Estimating concrete

Estimating concrete strength from ultrasonic measurements using a PUNDIT is a well tested technique. Recent developments have meant that the technique can also be used in reflection mode as an assessment of condition as well as in the more traditional transmission mode for strength estimation. 

American Society for Testing and Materials, 2011. ASTM C1074 Standard Practice for Estimating Concrete Strength by Maturity Method. ... 

Although the consistency is defined by the VC value, this measurement is neither practical nor easy to estimate concrete properties of all mixes. In this respect, AE measurement was applied to estimate quiekly the consistency of fresh concrete during mixing, where AE sensor was attached directly to the outer surface of a concrete mixer. 

Various electromagnetic and acoustic techniques are used for nondestructive examination of concrete. These include radar for locating delaminations, radiography for mapping the rebar network, ultrasonic techniques like pulse velocity and PUNDIT, which can estimate concrete strength and quality and find defects like voids, honeycombing, crack.s, etc. All of these techniques require. specialized equipment and most require specialists to operate and interpret them. Figure.s 4.18(a) and (b) illustrate the equipment and use of pulse velocity and impact echo. 

ASTM C1074 (2011). Standard practice for estimating concrete strength by the maturity method. 

UPV will indicate if the concrete is homogenius or if there could be a defect. The measurements are made between two trtmsducers on opposite sides of the construction. If a problem does occur its depth and form can be estimated by so called tomography (se figure down below). 

Naphthalenesulfonic Acid—Formaldehyde Condensates. The sodium salts of the condensation products of naphthalenesulfonic acid with formaldehyde constitute an important class of compounds which are mainly used in the area of concrete additives (32,33), agricultural formulations, mbber formulations, and synthetic tanning agents. They are also used in photographic materials (34). Hampshire Chemical Co. and Henkel of America, Inc., are the largest suppHers of naphthalene sulfonate in concrete additives (superplasticizer) and reportedly hold 75—80% of this market. It was estimated that naphthalene sulfonate demand from U.S. producers would reach approximately... 

Constmction and dem olition (C D) debris is a potentiahy large source of recyclables. However, as of 1995, generation rates and ferrous scrap content were not weh estabUshed and estimates were highly variable. Eerrous materials in C D debris are typicahy reinforcing bars, wire mesh, and stmctural steel. Some of the scrap is sold for recycling once concrete is effectively removed and the scrap is sized to specification (17). 

Roads and Walkways The cost of roads and walkways in chemical plants is difficult to estimate, since these vaiy with type of construction and thickness of applied cover. Some typical unit costs for roads are as follows For 305-mm (12-in) gravel base covered with 76-mm (3-in) asphalt, the cost is 17.10 per square meter ( 14.30 per square yard) for a reinforced concrete slab with a 152-mm (6-in) subbase, the cost is from 28.40 to 35.10 per square meter ( 23.80 to 29.30 per square yard), depending on the thickness of concrete (for M S = 1000). 

At the end of each month, the field cost engineer collects all current information on a detailed cost report form. As these are actual costs, they can be used to estimate future job costs to completion. Daily reports of unit-cost progress for concrete, excavation, masonry, steel, piping, and electrical work, etc., are then used to predict possible overruns or underruns for the various items. Analysis and comparison with the original estimate point out trouble spots for early attention. If an item is running into difficulty, it is red-flagged to the resident and projec t engineers for remedial action. 

ESTIMATION OF SOME CHARACTERISTICS OF THE CHERNOBYL S INCIDENT ON ELEMENT DISTRIBUTIONS IN SAMPLES TAKEN FROM REACTOR CONCRETE CASING... 

Comparison of the measured isotope distributions with simulation data is carried out within the framework of the models corresponding to various developments, accompanied accident of 1986. Estimations of characteristics of physical influence (temperature, etc.) to which ChAPS s concrete stmcture have been undergone are discussed. 

A concrete consists of 60% by volume of limestone aggregate plus 40% by volume of cement paste. Estimate the Young s modulus of the concrete, given that E for limestone is 63 GPa and E for cement paste is 25 GPa. 

