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This paper reports the results of a study conducted to investigate the effect of casting temperature and curing under hot weather conditions on the compressive and tensile strength and density (evaluated by measuring pulse velocity) of plain and blended cement concretes. The concrete specimens were cast at 25, 32, 38 or 45 °C and cured outdoors by covering them with wet burlap. The optimum casting temperature for the plain and blended cement concretes was evaluated by measuring compressive and split tensile strength and pulse velocity. Further, correlations between these properties was developed. The optimum casting temperature was noted to be 32 °C for OPC and SF cement concretes while it was 38 °C for VFFA, FA, GGBFS and NP cement concretes. A good correlation was noted between the concrete casting temperature, period of curing and the concrete properties.

The formation of depressions and settlement in roads shortly after being constructed is one of the major challenges facing the road authorities in the Arabian Gulf States. Such problems have been closely related to the nature of pavement materials and loading conditions as well as to the proximity of groundwater tables to the surface. A major road in eastern Saudi Arabia was reported for frequent deterioration even when the construction was properly carried out. A preliminary investigation was conducted to quantify the properties of the base course material (i.e. marl soil) and the cause of failure. The laboratory investigation indicated that the marl used in the construction, similar to other marls, has acute water sensitivity and loss of strength whenever the soil is inundated. A precautionary and immediate solution was proposed to stabilize the soil with cement. Consequently, a comprehensive laboratory program was carried out to assess the performance of cement-stabilized marl mixtures under different exposure conditions. Based on the laboratory results and the traffic data for the road under investigation, four sections were constructed, two of them being without any additive while in the other two the base course being treated with 4% cement. Continuous monitoring and evaluation of the four sections for 4 years indicated that the cement-treated road sections have exhibited superior performance over the untreated ones. Unlike the untreated sections, which have experienced various forms of deterioration within a few months after construction, the stabilized sections are still in an excellent condition.

This study was conducted to evaluate the effect of holidays and damage to fusion bonded epoxy coating (FBEC) on reinforcement corrosion in chloride-contaminated concrete. The effect of these parameters on the corrosion of FBEC bars was compared with corrosion of mild steel by measuring the corrosion potentials and corrosion current density at regular intervals. The corrosion current density measurements indicated that the defect-free FBEC bars were in a passive condition in the concrete specimens with up to 2% chloride by weight of cement. The long-term maintenance-free performance was not assured in the concrete specimens with chloride concentration of 1% and above and made with FBEC bars having >1% surface damage or with 3 holidays per linear foot. The long-term performance of FBEC bars with up to two pinholes (ASTM A 775 limit) was satisfactory in the concrete specimens with up to 2% chlorides, by weight of cement. Furthermore, surface damage to FBE coating is more critical compared to holidays, from the point of view of corrosion of FBEC bars, in chloride-bearing concrete.

A review of the literature indicates that research on the durability of reinforced concrete in sulphaterich environments has primarily been confined to studies on sulphate attack. Despite the small number of reports on the effect of sulphate ions on corrosion of reinforcing steel in concrete, the findings of these reports are controversial and inconclusive. Therefore, this investigation was conducted to assess the performance of 15 reinforced concrete mixtures in a mixed magnesium-sodium sulphate environment. These mixtures comprised a combination of three Portland cements, three mineral admixtures and two water-to-binder ratios. Deterioration of concrete due to sulphate attack and corrosion of reinforcing steel was evaluated by assessing the weight loss of concrete and measuring corrosion potentials and polarization resistance at periodic intervals. The results of this investigation indicated that plain cement concretes, irrespective of their C 3 A content, performed fairly well in terms of sulphate resistance; however, they failed to protect the rebars from corrosion. Blended cement concretes, particularly those made with fly ash and blast-furnace slag, exhibited an advanced degree of deterioration due to both sulphate attack and reinforcement corrosion. Despite its inferior performance in terms of sulphate resistance, silica fume cement concrete displayed the best performance with regard to corrosion protection. A reduction in the water-to-binder ratio was generally detrimental in terms of sulphate attack in plain and blended cement concretes.

The electrochemical behaviour of reinforcing steel in plain and blended cement concrete specimens placed in sulphate, chloride and sulphate-chloride environments was investigated. The effect of cement composition and the exposure condition on the corrosion behaviour of reinforcing steel was evaluated by measuring corrosion potentials at periodic intervals and conducting potentio-dynamic scans after two and half years of exposure. The corrosion potential data indicated passive corrosion in plain and blended cement concrete specimens placed in the pure sulphate environment. The time to initiation of reinforcement corrosion, however, was higher in blended cements than plain cements in all chloride and chloride-sulphate environments. The concomitant presence of suphate and chloride salts did not significantly influence the time to corrosion initiation. The corrosion rate, however, was significantly influenced by the quantum of sulphate ions associated with the chloride salts. The superior performance of silica fume blended cement, in terms of longer time to corrosion initiation and lower corrosion rate, indicates its potential in enhancing the useful service life of reinforced concrete structures placed in the chloride-sulphate environments.

The deterioration of concrete due to sulfate salts in soils, groundwater and marine environments is a well-known phenomenon. While it is known that the use of low-C3A cements can provide protection against sulfate attack, the combined effect of chloride and sulfate salts on such a deterioration is highly debated and inconclusive. Moreover, the use of blended cements incorporating supplementary cementing materials, such as natural pozzolan, fly ash, blast furnace slag and silica fume, is becoming common these days. The performance of these cements in environments characterized by the conjoint presence of chlorides and sulfates, however, is not well documented. In this investigation, the effect of sulfate and sulfate-chloride environments on the expansion and reduction in strength of mortar specimens due to sulfate attack was evaluated. Results indicated that the presence of chloride ions in the sulfate environments mitigated the sulfate attack in plain and blended cements. The performance of plain cements was better than that of all blended cements. However, the performance of blended cements was observed to depend on the type of mineral admixture used, both in the sulfate and the sulfate-chloride environments.