Compressive Strength Of Self-compacting Concrete Research Articles

Properties of self-compacting concrete mixtures containing metakaolin and blast furnace slag

Rheological, mechanical and durability properties of self-compacting concrete (SCC) mixes produced using blended binders containing metakaolin and blast furnace slag are studied. The rheological properties of SCC mix with metakaolin are characterized by significant yield stress and relatively low viscosity, while the mix with blast furnace slag shows zero yield stress and higher viscosity. The compressive strength of SCC with metakaolin grows very fast during the initial hardening period and remains significantly higher, as compared with the mix with blast furnace slag, up to 90 days. Durability properties of the mix containing metakaolin are excellent. Water absorption coefficient and water penetration depths are very low. The freeze resistance tests show zero mass loss after 56 cycles in deicing salt solution.

Compressive Strength of Self-Compacting Concrete during High-Temperature Exposure

Self-compacting concrete (SCC) is being used in high-rise buildings and industrial structures which may be subjected to high temperatures during operation or in case of an accidental fire. The proper understanding of the effects of elevated temperatures on the properties of SCC is necessary. This paper reports the results of laboratory investigations carried out to study the effects of high temperatures ranging from room temperature to 800°C on the compressive strength of different water-cement ratio SCC and high-strength concrete. It is found that the hot compressive strength of SCC decreases with increasing temperature. Compared with normal-strength SCC, high-strength SCC possesses a larger compressive strength exposed to high temperature. Another result of tests is that addition of polypropylene fibers decreased the strength and probability of explosive spalling.

Mix-design method of self-compacting concretes for pre-cast industry

Some mix-design methods for self-compacting concrete (SCC) have been proposed since the 1990s, but these methods do not address all practical needs. This paper proposes a method that enables the composition of SCC to be designed for a given strength (in this study, from 10 to 50 MPa at age 1 day or from 30 to 70 MPa at age 28 days). In this method, the compressive strength of SCC at an early age is considered an important parameter to answer the needs of the precast industry. The proposed mix-design method is based on optimizing the packing density of aggregates and ensuring the necessary quantity of paste to fill the voids between aggregates and to provide good fluidity of the SCC. The compressive strength of SCC can be estimated according to the Bolomey formula, and the quantity of superplasticizer can be determined by the proposed method.

Genetic programming based formulation for fresh and hardened properties of self-compacting concrete containing pulverised fuel ash

Self-compacting concrete (SCC) flows into place and around obstructions under its own weight to fill the formwork completely and self-compact without any segregation and blocking. Elimination of the need for compaction leads to better quality concrete and substantial improvement of working conditions. This investigation aimed to show possible applicability of genetic programming (GP) to model and formulate the fresh and hardened properties of self-compacting concrete (SCC) containing pulverised fuel ash (PFA) based on experimental data. Twenty-six mixes were made with 0.38 to 0.72 water-to-binder ratio ( W/ B), 183–317 kg/m 3 of cement content, 29–261 kg/m 3 of PFA, and 0 to 1% of superplasticizer, by mass of powder. Parameters of SCC mixes modelled by genetic programming were the slump flow, JRing combined to the Orimet, JRing combined to cone, and the compressive strength at 7, 28 and 90 days. GP is constructed of training and testing data using the experimental results obtained in this study. The results of genetic programming models are compared with experimental results and are found to be quite accurate. GP has showed a strong potential as a feasible tool for modelling the fresh properties and the compressive strength of SCC containing PFA and produced analytical prediction of these properties as a function as the mix ingredients. Results showed that the GP model thus developed is not only capable of accurately predicting the slump flow, JRing combined to the Orimet, JRing combined to cone, and the compressive strength used in the training process, but it can also effectively predict the above properties for new mixes designed within the practical range with the variation of mix ingredients.

Effect of mineral admixtures on the correlation between ultrasonic velocity and compressive strength for self-compacting concrete

Nondestructive testing of concrete is preferred due to its distinct advantage over conventional compression tests. The evaluation by nondestructive methods of the actual compressive strength of concrete in existing structures is based on empirical relations between strength and nondestructive parameters. The aim of the study was to investigate the effects of different types and dosages of mineral admixtures on the correlation between ultrasonic pulse velocity (UPV) and compressive strength for self-compacting concrete (SCC). Different proportions of fly ash (FA) and silica fume (SF) are used as the mineral admixtures in replacement of portland cement (PC) in SCC. The work focused on concrete mixes having a slump flow between 700 and 710 mm. Specimens were prepared and cured in standard 20 ± 3°C water for periods of 3, 7, 28, and 130 days. At the end of each curing period, compressive strength and UPV were determined. Tests were carried out on 150-mm cubic specimens to evaluate the compressive strength and UPV of SCC. The results of this research indicate that reductions in the compressive strength due to SF were lower than those for FA at all levels of replacement at 3 days, while both UPV and compressive strength at early ages were very low at all levels of mineral admixtures. However, with the increase of the curing period, both UPV and compressive strength of SCCs containing both FA and SF increased. The correlation between UPV and compressive strength is also exponential for SCCs containing both FA and SF. However, constants for each pozzolana were different for each level of replacement of PC in SCCs.

Permeability, porosity and compressive strength of self-compacting concrete

Most deterioration affecting the durability of self-compacting concrete structures is mediated by water penetration in the concrete, a condition related to its porous structure. The present study analyzes these two factors. To this end, two types of concrete were prepared, a self-compacting and a traditional vibrated concrete, with different W/C ratios and different types of cement. The results of low-pressure water testing to evaluate permeability and analyses to determine compressive strength and pore size distribution showed that self-compacting concrete has lower capillary porosity than traditional concrete, which would explain its greater resistance to water penetration. Such concrete likewise reached higher strength values, except where large proportions of lime powder with low sand equivalents were used in its manufacture, when lower strength was recorded. Lastly, the depth of water penetration and compressive strength were found to be linearly correlated. That correlation was seen to depend, in turn, on the type of concrete, since for any given strength level, self-compacting concrete was less permeable than the traditional material.