Frequently Asked Questions

Voss Labs works primarily on the assessment, testing, and repair of existing concrete infrastructure. Our projects include dams and spillways, water and wastewater facilities, power plants, pipelines and conveyance structures, bridges and transportation infrastructure, and commercial and public structures. We support projects ranging from targeted concrete testing and investigations to comprehensive condition assessments and repair programs. Voss Labs can provide non-destructive testing, visual inspection, concrete coring, anchor testing, laboratory testing of concrete cores and cylinders, concrete mix design consulting, and comprehensive condition assessments.

Our consulting engineers specialize in non-destructive testing techniques to assess reinforced concrete structures. Some of our NDT services include ground penetrating radar, impact echo, impulse response, half-cell testing, ultrasonic pulse velocity testing, rebound hammer, and concrete resistivity. Voss Labs Non-Destructive Test Capabilities:Ground Penetrating Radar (GPR) - Locate reinforcing steel and other embedded objects, measure thickness of slabs and walls, and evaluate cracks and delaminations. Impact-Echo Testing: ASTM C1383, P-Wave Speed and Thickness of Concrete Plates Using Impact-Echo, Determine thickness of slabs and walls and locate internal voids or reflectors Impulse Response Testing - Evaluate for loss of support beneath slabs, spillways, and basins. Half-Cell Testing: ASTM C876. Corrosion Potentials of Uncoated Reinforcing Steel in Concrete, Evaluate structures for probability and location of reinforcing steel corrosion. Concrete Resistivity - ASTM C1876, Bulk Electrical Resistivity of Concrete, Evaluate concrete's electrical resistivity which is related corrosion rates Ultrasonic Pulse Velocity Testing: ASTM C597, Pulse Velocity Through Concrete, Evaluate concrete uniformity consolidation and detect anomalies. Can be utilized to evaluate crack penetration. Rebound Hammer Testing: ASTM C805, Rebound Number of Hardened Concrete, Determine relative surface hardness and uniformity.

Our engineers are trained to safely perform work in a number of challenging environments that may include confined spaces, steep slopes, tidal environments, and remote areas. Reach out and we can discuss access options to safely perform the work.

Yes, Voss Labs routinely performs testing on cores that are shipped to our Benicia laboratory. Contact us for a quote and shipping information. Turn around time for most lab testing is approximately one week.

Exposed to the atmosphere, conventional (uncoated) steel reinforcement will readily corrode in the presence of sufficient oxygen and water. Steel is protected from corrosion in the high pH alkaline environment of new, uncontaminated concrete. At pH levels above ~ 9.5, steel reinforcement is “passivated” by a microscopic oxide layer (Fe2O3) on the surface which effectively blocks continued corrosion.Chlorides (chloride ions) are present in high concentrations in ocean and brackish waters, in salts used to deice roads, and in hypochlorite treatments used in many wastewater facilities. In some cases, chlorides were added to the original concrete mix. When reinforced concrete structures are exposed to these environmental chloride sources, the chloride ions can begin to migrate into the concrete pore structure. If the chlorides reach the depth of reinforcing steel at a significant enough concentration, a process occurs that breaks down the protective passivating layer around the steel. If sufficient oxygen and moisture is available, corrosion will begin to occur. The corrosion product (rust) is 7 to 9 times larger in volume than the original steel, this growth in volume creates expansive forces that delaminate and/or spall the concrete cover.

Tensile pull off testing is the ultimate test of whether a repair achieved a durable long lasting bond or whether it is going to require another repair in the near future. VL engineers perform pull off tests two times during the repair process. The first test occurs as a check after the contractor has performed all chipping and surface preparation. If the pull off values are low, it is a sign that the substrate was not properly prepared for placement. At this point, Voss will work with the contractor to improve surface preparation (may also mean chipping more) in order to move forward with placement of the repair. Voss Labs will also perform testing after the repair material has been placed. Ideally, the bond value is high or the test fails in the substrate indicating that the bond was not the weak point. All Voss engineers are ICRI Concrete Surface Repair Technician certified.

Concrete voids are gaps or holes within a wall, column, or slab where the concrete was unable to flow properly. Often times, voiding is not detectable from the exposed surface and can cause structural risk if not fixed. To locate voiding in a concrete element, a combination of impact echo and GPR testing can be applied in a grid like manner. Impact echo results will normally measure the thickness of a concrete element, when tested in an area of voiding the result will show a thinner depth - indicating that an area of voiding or poor consolidation may be present. Areas of potential voiding are typically confirmed via small diameter coring or drilling. GPR is also capable of detecting abnormalities in a concrete section.

Voss Labs engineers perform all of the steps of a concrete structure investigation. From inspection scope creation, to access and safety planning, to concrete coring, non-destructive testing, lab testing, report writing, and repair recommendations - with Voss Labs you are getting a small team of focused engineers who are active throughout all steps of the investigation and do not have to hand off portions of the work to outside entities.