June 1995 Table of Contents

Features Overcoming All Barriers

With today's congested roadways, concrete median barriers are essential elements of many highway construction and reconstruction projects. However, slipforming these barriers can be as challenging as placing the highway they divide. Fortunately, contractors can tackle much of this difficult work using one machine - a multipurpose paver. Using these machines, contractors have placed barrier wall at rates exceeding a mile a day. Read more

Features Understanding Slipform Pavers

All modern slipform pavers consolidate and shape concrete using an extrusion process that pulls or "slips" the forms continuously over and through the plastic concrete. Plastic concrete acts like a fluid, which means it cannot be compressed. When confined inside the paving machine, the energy applied to the concrete for consolidation or finishing is transmitted through the concrete in all directions back to the paver. Read more

Features Whitetopping Restores Air Traffic at Spirit of St. Louis

One of the largest general-aviation airports in the Midwest, Spirit of St. Louis Airport accommodates 1,000 takeoffs and landings daily. The airport opened in 1964 to relieve air traffic at Lambert Airport, the major airport in the St. Louis area. Over the years, the heavy plane traffic caused severe deterioration of the asphalt. In some sections, exposure to jet fuel turned the asphalt to mush. A devastating flood in 1993 that submerged the ramp under 9 feet of water aggravated the damage, making the apron unusable. Read more

Features Walk-Behind Plate Compactors

Like any piece of soil-compaction equipment, plate compactors increase the density of materials supporting various construction projects. When concrete contractors need to compact soil for projects such as sidewalks and driveways - particularly in relatively inaccessible locations along foundations or walls - walk-behind plate compactors can be quite useful. They are ideal for compacting granular material - particularly uniform sands and gravels. Plate compactors can also be used to compact mixed soils with little cohesive content (generally containing less than 35% fines). Read more

Features French Drains Help Keep Residential Basements Dry

A French drain is an underground trench filled with loose stones or rubble surrounding a perforated PVC pipe. The trench, which runs along the interior side of the footing beneath the floor slab, intercepts water and channels it to a sump pump system for removal. Read more

Problem Clinic How to Tell If Scaling Is Caused By Deicing Salts or Finishing Problems

We have to troubleshoot exterior flatwork problems including scaling. Is there any way to tell if scaling was caused by deicing salts and freeze-thaw cycles or poor finishing methods? Read more

Problem Clinic Elevated-Slab Thickness Tolerance

We are working on a project where we placed a waffle-pan slab. Recently, we cored through the slab to install piping and conduit. The slab thickness above the pans was specified to be 4 inches. After analyzing the cores, we discovered that the slab is as Read more

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