Journal of Cement Based Composites (CEBACOM)

Ferhad Karim Ashti Sedeeq Ali

The demand for construction of high strength concrete (HSC) in civil engineering zone is growing, particularly in the last couple of years due to the allowability of sustainable and economic buildings with an extraordinary slim design. The concrete curing in the prosses of construction is an operative manner and very essential to provide that concrete structures meet future performance and durability, ACI definition of internal curing (IC) as a procedure by which the hydration of cement continues because of the availability of internal water that is not part of the mixing water. HSC has a low water-to-binder (w/b) ratio, proper curing of concrete is important to ensure that it achieves its planned performance and durability. Conventionally, exterior curing, applied after placing and casting concrete, stays warm and moist to provide continued cement hydration. Lately, theoretically and experimentally comprehends that internal curing (IC) is an important tool to provide additional moisture in the concrete to enhance cement's hydration. Internal curing of HSC is an active technique to lessen or even remove autogenous shrinkage and effects on chemical shrinkage, dry shrinkage, etc. Generally, for internal curing, super-absorbent polymer (SAP) and porous materials like lightweight aggregate (LWA) are used. Built on both water-absorbing mechanism sorts, the influence of internal curing materials on high-strength concrete is studied in this paper.

https://doi.org/10.36937/cebacom.2020.003.001

İlker Tekin Mahfuz Pekgöz Mustafa Uslu

The compressive strength of concrete is the most basic and considerable material property while reinforced concrete structures are designed. It has become a problem to use this value, however, because the control specimen sizes and shapes from country to country may be dissimilar. The study presents the results of an experiment that examined the effect of specimen size on the different classes of compressive strengths of concrete. The study included casting specimens, cubes, and six different classes of the concrete mixture. Compression tests were conducted at the age of 3, 7, and 28 days on 150 mm & 100 mm cube samples. The fresh properties of concrete were measured by slump and unit weights tests. Moreover, the specimen size of concrete has an important role both on the compressive strength and capacity of a curing cabinet. Correlations between compressive strengths and sizes of specimens are compatible for classes of structural concretes. Therefore, it can be used in curing cabinet varying sizes of concretes like 150 mm & 100 mm cube samples. Although almost 220 concrete specimens sized of 150 mm cube can be poured in curing tank, roughly 585 concrete specimens can be poured with using 100 mm cube concrete specimens. The most convenient size resulted from this study is suggested as 100 mm sized cubic specimen that it promote to change the law for concrete both curing and compressive strength test.

https://doi.org/10.36937/cebacom.2020.003.002

Wasiu Ajagbe Sesugh Terlumun Michael Tiza

This work examines the thermal resistance of cement slag concrete. The physical, chemical, and mechanical characteristics of concrete change with heat-fire. The effect of thermal load on cement slag concrete output must be measured because of the crucial role of thermal resistance in concrete structure performance and operation. 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 variations 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, normal concrete loss at 300 °C exceeds 20 percent of its compressive strength. This means that higher temperatures have negative 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 noteworthy loss of concrete strength was observed. The results indicate that slag concrete has a significantly higher thermal resistance potential than traditional concrete, and can, therefore, be used even in industrial applications.

https://doi.org/10.36937/cebacom.2020.003.003

Mahfuz Pekgöz Iyad Asri Ahmed İlker Tekin

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.

https://doi.org/10.36937/cebacom.2020.003.004

Saad Issa Sarsam

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://doi.org/10.36937/cebacom.2020.003.005