Production of High Strength Concrete

Abstract

The aim of this study was to evaluate the performance of high strength concretes (HSC) containing supplementary cementitious materials. Now a days concrete had demanding requirements both in terms technical performance and economy. The main aim of the investigation program is first to prepare the strength of concrete of grade M80 with locally available ingredients and then to study the effects of different proportions of silica fume and silica fume in conjunction with fly ash in the mix and to find optimum range of silica fume and fly ash content in the mix. The silica fume and fly ash is added by weight of cement as a replacement. The concrete specimens were tested at different age levels,7-days and 28-days for mechanical properties of concrete, namely, cube compressive strength, and length change due to drying shrinkage tests also fresh concrete properties, using slump test has been made. This research presents a part of an ongoing experimental laboratory investigation being carried out for production and characterization of high strength concrete (HSC) for heightening of an existing concrete dam in the south of Sudan, brief description of the main features of the dam and concrete works is presented. Hundreds of specimens were performed and tested using local Sudanese aggregates with addition of supplementary cementitious materials (Silica Fume and Fly Ash) and super plasticizers. Various percentages of silica fume (SF) and fly ash (FA) were added at different water/cementitious materials ratios (w/cm). Thirty three trial mix design of grade (80 MPa) HSC had been success fully produced and their mechanical properties were measured and documented. Two approaches were used in the study statistical approach which described in ACI 211.4 and another one is use JMP statistical program to make a modeling for predicting Compressive Strength and Slump for HSC. The results have offered an important insight for optimizing the rheological characteristics of HSC and permitted to develop guidelines for optimum mix design methods for HSC from locally available aggregates in Sudan. Optimum w/cm ratio it ranges from 0.19 to 0.3. Optimum replacement percentage of SF is not a constant one but depends on the w/cm ratio of the mix it ranges between7 to 15% of cementitious materials. SF contributed to both short and long-term properties of concrete. It is concluded that local concrete materials, in combination with supplementary cementitious materials can be utilized in producing high strength concrete in Sudan