4 th International Conference on Rehabilitation and Maintenance in Civil Engineering Best Western Premier Hotel, Solo Baru, July,11‐12 2018 Strength development of cement-treated sand using different cement types cured at different temperatures Lanh Si Ho 1,2 , Kenta Eguchi 1 , Kenichiro Nakarai 1* 1 Hiroshima University, Japan 2 University of Transport Technology, Viet Nam Minoru Morioka 3 , Takashi Sasaki 3 Denka Co., Ltd, Japan 11-12 July 2018, Solo, Indonesia 1
1. Introduction Cement-treated soils are composite materials by mixing soil, cement, and water. Cement-treated soils are used as an improvement method of soft ground such as road- Deep mixing base, dam, air port, other structures etc. Shallow mixing Cement-treated soil used to improve the Cement treated soil used to improve soft properties for subgrade of pavement ground of dam (https://www.martinmarietta.com/products/cement-treated- materials/) (https://www.liebherr.com/en/ita/products/construction-machines/deep- foundation/methods/soil-improvement/ground- improvement.html#lightbox) 2
1. Introduction Strength development of cement-treated clay ( Kitazume and Terashi, 2013 ) There are many factors affect strength of strength cement-treated soils: -Material (cement type and soil condition) -Mix proportion (cement content, water/soil ratio) Cement hydration -Construction method (Mixing method, curing , curing temperature , age) etc. Improvement of physical property Original strength of soil Age Short-term Long-term Pozzolanic reaction is the reaction between Ca(OH) 2 (CH) with clay minerology (SiO 2 , Al 2 O 3 ) produces C- S-H, C-A-H, C-A-S-H 3
1. Introduction Effect of curing temperature Lime/cement treated soils Upper marine clay; cement/dried soil=11.8% Normal concrete 48 C increased 37 C 23 C 23 C Deceased 93 C However, there are no studies considering different cement type cured under different curing temperature. Compressive strength of concrete under different temperatures (A.R. Chini and L. Strength development over time under different Acquaye, 2005) curing temperature (D. Wang et al., 2016) Purpose This study investigated strength development of cement-treated sand using different cement types cured at different temperatures. 4
2. Methods and measurements Specimen preparation Mix proportions: Cement: ordinary Portland cement (OPC), high early Portland cement (HPC), and moderate heat Portland cement (MPC) were used to discuss effects of cement type. Sand mixture: Cement/sand=0.08, W/C=1.0, to discuss effects of curing temperature and cement type on strength development of cement-treated soils (high porosity). Mortar with W/C = 1.0: Cement/sand = 0.25, W/C = 1.0 , to create the mixture with the same W/C ratio (high porosity -similar to cement-treated soils) for explaining strength development. Mortar with W/C = 0.5 : Cement/sand = 0.5, W/C = 0.5 , to discuss strength development of mortar with dense structure for comparing. curing condition Compaction specimen size Sealed at 20 C, 40 C The sand mixture 50mm specimens Hammer 1.5kg Cylind rical 100mm 3 layers speci 12 times/layer; men Mortar : Tapping 5
2. Methods and measurements Measurements ➢ Unconfined compression test LDTs The tests were performed at a constant placed at centers loading rate of 0.1 mm/min for both mortar and cement-treated sand. ➢ Thermal analysis test The amounts of chemically bound water and Ca(OH) 2 (CH) were determined by thermal analysis (TG-DTA) to evaluate the degree of hydration and pozzolanic reaction. 6
3. Results and discussion 3.1 Compressive strength Effect of cement content At 7 days At 91 days Increased Mortar Increased Mortar Almost Almost constant constant Cement-treated Mortar Cement- sand Mortar treated sand 50% 25% 50% 25% 8% 8% 7
3. Results and discussion 3.1 Compressive strength Effect of cement content At 7 days At 91 days 2.0 Increased 2.0 O,20°C H,20°C Normalised compressive strength at Normalsied compressive strength at Increased M,20°C O,40°C Mortar H,40°C M,40°C Mortar 1.5 1.5 W/C = 50% 91 days (/OPC20 C) 7 days (/OPC20 C) W/C = 100% 1.0 1.0 Much smaller 0.5 0.5 Cement- O,20°C M,20°C W/C = 50% treated H,20°C O,40°C W/C = 100% H,40°C M,40°C 8% 50% 25% sand 0.0 0.0 50% Mortar Mortar 25% 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Cement content (%) Cement content (%) Cement-treated sand 8
