreasing rate beyond 28 days. The target compressive strength of 25N/mm2 was achieved for this mixture at 90 days of curing. VA content and curing age was noted to have significant effect (α 0.5) on the compressive strength of the VA-blended cement laterized concrete

Effect of granite dust on the performance characteristics of kernelrazzo floor finish

This study is part of an on-going research on the durability performance of kernelrazzo, a type of terrazzo floor finish. It investigated the effect of partial replacement of the coarse aggregate with granite dust on the compressive strength, water absorption capacity and density of kernelrazzo. Two mix ratios (1:3 and 1:4), varying aggregate replacements of marble chipping with burnt palm kernel shells amounting to 0%, 25%, 50%, 75% and 100%, varying percentage replacements of all coarse aggregates with granite dust amounting to 0%, 10%, 30% and 50% were used. Cost comparisons were also made. Test results showed that the compressive strength of kernelrazzo increases up to a maximum of 30% coarse aggregate replacement by granite dust for both mixes for 0–50% replacement of marble chippings with palm kernel shells. For 75–100% marble chippings replacement, the compressive strength increases with increasing amount of granite dust. The water absorption capacity and density (upto 30% of granite dust) decrease and increase, respectively, with increase in percentage of granite dust. The cost of kernelrazo decreases with increase in the percentage of replacement of coarse aggregates with granite dust, except for 100% marble chipping replacement. It was recommended that to produce a good kernelrazzo floor finish in terms of strength, durability, density, water absorption capacity and cost, the overall coarse aggregate should not contain more than 50% of palm kernel shells for 1:4 and 1:3 mix ratios with a maximum of 30% aggregate replacement with granite dust. ? 2004 Elsevier Ltd. All rights reserved

An Investigation into the Pozzolanic properties of Dutsin Dushowa volcanic ash of Jos Plateau

This study investigates the pozzolanic properties of the volcanic ash (VA) sample obtained from Dutsin Dushowa, Kerang in Mangu Local Government Area of Plateau State. Chemical Analysis of the VA sample was carried out to determine the oxide contents, so also were some physical properties (specific gravity, fineness, soundness, consistency, and water requirement and setting times (initial and final)) tests carried out on the VA sample and VA-blended cement samples. The result reflects a Silicon Dioxide (SiO2) content of 41.13% and a total Silicon Dioxide, Iron Oxide, and Aluminium Oxide (SiO2+Fe2O3+Al2O3) content of 70.99%. The VA sample has a specific gravity value of 2.65 kg/m3 while the VA-blended cement was noted to be finer than the control (Dangote - Obajana) cement. The soundness of the VA-blended cement ranged between 1.5 and 4.5 for replacement levels of 0% to 30%. The consistency increased from 30.0% to 31.5% as VA substitution increased from 0% to 30%. The water required for a standard consistency was noted to increase as the VA content increased. The initial and final setting times increased from 50 to 105 minutes and 135 to 180 minutes respectively for this replacement levels. All the VA-blended cements thereby satisfy the various code requirements up to the 30% replacement levels

Effect of Batching Methods on the fresh and hardened properties of Concrete

This paper investigated the effect of batching by mass and volume on concrete’s compressive strength and workability. Influence of mix proportion at five levels and various water-cement ratios were also studied. All samples were cured by complete immersion in water and tested up to 28 days. The results indicated higher workabilities for concrete batched by mass than concrete batched by volume at all w/c ratios and mix proportions investigated. The workability increased with increase in w/c ratios in both methods. The compressive strength results showed that for rich structural mixes (1:1:2 and 1:1.5:3), concrete batched by mass had 20 % and 6 % strength increases respectively over the concrete batched by volume. Ordinary structural mix (1:2:4) had 14 % increase while non-structural mixes (1:3:6 and 1:4:8) had 8 % and 6 % increases respectively. In all cases, concrete batched by mass had better fresh and hardened properties of concrete

Performance assessment of Makurdi burnt Bricks.

This work involved onsite observation of the production process; determination of physical properties and chemical composition of the soil sample used for production of Makurdi burnt bricks (MBB). A total of 22 brick specimens, of the MBB was examined in the laboratory for compressive strength, water absorption and abrasion resistance. The results reveal the soil sample as a true laterite having a Silica-Sesquioxide ratio of 1.01, Silica content of 42.95 and clay content of 27.38 and total clay + silt content of 30.78. The Atterberg’s limit test gave the liquid limit as 36.79; plastic limit, 26.11and plastic index, 10.68. Compressive strength was 3.46 N/mm2 and 11.75 N/mm2 for Samples A and B respectively; Average water absorption for Sample B (16.49%) was double that of Sample A (8.58%) while the Abrasion resistance ability of Sample B (33.67%) was four times better than Sample A (9.32%)

Organisational Culture and Employees Commitment in Public Tertiary Institutions in Lagos State, Nigeria

DU study investigated the relationship between organizational culture and employees' C0111111ltment in public tertiary institutions in Lagos State, Nigeria. Four hypotheses were tated In this study. The descriptive research design type was adopted for the study. The population of the study comprises all the non-teaching and teaching employees in public tertiary institutions in Lagos State. The simple random sampling technique was first adopted to select four out of the seven public tertiary institutions in Lagos State for the study. The simple random sampling was fUrther used to select 50 employees from each of the four public tertiary institutions comprising a total of 200 samples for the study. An instrument tagged "Organizational Culture and Employees Commitment Questionnaire" was used to collect data for the study. The instrument was validated and a reliability coefficient of 0. 78 was obtained for the instrument. Data collected were analyzed using descriptive and inferential statistics. Results from the data analysis indicated that significant relationship exist between organizational culture and employees' commitment in public tertiary institutions in Lagos State. It was fUrther found that significant difference exist in the commitment of employees of different sex, ages and length of service to their institutions in Lagos State should Management improve on the cu"ent rewards system in their institutions to enhance employees' commitment levels as well as output among other

An Analysis of Factors Influencing Hiring/ Placement of University Graduates in Nigeria

1bia study notes the alarming rate of graduate unemployment and analyses the factors iaftuencing labour market demand for University graduates in Nigeria. A total of II 0 Labour Orpnizations was randomly sampled within Lagos metropolis. The study adopts a descriptive survey design. With the aid of a structured questionnaire and unstructured interview questions, relevant information was collected. Four hypotheses were postulated and tested at 0.05 level of significance using the chi-square. Finding shows that there are significant relationships between the experience, Government's economic policies, Quality of degree, Area of specialization and hiring I placement of Labour by Employer. The study concludes by suggesting the way out for the endemic state of unemployment in general and graduates from Nigeria Universities in particular