This paper investigates the design of a concrete mix to a specified strength. In particular, it studies the behavior of concrete under compressive loading in order to determine properties such as (1) the compressive strength taken on concrete cylinders taken at 2, 7, 14 and 28-day intervals and (2) the compressive strength taken on a concrete cylinder exposed to freeze-thaw cycles during its curing.
The process of designing the concrete mix is presented in section 1. In section 2, slump test and compression test are investigated. The experiment is presented in section 3 by analyzing the list of abbreviations, description of apparatus, procedure, summary of results, observations / conclusions and discussion of results.
Tags: Concrete, slump test, compression test, Concrete mix procedure, Concrete mix technique, Slump test and compression specs, Slump cone and compression test, Concrete mix protocol
[...] The tamping rod should be smooth and bullet-pointed (Buza, 1993) Slump test determines the “workability” of concrete, which provides a scale on how easy it is to handle, compact, and cure concrete (Cement Concrete & Aggregates Australia, 2004). Engineers use the results to then alter the concrete mix by adjusting the cement/water ratios or adding plasticizers to increase the strength of the outcome concrete mix. Figure 1 A Slump Cone b. Compression Test Compression test determines behavior of materials under crushing loads and measures concrete strength in the hardened state. [...]
[...] OHAUS balance 20 kg 1714, Calibrated: 3-98; Next: 3-99 Apparatus used for PREPARING CONCRETE MIXTURE and for the slump test: 1. Metal container for concrete hand mixing Long-hand plow for concrete hand-mixing 3. Weight scale (to measure concrete components: aggregate, water and cement) Wooden Board 5. Metal Cone Shell 300 mm high Metal Rod (for 25-times-penetration of concrete mixture). Apparatus used for CONCRETE-CYLINDERS STRENGTH TESTING: Tinius Olsen s/n Procedure Slump Test Slump Test shows the consistency of concrete. Slum Test was performed with a slump cone and the metal rod. [...]
[...] Cement's hydration is essential for hardening of concrete and gaining the strength. Cement paste is usually 25-40% of the total volume of concrete. Additives could be used to improve workability of concrete, retard hardening in summer high-temperature heat, or retard hardening in low temperature, or during the transportation fresh concrete mixture. Additives can increase heat necessary in winter, low-temperature curing conditions. Also, in high-temperature curing, water evaporates quickly from concrete mix and enables cement hydration. In this case, additives are used to lower the temperature during the curing. [...]
[...] Tinius Olsen testing machine was loaded with the cylinder At the top of the cylinder was put cap so load was equally distributed at the cylinder's top surface Rupture point was recorded, and the sample was observed Summary of results DAYS DESIGN STRENGTH ACTUAL STRENGTH % STRENGTH (PSI) (PSI) ACHIEVED Note: Predicted load was 169,646 lb, 0.4 *Note: Strengths for 28-days (regular cure), and 28-days (freeze-thaw) are projected values Observations / Conclusions All five cylinders had W/C ratio the same After 2 days curing on room temperature cylinder reached the strength of 4,649 psi, what is 77% of designed strength (design strength is the strength concrete reach after 28 days) for the W/C factor After 7 days curing on room temperature and soaked in the water cylinder reached the strength of 6,550 psi, what is 109% of designed strength (design strength is the strength concrete reach after 28 days) for the W/C factor After 14 days curing on room temperature and soaked in the water cylinder reached the strength of 7,435 psi, what is 123% of designed strength (design strength is the strength concrete reach after 28 days) for the W/C factor After 28 days curing on room temperature and soaked in the water cylinder would reach (projected) the strength of 7,935 psi, what is of designed strength (design strength is the strength concrete reach after 28 days) for the W/C factor After 28 days curing on freeze-thaw cycles cylinder would reach (projected) the strength of 3,968 psi, what is of designed strength (design strength is the strength concrete reach after 28 days) for the W/C factor It is lower strength than the strength achieved after the same time with the cylinder normally cured, on room temperature soaked in the water Discussion of results Concrete mix was design for 5.5 cylinders. [...]
[...] Temperature below 32F affected the rate at which hydration of cement occurred. Low temperature retarded hydration, hardening and strength gaining. Aggregate Grading Grading is the distribution of aggregate particles (stones and sand) among various sizes. It is expressed as cumulative percentage. Retained percentage defines how much material was kept on each of the sieves. Material passing 4.76 mm and smaller sieves is considered fine aggregate (FA). All greater particles were called coarse aggregate (CA). Concrete contain 2-3 gradation of fine aggregate and several sizes of coarse aggregate. [...]
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