3. Results and discussion 3.1 Compressive strength Effect of cement content At 7 days At 91 days 2.0 2.0 O,20°C H,20°C Normalised compressive strength at Normalsied compressive strength at M,20°C O,40°C Mortar H,40°C M,40°C Mortar 1.5 1.5 W/C = 50% 91 days (/OPC20 C) 7 days (/OPC20 C) W/C = 100% 1.0 1.0 Cement- 0.5 0.5 treated O,20°C M,20°C W/C = 50% H,20°C O,40°C sand W/C = 100% H,40°C M,40°C 50% 25% 8% 0.0 0.0 8% 50% Cement-treated Mortar Mortar 25% 0 10 20 30 40 50 60 0 10 20 30 40 50 60 sand Cement content (%) Cement content (%) - When cement content decreased and sand content increased , the effects of cement content and curing temperature on strength development increased both short and long term in HPC and OPC at 40 C 9
3. Results and discussion 3.1 Compressive strength Comparison of cement type 4.0 4.0 4.0 4.0 Mortar Compressive strength 1day 1day Cement-treated sand Compressive strength 7days ratio (40 C/20 C) (W/C=50%, C=50%) o h ratio 7days Compressive strength ratio (W/C=100%, C=8%) ratio (40 C/20 C) 3.0 28days 3.0 28days 3.0 ngth 3.0 91days 91days pressive streng (40 C/20 C) C) (40 C/20 C) C) 2.0 2.0 2.0 2.0 Compr 1.0 1.0 1.0 1.0 0.0 0.0 0.0 0.0 HPC OPC MPC HP HPC OPC MPC 4.0 4.0 3day Compressive strength ratio (40 C/20 C) C) Compressive strength 7days Mortar ratio (40 C/20 C) 28days For both mortar and cement- 3.0 3.0 (W/C=100%, C=25%) 91days treated sand 2.0 2.0 → the strengh ratio increased in order of MPC OPC HPC 1.0 1.0 0.0 0.0 HPC HP OPC MPC 10
3. Results and discussion 3.1 Compressive strength Comparison of cement type 100 Effect of temperature Other on strength 80 CaCO3 MPC OPC HPC Content (%) CaSO4 60 C4AF Suggest that 40 C3A When C 2 S C 3 S C2S 20 C3S Effect of temperature on 0 cement mineral reactions: HPC OPC MPC MPC OPC HPC or C 2 S can C 3 S ： mainly contribute to early strength reduce negative effect of high development curing temperatures C 2 S ： mainly contribute to long-term strength development 11
3. Results and discussion 3.2 Amount of chemically bound water Strength development mechanism of cement-treated soil Mortar Cement-treated sand 30 Amount of chemically 25 bound water (%) 20 15 10 S-8(O,20°C) S-8(O,40°C) 5 S-8(H,20°C) S-8(H,40°C) S-8(M,20°C) S-8(M,40°C) 0 1 10 100 Age (days) Amount of chemically bound Amount of chemically bound water water over time of mortars. over time of cement-treated sand. 12
3. Results and discussion 3.2 Amount of chemically bound water Strength development mechanism of cement-treated soil Mortar Cement-treated sand 30 > 20% > 20% Amount of chemically 25 bound water (%) 20 15 10 S-8(O,20°C) S-8(O,40°C) 5 S-8(H,20°C) S-8(H,40°C) S-8(M,20°C) S-8(M,40°C) 0 1 10 100 Age (days) The high water cement ratio caused the increase in amount of chemically bound water from the early age due to cement type (HPC) and curing temperature (40 C) 13
3. Results and discussion 3.3. Relationship between amount of chemically bound water and strength Strength development mechanism of cement-treated soil The increase of chemically bound 3 days 91 days water led to the increase in strength both short and long 3.0 Ratio of compressive strength at 91 2.0 Ratio of compressive strength at 3 S-8(O,40°C) S-8(O,40°C) term S-8(H,20°C) S-8(H,20°C) 2.5 S-8(H,40°C) S-8(H,40°C) days (/OPC 20 C) 1.5 days(/OPC 20 C) M100(O,40°C) M100(O,40°C) 2.0 M100(H,20°C) M100(H,20°C) M100(H,40°C) M100(H,40°C) 1.5 M50(O,40°C) M50(O,40°C) 1.0 M50(H,20°C) M50(H,20°C) 1.0 M50(H,40°C) M50(H,40°C) O,20°C O,20°C 0.5 0.5 0.5 1.0 1.5 0.5 1.0 1.5 2.0 2.5 3.0 Ratio of chemically bound water at 3 days Ratio of chemically bound water at 91 days (/OPC20 C) (/OPC20 C) The strength increase by curing temperature in cement-treated soil was influenced greatly by cement type, and the strength increase both short and long term was caused by the increase in amount of chemically bound water This phenomenon may be caused by a high water cement ratio and a large amount of sand 14
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