Journal of Cement Based Composites (CEBACOM)

İlker USTABAŞ Fatih DEŞİK

The aim of this study is to compare the compressive strength determined by weight maturity method in dam concretes with compressive strength obtained from fresh concrete and core samples. Within the scope of the study, normal concretes of C25/30 strength class were produced. Samples were taken from ø15x30 cm cylinder molds from normal concrete mixtures having maximum aggregate grain diameter (Dmax) of 25 mm. In this study, the estimated compressive strengths were measured by using a maturity device and the compressive strengths obtained from samples taken from fresh concrete and core samples taken from hardened concrete were measured at close values. In this context, instead of taking samples from fresh concrete and concrete productions, it was concluded that the pressure resistance measurements made by using a maturity device in fresh concrete are reliable.

https://doi.org/10.36937/cebacom.2020.001.001

Yousif Hummaida Ahmed Khalid Salah

Self-compacting concrete (SCC) is a special type of concrete able to flow and compact under its self-weight. The SCC requires high powder content (mainly of cement) up to 600kg/m3 to achieve its properties. This will be problematic if all cement content in the powder exceeded 400 kg/m3used in hot weather of Sudan. This paper investigates addition of Sudanese limestone powder (LSP) to reduce cement content. The LSP dosages between 20% and 28 % (by cement weight) are used in six mixes having maximum cement content 380kg/m3. Results show that five trial mixes achieved the self-compactibility tested by slump flow, sieve segregation, V-funnel and U-box tests. Compressive strength of these mixes show that the LSP increases strength with dosage. Therefore, further investigations of hardened concrete properties are recommended for the successful mixes to be applied in real projects in the Sudan. Also it has been found that dry batching and forced-action pan mixers are the most suitable for producing SCC with high homogeneity compared to commercial tilted-drum mixers.

https://doi.org/10.36937/cebacom.2020.001.002

Abdulkadir Cuneyt AYDIN Abdulkadir KAN Fuat CANDAN Ulviye Gulsum Hasiloglu ARAS Ali ÖZ

The sulphate resistance of variable concretes, including Boron active belite cement (BABC), CEM I 42.5 R and CEM II 32.5 B-S cements, were determined in the present study. The compressive strength, ultrasonic velocity, Schmidt, and unit weight tests were applied to steam cured and water cured samples. Three Na2SO4 solutions of %5, %10 and %20 were prepared for each type of concrete except for the control group and the samples were exposed to the effect of sulphate solutions for 24 weeks. As a result, weight increase was determined in CEM I 42.5 R cement samples the least, and in BAB cement samples the most. As expected, pronounced chemical effect was not observed in samples of cement CEM II.32.5 B-S. On the other hand, while decreases or slight increases were observed in the ultrasound measurements of CEM I 42.5 R cement samples after sulphate test, critical increases were observed in BAB and CEM II 32.5 B-S cement samples. Under sulphate effect, water and steam cures had explicit effects on pressure resistances.

https://doi.org/10.36937/cebacom.2020.001.003

Saeid Golizadeh Fard

This paper investigates the possibility of combining steel fibers with different weight percentages along with their functions in increasing compressive strength, indirect tensile strength and bending strength. It`s been considered an important economic issue for a long time the ability to service and increase the load-bearing capacity of structural materials. Concrete as a widely used structural material is widely used today. Despite its remarkable properties including high ductility, high durability, longevity, availability and low cost, concrete is a brittle material and performs extremely poor under flexural and tensile loads. In general, the breakdown and destruction of concrete is strongly dependent on the formation of cracks and micro-cracks. As the loading increases, the micro-cracks interconnect and form cracks. In order to address this problem and to create homogeneous conditions, a series of thin filaments has been used throughout the concrete in recent decades; They are called fibers. Steel fiber is one of the most commonly used fibers in concrete. In this study, the compressive strength of concrete was investigated which in some specimens reinforced with steel and containing pozzolanic materials, the compressive strength of control samples increased with the use of fiber etc. In the present study, the flexural and tensile strength of steel fiber reinforced specimens were investigated. According to the results, flexural strength increases with increase in steel fibers. The designs contain 1%, 1.5% and 2% of the Dramix hooked steel fibers used in the research. By reinforcing the specimens with steel fibers, the behaviour of tensile concrete is much more flexible than that of non-steel specimens.

https://doi.org/10.36937/cebacom.2020.001.004

Anwar Khitab Sajjad Ahmad Affan Jalil Zain-Ul-Abdin

Concrete is one of the most significant materials, man has produced. Conventionally, it is a mixture of cement, sand, coarse aggregates and water. It is versatile, and gains strength in a few weeks after its casting. It can withstand extreme weather conditions. However, traditional concrete also has some drawbacks. It has low tensile strength and develops cracks, which limit its usefulness. The performance of concrete can be enhanced by carefully selecting its ingredients and employing appropriate modern techniques. One such technique is the use of nano particles. Nano particles, due to their small size, possess very high surface area to volume ratio. They can be used as inert filler as well as chemically active ingredients in cementitious composites. Being filler, they can fill up very small voids in the matrix. As active ingredients, they can result in higher chemical reactivity. This work focuses on the wonders, nano particles have brought in concrete technology. The topics include self-healing, de-pollutant, de-icing and energy-saving concrete materials.

https://doi.org/10.36937/cebacom.2020.001.005