Topic 6 - Setting Time of Hydraulic Cement PDF

CE312: Construction Materials and Testing Determination of setting time of Hydraulic cement By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction...

CE312: Construction Materials and Testing Determination of setting time of Hydraulic cement By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing Discussion: Cement has many important properties which are gained by adding required amount of water to start the reaction between them. When water is mixed with cement, the paste is formed and it remains in the plastic state for a first few minute. During these first few minutes, the paste can be molded in any required shape due to its plasticity. By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing Discussion: However, within this specific time, reaction continues between cement and water. During this reaction, paste loses its plasticity and gets hardened. Afterwards, molding the hardened paste in the desired shape is difficult. The early time of the hardening of cement paste is known as “Setting time of Cement” By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing Setting time of cement paste is that the interval during which the cement paste losses its plasticity after adding water in cement. It is defined as a specified time required for concrete or mortar to change from liquid state to plastic state and plastic state to solid state so that the surface becomes sufficiently rigid to withstand a definite amount of pressure. It is necessary to place and consolidate the concrete or the mortar before initial setting to start and do not disturb till the final setting of mortar or concrete has taken place. By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing Setting time of cement is calculated in two parts: (1) Initial setting time is regarded as the time elapsed between the moments that the water is added to the cement to the time that the paste starts losing its plasticity and the hardening of the cement starts. It is the time within which the cement can be molded in any desired shape without losing its strength. (2) final setting time is the time elapsed between the moment when water is added to the cement and the time when the paste has completely lost its plasticity and has attained the sufficient firmness to resist certain and definite pressure. This is the time taken for the cement paste to becomes hard and attain the shape of the mould in which it is cast. By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing Standard Reference: ASTM C191 : Standard Test Method for Time of Setting of Hydraulic Cement by Vicat Needle Apparatus: 1. Vicat Apparatus with the needle end, 1mm in diameter 2. Weights and weighing device 3. Glass Graduates(200 or 250) ml capacity 4. A trowel and containers By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing Procedure: 1. Weigh 400g cement. 2. Prepare amount of water as to that calculated in normal consistency test. By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing 3. Prepare a cement paste. Place in Vicat conical 4. Allow the time of setting specimen to ring. Don’t forget to record the time since the remain in the moist cabinet for 30 min after cement is added to the water. molding without being disturbed. Determine the penetration of the 1mm needle at this time and every 15 min until a penetration of 25mm or less is obtained. By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing 5. To read the penetration, lower the needle of Vicat Apparatus until it touches the surface of the cement paste. Tighten the crew and take an initial reading. Release the set screw and allow the needle to settle for 30 sec, and then take reading to determine the penetration. By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing 6. Note that no penetration shall be made closer than 6 mm from any previous penetration and no penetration shall be made closer than 9.5mm from the inside of the mold. Record the results of all penetration, then by drawing a curve determine the time when a penetration of 25mm is obtained. This is the initial setting time. 7. The final setting time is when the needle dose not sinks visible into the paste. 8. Draw a graph for (Penetration-time). Show the time which gives penetration 25mm this will be the initial setting time. By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing Temperature and Humidity:  The temperature of the air in the vicinity of the mixing slab, the dry cement, molds, and base plates shall be maintained between 20 and 27.5 °C (68 and 81.5 °F).  The temperature of the mixing water shall not vary from 23.0 °C (73.5 °F) by more than 62.0 °C (3.5 °F).  The relative humidity of the laboratory shall be not less than 50 %. Precautions:  Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure. The use of gloves, protective clothing, and eye protection is recommended.  Wash contact area with copious amounts of water after contact. Wash eyes for a minimum of 15 min.  Avoid exposure of the body to clothing saturated with the liquid phase of the unhardened material. Remove contaminated clothing immediately after exposure  The apparatus should be free from vibrations during all the test. By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing Example: # Description Time Interval Time Elapsed Penetration min min mm 1 Addition of water in cement 0 – 2 Mixing & filling of mold 5 5 3 1st Reading 30 35 40 4 2nd Reading 15 50 40 5 3rd Reading 15 65 40 6 4th Reading 15 80 40 7 5th Reading 15 95 40 8 6th Reading 15 110 40 9 7th Reading 15 125 37 10 8th Reading 15 140 37 11 9th Reading 15 155 35 12 10th Reading 15 170 33 13 11th Reading 15 185 32 14 12th Reading 15 200 29 15 13th Reading 15 215 25 By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing Example: # Description Time Interval Time Elapsed Penetration min min mm 16 14th Reading 15 230 20 17 15th Reading 15 245 18 18 16th Reading 15 260 14 19 17th Reading 15 275 6 20 18th Reading 15 290 4 21 19th Reading 15 305 2 22 20th Reading 15 320 1 23 21st Reading 15 335 0 By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing Example: Initial setting time = 220 min (3.67 hrs) Final setting time = 335 min (5.58 hrs) By: Engr. Vera Karla S. Caingles Determination of setting time of Hydraulic cement CE312: Construction Materials and Testing Youtube Links: https://www.youtube.com/watch?v=3tKuexK4 zto&t=107s https://www.youtube.com/watch?v=qYIh43yz BWQ&t=50s By: Engr. Vera Karla S. Caingles