Civil Engineering

Sand layer is generally found when segregation occurs in a concrete mix. A certain portion of the casted wall/slab is found to contain only sand & somewhere the aggregates are found free from binding materials. Repairing methodology for sand layer: ·         First we have to determine the extent of sand layer in a particular structural member. ·         Secondly, using chisel/steel wire brush we have to get rid of the loose sand till we find good concrete. ·         If the depth of the damage is less than 5 mm then the void shall be filled with finish materials such as gypsum/putty as per client's instruction. ·         If the depth is more than 5 mm but less than 10 mm, then the void shall be cleaned properly followed by application of concrete bonding agent such as Fosroc Nitobond EP. After which modified cement mortar such as Sika Microcrete 4 or Sika 122 top HS shall be used to fill up the void. ·         If the depth is more than 10 mm but less than th

           Fly ash is a fine powder which is a by-product of coal-fired electric generating plants which is considered to have a small environmental footprint, as no energy is required to manufacture it, which can be replaced in place of concrete. Fly ash is a pozzolan material & during the hydration of cement it forms cementitious material by reacting with lime in presence of moisture.         Introduction of fly ash in concrete reduces the cement consumption as it acts as a cementitious material resulting in more economic mix design as it is a by-product. It also increases long-term strength, workability, flowability (The ability of concrete to flow freely) of the concrete. Some advantages of using fly ash :- 1.     Produces various set times of Concrete: The use of fly ash in concrete enables us to control of setting time of concrete, from 0- 10% fly ash content by weight of cementitious material doesn’t have any effect on initial & final setting time of co

In order to determine the mix design quantities of different ingredients for a particular grade of concrete, few steps are required which are as follows: 1.        Determine the target compressive strength The target compressive strength can be calculated by the following formula                                 T fck = T cs + 1.65 SD ……… [IS CODE: 10262-2009]                  Where, T fck is the target compressive strength of concrete.                              T cs is the compressive strength of concrete.                               SD is the Standard deviation.             T he grade of concrete to be designed is M25, then                                            T fck = 25 + 1.65 x 4 = 31.6 N/mm 2                                        2.        Determine the water-cement ratio of the mix & free water content. Determining the water cement ratio is critical for any mix design, no IS Code states any particular w/c ratio for any given mix. I