All methods of placing concrete under water are designed to prevent cement washout and the consequent formation of weakly cemented sand and gravel pockets. Read more
Concrete Pavers
Concrete pavers offer a variety of patterns and colors that add to the character of any home, providing durable yet low maintenance surfaces. Read more
The decision to remove and replace faulty concrete can be a costly one. Read more
The slump test is a commonly used tool for quality control of fresh concrete at the jobsite and for enforcement of specifications. It has limitations however, that should be recognized. Unfortunately, slump does not describe the properties of workability, pumpability, and finishability that are so important to the contractor. Read more
Because accounting and estimating software programs follow most contractors' existing manual procedures, the contractor has to adjust his operating procedures only slightly to benefit from computerization in these areas. Read more
Ferrocement was the medium chosen by sculptor Frederic A. Nassaux for creation of the white danseuse Isadora. This composite material gave him plasticity without the massive weight of conventionally cast concrete. Read more
With a few notable exceptions, tilt-up construction methods have traditionally been applied to buildings of one or two stories. However, the economies that are possible using conventional tilt-up construction methods are realized to an even greater degree in multistory applications, where panel heights may exceed 50 feet. Read more
Lift slab construction has become a basic method of economical concrete construction, especially for office buildings, apartments, parking garages, hotels and other structures characterized by repetitive framing from floor to floor. Read more
By fast-tracking precasting and erection operations, Forest City Dillon Precast Systems was able to complete the building frame for the Chilicothe Correctional Institution Number 2 in Ohio in about 8 months. Read more
Delays on a construction project can greatly increase the contractor's costs. And often the contractor incurs further expense as a result of forced acceleration made necessary by the delay. At other times, acceleration is requested by the owner when there was no original delay involved. In either case, legal action or arbitration may be needed if forced acceleration is necessary, the job is completed on time, and the owner refuses to pay for increased costs. To successfully present his case, the contractor must first prove his right to damages and must then substantiate increased costs. Read more
Adequate insurance coverage is an important management problem for contractors. Part of the solution is to obtain a good understanding of the coverage provided by various types of policies and to become familiar with some of the grey areas that need to be covered at the time such policies are written. Read more
Once events occur that might lead to claims, both parties should immediately attempt resolution of the issues. Deferring claims normally results in larger claims eventually. Read more
When a ready mix concrete firm submits a bid to a contractor or owner, his per-cubic-yard bid or proposal may be based on someone else's estimate of the volume of work or materials required. Read more
Determining the actual costs of owning and operating your equipment is one of a contractor's greatest challenges in bidding. Jobs must be bid with equipment costs in mind, and the items included and methods used must be acceptable in costing claims. There are several elements of ownership cost: Read more
We contracted to remove and replace a cracked and broken topping in a 6 x 40-foot area of the second floor of a two-story concrete garage. The structural steel of this building, built about 50 years ago, is buried in the concrete. Although the owner thoug Read more
Last December we cast the first and second floors of a building by placing concrete 2 1/2 inches thick over precast plank. Late in April the owner reported that extensive random cracking has appeared on the first floor and a small amount on the second flo Read more
Our company has a room in which machines are located directly below the hoppers of some 15-foot-square reinforced concrete bins that hold raw popcorn. Sometime in the past the bins were sprayed on the inside with an epoxy coating. Now small rock-size chun Read more
We are replacing the deck of a 15-year-old parking garage one section at a time, using expansive cement concrete. The water-cement ratio is 0.40 in a mix containing 750 pounds of cement per cubic yard, and we are meeting the early strength requirement of Read more
It has been proposed that we try to provide good protection for the rebars in our city bridge decks by covering the decks with concrete toppings that have low permeability. Air-entrained mixes with slumps of 1 inch, made at very low water-cement ratios, h Read more
This picture shows a foamy area that showed up on a 35-foot column after the forms were stripped. On close inspection you can see exposed aggregate, both fine and coarse, in the defective area. In some places you can even see exposed rebar. Read more
Why does good concrete crack at random locations even though the sidewalk has been jointed? Read more