KB Engineering LLC

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http://kbengllc.com/

Phone:3076357240

More info on KB Engineering LLC

KB Engineering offers scientific engineering services for the concrete industry.

Kim Basham, PhD PE FACI

Form Wall Contraction Joints

How To Control Unsightly Wall Cracks

Vertical wall cracks can be minimized by installing contraction joints to control the location of cracks or reinforcing to control the width of cracks.

A Summary of Concrete Crack Repair Options - Rout and Fill

A Summary of Concrete Crack Repair Options

Sometimes cracks require repairing but with so many options, how do we design and select the best repair option? It’s not as difficult as you may think.

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How to Evaluate & Troubleshoot Concrete Cracks

Cracks may represent the total extent of damage or the first signs of serious trouble. Some recommendations for troubleshooting concrete cracks prior to designing or performing repairs.

Above and below: Properly placed/supported reinforcement will result in properly located reinforcement in the slab. Consult manufacturers' literature for maximum chair and other support spacing and use a 12-inch minimum reinforcement spacing so workers can avoid walking on the reinforcement.

How To Reinforce Concrete Slab on Ground to Control Cracking

Steel reinforcing bars and welded wire reinforcement provide crack width control in nonstructural slabs-on-ground.

Concrete control joint.

Rules for Designing Contraction Joints

To minimize random concrete cracking in slabs-on-ground, follow these simple rules.

Best practice includes a form watcher measuring wall form deflections associated with concrete pressures due to the height of concrete and vibration. Not only a safety issue but monitoring form deflections can avoid out-of-tolerance walls.

Good Vibration is Key to Quality Concrete

Proper use of an internal vibrator will minimize surface defects and blemishes

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Form Wall Contraction Joints

How To Control Unsightly Wall Cracks

Vertical wall cracks can be minimized by installing contraction joints to control the location of cracks or reinforcing to control the width of cracks.

A Summary of Concrete Crack Repair Options - Rout and Fill

A Summary of Concrete Crack Repair Options

Sometimes cracks require repairing but with so many options, how do we design and select the best repair option? It’s not as difficult as you may think.

Adobe Stock 329976094

How to Evaluate & Troubleshoot Concrete Cracks

Cracks may represent the total extent of damage or the first signs of serious trouble. Some recommendations for troubleshooting concrete cracks prior to designing or performing repairs.

Above and below: Properly placed/supported reinforcement will result in properly located reinforcement in the slab. Consult manufacturers' literature for maximum chair and other support spacing and use a 12-inch minimum reinforcement spacing so workers can avoid walking on the reinforcement.

How To Reinforce Concrete Slab on Ground to Control Cracking

Steel reinforcing bars and welded wire reinforcement provide crack width control in nonstructural slabs-on-ground.

Concrete control joint.

Rules for Designing Contraction Joints

To minimize random concrete cracking in slabs-on-ground, follow these simple rules.

Best practice includes a form watcher measuring wall form deflections associated with concrete pressures due to the height of concrete and vibration. Not only a safety issue but monitoring form deflections can avoid out-of-tolerance walls.

Good Vibration is Key to Quality Concrete

Proper use of an internal vibrator will minimize surface defects and blemishes

Handleless rope brushes work well on large slabs and in confined areas where handles are awkward.

How to Avoid Broomed Concrete Finish Disputes

Best practices can protect contractors and minimize disputes between job owners and architects.

Unrestricted crack width growth leads to spalled edges along out-of-joint cracks when exposed to wheeled traffic.

Concrete Slabs-on-Ground Crack Control Options

When it comes to slabs-on-ground, you can either control the location of cracking or the width of cracks.

When slabs are placed on problematic subbases with risks of non-uniform support or consist of moderate to high shrinkage concrete or joint spacings exceed 15 ft., then reinforcement is necessary to limit widths of cracks should they occur.

Tips to Control Crack Width in Concrete Slab on Ground

Ten tips when using reinforcement to provide crack width control in nonstructural slabs-on-ground

Occurring in both random and parallel patterns, plastic shrinkage cracks are discontinuous, relatively short and typically fairly shallow. Occasionally they can become full-depth cracks. Parallel cracks are typically spaced between a few inches to several feet apart and many times are oriented perpendicular to the prevailing wind direction. Cracks widths at the surface can be fairly wide (as much as 1/8 in.) but rapidly diminish with depth.

