2 1, what is the reason for the subsidence of backfill soil?
(1) The soil selected for backfill has high water content.
(2) If the selected soil material is clay, it will become clay due to excessive water content during compaction. Rubber soil? As a concrete cushion on this foundation soil, it is easy to crack.
(3) The backfill soil is not compacted (pressed) in layers, or the compaction density is not in conformity with the regulations, resulting in excessive settlement and backfill soil sinking.
(4) There is rubber soil in the basement, which has not been treated.
22, backfill soil subsidence what preventive measures?
(1) Strictly control the soil quality and water content of backfill soil.
(2) The fill must be compacted by layers; Paving thickness and compaction times should meet the design requirements and specifications.
(3) It is forbidden to fill undisturbed soil such as humus, loam, peat soil and silt with excessive water content.
(4) Before filling, the rubber soil of the basement should be treated, and the treatment methods can be adopted:
(1) After drying, tamp it;
② Soil replacement. Remove rubber soil and replace it with dry soil, or backfill graded sand;
(3) Adding dry soil, quicklime powder, broken bricks and other materials with strong water absorption into rubber soil to absorb the water in the soil and reduce the water content of the soil.
23. What are the reasons why mortar does not meet the requirements?
(1) The cement quality is unqualified.
(2) The silt content of sand is large.
(3) The measurement of mortar mixture ratio is inaccurate.
(4) The feeding order is reversed, and the mortar mixing is uneven.
(5) Artificial stirring.
(6) Poor water-cement ratio control and poor workability.
(7) Poor water retention of mortar.
(8) Mortar varieties are not in conformity with the design, or there are no corresponding measures after admixture is added.
The above reasons will lead to the low strength of masonry mortar, which can not reach the design masonry strength, resulting in horizontal cracks, vertical cracks and oblique cracks in brick masonry.
24. What are the reasons why the roof leveling layer does not meet the requirements?
(1) The integral cement mortar leveling layer is not retained in the frame joint or the joint is not filled with sealing material, and the thickness of plastering leveling layer is quite different, which leads to irregular cracking of the coiled material roof.
(2) Protruding the root of the roof structure into a right angle will affect the laying of the waterproof layer.
(3) The main reason of roof water accumulation is that the leveling layer did not put the slope as required.
(4) The mixture ratio of mortar used for leveling layer is inaccurate, the surface is not dense, maintenance is not paid attention to, and the mortar strength is low, resulting in sand.
25. What are the causes of leakage of coiled material waterproof roof?
(1) The quality of raw materials does not meet the design requirements and the relevant provisions of specifications and standards;
(2) The coiled material was laid on the base with high water content, and no corresponding technical measures were taken;
(3) The boiling temperature of asphalt binder is low, and it does not achieve sufficient dehydration;
(4) There is floating talcum powder or dust on the surface of the coil;
(5) Due to the temperature change, the roof panel expands with heat and contracts with cold, which leads to the warping of the plate end. The quality of coil is poor, aging or cold brittleness at low temperature, which reduces toughness and elongation;
(6) If the lap length is too small, the joint will crack and warp after the coil shrinks; Or because of the aging and cracking of the coil, the coil is cracked, which leads to the leakage of the roof waterproof layer.
(7) Improper protection or treatment of waterproof layer leads to cracking, embrittlement and even destruction of coiled materials and cementing materials.
25, external wall plastering empty drum, what is the cause of cracking?
(1) The joint between partition wall or infilled wall and concrete is not reinforced according to the requirements of drawings and specifications, and cracks appear along the joint. The cracks in masonry structure in 2-6 of this book lead to plastering cracking.
(2) grass-roots treatment or cleaning is not in place.
(3) Insufficient watering at the grass-roots level and dehydration of plastering mortar will affect the cohesive force.
(4) Plastering is not done in time according to the operation procedures, so it's faster? In one go? The shrinkage deformation of ash is concentrated in the surface layer every time, which increases the deformation several times.
(5) The quality of raw materials is not good.
(6) Poor mortar preparation and improper use.
(7) Cement mortar shall be plastered on lime mortar or mixed mortar.
26, external wall plastering empty drum, cracking prevention measures?
(1) Rachel bars shall be embedded at the junction of wall and concrete in strict accordance with the requirements of drawings and specifications, and reinforcement measures shall be studied with the design department when Rachel bars are found missing.
(2) Before plastering, the oil stain, paint and isolation agent on the concrete surface should be removed. When plastering the smooth concrete surface, its performance should be treated by interface treatment agent or chiseling, and when plastering cement mortar, it should be chopped tightly. When plastering with yellow sand gravel mortar, the hair can be cut into a star shape, that is, the distance between the cut marks is about 30mm and the depth of the mark is 3-5 mm. The uneven place should be leveled in advance or leveled with 1: 3 cement mortar. When the plaster thickness is greater than 40mm, technical measures should be taken to tighten the plaster layer with steel wire mesh or steel wire mesh and nails, and the steel wire mesh must be placed in the middle of the extra-thick plaster layer.
