This paper deals with variability in the performances of seven different superplasticizers chosen among those of most common use belonging to the naphthalene (NSF) and polycarboxylate-based (PCE) families. In particular, compatibility of two naphthalene-based and five polycarboxylate-based admixtures with six different cements available on the Italian market was evaluated by measuring water reduction to manufacture mortars with the same workability at the end of mixing. Two different lots of the same cement (same plant) were used: lot 1 and 2 produced, respectively, on September 2005 and March 2006. Flow retention up to sixty minutes and tendency to entrap air in the mortars were measured. Results confirmed that the average water reduction and flow retention properties are better for PCE compared to NSF superplasticizers. However, experimental data confirm as performances of PCE admixtures are more strongly dependent on the cement type than those of NSF polymers. No differences were detected in terms of the air entrapped between the two superplasticizer families, except for the ACR5 superplasticizer.

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.

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.

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.

This paper presents the evaluation of a new high tenacity monofilament polypropylene fiber for reduction of plastic shrinkage cracks in concrete. The crack reduction potential of the fiber was studied using cement-rich concrete and the performance of the fiber was compared with that of three other presently available fibers (Fiber B, Fiber C, and Fiber D). Performance of these fibers was evaluated by comparing the area of plastic shrinkage cracks developed in control slabs (with no fibers) with the crack area of fiber reinforced concrete slabs. For example, the reduction of crack area due to the addition of the new high tenacity monofilament fiber was 91 percent for a dosage of 0.593 kg/m3 [1.0 lb/yd3], 86 percent for 0.297 kg/m3 [0.5 lbs/yd3] and 57 percent for 0.196 kg/m3 [0.33 lbs/yd3]. The results indicate that the new fiber with fiber length of about 18 mm [¾ inch], and a fiber dosage of 0.593 kg/m3 [1.0 lb/yd3] was most effective in reducing the plastic shrinkage cracks in concrete. For the same fiber quantity, three other fibers were less effective in reducing cracks.