This paper presents the results of an experimental investigation to determine the validity of 0.45-power chart in obtaining the optimized aggregate gradation for improving the strength characteristics of high-performance concrete (HPC). Historically, the 0.45 power chart has been used to develop uniform gradations for asphalt mixture designs; however it has now been widely used to develop uniform gradations for portland cement concrete mixture designs. Some reports have circulated in the industry that plotting the sieve opening raised to the 0.45 power may not be universally applicable for all aggregates. In this paper the validity of 0.45 power chart has been evaluated using quartzite aggregates. Aggregates of different sizes and gradations were blended to fit exactly the gradations of curves raised to 0.35, 0.40, 0.45, 0.50 and 0.55. Five mixtures, which incorporated the aggregate gradations of the five power curves, were made and tested for compressive strength and flexural strength. A control mixture was also made whose aggregate gradations did not match the straight-line gradations of the 0.45 power curve. This was achieved by using a single size aggregate and sand. The water-cement ratio and the cement content were kept constant for all the six mixtures. The results showed that the mixture incorporating the 0.45 power chart gradations gave the highest strength when compared to other power charts and the control concrete. Thus the 0.45 power curve can be adopted with confidence to obtain the densest packing of aggregates and it may be universally applicable for all aggregates.

In this project several reactive powder concretes (RPCs) were studied. In particular their mechanical performance in relation to the type of cement used, the dosage of silica fume, and the amount of steel fibers. Compressive strength, flexural strength, and tangent elastic modulus was monitored with age for RPCs prepared with a water to cement ratio of 0.25. Silica fume was added to the mixture at a dosage up to 27% by weight of cement. An acrylic-based superplasticizing admixture was used at a very high dosage of about 10% by weight of cement in order to achieve very fluid workability. Optimum mechanical performance was obtained for the mixture prepared by using steel fibers at 20% by weight of cement and by adding silica fume at 26% by weight of cement. This mixture was characterized by 28-day compressive strength of 145 MPa, flexural strength of 35 MPa, and tangent elastic modulus of about 57 GPa. On the basis of experimental results, the use of reactive powder concretes for manufacturing thin precast elements appears to be competitive with other and more traditional materials and technologies.

The roadside safety barrier is a protective barrier that is erected around a racetrack or in the middle of a dual-lane highway in order to reduce the severity of accidents. Recently, interest in portable roadside safety barriers has heightened the interest in the development of a low-cost and high-performance alternative to the conventional safety barrier system. A study has been undertaken to characterize fresh and hardened properties of flue gas desulfurization (FGD) cellular concrete (CC) using foaming admixture towards the development of a lightweight roadside safety barrier. Test results indicate that FGD CC using a foaming admixture can be effectively used in manufacturing lightweight roadside safety barriers.

Today, a number of engineering structures and building are being constructed to match environment and urban landscape. From an aesthetics point of view, occurrences of efflorescence on colored concrete, unfinished concrete and concrete products of these structures are critical problems. This research aimed to study and compare the efflorescence of concrete products that substituted cement with industrial by-products namely, fly ash, blast furnace slag and gypsum and normal concrete. Both concrete products and normal concrete were manufacture for paving application in form of interlocking blocks. In this paper, we use the term "non-cement" concrete to refer to the concrete not using industrial cement. A methodology is presented that enables a quantitative evaluation of the total, soluble and insoluble efflorescence and this methodology was used to analyze both non-cement concrete and normal concrete specimens. The results show that the insoluble efflorescence of non-cement concrete is less than that of normal concrete.

The balance between productive construction operations and a quality final product is a constant challenge facing today’s owners and contractors. In the pavement industry, innovative technologies such as the HIPERPAV® II system allow this balanced goal to be obtainable. The software is also a viable option for addressing forensic studies of premature distress. Both proactive and forensic applications are addressed through case studies in this paper. HIPERPAV® models the impact of specific construction operations, concrete mixtures, geometric design, and environmental factors on early age strength and stress development during the construction phase. These combined factors in addition to the traffic loading affect the overall long-term performance of the pavement. The first three case studies review the proactive scheduling of the sawing operations, changes that can be made to minimize the risk of high thermal stresses when a cold front is expected soon after concrete placement, and the time of concrete placement during high temperature conditions. The last case study addresses a forensic investigation where the effect of coarse aggregate type on a continuously reinforced concrete pavement (CRCP) is determined. All case studies emphasize the influence of HIPERPAV® II during the construction planning phase or the usefulness of the software in a forensic investigation.