Effect of Bogue Potential Phases of Clinker on the Mechanical Strength of Fly ash-Limestone Based Portland Composite Cement

Continuous rise in population coupled with infrastructural requirements leads to increasing demand of cement which is projected to be around 4.8 billion tons by 2030 and 6.0 billion tons annually by 2050 from current production level of more than 4.2 billion tons [1], and this further requires judicious use of natural resources, particularly limestone on one side and to mitigate carbon and energy footprints on other for sustainable development. Therefore, to bring down environmental impact during cement production, cement industries have been engaged over the years to substitute Portland cement with alternative cementitious materials; fly ash, granulated blast furnace slag, limestone etc individually or in combination of two-three mineral constituents in the manufacture of blended cements, which showed better durability characteristics in comparison to ordinary Portland cement. The formulation and commercialisation of these cements largely depends on the quality of Portland clinkers in terms of oxide constituents, potential as well as actual phase composition, morphology and granulometry of alite and belite grains, along with availability and quality of the cementing materials, prevalent standard norms and regulations. In view of above, present paper highlights the effect of different clinkers in terms of potential minerals as per Bogue calculations (CL-1:C3S-48.20%, C3A-6.30%; CL-2:C3S-54.20%, C3A-9.30% and CL-3: C3S-60.05%, C3A-9.0%) on mechanical strength of fly ash-limestone based ternary cement blends, Portland composite cements, similar to CEM-II/A, B-M as per EN-197-1, prepared with 15, 20, 25, 30 and 35% by weight fly ash and 5 & 10% by weight limestone, by inter-grinding of all cement constituents process, maintaining Blaine’s fineness at 370±10m2/kg, and the results of compressive strength at different curing ages showed optimum strength development in case of clinker CL-2 with potential phases, C3S-54.20% and C3A-9.30%, thus leading to better management of natural resources and extended mine life.

Energy Absorption Capacity of uPVC-Confined Concrete

This research documents the results of tests on stub columns tested under repeated monotonic compression load. Two unplasticized polyvinyl chloride (uPVC) tubes were filled with normal and high strength concrete. From each type of concrete three control specimens were also cast for comparison purposes. The experimental test results show that the unconfined specimens were crushed in the first cycle of loading in contrast to the confined specimens which continued to resist the applied load after several cycles of repeated loading. Furthermore, by using the polymeric tube, the failure of concrete core switches from sudden explosive failure to non-brittle failure with the composite specimen undergoing large progressive deformation in each cycle of loading. For each cycle of loading, the material damage in the composite system was evaluated in terms of the deformations in both the lateral and axial directions.

Short-Term Study on Mechanical and Fresh properties of Micro-silica based Self Consolidating Concrete in Nigeria

The ever increasing environmental challenge arising from improper waste management has been a great concern to researchers and the society. One of such industrial waste is micro silica; a bye-product of the Carbothermic reduction of high purity quartz at temperature of about 2000oC in the presence of coke. The finess of this material and its pozollanic nature makes it suitable for use in the production of self-compacting concrete. In this research micro silica was introduced in percentages of, 5, 10 and 15% as partial replacement of cement in the production of self-compacting concrete. The fresh properties were examined using slump flow, T50cm, slump flow, V-funnel and blockage ratio using L-Box. As the Micro silica were introduced, T50cm time increased, Slump flow reduced, V-funnel flow time increased and L-Box value reduced, due to increase in viscosity. Comparing the experimental results with European Federation of National Associations of Representing for Concrete EFNARC 2002, blockage ratio for 15% was below 0.8. The compressive stresses at 28days were higher than the control at 28days compressive stress with 8.6%, 19.04% and 11.9% for 5%, 10% and 15% respectively. Thus, cement can be partially substituted with micro silica up to 15% with improvement in compressive strength in self-compacting concrete.

Effect of Change in Ambient Temperature on Creep of Concrete

This article reviews the studies on the effect of temperature on the creep of concrete. Indeed, the temperature is one of the most important factors, as its rise leads to an acceleration of creep of concrete and thus an increase in its value compared to concrete under normal temperature. However, creep increases significantly if concrete under load is exposed to a high temperature. Thus, the creep value becomes higher than that of concrete exposed to a constant temperature (of the same level). Unfortunately, some of the codes for predicting creep of concrete (for instance the Eurocode) do not take into account the effect of high temperature on the creep of concrete under load. To clarify the impact of heating concrete under load (on creep) and distinguish it from its effect where it is constant, this study was carried out.

Study of the Influence of the Aggressive Environment on the Behavior of Reactive Powder Concrete

Reactive Powder Concrete (RPC) currently represents the family of cementitious matrix materials with properties the most exceptional mechanics and durability. This study aims to investigate the physico-mechanical properties, and the durability in a sulphated environment of a reactive powder concrete using materials available in our region, we have integrated materials rich in silica (slag, silica fume and crushed quartz) in Portland cement with 15, 23 and 25%, respectively. After The remove of the specimens from the mold and place the RPC in the curing box under steam curing conditions of 90 ° C for 72h, let them cool naturally for 24 h, the test pieces are immersed in water at 20 ° C, the specimens are broken in flexion and compression. From this study we can make the following conclusions: The incorporation of additions increases the compressive and flexural tensile strengths, which gives an improvement in the compactness of the mixtures by the pozzolanic effect of these last, by removing the particle size phase in the RPC and the affluence of dune sand (southern Algeria) and slag (industrial waste from the iron ore blast furnace), because Na2SO4 has a major effect on the compressive strength notably for non-fibrous formulations. NaOH improve the compressive strength for all formulation.

