A discussion of an earlier paper with the aforementioned title by E. Cokca, published in this journal (Volume 127, Number 7, July 2001), is presented. The discusser states that the author has presented an interesting paper that enriches the literature and furthers knowledge on fly ash, especially as it concerns this product outside the U.S. Based on his experience in this field, the discusser offers some comments on: fly ash; the origin of coal; lime, cement, and fly ash; swelling potential; and x-ray diffraction and scanning electron microscopy, as they relate to the author's work. Closure from the author is included.

Use of class c fly ashes for the stabilization of an expansive soil. discussion and closure

This note presents a study of the efficacy of fly ash as an additive in improving the engineering characteristics of expansive soils. An experimental program has evaluated the effect of the fly ash content on the free swell index, swell potential, swelling pressure, plasticity, compaction, strength, and hydraulic conductivity characteristics of expansive soil. The plasticity, hydraulic conductivity and swelling properties of the blends decreased and the dry unit weight and strength increased with an increase in fly ash content. The resistance to penetration of the blends increased significantly with an increase in fly ash content for a given water content. Excellent correlation was obtained between the measured and predicted undrained shear strengths.

Effect of fly ash on engineering properties of expansive soils

Excessive heave associated with swelling of expansive soils can cause considerable distress to lightweight civil engineering structures. Several methods have been suggested to control this problem....

Use of class c fly ashes for the stabilization of an expansive soil

Expansive clay soils—those that change significantly in volume with changes in water content—are the cause of distortions to structures that cost taxpayers several billion dollars annually in the United States. Much has been learned about their behavior over the past 60 years, and relatively successful methods have been developed to modify and stabilize them. This paper reviews some of the key advances developed over the past 60 years in improving our understanding of the nature and methods of modifying and stabilizing expansive clay soils. The state of the practice in stabilization is presented, and practical and research needs to help improve the state of the practice are discussed.

Review of Stabilization of Clays and Expansive Soils in Pavements and Lightly Loaded Structures—History, Practice, and Future

This report presents information on the characterization of cementitiously stabilized layers and the properties that influence pavement performance. It also contains recommended performance-related procedures for characterizing these layers and performance-prediction models for incorporation into the mechanistic–empirical pavement analysis methods. Individual chapters highlight pavement distresses of hot-mix asphalt pavements and concrete pavements, laboratory tests and model development, and model calibration. The material contained in the report will be of immediate interest to state materials, pavement, and construction engineers and others involved in the different aspects of pavement design and construction.

Characterization of Cementitiously Stabilized Layers for Use in Pavement Design and Analysis

A 3.5-km (2.2 mi) section of a road in Georgia developed unexpected transverse bumps within 6 months after construction. The source of the bumps appeared to be expansion within the cement-stabilized base course. Laboratory examination of samples from areas showing distress revealed the presence of ettringite, a calcium sulfoaluminate the formation of which can be accompanied by severe expansion. This expansive materials was the probable cause of the volume changes causing the transverse bumps. The calcium and alumina needed to form ettringite ware available from the portland cement and the stabilized soil`s clay minerals. The source of the sulfur was identified as the well water that was mixed with the cement-stabilized base. Sulfate attack of cement-stabilized soils is a relatively infrequent problem, but it is highly destructive when it occurs. Currently, there are no firm criteria for identifying when sulfate attack of a cement-stabilized soil is a potential problem nor are there established methods of preventing the attack.

Sulfate attack on cement-stabilized sand

Part 1 Setting the stage: incentives and issues of pollution prevention equipment for pollution prevention pollution prevention and process integration - two complementary philosophies. Part 2 Pinch (thermodynamic) analysis: introduction to pinch analysis site-wide pinch analysis and emissions targeting concentration pinch and wastewater minimization. Part 3 Knowledge-based approaches: introduction to knowledge-based approaches heuristics from the petrochemical industry transfer waste minimization solutions between industries - unit operations approach hierarchical design analysis artificial intelligence applicaitons in pollution prevention. Part 4 Numerical approaches: introduction to numerical approaches minimum cost solutions for air emissions wastewater minimization using NLP analyzing mass separation agent systems multi-objective optimization analysis. Part 5 Putting it into action: management of pinch analysis SCE's experience with pinch analysis in pollution prevention.

Geotechnical materials in construction

Pavement failure is a common and recurring problem. The results of such failures are not catastrophic like the collapse of a building or a failure of a dam, but they represent a serious financial loss and are a nuisance to the public. Despite a long history of road and pavement construction, engineers continue to design and build pavements that fail. This paper uses specific examples to illustrate common design and construction problems. Examples of design errors illustrate problems of not recognizing both critical assumptions used in a “standard” design curve and natural conditions that affect design. Materials are critical to proper performance, and examples of improper material selection or specification use are presented. No pavement design is any better than its construction or maintenance, so examples of typical construction problems and maintenance failures are also included. The 12 examples covered in this paper illustrate that these failures are more likely due to our failure to practice engineer...

Pavement Failures: Oversights, Omissions and Wishful Thinking

Heaving of pavements and a building foundation became progressively worse on a project at Holloman Air Force Base (AFB), N.M. The cause of the heaving was identified as sulfate attack on recycled concrete used as fill and base course below the buildings and pavements. This recycled concrete came from sulfate-resistant airfield Portland concrete pavement that had existed for decades at Holloman AFB without distress. However, severe sulfate exposure conditions, ready availability of water, the more permeable nature of the crushed recycled concrete, less common thaumasite attack, possible soil contamination as a secondary source of alumina, or some combination of these factors allowed sulfate attack to develop in the recycled material even though it had not in the original concrete pavement.

Investigation of Heaving at Holloman Air Force Base, New Mexico

Geology and related earth processes are an inherent part of civil engineering design and construction. This paper examines eight specific examples to illustrate how geologic factors can dominate project behavior. The examples are from a spectrum of environments associated with design and construction of roads and airfields and vary from the apparently obvious to the more subtle. Failure to understand the geologic conditions at a site almost invariably results in unsatisfactory performance. This complex interplay between geology and engineering is at the heart of the geotechnical profession and should be appreciated by all.

Marian P. Rollings

Papers

Sulfate attack on cement-stabilized sand

Geotechnical materials in construction

Pavement Failures: Oversights, Omissions and Wishful Thinking

Investigation of Heaving at Holloman Air Force Base, New Mexico

Geology: Engineer Ignore it at Your Peril