This paper presents the influence of sulphuric acid on compressive strength of concrete made with cement blended with periwinkle shell ash (PSA). The cement component was replaced with PSA at 0 %, 5 %, 10 %, 15 % and 20 %. Concrete mix ratio of 1:2:4 and a constant water cement ratio of 0.6 was used. A total of 180 cube specimens (150mm x 150mm x 150mm) were cast and tested for compressive strength at 7, 14, 21 and 28 days of immersion in potable tap water (as control) and (5 % and 10 %) sulphuric acid solutions. Test results showed that the compressive strength increased with age and decreased with PSA content for specimen cured in water (control); while for specimen cured in sulphuric acid solutions, the compressive strength decreased with age, PSA content as well as sulphuric acid content. The statistical analysis of variance showed that the sulphuric acid concentrations, PSA contents and curing age have effect on the concrete compressive strength. Regardless of the concentration of exposure conditions, it is concluded that PSA did not lighten the adverse effects of sulphuric acid on the compressive strength of cement blended with PSA.

No abstract

No abstract

No abstract

In this research study, Scheffe's second degree polynomial based model was adapted for the optimization of the mechanical properties of a five component concrete. Here, rice husk ash which is derived from solid waste and contains high quantity of aluminosilicates which makes it a pozzolanic material is used as the fifth component in the concrete mixture. Applying Scheffe's statistical simplex methodology, the mixture formulations; a total of ninety concrete cubes of 150 × 150 × 150 mm dimension were produced including the control points used for testing the adequacy of the model. The concrete sample were cured for 28 days before crushing test is carried out to obtain its compressive strength. The maximum compressive strength of 33.45 N/mm 2 was achieved with a corresponding mix ratio of 0.60:0.65:1.30:1.60:0.35 for fraction of water, cement, fine aggregate, coarse aggregate and rice husk ash respectively. The Scheffe's model equation developed is Ŷ = . The formulated mathematical model was validated and a suitable relationship was observed between the experimental and predicted values based on the outcomes of student t test and analysis of variance. The model can predict the compressive strength of rice husk ash blended cement concrete so as to inform early decision making when used as construction material.

No abstract

No abstract

Construction industry is complex in nature because it contains large number of parties such as clients, consultants and contractors. The factors that influence construction management practice differ from country to country, due to prevailing conditions. The objective of this project is to identify factors that influence construction management practice in Nigeria construction industry and elicit perceptions/ranking of the severity using relative importance index of the various factors. A comprehensive literature review was conducted to generate a set of factors believed to influence construction management practice in Nigeria. A questionnaire survey was conducted and fifty-seven (57) factors were identified, grouped into nine (9) categories, evaluated and ranked from the construction actor's perspectives. 108 questionnaires were distributed to the key construction actors as follows: 45 to contractors, 33 to consultants and 30 to clients. Out of these questionnaires distributed, 92 were received (85%) as follows: 40 (88.9%) from contractors, 28(84.8%) from consultants and 24 (80%) from clients as respondents. The enlarged features included those from both previous Nigerian studies and other related international studies represented in the literature. The degree of agreement between parties regarding the ranking of factors was determined according to Kendall's Coefficient of Concordance and the survey findings indicate from three target groups (contractors, consultants and clients) agree that the most important factors that influence management of construction projects are as follows: conflicting design information, effective co-ordination of resources, critical path method, materials availability, setting timeliness, civil strife of riots, sense of belonging & identification with the project team, lack of construction management knowledge and known work progress.