(3) Water the wall before plastering, and water it twice overnight at room temperature. If the climate and operating environment change greatly, it should be grasped as appropriate according to the actual situation.
(4) Raw materials such as cement, sand, lime and additives shall meet the quality requirements. Cement, fine sand, ultra-fine sand and frozen lime putty with unqualified strength and stability are strictly prohibited.
(5) Strictly control the proportion of mortar. Plastering mortar must have good workability and water retention. When the water retention performance of cement mortar is poor, lime paste, fly ash or plasticizer can be added to adjust the proportion to improve its water retention performance. The slump of commonly used plastering mortar should be controlled as follows:
The bottom plastering mortar is10-12 cm;
The middle plastering mortar is 7-8cm;
Surface plastering mortar10cm;
Plastering mortar must be firmly bonded with the grassroots. If necessary, the mortar can be mixed with environmentally friendly cementing materials (used as required) to improve the bonding strength of plastering mortar.
(6) When the plastering base is not normal, the middle plastering should be leveled by layers, and the thickness of each layer of plastering should be controlled at 7- 10 mm ... Cement mortar and mixed slurry should be leveled and solidified first, and then the next layer should be wiped. It usually takes overnight. Lime mortar should be smeared on the next layer after the previous layer turns white. If several layers are applied in succession. Because the wet mortar sticks together and cannot be layered, the mortar shrinks too much and cracks.
(7) Cement mortar shall not be plastered on lime mortar or mixed mortar.
(8) In order to prevent cracks in the parapet root and two external longitudinal walls at the top of both ends of the building, how to strengthen masonry structural measures should be studied when the blue prints.the design before construction.
(9) In order to prevent vertical cracks in the double balcony partition railings, two vertical partitions can be left, and the joints are embedded with weather-resistant glue.
27. What is the reason for the poor visual quality of plastering surface of external wall?
(1) Improper operation method of grey calendering on coating surface leads to smearing.
(2) There is no border on the wall or the border is too large, which makes it impossible to leave a gap at the border. Although there is a frame, it is not left at the frame, resulting in obvious connection.
(3) The raw materials used in mortar are inconsistent, there is no uniform ingredient, and the grass-roots watering is uneven.
28. What are the preventive measures for poor visual quality of plastering surface of external wall?
(1) Exterior wall plastering should be made into a rough surface (vertical stripes) and should not be polished. When wiping with a wooden trowel, you should master the wet and dry, not dry, and not dipped in water. The strength should be consistent, and it must be scraped up and down in the same direction.
(2) If the connection position should be left in the frame, waist line, Yin and Yang angle or downpipe, the plastering of Yang angle should be done by sticking eight feet.
(3) Exterior wall plastering surface ash, using raw materials should be consistent, cement should be the same variety, the same label, the same batch. Moreover, there should be a surplus, and the yellow sand should be of the same origin and batch, and there should be a surplus and a unified composition.
29, external wall plastering frame joints uneven, lack of edge break what are the reasons?
(1) The elastic line on the wall is uneven; No horizontal tool ruler or transparent nylon tube was used for irrigation and leveling.
(2) The material of the frame strip is poor, and it is not fully soaked before use, and it warps and deforms after use.
(3) Improper operation when pasting and lifting frame strips leads to lack of edges and corners or staggered joints on both sides of the seam.
30, external wall plastering frame joints uneven, lack of edge break what are the preventive measures?
(1) Pull-through line pops up the horizontal frame line, and the side surfaces such as columns are leveled with a spirit level to ensure straightness. Vertical frame joints shall be unified with hanging wire blocks.
(2) Plastic or aluminum alloy strips should be used as the frame.
(3) The horizontal frame bars should generally be posted below the horizontal line, and the vertical frame bars should generally be posted on the left side of the vertical line to check their accuracy and prevent staggered joints and unevenness. Both sides of the frame can be fixed with pure cement slurry, and the edges should be wiped at the horizontal line first. If the day is covered with ash, both sides can be covered with 45 degrees, otherwise the slope should be covered with 60 degrees.
When the surface layer is calendered, the cement mortar of the frame reinforcement shall be cleaned up, and the frame reinforcement can be lifted only after the cement mortar reaches a certain strength, so as to avoid damaging the edges and corners when lifting, and the false bottom ash of the frame reinforcement shall be repaired with cement slurry. After pulling it out, it should be cleaned with cement slurry in time for reuse.
(4) The grid strips can be plastic strips or aluminum alloy strips that meet the width and depth of the grid strips at one time, and the grid strips are permanently embedded in the wall. The cross-sectional form of the frame should prevent plaster from popping up after shrinkage.
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