Journal of Materials in Civil Engineering

The critical strain energy release rate for the interfacial zone is experimentally obtained by applying the compliance method to the single‐fiber pull‐out test. Effects of the embedded length and the addition of silica fume on the critical strain energy release rate are discussed. The microstructure of the interfacial zone is characterized by means of microhardness measurements. Correspondence between the critical strain energy release rate and the microstructures of the interfacial zone is also discussed. The formation of the dense microstructure in the interfacial zone due to the addition of silica fume does not always lead to the improvement of its critical strain energy release rate. On the contrary, the critical strain energy release rate for the interfacial zone is decreased by the addition of silica fume. It is concluded that the improvement of bond strength by the addition of silica fume is mainly due to the greater frictional resistance along the debonded interface.

Approximately 50% of the southern pine lumber produced in the United States is subsequently pressure treated with chromated copper arsenate (CCA) preservative. This report discusses the influence of initial kiln‐drying temperature, CCA preservative treatment, post‐treatment redrying temperature, and grade on the tensile properties of southern pine dimension lumber. Tensile strength was not significantly affected by initial kiln‐drying temperature, but it was reduced when CCA treatment was followed by high‐temperature redrying. When comparing No. 2 and better southern pine nominal 2‐ by 4‐in. (actual 38‐ by 89‐mm) lumber initially kiln dried at either 91 °C or 113 °C, a consistent reduction in tensile strength of 7–10% was noted when initial kiln drying at 113 °C was followed by CCA treatment and any level of redrying. This effect is consistent with previously reported results for bending strength.

This three‐phase study examines whether flowable fly ash is an economically and technically feasible material for use as backfill around municipal water, sewer, and storm‐drainage pipelines. The scope of this paper is limited to the mix design methodology of the high‐ash slurry. The proportions of fly ash and cement are determined to yield the properties sought. Properties of interest are strength characteristics, durability, workability, and set time for construction considerations. Phases II and III involve testing of flowable fly‐ash design mix on selected instrumented pipe sections under field‐simulated static and dynamic conditions. A mix of 90% fly ash, 10% cement, 35% water/fly‐ash ratio, 6% super‐plasticizer/fly‐ash ratio, and 0.75% accelerator/fly‐ash ratio is found to serve well, even under severe seasonal cycles. The mix ingredients are also seen as environmentally safe to use as a backfill material.

An in‐place shear tester was developed to test the adhesion between tile and tile adhesives in actual tile installations. In the paper, this new field tester is compared to a modified laboratory test, ASTM C 482 “Bond Strength of Ceramic Tile to Portland Cement.” Fifty‐five laboratory and 30 simulated field tests were compared. The average and standard deviation of the laboratory tests were 322 psi (2,219 kPa) and 44 psi (303 kPa), respectively. The average and standard deviation of the simulated field tests using the in‐place shear tester was 347 psi (2,391 kPa) and 31 psi (214 kPa), respectively. Statistical procedures used to evaluate the data indicate that the standard deviation and averages are different. The in‐place shear tester was used on an actual project that demonstrated its ease of use, portability, and effectiveness.

Wood fiber‐reinforced cement can provide the highest performance‐to‐cost ratio among fibrous cement composites considered for the replacement of asbestos cement. Such composites can find applications in the production of flat and corrugated cement sheets, nonpressure pipes, and many other thin‐sheet cement products. There are, however, concerns regarding the moisture resistance of these composites. This paper presents the results of a comprehensive experimental study concerned with the effects of moisture content on the flexural performance of wood‐fiber‐reinforced cement composites. The cement composites considered in this investigation incorporate 1% and 2% mass fractions of mechanical and kraft pulps. Comprehensive sets of replicated flexural test data were generated, and were analyzed statistically. The results generated in this study were indicative of significant effects of moisture content on flexural performance of wood‐fiber‐reinforced cement. Microstructural studies indicate that high moisture contents tend to lower the fiber‐to‐matrix bond strength, leading to changes in failure mechanism that can describe the trends observed in moisture effects on flexural performance of wood‐cement composites.

Chloride ion attack is known to be the major cause of reinforcing steel corrosion in concrete. This study aims to demonstrate that not only chloride ions but also sulfate ions corrode the reinforcing steel embedded in concrete. Reinforced concrete specimens are prepared with different water‐cement ratios of 0.40, 0.55, and 0.70. A single piece of reinforcing steel is centrally embedded in the specimens at a clear concrete cover of 31 mm (1.25 in.). The reinforced concrete specimens are immersed in a 5% ${\mathrm{MgSO}}_4$ solution and subjected to corrosion monitoring for a period of 43 months. Half‐cell potential and linear polarization resistance techniques are used for corrosion monitoring. The test results indicate that the sulfate ions are corrosive to reinforcing steel, but their severity is less than that of chloride ions. The reduction in the alkalinity of concrete due to a reaction between sulfate salts and calcium hydroxide of the hydrated cement paste is believed to be responsible for the sulfate‐induced reinforcing steel corrosion.

Advanced forms of wood construction can enable contemporary wood structures such as bridges to be competitive with those constructed from any other conventional material. This paper presents the results of an analytical and experimental investigation of a new form of wood construction involving external bonding of thin fiber‐reinforced plastic (FRP) sheets on the tension zones of wood beams and beam columns using epoxy resins. Here, we examine the effect of external composite reinforcement on the collapse mechanisms and loads, the stiffness and the curvature ductility of hybrid FRP wood members under a combination of bending moments and axial forces. We then give the results of three‐point bending and eccentric compression tests confirming our analysis. The analysis is extended to establish a methodology for the optimum selection of the FRP reinforcement to optimize mechanical performance.

Previously the writer presented the results of a study on the creep and shrinkage behavior of prepacked aggregate concrete. In the same study strain on removal of sustained load was also measured. In this article, results on creep recovery of normal and prepacked aggregate concrete are presented and discussed. It has been observed that the creep recovery of prepacked aggregate concrete is lower than that of normal concrete.