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Properties Of Concrete

Annual Book Of Astm Standards

The properties of RHA samples obtained at different conditions in muffle furnace and their effects on the mechanical behavior of cement have been studied. The properties were characterized by SEM, XRF, XRD and specific surface area. The effect of using RHA as a partial replacement for cement has been investigated by compressive and flexural strengths test. It is showed that in muffle furnace 600 °C is the appropriate temperature for RHA preparation with large specific surface area due to the existences of nanoscale and amorphous SiO 2 . While, long combustion time could increase pozzolanic activity of RHA. The presence of K could decrease the specific surface area and increase the residual carbon content which content should be control strictly. RHA obtained in proper conditions can be used as cement additive to increase compressive and flexural strengths of cement mortar specimens. It is verified that RHA replacement ratio of 10% (by weight) has the best enhancement effect on cement strength.

Studies on effects of burning conditions and rice husk ash (RHA) blending amount on the mechanical behavior of cement

Green Concrete mix using solid waste and nanoparticles as alternatives – A review

A new hydration model of OPC [1, 2] was used in this study. The quantities of hydration products were calculated for saturated state hydration and for samples that have been dried to 11% rh after hydration. The chloride binding of several hydrated phases (C-S-H, monosulfate, hydroxy-AFm, AFt, CH, and Friedel's salt) has been studied and estimated in relation to the chloride content of the pore solution. Combining two new isotherms, for C-S-H and AFm chloride binding in hardened cement paste, and the computed quantities of all hydration products, a new formula for the chloride binding capacity of OPC pastes has been deduced. The new model is based on the chloride binding abilities of each hydrated phase, and therefore can distinguish between their contributions at different free chloride concentrations. When compared to experimental data, the results obtained using this new chloride binding isotherm have proven to accurately describe the chloride binding capacity of OPC pastes, results being within 12% of the experimental values for the whole range of free chloride concentrations considered, of up to 3 M.

Chloride binding related to hydration products part I : Ordinary Portland cement

This research was experimentally carried out to investigate the effects of introducing Rice Husk Ash (RHA) as a Partial Replacement of Ordinary Portland Cement (OPC) on the Structural Properties of Concrete. Rice Husk Ash which is an Agro-Waste and known to be a Super Pozzoland have been used for mass concrete and found to have compressive strength ranging from 33-38.4N/mm 2 at replacement percentages of 10-25% in a mix of 1:1.5:3. A further study was carried out on its flexural properties to determine their moduli of rupture as well as its tensile strength characteristics for the determination of cracking, the values obtained at 28days are 3, 2.5 and 2.4N/mm 2 while the tensile strength values are 1.94, 1.17 and 0.91N/mm 2 at replacement percentages of 10%, 20% and 25%. This research has proved that RHA Concrete can be used as a Structural Concrete at suitable replacement percentages. This research therefore is an investigation of the performance of the concrete made of partially replacing OPC with RHA on the structural integrity and properties of RHA concrete.

Structural properties of rice husk ash concrete.

Slag hydration and chloride binding in slag cements exposed to a combined chloride-sulphate solution

Expansion of CEM I and slag-blended cement mortars exposed to combined chloride-sulphate environments

This paper investigates traffic congestion which has become a common sight in most urban cities of Nigeria. A survey was conducted during the Annual National Conference of the Nigerian Society of Engineers (NSE) which held between 5 th and 9 th December 2011 at the Calabar Tinapa Business and Leisure Resort. 300 questionnaires were distributed among participants comprising experts in transportation planning and design as well as engineers of other disciplines, students, wives of engineers and other invited guests who constitute commuters, car owners/drivers, etc. 196 returns were made and these were analysed to ascertain the broad perspectives concerning the causes of traffic congestion in most urban cities in Nigeria. The results show that poor driving habits, poor road network, inadequate road capacity, and lack of parking facilities constitute the greatest causes of traffic congestion in Nigeria. Also, Lagos, Port Harcourt and Abuja were identified as cities most affected by traffic congestion.

Traffic Congestion in Major Cities of Nigeria

This study investigated the effect of chloride ingress on the hydration mechanism and strength development of plain and slag blended cements. The slag blends were prepared by combining two slags with a CEM I 52.5R-type cement at 30%wt. replacement, while a CEM I 42.5R-type cement was selected as the plain cement. Mortar and paste samples were prepared using a water/binder ratio of 0.5. These were subjected to three different curing regimes – control, 7 and 28 days control curing followed by curing by immersion in a 3% NaCl solution, and tested for compressive strength and hydration using TGA and XRD. Results showed that chloride ingress accelerated the early hydration up to 28 days, and decelerated the later hydration. This effect was more pronounced on samples that were cured for shorter durations before exposure. The slag blends had better strength performance than the plain cement in all curing and exposure conditions.

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Joseph O. Ukpata

Papers

Structural properties of rice husk ash concrete.

Slag hydration and chloride binding in slag cements exposed to a combined chloride-sulphate solution

Expansion of CEM I and slag-blended cement mortars exposed to combined chloride-sulphate environments

Traffic Congestion in Major Cities of Nigeria

Effect of Chlorides and Curing Duration on the Hydration and Strength Development of Plain and Slag Blended Cements