Understanding Surface Cracking Caused by Rapid Moisture Loss

Acknowledging the causes and implementing preventive measures can help contractors minimize plastic shrinkage cracking.

Surface delaminations are separations of the top surface from the underlying concrete.

How to Avoid the Delamination of Steel-troweled Floors

Understanding the failure mechanism and causes is the key to avoiding floor delaminations.

Photo 3 - For misaligned or bent anchor bolts that will not allow the base plate to fit over the bolts, consider bending the bolts into position.

Anchor Bolt Tolerances

Misplaced or misaligned anchor bolts are a common field problem.

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How to Manage Moisture Loss and Temperature of Freshly Placed Concrete

Curing, the action taken by contractors to maintain adequate moisture and temperature of freshly placed concrete, promotes the chemical hydration of the cementitious materials within the concrete.

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Curing Part I – Why cure?

Curing is the action taken by the contractor to maintain the moisture and temperature conditions in freshly placed concrete. Curing promotes the chemical hydration of the cementitious materials so the potential properties of the mixture may develop.

Bases for slabs-on-ground must be smooth, hard and compacted.

Slabs-On-Ground: Slab Thickness and Base Tolerances

Slab thickness is the greatest single factor controlling the load-carry capacity of a slab-on-ground.

Random cracks in reinforced slabs caused by thermal contraction and drying shrinkage are not longitudinal cracks and typically do not increase the risk of reinforcement corrosion in concrete.

Two Theories Related to Cracks and Rebar Corrosion

Do cracks increase the risk of steel reinforcement corrosion?

1. Mass concreting practices were primarily developed for dam construction where thermal cracking was first identified. However, now mass concreting practices are used for large structural elements including mat foundations, pile caps, bridge piers, large beams and girders, and thick walls and slabs.

How To Plan & Manage Curing for Mass Concrete Pours

Specifications for mass concrete limit fresh and in-place concrete temperatures and typically require a thermal control plan by the contractor for each mass concrete placement.

What You Need to Know About Plastic Shrinkage Cracking

What You Need to Know About Plastic Shrinkage Cracking

Understanding the causes of plastic shrinkage cracks, monitoring jobsite conditions, and implementing precautionary measures can prevent or at least minimize these unsightly cracks from occurring.

Water content is the single most important factor affecting workability or the ease of mixing and placing concrete.

Water in Concrete

The amount of water in concrete controls many fresh and hardened properties in concrete including workability, compressive strengths, permeability and watertightness, durability and weathering, drying shrinkage and potential for cracking.

Hydronic heaters provide an even distribution of heat to the concrete. Here, a poly sheet covers a slab-on-grade. Hydronic heating tubes were placed on top of the poly and the entire system is being covered with insulated blankets.

How to Protect Concrete During Cold Weather Pours

Cold weather concreting requires contractors to maintain minimal concrete temperatures to ensure proper strength gain and cure.

In-place concrete strengths represented by cores are typically less than lab-cured cylinder strengths due to field factors like consolidation and curing.

How to Get the Best Results from Concrete Core Testing

Understanding the factors that affect core testing results will help you achieve accurate in-place concrete strengths.

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How to Make and Cure Standard Test Cylinders in the Field

Follow these seven steps to make and cure a standard concrete test cylinder in the field.

Make cylinders in strict accordance with ASTM C31 and store cylinders in a concrete cure box for the initial curing period.

Avoid the False Alarm for Low-Strength Concrete

Ensure your cylinder strengths are correctly reported to avoid rejected concrete, delays and investigations.

Field-cured test cylinders should be cured in the same manner as the concrete they represent. The temperature-time history of the test cylinders should match the in-place concrete curing conditions. In this case, the field-cured test cylinders overestimated the in-place concrete strength because they were sitting adjacent to a jobsite heater..

How to Estimate In-place Strength of Concrete

Contractors need to know how to correctly evaluate the in-place strength of concrete so they can determine to proper time to remove formwork, backfill or open up a pavement to traffic.