The performance of Portland cement in concrete or mortar formation is very well influenced by chemical compositions among other factors. Many engineers usually have little information on the chemical compositions of cement in making decisions for the choice of commercially available Portland cement in Ghana. This work analyzed five different brands of Portland cement in Ghana, namely, Ghacem ordinary Portland cement (OPC) and Portland limestone cement (PLC), CSIR-BRRI Pozzomix, Dangote OPC, and Diamond PLC. The chemical compositions were analyzed with X-Ray Fluorescence (XRF) spectrometer. Student’st-test was used to test the significance of the variation in chemical composition between standard literature values and each of the commercial cement brands. Analysis of variance (ANOVA) was also used to establish the extent of variations between chemical compositions and brand name of the all commercial Portland cement brands. Student’st-test results showed that there were no significant differences between standard chemical composition values and that of commercial Portland cement. The ANOVA results also indicated that each brand of commercial Portland cement varies in terms of chemical composition; however, the specific brands of cement had no significant differences. The study recommended that using any brand of cement in Ghana was good for any construction works be it concrete or mortar formation.

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Curing of cement based products such as concrete and mortar, is very important to achieve good strength and durable products. However the curing environment plays a pivotal role in the overall quality of cement based products in terms of strength development. ASTM C192 allows moist curing either in a fog room or under water. However, these must meet ASTM C511 which controls temperature, and specifically for water curing, the concentration of calcium ions in the curing solution. Unfortunately in many parts of the world, water curing literally means curing in tap water. This is done primarily because there is a lack of knowledge or ignorance regarding the mobility and roll of calcium hydroxide in the curing process. To illustrate the differences, in this study, straight ASTM Type I/II Portland cement and that mixed with powdered waste clay bricks as a cement extender were used to prepare two different batches of mortars. The chemical properties of the powdered waste clay brick met the ASTM C618 standard specifications for Class N pozzolans. Both mortar specimens were cured under two different environment comprising of either water and lime saturated water. Mortar specimens were tested for compressive strength at 3, 7, 14 and 28 days of either curing conditions. Test results indicated that mortar specimens cured in lime saturated water obtained higher strength than those cured in fresh water at all ages of curing. Statistical inference drawn from ANOVA testing showed that curing conditions had significant impact on strength development of the blended and unblended cement systems. The study recommends that testing of concrete and mortar samples and other research related works be performed in lime saturated water other than fresh water. * Corresponding author. M. Bediako et al. 34

Cost estimation is particularly difficult, often leading to considerable deviations. For capital projects, especially transport infrastructure projects, deviations hover around an average of 28% of the estimated cost. There are several factors that cause these deviations between the final accounts and the contract sum. How these factors combine to cause deviations between the contract sum and the final account in recent times has been of great concern to construction managers and researchers alike. This study sought to identify the significant factors that result in deviations between contract sums and the final accounts of capital projects. Using a sample size of 45, comprising contractors, consultants, and clients, the factors identified using Relative Important Indices were “price fluctuations,” “late material delivery,” “changes in the scope of work,” “fluctuations in the market demand,” and “changes in design.” Using Kendall’s coefficient of concordance, a coefficient p value of 0.068 was obtained. As such, the null hypothesis was rejected as there was a level of agreement among the respondents. Again, based on a significance test run, 26 out of the 40 identified factors used for the analysis were seen to be significant in influencing the deviations between contract sums and final accounts figures.

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