Towards Sustainable Self-Compacting Concrete: Effect of Recycled Slag Coarse Aggregate on the Fresh Properties of SCC

Steel industry results in accumulation of steel slag wastes causing severe environmental problems. These wastes can be recycled and replace natural aggregates resulting in sustainable green concrete. In this research, natural aggregates in self-compacting concrete (SCC) are replaced, wholly or partly, by steel slag coarse aggregates that were produced by crushing by-product boulders obtained from the steel industry. Fresh properties, (workability, stability, bleeding, air content, and fresh density) are the crucial ones that affect the final properties of SCC. Therefore, it becomes important to evaluate the impact of SSA on the fresh properties of SCC mixes. The properties that are studied include stability, flowability, blocking, segregation, and bleeding. Furthermore, air content and fresh density are measured. In order to evaluate the impact of SSA on SCC properties, several testing methods are employed. Slump flow, V-funnel, column segregation, sieve segregation, segregation probe, U-shaped box, and VSI tests have been used in the study. The results show that it is possible to produce SCC using steel slag aggregate. Hence, green sustainable SCC can be produced. The results show that the fresh properties become sensitive for SSA replacement ratios exceeding 50%

Design of Normal Concrete Mixtures Using Workability-Dispersion-Cohesion Method

The workability-dispersion-cohesion method is a new proposed method for the design of normal concrete mixes. The method uses special coefficients called workability-dispersion and workability-cohesion factors. These coefficients relate workability to mobility and stability of the concrete mix. The coefficients are obtained from special charts depending on mix requirements and aggregate properties. The method is practical because it covers various types of aggregates that may not be within standard specifications, different water to cement ratios, and various degrees of workability. Simple linear relationships were developed for variables encountered in the mix design and were presented in graphical forms. The method can be used in countries where the grading or fineness of the available materials is different from the common international specifications (such as ASTM or BS). Results were compared to the ACI and British methods of mix design. The method can be extended to cover all types of concrete

Towards Better Understanding of Concrete Containing Recycled Concrete Aggregate

The effect of using recycled concrete aggregates (RCA) on the basic properties of normal concrete is studied. First, recycled aggregate properties have been determined and compared to those of normal aggregates. Except for absorption, there was not a significant difference between the two. Later, recycled aggregates were introduced in concrete mixes. In these mixes, natural coarse aggregate was partly or totally replaced by recycled aggregates. Results show that the use of recycled aggregates has an adverse effect on the workability and air content of fresh concrete. Depending on the water/cement ratio and on the percent of the normal aggregate replaced by RCA, the concrete strength is reduced by 5% to 25%, while the tensile strength is reduced by 4% to 14%. All results are compared with previous research. As new in this research, the paper introduces a simple formula for the prediction of the modulus of elasticity of RCA concrete. Furthermore, the paper shows the variation of the air content of RAC

Design of Normal Concrete Mixtures Using Workability-Dispersion-Cohesion Method

The workability-dispersion-cohesion method is a new proposed method for the design of normal concrete mixes. The method uses special coefficients called workability-dispersion and workability-cohesion factors. These coefficients relate workability to mobility and stability of the concrete mix. The coefficients are obtained from special charts depending on mix requirements and aggregate properties. The method is practical because it covers various types of aggregates that may not be within standard specifications, different water to cement ratios, and various degrees of workability. Simple linear relationships were developed for variables encountered in the mix design and were presented in graphical forms. The method can be used in countries where the grading or fineness of the available materials is different from the common international specifications (such as ASTM or BS). Results were compared to the ACI and British methods of mix design. The method can be extended to cover all types of concrete

Effect of by-product steel slag on the engineering properties of clay soils

AbstractClay soils, mainly if they contain swelling minerals such as smectite or illite, may cause severe damage to structures, especially when these soils are subjected to wetting and drying conditions. High expansion and reduction in shear strength and foundation bearing capacity will take place due to the increase in water content of these soils. The engineering properties of these kinds of soils can be improved by using additives and chemical stabilizers. In this work, by-product steel slag was used to improve the engineering properties of clay soils. Lab and field experimental programs were developed to investigate the effect of adding different percentages of steel slag on plasticity, swelling, compressibility, shear strength, compaction, and California bearing ratio (CBR) of the treated materials. The results of tests on the clay soil showed that as steel slag content increased, the soil dry density, plasticity, swelling potential, and cohesion intercept decreased and the angle of internal friction increased. For the CBR, the results of the tests showed an increase in the CBR value with the increase in slag content