By Todd Gerlach Since its introduction in the early 1990’s, the diamond chain category has evolved over the span of nearly three decades. In the early years, diamond chains were modeled after the basic architecture of woodcutting saw chain and typically suffered from excessive chain stretch and limited diamond life. As the years progressed, so did the technology and design. Through advancements in materials, component features and manufacturing processes, modern diamond chain as we know it today is more durable, performs better, stretches less and lasts longer than ever before. Although performance and cutting efficiency have improved steadily over time, one fundamental characteristic has remained. Sawing with a diamond chain power cutter typically requires significant physical effort by the operator to cut effectively. This can lead to operator fatigue and loss of productivity, which has generally confined this cutting method to a relatively narrow set of applications. As the concrete sawing and drilling market continues to expand, safety and ergonomic requirements become more stringent and new applications emerge that require use of a power cutter with diamond chain, it is becoming increasingly important that the issue of operator effort and fatigue is addressed. With focus on safety and productivity, a new generation of diamond chain has entered the market. The basis of this innovative design is no longer traced back to the origins of the woodcutting saw chain; rather it is an all-new chassis architecture that is specifically engineered to better support and stabilize the diamonds in the cut. This enhanced, more rigid interface between the diamond segments and work piece serves to extend the life of the diamonds by significantly reducing vibration and impact loads in the cut, thereby minimizing diamond fractures and pullouts. The result is a far softer, freer cutting segment formulation that does not sacrifice diamond life. So, what does this mean to the operator on the jobsite? A revolutionary diamond chain that requires less feed load and cuts smoother and straighter. In typical diamond chain cutting applications, an operator’s effort is consumed by several different modes. First is most obvious, the feed load the operator applies directly to the power cutter to engage the chain in the workpiece. The second and perhaps less obvious mode is cutting vibration. This high frequency response from the chain is transmitted through the handles of the power cutter...
GPR technology has been an accepted and routinely used nondestructive method for imaging objects embedded in concrete prior to cutting or coring for several decades. On July 17, 2009, the CSDA released a Best Practice for GPR Concrete Inspection, CSDA-BP-007. It details the general use of GPR for concrete imaging, normal survey applications, and includes scanning with single sided access and slab-on-grade application. However, it was never intended to outline difficult or challenging survey conditions. It is not uncommon for concrete contractors to request the location of rebar, conduits, post-tension cables, electrical, or plumbing in order to aid in remediation risks. Additionally, savvy contractors have been using GPR technology to determine concrete slab thickness. This provides the concrete contractor with several benefits including the proper assignment of concrete cutting and coring tools, as well as the ability to better quote the work required. Trained and CSDA Certified GPR operators understand the benefits and limitations of the technology and how to determine the best course of action in challenging survey conditions. Yet, even the most knowledgeable operators will wonder if there’s a tip or trick that they can deploy in the field to collect better data. Here we explore the difference between suspended slab and slab-on-grade surveys, as well as infield processing techniques which operators can use to get the best out of their slab-on-grade data. The detectability of the slab bottom depends on the underlying material and amount of steel within the slab. It is easier to see when a contrasting material such as water, air or metal is under the slab because they will have a stronger dielectric contrast. In Figure 1, the data is representative of an elevated concrete slab. Note the several hyperbolic reflections on the screen, this is indicative of a double rebar mat. Towards the bottom of the data image, there is a strong dielectric contrast at the concrete-to-air boundary and therefore produces a clear indicator of the bottom of the slab. In slab-on-grade situations, the bottom may be very weak or invisible if the slab rests on sand or another concrete structure (supporting beam, for instance) with similar dielectric properties. This can be challenging due to the low dielectric contrast for the concrete-to-sand boundary and intersecting hyperbolic tails from objects embedded in the slab. The former results in weak or non-existent reflections and...
Because of their unique capabilities, demolition robots are frequently placed in quite challenging and rigorous situations. If attention isn’t paid to some basic preventative maintenance routines, their availability can be affected.
