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This paper presents the development of ambient temperature cured ultra-high-performance geopolymer concrete (UHPGPC). Ultra-high-performance concrete (UHPC) mixtures were developed by completely eliminating Portland cement and activating industrial by-product materials such as ground granulated blastfurnace slag and silica fume.Local standard sand (maximum size 2 mm), quartz sand (600 ìm) and 0 . 16 mm diameter steel fibres of 13 and 6 mm length were used. Fresh properties (density and flowability) and mechanical properties (compressive strength) of the UHPGPC produced under ambient temperature curing conditions were evaluated. Four mixtures with fibres and one mix without fibre addition were studied as the UHPGPC mixtures. The highest average compressive strengths obtained were 175 MPa for UHPGPC with steel fibres (1% 6 mm and 2% 13 mm) and 124 MPa for UHPGPC without fibres. Prismatic specimens (100 3 100 3 500 mm) were cast to determine the flexural strength, which was found to be 10 . 3-13 . 5 MPa and 9 . 1 MPa for mixes with and without steel fibres respectively. The compressive and flexural strengths obtained in this work are comparable to UHPC strengths presented in the literature. Production of this innovative material with industrial by-products and without the conventional curing regimes used for UHPC will improve sustainability and lead to cast-in-situ applications of UHPC.

To cite this article: Senthil Muthalvan Renuka and Chockkalingam Umarani (2018). Effect of critical risk factors causing cost deviation in medium sized construction projects. Journal of Construction in Developing Countries, 23(2): 63-85.Abstract: Risk is the outcome of an event which may be predicted on the basis of statistical probability. Construction projects have inherent risks associated with it. The main aim of this paper is to identify the critical risk factors and to propose a model to find the probability of cost deviation in medium sized construction projects. A total of 46 risk factors were shortlisted based on pilot study and experts' opinion. A questionnaire survey was conducted among 223 various construction professionals each representing one project i.e. from 223 different projects. Based on factor analysis, 46 risk factors which influence the cost deviation in construction projects were classified under nine key risk groups viz. project scope and evaluation risk, work environment risk, documentation and legal framework risk, construction and operational risk, resource productivity risk, knowledge sharing risk, site supervision risk, financial viability risk and lean construction risk. Logistic regression analysis was also carried out to develop a model to find the probability of cost deviation in construction projects. It is concluded that the risk groups such as project scope and evaluation risk, site supervision risk, knowledge sharing risk and lean construction risk are having higher influence in the cost deviation in medium sized construction projects. By setting the effective baseline of the project like estimation of original project cost and detailed project report, cost deviations in medium size construction projects can be eliminated. Detailed recommendations are also provided.

In this study, an attempt has been made to study the effect of alkali activator on the standard consistency and setting times of low calcium fly ash (FA) and ground granulated blast furnace slag (GGBS)- based sustainable geopolymer pastes. Different proportions of FA and GGBS were blended into mixes of geopolymer paste using sodium hydroxide (SH) and sodium silicate (SS) as alkaline activator solution (AAS). Tests on geopolymer pastes for consistency and initial and final setting times were carried out for three different SH : SS ratios of 1 : 1, 1 : 2, and 1 : 3 for both 2.5 M (molarity) and 5.0 M of SH concentration. While increasing the molarity of SH, both consistency and setting time decreased. For all the blended binder mix, the setting time decreases with an increase in the quantity of SS in the alkali activator solution. An increase in the amount of GGBS content in the geopolymer blended binder mix increases the consistency and decreases the setting time. For both 2.5 M and 5 M blended geopolymer mixes, a decrease in the percentage of GGBS and an increase in the percentage of FA increased the setting time. Microstructural studies such as X-ray fluorescence analysis (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR) analyses were carried out, and the results are presented. The FT-IR spectra for the blended binder mixes demonstrated the formation of geopolymerization and the presence of the functional groups.