Compressive strength of the concrete

The cement pastes, with or without colloidal sihca, had a water to cement ratio of 0.35 and contained sulfo-nated naftalene formaldehyde resin (NSF) superplasticizer. The colloidal silica was added to the concrete mixture after the superplasticizer so as to minimize prema-mre gelling. The compressive strength of the concrete samples are shown in Table 57.5. 

The compressive strength of the concrete was determined by crushing three cubes of 150 mm size at the age of 7 and 28 days for each mix. The test was carried out according to GB/ T50081-2002. 

Once the concrete maturity curve has been developed, using the elapsed time-temperature calculated from the heat transfer analysis of the laboratory sample, the compressive strength of the concrete at any time can be estimated. 

An appropriate minimum compressive strength of the concrete should be determined to ensure that the ultimate strength of the structural members is governed by the reinforcement. 

Schmidt Hammer. A device for the nondestructive testing of set concrete it is based on the principle that the rebound of a steel hammer, after impact against the concrete, is proportional to the compressive strength of the concrete. (E. Schmidt. Schweiz. Bauzeitung. 15/7/50). 

In this research the polymer superplasticiser (PSP) was found to be more efficient than ordinary superplasticiser (SP) in increasing the flow of the mix, but appeared to have a negative effect on the compressive strength of the concrete (Figures 53 and 54). This might be due to the retarding effect of this type of superplasticiser on the blended binder. Moreover, it would impose an extra cost when using this type of concrete made with waste materials. 

For resource reutilization, scrap tires have been investigated for a long time as an additive to concrete to form Rubcrete for various applications and have shown promising results (55). However, the addition of rubber particles leads to a degradation of physical properties, in particular, the compressive strength of the concrete. 

It can be concluded that the presence of FRC in the tensile area or any part of it leads to the appearance of larger compressive stresses. Thus, the considerable compressive strength of the concrete matrix will be used more effectively. This is valid for concrete as well as reinforced concrete elements. 

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