However, if the interpretation of the potentials measured for regions with a covering as uniform as possible and aeration or moisture is extended to estimate the potential gradients corresponding to the explanation for Fig. 3-24, there follows the possibility of classifying the state of corrosion [52-54]. Furthermore, the sensitivity of the estimate can be raised by anodic polarization according to the explanation given for Fig. 2-7, because the depassivated steel is less polarizable than the passive steel in concrete [43]. 

The question can be asked, Why estimate the concrete, steel, piping, electrical, etc., when the total plant can be estimated from major equipment in one step It is better to show all of the accounts because later estimates will be made this way and the preliminary estimate can be used to check the new estimate. Further, an experienced estimator gets a feel for each account, which allows recognition of errors in early estimates. 

Its unique design suggests several accident scenarios that could not occur at other reactors. For example, failure to supply ECC to 1/16 of the core due to the failure of an ECC inlet valve. On the other hand, some phenomena of concern to other types of reactors seem impossible (e.g., core-concrete interactions). The list of phenomena for consideration came from previous studies, comments of an external review group and from literature review. From this, came the issues selected for the accident progression event tree (APET) according to uncertainty and point estimates. 

In a later paper, Brasie (1976) gives more concrete recommendations for determining the quantity of fuel released. A leak potential can be based on the flashing potential of the full amount of liquid (gas) stored or in process. For a continuous release, a cloud size can be determined by estimating the leak rate. For a combined liquid-vapor flow through holes of very short nozzles, the leak rate (mass flow per leak orifice area) is approximately related to the operating overpressure according to ... 

Rindner et al, Preliminary Estimate of Concrete Thicknesses and Construction Costs of Laced Reinforced Concrete Structures , PATR 4441... 

In summary AC impedance spectroscopy provides concrete evidence for the formation of an effective electrochemical double layer over the entire gas-exposed electrode surface. The capacitance of this metal/gas double layer is of the order of 100-300 pF/cm2, comparable to that corresponding to the metal/solid electrolyte double layer. Furthermore it permits estimation of the three-phase-boundary length via Eq. 5.62 once the gas exposed electrode surface area NG is known. 

In the estimation of the approximation error the well-founded choice of the norm depends on the structure of an operator and needs investigation in every particular case. A precise relationship between an operator and a norm in the process of searching the error of approximation will be established in the general case in Section 4. Its concretization for the example of interest leads naturally to the appearance of the negative norm ... 

In this chapter we study the stability with respect to the initial data and the right-hand side of two-layer and three-layer difference schemes that are treated as operator-difference schemes with operators in Hilbert space. Necessary and sufficient stability conditions are discovered and then the corresponding a priori estimates are obtained through such an analysis by means of the energy inequality method. A regularization method for the further development of various difference schemes of a desired quality (in accuracy and economy) in the class of stability schemes is well-established. Numerous concrete schemes for equations of parabolic and hyperbolic types are available as possible applications, bring out the indisputable merit of these methods and unveil their potential. 

A small engineering building is located 350 ft (107 m) from the process unit discussed in Example 8. It has an occupancy load of 500 person-hours, which exceeds the company s occupancy criteria. The building is constructed of unreinforced concrete and contains several windows. Earlier calculations estimated the incident side-on overpressure to be 0.5 psi at 350 ft (0.069 bar at 105 m). 

Fig. 6.9 Estimation of ion diffusion and a concrete example of time to reach complete diffusion.

All these comparisons support the hypothesis of an increase. The arithmetic means and thereby the collective doses seem to have increased by about a factor of four to six. If the aerated concrete based on alum-shale had not been used, the country-wide average has been estimated to be 30 % lower (Swedjemark 1985). 

After the concrete floor had been installed, measurements indicated radon decay-product concentrations of 160 mWL and 140 mWL on the ground floor and upstairs, respectively. There were noticeable gaps between the concrete floor and the wall surfaces in a number of places, some of which extended to the foundations. The radon production rate was estimated to be 1300 Bq m"3 h"1, more than four times the value found in the initial study with all internal doors open. Radon was obviously entering the dwelling with ease, even though the area of underlying material exposed in gaps between the floor and the walls was much smaller than that exposed beneath... 

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