INFLUENCE OF STEEL FIBRE ON CONCRETE
Advancements in technology enhances not only human comforts but also damages the environment. Use of steel fibre has become popular and safe now. Today the construction industry is in need of finding cost effective materials for increasing the strength of concrete structures. Hence an attempt has been made in the present investigations to study the influence of crimpled steel fibre concrete at a dosage of 0.8 % volume of concrete. Experimental investigation was done using M20 mix and tests were carried out as per recommended procedures by relevant codes. The study parameters of this investigation included compressive strength, split tensile strength and flexural strength of conventional and fibre reinforced concrete. The results indicated that the compressive, split tensile and flexural strength of fibre reinforced concrete is increased by 32.14%, 52.38%, 12.68% respectively when compared to the conventional concrete.
The high - calcium fly ash as a component of self-compacting concrete
In the paper the basic influence trends of different composition and properties High Calcium Fly Ash (HCFA) on fresh mixture properties of Self-Compacting Concrete. HCFA was used as a replacement for a part of cement in the mixture (2 types of fly ashes, also activated by grinding) or as an additive to cement (also in combination with other additives as F-class ash and ground granulated blast furnace). Primary and secondary effects of admixtures action were investigated – in the first place: rheology (using rheometrical test). Discussion about the results covers mechanism of high - calcium fly ashes (C-class) influence on effectiveness of admixtures. The research has shown the negative influence of raw calcium fly ash (without grinding) added to concrete mix on its rheological properties and workability. Activation of fly ash (by grinding) improves its properties, and becomes positive as an additive to concrete mixes. Without a doubt, in many cases the problem is the loss of workability, but it does not concern cement composites. The current state of knowledge is not sufficient to effectively control of SCC mixtures with HCFA. Further research is needed, especially taking into consideration the impact which the changeable physical and chemical properties of HCFA and cement type have. The possibility of applying calcium fly ash as a partial replacement for cement in concrete and other cement components has been ascertained. An analysis on the effect of HCFA content on the properties of selected concretes of the new generation is the subject of this article. The paper presents test results for the self-compacting concrete SCC modified by HCFA, SCC mixes with cement modified by HCFA, high performance self-compacting concrete HPSCC modified by HCFA, and FRSCC mixes modified by selected types of steel and synthetic fibers. The results include studies on samples belonging to classes of slump flow SF, classes of viscosity T500, the compressive strength tests: ƒcm,28. The concrete mix was tested with a varying amount of lime fly ash lime (10-20-30%), as equivalent of cement. The studies have confirmed the possibility of using HCFA in new generation concretes while maintaining the assumed technological parameters for concrete mixtures, especially their workability.
FLEXURAL STRENGTH OF REINFORCED POLYMER CONCRETE MADE WITH RECYCLED PLASTIC WASTE
Investigators evaluated the flexural behavior and strength prediction of steel-reinforced polymer concrete (PC) using unsaturated polyester resins based on recycled polyethylene terephthalate (PET) plastic waste. Most beams were singly reinforced with steel bars in the tensile zone. Some beams used double reinforcement with steel bars in the tensile and compression zones. Test results revealed that very good flexural strength can be obtained with reinforced PC using unsaturated polyester resins based on recycled PET. Researchers first investigated prediction of the ultimate flexural strength of steel-reinforced PC beams by using the traditional American Concrete Institute (ACI) approach developed specifically for steel-reinforced portland cement concrete. The findings of this analysis revealed that the ACI method produces conservative results when applied to reinforced PC. An alternative method of predicting the ultimate flexural strength of PC is introduced using multiple regression analysis on the experimental data.