Journal of Materials in Civil Engineering

The durability of reactive powder concretes (RPC) has been defined by measuring porosity, air permeability, water absorption, diffusion, and migration of chloride ions, accelerated carbonation, resistance to reinforcement corrosion, resistivity, and resistance to mechanical abrasion. Results were compared with the characteristics of a grade 30 MPa concrete with a low cement content and a grade 80 MPa very high performance concrete. The RPC displays excellent granular compactness, and its low water content helps reduce porosity. This results in an excellent resistance to the penetration of aggressive agents with respect to the reference concretes, and structures built with RPC are expected to significantly outlast those built with ordinary concrete.

This paper presents the findings of a preliminary study of the dependence of resilient modulus of cement-stabilized phosphogypsum on various material parameters. In particular, the dependence of the resilient modulus on cement content, dry unit weight, moisture content, and curing time was determined. It was found that the resilient modulus increases with increasing density, cement content, and time of curing before testing, but decreases with increasing moisture content. Relationships between resilient modulus and the parameters were estimated and a multiple correlation between the resilient modulus all four parameters mentioned was also derived.

The effects of the tricalcium aluminate (C ₃ A) content of the stabilizing cement [Type II (1.3% C ₃ A) cement and Type III cement (9.3% C ₃ A)], curing time (seven to 90 days), proportion of PG (5–60%), grain size, and impurities in phosphogypsum (PG) (PG compared to gypsum) on the microstructural (by scanning electron microscopy) and phase properties of gypsum/PG and cement mixtures, a potential road-base material, were studied (by derivative thermogravimetry). Morphologically, two types of ettringite (well-defined crystals, >2 μm in lengths and ill-defined crystals, below 1 μm in length) were present in the cement and gypsum/PG mixtures. The impurities in PG retarded the initial hydration of cement in direct proportion to its amount in the mixtures. However, gypsum/PG increased the degree of hydration of cement in the mixtures in the long term. The reacted gypsum/PG produced a large amount of ettringite (within two months) compared to cement only. The amount of carbonation was uniformly low.

This investigation was carried out: (1) to study the effect of fly ash on the mechanical properties of asphalt mixtures; and (2) to evaluate the effect of using fly ash in mitigating pavement distress and improving performance of asphalt concrete pavement. In this study, four groups of specimens with various fly ash contents were studied. The mechanical properties (resilient modulus, creep, permanent deformation, and fatigue) were determined at three different temperatures. Moisture damage tests were carried out. The VESYS model was used to predict pavement performance. Results from this study indicated that fly ash can be used as a mineral filler to improve resilient modulus characteristics and stripping resistance. The addition of fly ash did not significantly reduce field performance of asphalt concrete mix in terms of rut depth and present serviceability index but increase the amount of surface cracking in the pavement.

An ASCE task committee of the Materials Division has reviewed, updated, revised, and rewritten the paper entitled “Significance of Tests for Highway Materials” that was published in the ASCE Journal of the Highway Division , in September, 1957. The committee believed that an update of the 1957 paper would be a significant benefit to present and future engineers in a wide variety of occupations. This bituminous materials section is the first of a series of articles to be published in the Journal of Materials in Civil Engineering , and it is the committee's intent to publish them together as a single special publication covering all civil engineering materials; that is, bituminous materials, aggregates, soils, and portland cement concrete, for distribution to the engineering and education community.

A mathematical model is developed to predict pressures generated by water and air in the pores of airfield concrete being heated by a jet exhaust. The foundation of this model is a constitutive relationship to characterize the flow of high-velocity, compressible, heated gases through a high-resistance porous medium. The key premise is that the resistance to flow can be modeled with friction coefficients analogous to the method used for simpler geometries. Pore pressure predicted using this model suggest that moisture in the pores of the cement paste is a probable cause of material failure when the pavement is being heated by the exhaust of a vertical takeoff aircraft such as the Harrier. With an initial pore saturation of 90% or greater, high pore pressures and pressure gradients result from air being compressed by the expansion of liquid water. Concrete temperatures beneath a Harrier reach 300°C in about 2 min. Even with a low saturation, the water vapor pressure could eventually be sufficient to cause a tensile failure in portland cement concrete.

Results of an experimental investigation of the structural properties of used slab formwork stringers are presented. The samples tested were obtained from eight concrete construction sites in Chicago, Milwaukee, and Minneapolis–St. Paul. All samples collected were 100 × 150 mm (4 × 6 in.) nominal-size solid lumber. Samples with legible mill stamp were Douglas fir. Grades varied from Select Structural to No. 2. Samples were tested according to the guidelines specified by ASTM for lumber in structural sizes. This paper presents the observed values for shear modulus, modulus of elasticity, modulus of rupture, and shear strength parallel to grain. The observed structural properties are modeled with appropriate probability distributions. The observed data are used to investigate the correlation between stringer modulus of rupture and modulus of elasticity and modulus of rupture and shear strength.