Influence of Additives on Flexural Strength of Roller Compacted Concrete

Roller compacted concrete is considered as a sustainable solution. In the present investigation, three types of additives namely (fly ash, fumed silica, and hydrated lime) are implemented as partial replacement of Portland cement for preparation of roller compacted concrete slab samples using dense and gap aggregate gradation. The slab samples were prepared at optimum cement requirement of 12 % and at (2 and 4) % cement below and above the optimum. Beam specimens of (38 x 10 x 8) Cm were extracted from the slab samples using diamond saw. The specimens were subjected to flexural strength determination using two testing modes, the three and the four points loading. It was noticed that the flexural strength under four-points loading mode is lower by a range of (0.787 to 0.732) folds than that under three-points loading mode for dense and gap graded mixtures respectively. It was concluded that the flexural strength increases by (96.2, 84, and 17.2) % and (109, 86, and 9.3) % after replacement of (10, 12, and 15) % of cement by hydrated lime while it declines by (50, 64.6, and 77) % and (0.1, 30.8, and 63.5) % after replacement of (5, 7, and 10) % of cement by fumed silica for dense and gap graded aggregates respectively. The flexural strength of dense graded mixtures increases by 63 % at 20 % replacement by fly ash, however, it increases by (99.7, 53.8, and 1.0) % after replacement of (10, 12, and 15) % of cement by fly ash for gap graded aggregates respectively.

Correlating the Durability Properties of Roller Compacted Concrete

Roller compacted concrete is the zero-slump concrete mixture, usually prepared at low cement content and low workability, and subjected to compaction by rollers to increase the density and improve the aggregate particles interlock. It is recommended for heavy duty pavement and can withstand harsh environment. Modeling the physical behavior of roller compacted concrete exhibits a quick and easy start to predict the future behavior of the material. In the present assessment, roller compacted concrete mixtures have been prepared in the laboratory using three percentages of Portland cement (10, 12, and 16) % to simulate low, medium, and high cement content from roller compacted concrete point of view. The mixtures were poured into the cylinder mold of 101.6 mm diameter and 116.4 mm height in five successive layers. Each layer had practiced 25 blows of the modified Proctor hammer with 4.5 kg weight, falling from 450 mm height. Specimens were withdrawn from the mold after 24 hours and cured for 28 days in a water bath at 20°C. Specimens were subjected to bulk density, absorption, and porosity determination. Test results were analyzed and modeled. It can be observed that the gradation of aggregates (dense or gap)does not exhibit a significant issue in the absorption-density relationship. However, Dense gradation exhibits lower porosity than gap gradation. It can be concluded that the obtained mathematical models may be implemented to predict the relationship between the durability parameters of roller compacted concrete in terms of porosity, absorption, and density with high coefficients of determination.

https://www.acapublishing.com/dosyalar/baski/CEBACOM_2021_196.pdf

The compressive strength of concrete could be evaluated during and after construction because of a weakness in a reinforced concrete structural member appeared. Quality control of concrete in existing and new constructions can be evaluated by several methods. If the compressive strength did not comply with the design requirements, core samples from the low strength structural members are usually taken to evaluate the structural capability. In the construction sites, compressive strengths of columns and shear walls are the most important. Also, the preparing of quite simple reports for the quality control analyses of a construction is common especially in slab and beam analyses. Hence, in this paper, a new sightseeing assessment is recommended to this analysis. In this study, in-situ non-destructive and destructive investigations in newly constructed building slabs and beams were performed because of the weakness of concrete. With this scope, non-destructive and core sampling examinations were performed on slabs and beams according to the TS EN 13791. Building was constructed by using ready-mixed concrete with CEM I 42.5R and CEM II/B-S 42.5N type cement. As a result of this study, it is thought that the TS EN 13791 contains limited information for the evaluation of newly constructed building for concrete because of its varied ingredients. Compressive strength of concrete produced with granulated blast furnace slag like pozzolanic materials instead of cement needs more time to reach required strength if it is not designed for early strength.

Evaluation of Thermal Effects on Slag Cement Concrete’s Strength Properties

The physical, chemical, and mechanical characteristics of concrete change with heat-fire. The effect of thermal load on Slag cement concrete output must be measured because of the crucial role of thermal resistance in concrete structure performance and operation. This work examines the thermal resistance of Slag cement concrete. The concrete cubes were produced and cured for 28 days and then subjected to varying temperatures range of 100°C, 150°C, 200°C, 250°C, and 300°C. Hardness and compressive strength were measured at 30, 45, and 60 minutes; the sample results were compared to those of ordinary Portland cement used for the study. The findings of this experiment demonstrate that strength loss was 0.45% at 100 °C, 1.75% at 150 °C, 2.67% at 200°C, 5.98% at 250°C and 12.04 % at 300 °C, the hardness property increased from 100° to 150°C but decreased with higher temperatures. However, average concrete loss at 300 °C exceeds 20 percent of its compressive strength. This means that higher temperatures have adverse effects on concrete strength. From the test, however, it has been noted that there was an insignificant loss of strength of concrete at temperatures below 250°C and however, above 250 °C, a significant loss of concrete strength was observed. The results indicate that slag concrete has a significantly higher thermal resistance potential than traditional concrete and can be used even in industrial applications.